[Repeater-Builder] duplexers 2 meter
hi my friends where to get the duplexes 2meter and how much 9w2yii...73 tq
Re: [Repeater-Builder] Duplexers
On 8/31/2010 2:05 PM, ka9qjg wrote: OK Great , Thanks to Everyone who answered , I will sleep better now one less thing to worry about Don KA9QJG Not the same thing, but something else to remember: Mount them vertically! If you mount them horizontally, you run the risk of the rods warping from gravity, which besides detuning, also results in uneven tuning when you try to touch them up again...
RE: [Repeater-Builder] Duplexers
Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
Re: [Repeater-Builder] Duplexers
No problem. Most are in non-climate controlled environments. Chuck WB2EDV - Original Message - From: ka9qjg To: Repeater-Builder@yahoogroups.com Sent: Tuesday, August 31, 2010 1:42 PM Subject: RE: [Repeater-Builder] Duplexers Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
Re: [Repeater-Builder] Duplexers
I haven't seen problems from condensation. Now salt water corrosion from installations on a coast, that's a pretty big problem. I've got a set of cans where the invar has actually rusted, and the connectors were all shot. On Tue, Aug 31, 2010 at 10:42 AM, ka9qjg ka9...@wowway.com wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG *From:* Repeater-Builder@yahoogroups.com [mailto: repeater-buil...@yahoogroups.com] *On Behalf Of *ka9qjg *Sent:* Monday, August 30, 2010 9:07 PM *To:* Repeater-Builder@yahoogroups.com *Subject:* RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
RE: [Repeater-Builder] Duplexers
I have a set of Wacoms on 2-meters in a totally uncompensated shack, running from the teens in the winter to probably 150 in the summer. I've never had an issued. I have another set in a similar shack, but it it air conditioned in the summer. They've been out there for 10 years and are pristine. Last time I checked them for alignment, they were still perfect. 73, Mike WM4B On Tue, Aug 31, 2010 at 1:42 PM, ka9qjg wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Duplexers
OK Great , Thanks to Everyone who answered , I will sleep better now one less thing to worry about Don KA9QJG From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of mwbese...@cox.net Sent: Tuesday, August 31, 2010 12:51 PM To: repeater-builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers I have a set of Wacoms on 2-meters in a totally uncompensated shack, running from the teens in the winter to probably 150 in the summer. I've never had an issued. I have another set in a similar shack, but it it air conditioned in the summer. They've been out there for 10 years and are pristine. Last time I checked them for alignment, they were still perfect. 73, Mike WM4B On Tue, Aug 31, 2010 at 1:42 PM, ka9qjg wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
RE: [Repeater-Builder] Duplexers
For there to be condensation there must be humidity in the air. The more humidity, the more condensation. Duplexers are in harsh environments now and I don't think it has been a problem. Condensation on the outside of the cans should not cause any issue for what is going inside. On Tue, 2010-08-31 at 12:42 -0500, ka9qjg wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From:Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
RE: [Repeater-Builder] Duplexers
Typically, you'll get condensation when you have high humidity (with
HIGH being a relative term) and rapid changes in temperature. Working
in an air-conditioned building and walking outside into a hot, Georgia
afternoon, my glasses and I are quite familiar with the scenario.
73,
Mike
WM4B
On Tue, Aug 31, 2010 at 2:08 PM, Chris Fowler wrote:
For there to be condensation there must be humidity in the air. The
more
humidity, the more condensation.
Duplexers are in harsh environments now and I don't think it has been a
problem. Condensation on the outside of the cans should not cause any
issue for what is going inside.
On Tue, 2010-08-31 at 12:42 -0500, ka9qjg wrote:
Wow this must of Really been a Dumb question , No one answered it
Don KA9QJG
From: Repeater-Builder@yahoogroups.com
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] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To:
Repeater-Builder@yahoogroups.com
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Subject: RE: [Repeater-Builder] Duplexers
Since We are on the Topic of Duplexers, And some claim there is no
such thing as a Dumb Question but at the Risk of Asking one I will
take a chance , I have the Wacom 4 can on My 220 System,
The Question I have in a non controlled environment such as No Heat or
Air
Will the Duplexer have any problems inside with Condensation from
Heating up in use and Cooling down
Thanks Don
KA9QJG
javascript:parent.wgMail.openComposeWindow('Repeater-Builder@yahoogroups.com')
http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] Duplexers
Wow... that's UGLY!
I wonder if a small heat-tape would prevent that from happening?
73,
Mike
WM4B
On Tue, Aug 31, 2010 at 2:17 PM, Roger Stacey wrote:
On Vancouver Island B.C we do have humidity. The site is at 4400 ft.
Roger
VA7RS
- Original Message -
From: Chris Fowler k...@k4fh.com
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To: Repeater-Builder@yahoogroups.com
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Cc: ka9qjg ka9...@wowway.com
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Sent: Tuesday, August 31, 2010 11:08 AM
Subject: RE: [Repeater-Builder] Duplexers
For there to be condensation there must be humidity in the air. The
more humidity, the more condensation.
Duplexers are in harsh environments now and I don't think it has been
a problem. Condensation on the outside of the cans should not cause
any issue for what is going inside.
On Tue, 2010-08-31 at 12:42 -0500, ka9qjg wrote:
Wow this must of Really been a Dumb question , No one answered it
Don KA9QJG
From: Repeater-Builder@yahoogroups.com
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] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To:
Repeater-Builder@yahoogroups.com
javascript:parent.wgMail.openComposeWindow('Repeater-Builder@yahoogroups.com')
Subject: RE: [Repeater-Builder] Duplexers
Since We are on the Topic of Duplexers, And some claim there is no
such thing as a Dumb Question but at the Risk of Asking one I will
take a chance , I have the Wacom 4 can on My 220 System,
The Question I have in a non controlled environment such as No Heat
or Air
Will the Duplexer have any problems inside with Condensation from
Heating up in use and Cooling down
Thanks Don
KA9QJG
Yahoo! Groups Links
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Re: [Repeater-Builder] Duplexers
Guess that I should answer it then. I have had a 4 can Wacom 220 mhz duplexer in a 6 foot by 6 foot building for around 20 years and it still works. Also in the same building is a Phelps Dodge 6 can 146 mhz duplexer that has been there for about 35 years. This is in the middle of North Carolina where it gets up to around 100 in the summer and around 15 deg in the winter. The building only has a couple of repeaters in it and is not heated or cooled. Made out of cinder blocks. From: ka9qjg ka9...@wowway.com To: Repeater-Builder@yahoogroups.com Sent: Tue, August 31, 2010 1:42:32 PM Subject: RE: [Repeater-Builder] Duplexers Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From:Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
Re: [Repeater-Builder] Duplexers
I've never had a problem. I would say that if the duplexers are out of tune on the transmit side there is a possibility that they might get hot, then cool off. This may cause them to take in moist air and cause condensation. I've never seen it happen, but I can see how it could. 73, Jow, K1ike On 8/31/2010 2:05 PM, ka9qjg wrote: OK Great , Thanks to Everyone who answered , I will sleep better now one less thing to worry about
RE: [Repeater-Builder] Duplexers
Has anyone mentioned band-pass cavities? One on the RX side could be enough and one more on the TX would do it for sure. There're some for 220 for less then a $100 on ebay right now. This might sound off the wall but I once saw a DB4021 UHF band-pass cavity tune up quite well on 2 meters!!! Only about .6db insertion loss on 2 meters. So if you have a VHF or UHF band-pass I would try sweeping it with the resonator in a few different spots and see if you find any harmonics near your target frequency. And I would only do this on the RX side. That UHF cavity tuned to 2 meters did get warmer then the other db4001's, probably an impedance issue. Forgot to mention the swr on that cavity was about 1.3 . So is this the worst practice ever, or what happened? ~Ross -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
Re: [Repeater-Builder] Duplexers
My 2 duplexers are in a space with no heat and no air .. and no problems Keep them off a COLD floor and you should be fine as they can move with the temp in the room they are in On Tue, Aug 31, 2010 at 1:42 PM, ka9qjg ka9...@wowway.com wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG *From:* Repeater-Builder@yahoogroups.com [mailto: repeater-buil...@yahoogroups.com] *On Behalf Of *ka9qjg *Sent:* Monday, August 30, 2010 9:07 PM *To:* Repeater-Builder@yahoogroups.com *Subject:* RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
Re: [Repeater-Builder] Duplexers
Thats the same duplexer I had .. built my Bob Mortorn when he was at sinclair .. never had that problem here though Rick va3rzs On Tue, Aug 31, 2010 at 2:17 PM, Roger Stacey va...@telus.net wrote: On Vancouver Island B.C we do have humidity. The site is at 4400 ft. Roger VA7RS - Original Message - From: Chris Fowler k...@k4fh.com k4fh%40k4fh.com To: Repeater-Builder@yahoogroups.com Repeater-Builder%40yahoogroups.com Cc: ka9qjg ka9...@wowway.com KA9QJG%40WOWWAY.COM Sent: Tuesday, August 31, 2010 11:08 AM Subject: RE: [Repeater-Builder] Duplexers For there to be condensation there must be humidity in the air. The more humidity, the more condensation. Duplexers are in harsh environments now and I don't think it has been a problem. Condensation on the outside of the cans should not cause any issue for what is going inside. On Tue, 2010-08-31 at 12:42 -0500, ka9qjg wrote: Wow this must of Really been a Dumb question , No one answered it Don KA9QJG From:Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com] On Behalf Of ka9qjg Sent: Monday, August 30, 2010 9:07 PM To: Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3104 - Release Date: 08/30/10 23:34:00
Re: [Repeater-Builder] Duplexers
Don, this is a natural response, or lack thereof. If you ask, will I have this problem, and nobody else has had it, that doesn't mean they can guarantee YOU won't have it, so they refrain from commenting. I learned a lot from my experience with one outdoor, rooftop repeater I built. I was expecting condensation in places where I could find no evidence of it actually occurring. It finally dawned on me that even if the ambient humidity is 100%, and condensation is collecting on the outside of the cabinet, the equipment inside is safe as long as the temp there remains even slightly above the outside. If you have to mount the duplexers away from the transmitter and power supply, condensation may be more difficult to control. Whenever possible, I will always try to keep the cans (and all the equipment) slightly warmer than outside ambient. I believe that in most installations, even in non-climate-controlled buildings, this is likely to happen by default, especially if you are co-sited with lots of other people's stuff. On my rooftop repeater, I ended up using a completely sealed, gasketed steel cabinet, painted a light color, with no vents to the outside whatsoever, and relied on plain old heat loss through the cabinet walls for dissipation. When I changed out my 2-watt, solar-powered, Repco UHF repeater for a 35-watt, converted GE Mastr II powered from the AC mains, I expected problems, so I put a 119ºF attic fan switch on the transmitter's heatsink, wired to a logic input on the controller. It never triggered, even in the summer, and this was in orlando, FL. The commercial stuff is based on components which were designed to stay happy for years locked in a car trunk. It may be possible to overdo ventilation. I think I'd rather err on the side of staying a little warm in a repeater shack, within reason. 73, Paul, AE4KR - Original Message - From: ka9qjg To: Repeater-Builder@yahoogroups.com Sent: Tuesday, August 31, 2010 11:42 AM Subject: RE: [Repeater-Builder] Duplexers Wow this must of Really been a Dumb question , No one answered it Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down
Re: [Repeater-Builder] Duplexers
If the transmiter is sometimes desensitizing the receiver,then re tune the or readjust the duplexeur. --- On Tue, 8/31/10, cmcclel...@aol.com cmcclel...@aol.com wrote: From: cmcclel...@aol.com cmcclel...@aol.com Subject: Re: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Tuesday, August 31, 2010, 2:44 AM Thank you for your response. The problem is that the repeater is located on top of a building and the tower on that building is only about 20 feet tall. We can move the two antennas apart horizontally, but only 20 feet vertically. Duplexers are way too expensive and hard to find for the 200 Mhz band. We are running about 20 watts and the frequency separation is 1.6 mhz. Sometimes a week signal comes in and sometimes the transceiver is desensitizing the receiver and covers it up. Any suggestions? Thanks Chris In a message dated 8/30/2010 8:36:53 P.M. Eastern Daylight Time, wb6...@verizon.net writes: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
[Repeater-Builder] Duplexers
Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
RE: [Repeater-Builder] Duplexers
Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
Re: [Repeater-Builder] Duplexers
Thank you for your response. The problem is that the repeater is located on top of a building and the tower on that building is only about 20 feet tall. We can move the two antennas apart horizontally, but only 20 feet vertically. Duplexers are way too expensive and hard to find for the 200 Mhz band. We are running about 20 watts and the frequency separation is 1.6 mhz. Sometimes a week signal comes in and sometimes the transceiver is desensitizing the receiver and covers it up. Any suggestions? Thanks Chris In a message dated 8/30/2010 8:36:53 P.M. Eastern Daylight Time, wb6...@verizon.net writes: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: _repeater-buil...@yahoogroups.com_ (mailto:Repeater-Builder@yahoogroups.com) [mailto:_repeater-buil...@yahoogroups.com_ (mailto:Repeater-Builder@yahoogroups.com) ] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: _repeater-buil...@yahoogroups.com_ (mailto:Repeater-Builder@yahoogroups.com) Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
Re: [Repeater-Builder] Duplexers
if you keep your eyes open you can find 220 duplexers at a good price .. Email Bob Morton and I am sure he can find you one at a good price .. I had 2 from him and love his work and the shipping cost of a 220 duplexer is not that bad either On Mon, Aug 30, 2010 at 8:44 PM, cmcclel...@aol.com wrote: Thank you for your response. The problem is that the repeater is located on top of a building and the tower on that building is only about 20 feet tall. We can move the two antennas apart horizontally, but only 20 feet vertically. Duplexers are way too expensive and hard to find for the 200 Mhz band. We are running about 20 watts and the frequency separation is 1.6 mhz. Sometimes a week signal comes in and sometimes the transceiver is desensitizing the receiver and covers it up. Any suggestions? Thanks Chris In a message dated 8/30/2010 8:36:53 P.M. Eastern Daylight Time, wb6...@verizon.net writes: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.comRepeater-Builder%40yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
Re: [Repeater-Builder] Duplexers
Chris, There aren't many ways around the laws of physics. If you can't get adequate physical separation, and can't afford a duplexer...perhaps you just can't afford to operate a repeater. Can you gather enough interested users, and get everyone to chip in for a duplexer? If not, maybe your local user community isn't large enough to need a 220 MHz repeater! You might be able to gather a group adequate to fund and support a 220 repeater if you got closer to the Charleston area, linked into a hub in Charleston, etc. Your elevation might have some definite linking possibilities if folks in Charleston wanted a 220 MHz hub that could get them coverage farther west on US 26, for example. Generally, if you need to raise money to get a project done, you need to be able to cover a population center large enough to include a bunch of potential users. Given your area's population growth, if you have the connections, getting the town or county to help fund a sanctioned emergency repeater system might be an avenue, but you'd better have enough users on 220 to make it work if it's ever called up. The economy will be against you in this pursuit; your population growth will be an advantage. Remember, finding the money to get it built and installed is only the start of the financial fun. You'll need an ongoing budget for maintenance and repair, or the machine will spend too much time down, and the users will wander off to other pursuits. Good luck! 73, Paul, AE4KR - Original Message - From: cmcclel...@aol.com To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 6:44 PM Subject: Re: [Repeater-Builder] Duplexers Thank you for your response. The problem is that the repeater is located on top of a building and the tower on that building is only about 20 feet tall. We can move the two antennas apart horizontally, but only 20 feet vertically. Duplexers are way too expensive and hard to find for the 200 Mhz band. We are running about 20 watts and the frequency separation is 1.6 mhz. Sometimes a week signal comes in and sometimes the transceiver is desensitizing the receiver and covers it up. Any suggestions? Thanks Chris In a message dated 8/30/2010 8:36:53 P.M. Eastern Daylight Time, wb6...@verizon.net writes: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
RE: [Repeater-Builder] Duplexers
Chris, I plugged your frequency separation and power level into CommShop, and assumed a receiver sensitivity of 0.3 microvolts. The program responded that at least 77 dB of isolation is needed for zero desense- which is the obvious goal of any repeater builder. CommShop calculated that 77 dB of isolation can be achieved by 112 feet of vertical separation or 5,681 feet of horizontal separation. I will readily admit that CommShop is not perfect, since it makes many assumptions that may or may not be valid in your particular case. That said, it has been remarkably close in its projections- in my personal experience, anyway. The reality of your situation is that you do not have sufficient real estate or tower height to construct a workable repeater with separate TX and RX antennas. I strongly suggest that you give up on the two antenna idea and start looking for a good used 220 MHz duplexer. My own 220 MHz repeater uses a Telewave TPRD-2254 duplexer, and has been desense-free. Although this duplexer is available new for about $1,120 with a Ham discount, I have seen this exact duplexer on the used market for less than $500. More info about the TPRD-2254 duplexer is here: www.telewave.com/pdf/TWDS-6026.pdf 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of cmcclel...@aol.com Sent: Monday, August 30, 2010 5:45 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers Thank you for your response. The problem is that the repeater is located on top of a building and the tower on that building is only about 20 feet tall. We can move the two antennas apart horizontally, but only 20 feet vertically. Duplexers are way too expensive and hard to find for the 200 Mhz band. We are running about 20 watts and the frequency separation is 1.6 mhz. Sometimes a week signal comes in and sometimes the transceiver is desensitizing the receiver and covers it up. Any suggestions? Thanks Chris In a message dated 8/30/2010 8:36:53 P.M. Eastern Daylight Time, wb6...@verizon.net writes: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek
RE: [Repeater-Builder] Duplexers
Since We are on the Topic of Duplexers, And some claim there is no such thing as a Dumb Question but at the Risk of Asking one I will take a chance , I have the Wacom 4 can on My 220 System, The Question I have in a non controlled environment such as No Heat or Air Will the Duplexer have any problems inside with Condensation from Heating up in use and Cooling down Thanks Don KA9QJG
RE: [Repeater-Builder] Duplexers
Theory: http://www.repeater-builder.com/antenna/thoughts-on-isolation.html Applications: http://www.repeater-builder.com/antenna/separation.html Mike WA6ILQ At 05:36 PM 08/30/10, you wrote: Chris, You do not have to use a duplexer, but it makes building a repeater SO much easier! Keep in mind that antenna separation usually means vertical separation, not horizontal separation. Moreover, the same isolation provided by 1000 feet of horizontal separation might be provided by 10 feet of vertical separation. The amount of isolation you need is based generally on the transmit power, frequency separation between TX and RX, and the sensitivity of the receiver. The receiver bandwidth and antenna types also play a factor. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mackey Sent: Monday, August 30, 2010 4:44 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Our club was recently given a 220 repeater. We have two seperate antennas. We do not have a duplexer. My question is do we have to have a duplexer? How can we keep the transmitter from desensitizing the receiver? The antennas are apart but can be moved farther. Thanks Chris Kg4bek Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3103 - Release Date: 08/30/10 11:34:00
RE: [Repeater-Builder] Duplexers F S
The 4 WaCom UHF 10 cavities I believe were designed to be part of a simple duplexer for a UHF-Lo repeater. They *should* tune up to the 440 ham band based on what Telewave has listed for specs on the current modern day model number. Current config is Pass RX Reject TX on 3 cans and Pass TX Reject RX on the 4th can. I'm not a Batlabs member, nor do I care to be (not that I have anything against Batlabs, just suffering from information overload the way it is). Are these pass/reject cavities (I assume they are based on your description above). I'm in need of UHF bandpass cavities. Just straight bandpass, not pass/reject. Preferably quarter-wave rather than 3/4 wave, diameter doesn't matter. Have loads of stuff to trade or cash. Anyone? --- Jeff WN3A
Re: [Repeater-Builder] Duplexers F S
The cavities in this particular case are BpBr. Pics below: http://vwreact.org/sale/Item%2031-34.jpg http://vwreact.org/sale/Item%2031.1.jpg http://vwreact.org/sale/Item%2031.2.jpg On Sat, Feb 20, 2010 at 1:33 PM, Jeff DePolo j...@broadsci.com wrote: The 4 WaCom UHF 10 cavities I believe were designed to be part of a simple duplexer for a UHF-Lo repeater. They *should* tune up to the 440 ham band based on what Telewave has listed for specs on the current modern day model number. Current config is Pass RX Reject TX on 3 cans and Pass TX Reject RX on the 4th can. I'm not a Batlabs member, nor do I care to be (not that I have anything against Batlabs, just suffering from information overload the way it is). Are these pass/reject cavities (I assume they are based on your description above). I'm in need of UHF bandpass cavities. Just straight bandpass, not pass/reject. Preferably quarter-wave rather than 3/4 wave, diameter doesn't matter. Have loads of stuff to trade or cash. Anyone? --- Jeff WN3A
Re: [Repeater-Builder] Duplexers F S
Hi Jeff, I wouldn't worry about being a member of the Batboard Discussion Forum, it's quite impossible to sign up as the captcha security device (jumbled letters and numbers) is the most fascist I've EVER encountered. There's no way that someone with minor visual impairment could ever sign up to the Batboard; I have uncorrected vision and can't make out 30% of the letter/number combinations (after 6 attempts)... Maybe there's some trick to signing up that I'm not aware of...?!? 73 de Darren G7LWT On 20 February 2010 20:33, Jeff DePolo j...@broadsci.com wrote: The 4 WaCom UHF 10 cavities I believe were designed to be part of a simple duplexer for a UHF-Lo repeater. They *should* tune up to the 440 ham band based on what Telewave has listed for specs on the current modern day model number. Current config is Pass RX Reject TX on 3 cans and Pass TX Reject RX on the 4th can. I'm not a Batlabs member, nor do I care to be (not that I have anything against Batlabs, just suffering from information overload the way it is). Are these pass/reject cavities (I assume they are based on your description above). I'm in need of UHF bandpass cavities. Just straight bandpass, not pass/reject. Preferably quarter-wave rather than 3/4 wave, diameter doesn't matter. Have loads of stuff to trade or cash. Anyone? --- Jeff WN3A
[Repeater-Builder] Duplexers F S
I ran across this... http://batboard.batlabs.com/viewtopic.php?f=2t=89919
Re: [Repeater-Builder] Duplexers F S
Oddly enough, that's my ad ;) Thanks for the bump. The 4 WaCom UHF 10 cavities I believe were designed to be part of a simple duplexer for a UHF-Lo repeater. They *should* tune up to the 440 ham band based on what Telewave has listed for specs on the current modern day model number. Current config is Pass RX Reject TX on 3 cans and Pass TX Reject RX on the 4th can. I would be more than happy to email out specific high res pics to anyone directly off list. 73, AJ On Fri, Feb 19, 2010 at 7:44 PM, motarolla_doctor echoco...@hotmail.comwrote: I ran across this... http://batboard.batlabs.com/viewtopic.php?f=2t=89919
[Repeater-Builder] Duplexers
Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] wrote: From: Mung Bungholio [EMAIL PROTECTED] Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW
RE: [Repeater-Builder] Duplexers
The repeater is at my house so it's fairly safe as far as theft goes. It's a DB 2m 6 can duplexer in a metal case. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Piche Sent: Monday, October 27, 2008 9:24 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] wrote: From: Mung Bungholio [EMAIL PROTECTED] Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
I often thought about using a Rubbermaid product. Here is a deck box: Rubbermaid item #3743 or a vertical storage cabinet: Rubbermaid item #3749 I'm not saying these would be 100% waterproof, but I think they would work well enough. I think the last price I saw on the storage cabinet at wally-world was around $100 or so. Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Mung Bungholio To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 10:40 AM Subject: RE: [Repeater-Builder] Duplexers The repeater is at my house so it's fairly safe as far as theft goes. It's a DB 2m 6 can duplexer in a metal case. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Piche Sent: Monday, October 27, 2008 9:24 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] wrote: From: Mung Bungholio [EMAIL PROTECTED] Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW -- No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.8.4/1749 - Release Date: 10/27/2008 7:57 AM
Re: [Repeater-Builder] Duplexers
Yes I agree, something designed to be out in the elements a bit more. From: Scott Zimmerman [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 10:59:24 AM Subject: Re: [Repeater-Builder] Duplexers I often thought about using a Rubbermaid product. Here is a deck box: Rubbermaid item #3743 or a vertical storage cabinet: Rubbermaid item #3749 I'm not saying these would be 100% waterproof, but I think they would work well enough. I think the last price I saw on the storage cabinet at wally-world was around $100 or so. Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Mung Bungholio To: Repeater-Builder@ yahoogroups. com Sent: Monday, October 27, 2008 10:40 AM Subject: RE: [Repeater-Builder] Duplexers The repeater is at my house so it’s fairly safe as far as theft goes. It’s a DB 2m 6 can duplexer in a metal case. From:Repeater-Builder@ yahoogroups. com [mailto:Repeater- [EMAIL PROTECTED] ups.com] On Behalf Of David Piche Sent: Monday, October 27, 2008 9:24 AM To: Repeater-Builder@ yahoogroups. com Subject: Re: [Repeater-Builder] Duplexers I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] com wrote: From: Mung Bungholio [EMAIL PROTECTED] com Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@ yahoogroups. com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW No virus found in this incoming message. Checked by AVG - http://www.avg. com Version: 8.0.175 / Virus Database: 270.8.4/1749 - Release Date: 10/27/2008 7:57 AM
RE: [Repeater-Builder] Duplexers
That is what I was thinking of too. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Scott Zimmerman Sent: Monday, October 27, 2008 10:59 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I often thought about using a Rubbermaid product. Here is a deck box: Rubbermaid item #3743 or a vertical storage cabinet: Rubbermaid item #3749 I'm not saying these would be 100% waterproof, but I think they would work well enough. I think the last price I saw on the storage cabinet at wally-world was around $100 or so. Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Mung Bungholio mailto:[EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 10:40 AM Subject: RE: [Repeater-Builder] Duplexers The repeater is at my house so it's fairly safe as far as theft goes. It's a DB 2m 6 can duplexer in a metal case. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Piche Sent: Monday, October 27, 2008 9:24 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] wrote: From: Mung Bungholio [EMAIL PROTECTED] Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW _ No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.8.4/1749 - Release Date: 10/27/2008 7:57 AM
RE: [Repeater-Builder] Duplexers
That deck box would work. If I laid it down. I actually have a nice storage cabinet in my shed that if I put the stuff in it onto shelves I could have room for the duplexer and some other storage above it. Shelves are probably cheaper than the cabinet. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Scott Zimmerman Sent: Monday, October 27, 2008 10:59 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I often thought about using a Rubbermaid product. Here is a deck box: Rubbermaid item #3743 or a vertical storage cabinet: Rubbermaid item #3749 I'm not saying these would be 100% waterproof, but I think they would work well enough. I think the last price I saw on the storage cabinet at wally-world was around $100 or so. Scott Scott Zimmerman Amateur Radio Call N3XCC 474 Barnett Rd Boswell, PA 15531 - Original Message - From: Mung Bungholio mailto:[EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 10:40 AM Subject: RE: [Repeater-Builder] Duplexers The repeater is at my house so it's fairly safe as far as theft goes. It's a DB 2m 6 can duplexer in a metal case. From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of David Piche Sent: Monday, October 27, 2008 9:24 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers I would think that at the least you would want to build a small building, even something close to a large dog house, 3'D X 4'W x 4'H. Leaves at least a little room to breath and work around, heat may be a factor depending on the cans you use and may send them a bit out of tune from the hot/humid summer months to the cooler less humid winter ones. Maybe a hinged lid for ease of access and a padlock. Worked a several sites I have seen but just a small box, that may be too easy to blow around, steal, no room to work, but depends on where you are putting it as it is all relative. --- On Mon, 10/27/08, Mung Bungholio [EMAIL PROTECTED] wrote: From: Mung Bungholio [EMAIL PROTECTED] Subject: [Repeater-Builder] Duplexers To: Repeater-Builder@yahoogroups.com Date: Monday, October 27, 2008, 9:14 AM Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW _ No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.8.4/1749 - Release Date: 10/27/2008 7:57 AM
Re: [Repeater-Builder] Duplexers
Vern, This will probably raise some eyebrows, but I put up a ham repeater on the top of an 18-story office building in Orlando, and will tell you what i did. I used a very stout, steel rack box, cast off from the computer industry, sealed the few holes in it, weatherstripped the door and gasketed the latch, painted it with a light almond-colored Rust-O-Leum (similar to that beige used on zillions of computers) and put it out there with no ventilation whatsoever. It held an Astron supply, a UHF Mastr II mobile converted for dull duplex and running about 25 watts, an S-Com 7K controller, and a TX-RX duplexer. The only path for heat dissipation was whatever conduction transfer happened through the surface area of the metal cabinet. I used an attic fan thermal switch tied to a controler logic input to fire a macro and change the courtesy tone whenever the switch's 119-degree F threshhold was hit. Even on the hottest summer day and with heavy repeater use, it never tripped. I later mounted a digital thermometer which recorded highest and lowest observed temps on a rack panel, put it in the cabinet, and watched it through part of a summer. The hottest the inside of the cabinet ever got was about 4 degrees above ambient. If I recall, the highest ambient temp recorded by the NOAA for Orlando during those weeks was 94, and the highest recorded temp in the cabinet was 98. I did find a little condensation pooled on the floor of the cabinet once when made a visit. I bought a Damp Rid cup, a dessicant product designed for use in residential closets, from Ace Hardware, and never had that problem again. After I left town, the guys who took over the repeater added a 100W HF remote, IRLP node in the cabinet, and even provided some rack space to a Part 15 wireless internet provider in barter for their wireless connection for IRLP. Apparently the extra heat was not an issue. The repeater was installed in 1995. It's still there. By the way, when the repeater was still in its early stages, using solar power and 2-watt Repco transmitter strip, I did enclose the whole thing in a Rubbermaid Action Packer storage box. It didn't work out so well. In the Florida sun, the lid and the box will expand unevenly during warm-up, and spend part of each day misaligned, letting small insects find their way in, sometimes in large numbers. After a few weeks, it will get so beat up by UV that it will start to crack and warp. My feeling in taking the approach I did was that in that climate, bugs and condensation would be bigger problems than heat, especially for a moble rig designed to work properly in a car trunk. If you limit the ingress/egress of ambient air, and have equipment which holds the inside of the cabinet even a degree or two above outside temp, you will avoid condensation in the equipment itself. If you put just a duplexer in a box by itself, there will be very little heat generated inside the box, especially when the repeater is idle, so condensation may be a bigger issue for you. I'm guessing a duplexer that gets wet inside is no fun. I learned alot with that repeater. It started out with a cheapo hamfest duplexer, Belden 9913 jumpers and feedline to a Cushcraft Ringo Ranger, and a Repco UHF data receiver board with a homemade squelch circuit and a Motrac helical front end grafted on. Needless to say, there were newbie mistakes I wouldn't make again. But I was very happy with the way the cabinet worked out. Your mileage may vary. There has to be a reason they sell high-dollar NEMA cabinets with their own air conditioners, but they probably won't sell one to me! 73, Paul, AE4KR - Original Message - From: Mung Bungholio To: Repeater-Builder@yahoogroups.com Sent: Monday, October 27, 2008 7:14 AM Subject: [Repeater-Builder] Duplexers Is it OK to get some kind of storage container or something like that and put my duplexer outside? What would be the risks of doing so? I am in Florida so lots of rain and heat but no freezing months or anything like that? Thanks, Vern KI4ONW
[Repeater-Builder] Duplexers for 440 repeater
Good Afternoon, I am looking for a duplexer for a 440 repeater, 15 watts out of the radio. Thanks for your help. 73, Scott W9SBA
[Repeater-Builder] Duplexers vhf
hi all i have 3 little duplexers sinclair sd-220 rx 152.660 tx 157.950 if someone is interested send me an email direct please 73/s make me an offer will see,i dont need them as their GE radio connected too. gervais ve2ckn
[Repeater-Builder] duplexers
I wish to take an interest at American HAM's how much actually now to sell new duplexers in the USA. My company makes antennas and duplexers for a professional radio communication. Your opinion interests, I was not late for 20 years?) Evgeny, IK-Telecom
Re: [Repeater-Builder] duplexers
Are you seeking U.S. distribution? Please contact [EMAIL PROTECTED] directly. Thanks ua3ahm [EMAIL PROTECTED] wrote: I wish to take an interest at American HAM's how much actually now to sell new duplexers in the USA. My company makes antennas and duplexers for a professional radio communication. Your opinion interests, I was not late for 20 years?) Evgeny, IK-Telecom - Looking for last minute shopping deals? Find them fast with Yahoo! Search.
[Repeater-Builder] Duplexers
Repeater Builders, I pose to you all a question. I have two UHF duplexers, both 4 cavity pass-reject. One is a Wacom (the ubiquitous 3U rackmount guy) and the other is from a Motorola MSR2000. I have really poor equipment, and don't necessarily trust manufacturer specs. Anybody have an opinion on which one is better, or pros and cons to each? The rest of the RF equipment are Hamtronics T304 and R305 and a Mirage D-1010-RN. The T304 is throttled back so that the Mirage is making about 55-60W. I'm currently running on the MSR2000 duplexer, not tuned as well as it could be. Some desense, and some is probably curable with better tuning of the duplexer, helical preselector on the front end, etc. But so far, I'm finding the additional receiver sensitivity (over say a Mitrek/MSR or Micor) is far out-weighing the desense 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
[Repeater-Builder] Duplexers
Looking for factory alignment for the following Telwave TPRD 1554 Wacom WP655-R2 Ralph, W7HSG ---BeginMessage--- Check out COMTELCO antennas, they are on the web at www.comtelcoantennas.com I have many of them in service with 100% results. They are equal in gain and performance to other more expensive antennas. I recommend the ones with 1.5 inch tubes, not the smaller 1inch tube models. Lance - Original Message - From: Tony L. To: Repeater-Builder@yahoogroups.com Sent: Thursday, December 20, 2007 10:22 AM Subject: [Repeater-Builder] Re: antennas for gmrs repeater My first recommendation would be a RF Systems PD1151, but since you don't want to spend the money for a Station Master, how about a Hustler Newtronics G6-450-3?You should be able to pick one of these up for under $200. Reportedly, they stand up to the weather pretty well. The first choice PD1151 would run you about $650.--- In Repeater-Builder@yahoogroups.com, Jed Barton [EMAIL PROTECTED] wrote: Hey guys, Any opinions on an antenna for a gmrs repeater? It won't be going on a 300 foot tower, but it will be on the top of a hospital. I would rather not get a station master, but something that could withstand a little weather. Any ideas on the biggest bang for the buck? Thanks, Jed ---End Message---
RE: [Repeater-Builder] Duplexers
Ralph, Contact Telewave at www.telewave.com for both Telewave and Wacom duplexer tuning information. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Thursday, December 20, 2007 6:17 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Looking for factory alignment for the following Telwave TPRD 1554 Wacom WP655-R2 Ralph, W7HSG
Re: [Repeater-Builder] Duplexers
This makes sense. I guess what might help is to find a single VHF bandpass can to put in front of the receive side of the duplexer. How much does the power output effect the required filter attinuation? Right now I am running about 70w out would turning it down make much of a difference? From the charts I have seen it doesn't seem to be more than 3 or so db difference between 10w and 70w. Am I reading it wrong? Thanks, Vern On Wed, 26 Sep 2007 11:12:29 -0500 Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote: A transmitter may have broadband noise with considerable noise content at the receive frequency. The notch in the transmit side removes transmitter noise that may impair your receiver's capability. In an earlier post there was mention of a solid state transmitter. Traditionally tube transmitters have higher Q output circuits as opposed to wideband circuits in solid state transmitters, so a solid state transmitter may need more filtering. There are also combination band pass / band reject duplexers and also band pass only. Each has a characteristic suited for a particular job. Beware, a duplexer may pass an intended frequency PLUS unintended frequencies outside the normal band pass. I found that 158.100 radio paging was being received by a dual band antenna, and passed right thru a 440 duplexer to cause overload in the receiver front end. In this particular instance the best solution was to go to a monoband antenna. Wishing you best success, Steve NU5D [EMAIL PROTECTED] wrote: Thanks for the great info as soon as we get the service monitor back we are going to try these things. I have already seperated the 2 sides and have seen much improvement so I think that this is really my problem. I do have a question about duplexers in general. I am sure that this is a dumb question but What is the purpose of notching out the receive frequency on the transmit side? Since I have 6 cans couldn't I move one of the cans from the transmit side to the receive side to give me 4 on the receive and 2 on the transmit? Thanks, Vern
Re: [Repeater-Builder] Duplexers
Thanks for the great info as soon as we get the service monitor back we are going to try these things. I have already seperated the 2 sides and have seen much improvement so I think that this is really my problem. I do have a question about duplexers in general. I am sure that this is a dumb question but What is the purpose of notching out the receive frequency on the transmit side? Since I have 6 cans couldn't I move one of the cans from the transmit side to the receive side to give me 4 on the receive and 2 on the transmit? Thanks, Vern On Tue, 25 Sep 2007 23:46:12 -0600 Nate Duehr [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: I had them tuned because I had just bought them and didn't really trust that they were right. They were very far out so it's good that I got them tuned. I was having the same problem as now though very poor receive. Right now I have a radio on there for receive that was getting about 30 miles of coverage as an Echolink link node with home made antenna and now hooked up to the repeater using a big Tram Dualband antenna through the duplexer I am lucky if I am getting 3 miles. So I don't think the repeater's built in receiver is the problem which leads me to either desense or a bad antenna cable. Transmit is getting out very well and the swr is almost 1 to 1 so I think the cable is OK. I am running LMR 400 up the tower 95% of the way. I just have a short coax jumper that goes into the antenna. I am going to try to split them and see what I get. Thanks, Vern KI4ONW Before you do that. Have someone transmit a weak signal (or use an iso-T and transmit it in yourself, as someone else mentioned) into the repeater while you're at the site, listening to the receiver while the transmitter is on. Turn the transmitter off. If their signal gets better, you're fighting desense. It's that simple to find out. To find out exactly how bad it is, feeding a weak signal into the receiver with an iso-T and measuring the audio coming from the repeater receiver with a SINAD meter is the next level of knowing what's going on. (I've seen people do this by ear with practice and get close, but you need to see it on a meter first or have someone demonstrate to even try it. Hey... sometimes when you're starting out you don't have the gear, we understand...) Feed a weak signal (usually 12 dB SINAD for these tests, as a standard starting point) and then turn the transmitter on. The weak signal will disappear or be noisier if you have a desense problem, as mentione above. Increase the signal generator to the point where the weak signal is the same as before (usually 12 dB SINAD is used when you have a meter). The difference between where the signal generator was level-wise when you started, and where you end up, is how MUCH desense you're fighting, and how much more isolation you need in the overall system to make it work. Plus if gather numbers like this, folks here can tell you ballpark numbers to expect from your particular radio and setup. Also be forewarned, some antennas simply don't duplex well... it's difficult to explain, but you'll find antennas that throw all sorts of crap around when used in duplex operation, that are fine for simplex. I know nothing about the Tram antennas, but dual-band antennas for repeater operation, sets off warning bells for me. Use the best cables for interconnect you can possibly buy! Having nice double-shielded stuff built onto the duplexer by the manufacturer, only to run lossy/leaky crud from the repeater to the duplexer, is just asking for trouble. If you used your LMR 400 for that, good... it'll work in most cases, just fine. Many people do have problems with LMR 400 in duplexed service, other's don't. There's a long thread about it around here somewhere in the archives... If you can afford/get hardline - always do it. 1/2 will work fine at VHF unless you have an enormous run, and you might want 7/8 for UHF, depending on the length of your run. Keep an ear to the ground and scrounge hardline any which way you can. Hardline connectors too. They're not cheap. You can test your inside setup by replacing the antenna with a GOOD dummy load rated for the power you're pushing, and that is a solid 50 ohm load. (Don't use a cheap one for this. Find something big and stable. I found a 500W Bird load at a hamfest once for $12, best purchase that year.) See if the system desenses itself when not hooked to the outside antenna. If it does, you have something wrong right there in the repeater itself. Stop and figure that out. I could go on and on, but will stop and give the admonishment my elmers gave me... MEASURE IT... don't guess. Beg, borrow or steal test gear and get someone to show you how to use it. You can stumble into correct
Re: [Repeater-Builder] Duplexers
A transmitter may have broadband noise with considerable noise content at the receive frequency. The notch in the transmit side removes transmitter noise that may impair your receiver's capability. In an earlier post there was mention of a solid state transmitter. Traditionally tube transmitters have higher Q output circuits as opposed to wideband circuits in solid state transmitters, so a solid state transmitter may need more filtering. There are also combination band pass / band reject duplexers and also band pass only. Each has a characteristic suited for a particular job. Beware, a duplexer may pass an intended frequency PLUS unintended frequencies outside the normal band pass. I found that 158.100 radio paging was being received by a dual band antenna, and passed right thru a 440 duplexer to cause overload in the receiver front end. In this particular instance the best solution was to go to a monoband antenna. Wishing you best success, Steve NU5D [EMAIL PROTECTED] wrote: Thanks for the great info as soon as we get the service monitor back we are going to try these things. I have already seperated the 2 sides and have seen much improvement so I think that this is really my problem. I do have a question about duplexers in general. I am sure that this is a dumb question but What is the purpose of notching out the receive frequency on the transmit side? Since I have 6 cans couldn't I move one of the cans from the transmit side to the receive side to give me 4 on the receive and 2 on the transmit? Thanks, Vern
Re: [Repeater-Builder] Duplexers
At 11:12 AM 9/26/2007, Steve wrote: A transmitter may have broadband noise with considerable noise content at the receive frequency. The notch in the transmit side removes transmitter noise that may impair your receiver's capability. In my day job 99% of the problems I have with noise floor is related to transmitter noise that is in band on my RX freq. Usually it is another transmitter at the site and we ask them to install a bandpass/notch filter to lower the noise floor on our receiver. The notch is tuned to our receiver frequency. That happened two weeks ago in Hawaii. 73, Mark N5RFX
Re: [Repeater-Builder] Duplexers
Our local club recently installed a 2 meter repeater on a water tank adjacent to a cell site. Two cell towers are serviced by four buildings housing equipement, and we are having some desense due to noise pickup on the antenna. Running an iso-tee we found that our GE Mastr II receiver with GE preamp shows .6 uV for 12 dB SINAD using a dummy load in place of the antenna (.2 uV direct to the receiver bypassing the duplexer). With the antenna connected we see a 2 uV sensitivity for 12 dB SINAD. These readings are the same, with the repeater transmitter (40 watts) keyed or unkeyed. The noise floor is really decreasing the utility of the new repeater. The noise source seems to come and go as a quiet signal on the repeater input can become suddenly noisey, and vice versa - a noisey signal can become suddenly quiet. I hear the air conditioning units in the cell site buildings cycling and wonder if they might be the cause of the noise? Our antenna is only about 40 feet above the ground (at 7400 ft) while the cell antennas are at about 100 ft. So we are much closer to the cell site equipment buildings than the cell antennas. Two uV for the receiver sensitivity sure does limit the usefulness of the new repeater - Anyone have any thoughts? 73 - Jim W5ZIT [EMAIL PROTECTED] wrote: I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from the xmit cans and run to 2 seperate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through seperate cable, make a difference? Thanks, Vern KI4ONW - Yahoo! oneSearch: Finally, mobile search that gives answers, not web links.
Re: [Repeater-Builder] Duplexers
The duplexer is a DB-4048. I have had this repeater for a couple of months and it has always had problems. I don't have access to a service monitor or anything like that right now but I have a friend that has one however someone is borrowing it right now. From what I can tell the desense is pretty bad. I can key up the repeater a lot further than I can send audio through it. all of my cables are double shielded or better. Thanks, Vern On Mon, 24 Sep 2007 19:54:33 -0500 Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote: Decibel did make a 6 cavity notch duplexer - 4 full sized cavities - that would work nicely on a 110 Watt M2 station @ 600 kHz. Isolated TEE test into a dummy load - how bad is the receiver desense ? If you don't have some test equipment - signal gen, dummy load, and a TEE fitting with the side pin cut away (makes 60 dB lossy coupling, there abouts) you probably will need to find someone who does locally that can help. 73, Steve NU5D Eric Lemmon wrote: Vern, Did this problem exist before you had the duplexer tuned? Was anything at all done to your repeater system just before the problem was noticed? A band reject (notch) duplexer may be incapable of performing even satisfactorily at 2m. Please advise the model number of your duplexer, so we can understand your situation. Are all of your cables double-shielded? It might be a good idea to perform a noise-floor test using an iso-tee and a service monitor. Some helpful information about investigating desense problems can be found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-02.pdf 73, Eric Lemmon WB6FLY
RE: [Repeater-Builder] Duplexers
Hey Jim I have a few thoughts that come to mind. Based on my experience with VHF and UHF repeaters colocated in cell sites I would say that you may want to consider the following. First the AC unit motors etc will not be a problem to the excellent FM rec you have there with the GE M2 even with the preamp. Plain electrical noise is not going to be your problem. It is an RF issue. And Multi RCC sites are very often a big mess as far as RF goes. Its too bad you have to go through all this but it is a fact of life in crowded sites that are also the best ones to be on. The fact that your tests indicated the same actual values with the xmt on or off tells us that your duplexers are fine. And your rec tests direct connected are fine. Many cell sites are *real* bad with regard to rf on numerous freqs due to harmonics and mixing products/intermod. Some times you will only see your rf problem when 2 or more things occur at the same time aming it time consuming to pin it down. Sometimes the RF signal is slightly off your rcv freq but very strong and the skirts of the sweep are slightly coming into your channel. So you have to sweep the area with a good service monitor or Spectrum Analyzer to see what is going on. I use the IFR or R2200 plus the HP for this and it will show right up. It sounds like from the description you are in a very dirty site. You will have to consider 1. Moving to a new site even just a few hundred yards away on a new tower, or 2. Sweep with a spectrum analyzer to actually see if you can find the culprit(s) causing your problem and see if you can work with the equipment owner to clean it up. I doubt you will have much luck with this since if the techs at Verizon or Cell 1 ATT think their stuff is working fine they cant be bothered with your ham radio problems. They will tell you to take the site or leave it most of the time. 3. What I have had to do when the RF product was sitting just off our rcv freq and was fairly strong is install another cavity to clean it up. You may find it easier to use a pass type on your rcv channel unless you can definitely pin down the offending signal and reject it. Be aware that the preamp on your repeater can be a problem. GE and Moto reccomend those only for a base station and not a repeater unless you have a really clean site. They are notorious for intermod issues and most times are not worth the extra rvc gain in multi user sites. These suggestions are a start and may or may not do it for you but I would start with these basics. Keep an open mind to the fact that something at the site which is radiating some RF into your install may not be able to get fixed in practical terms and you may have to move either the frequency of your repeater or your site location, since I doubt you can get the cell guys/Paging RCCs to go away:) Let us know how this progresses 73 Glenn N1GBY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jim Brown Sent: Tuesday, September 25, 2007 8:20 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers Our local club recently installed a 2 meter repeater on a water tank adjacent to a cell site. Two cell towers are serviced by four buildings housing equipement, and we are having some desense due to noise pickup on the antenna. Running an iso-tee we found that our GE Mastr II receiver with GE preamp shows .6 uV for 12 dB SINAD using a dummy load in place of the antenna (.2 uV direct to the receiver bypassing the duplexer). With the antenna connected we see a 2 uV sensitivity for 12 dB SINAD. These readings are the same, with the repeater transmitter (40 watts) keyed or unkeyed. The noise floor is really decreasing the utility of the new repeater. The noise source seems to come and go as a quiet signal on the repeater input can become suddenly noisey, and vice versa - a noisey signal can become suddenly quiet. I hear the air conditioning units in the cell site buildings cycling and wonder if they might be the cause of the noise? Our antenna is only about 40 feet above the ground (at 7400 ft) while the cell antennas are at about 100 ft. So we are much closer to the cell site equipment buildings than the cell antennas. Two uV for the receiver sensitivity sure does limit the usefulness of the new repeater - Anyone have any thoughts? 73 - Jim W5ZIT [EMAIL PROTECTED] wrote: I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from
Re: [Repeater-Builder] Duplexers
At 9/25/2007 05:20, you wrote: Our local club recently installed a 2 meter repeater on a water tank adjacent to a cell site. Two cell towers are serviced by four buildings housing equipement, and we are having some desense due to noise pickup on the antenna. Running an iso-tee we found that our GE Mastr II receiver with GE preamp shows .6 uV for 12 dB SINAD using a dummy load in place of the antenna (.2 uV direct to the receiver bypassing the duplexer). With the antenna connected we see a 2 uV sensitivity for 12 dB SINAD. These readings are the same, with the repeater transmitter (40 watts) keyed or unkeyed. The noise floor is really decreasing the utility of the new repeater. The noise source seems to come and go as a quiet signal on the repeater input can become suddenly noisey, and vice versa - a noisey signal can become suddenly quiet. I hear the air conditioning units in the cell site buildings cycling and wonder if they might be the cause of the noise? Our antenna is only about 40 feet above the ground (at 7400 ft) while the cell antennas are at about 100 ft. So we are much closer to the cell site equipment buildings than the cell antennas. Two uV for the receiver sensitivity sure does limit the usefulness of the new repeater - Anyone have any thoughts? Anything with a CPU in it could be the culprit @ 2 meters. Anytime I drive within ~200 ft. of a local Foothill Transit bus the squelch on my mobile radio blows open; within 50 ft., normally full quieting signals are completely captured by the noise. I suspect it's the electronic scroll sign on the back of the bus. Fortunately I haven't seen this on 440 MHz, but with faster CPUs finding their way into everything it may only be a matter of time. Bob NO6B
Re: [Repeater-Builder] Duplexers
The noise floor is really decreasing the utility of the new repeater. The noise source seems to come and go as a quiet signal on the repeater input can become suddenly noisey, and vice versa - a noisey signal can become suddenly quiet. It looks like you have a 10dB degradation. Many times this is from phase noise from other transmitters, but intermod can give you the same problems. I would look for a VHF paging transmitter if phase noise is suspected. This type of troubleshooting requires a good spectrum analyzer in most cases. I typically use the RX part of a duplexer on the front end of an ANRITSU 2721B to keep the first mixer in the spectrum analyzer happy. I hook up a 10dBd Yagi to the duplexer and start looking for the noise floor to rise. Once I have found the site that is causing the increase in noise floor, then the hard part comes, getting the other site to cooperate in further testing. What we ultimately want is for the other site to completely shut down for the time it takes to test the sensitivity of the receiver that is experiencing the degradation. Since you mention that the degradation is intermittent, you may be able to monitor other signals and see a correlation between when the suspect transmitter keys, and an increase in the noise floor in your bandpass. If the problem is because of intermod, then it becomes a little more difficult as you have multiple culprits. The spectrum analyzer you use should have a noise floor of around -120 dBm @10 KHz bandwidth. 73, Mark N5RFX
Re: [Repeater-Builder] Duplexers
The 10dBd Yagi I mentioned is for 900MHz, something smaller would have to be used for VHF :) 73, Mark N5RFX
Re: [Repeater-Builder] Duplexers
At 9/25/2007 07:59, you wrote: The noise floor is really decreasing the utility of the new repeater. The noise source seems to come and go as a quiet signal on the repeater input can become suddenly noisey, and vice versa - a noisey signal can become suddenly quiet. It looks like you have a 10dB degradation. Many times this is from phase noise from other transmitters, but intermod can give you the same problems. I would look for a VHF paging transmitter if phase noise is suspected. This type of troubleshooting requires a good spectrum analyzer in most cases. I typically use the RX part of a duplexer on the front end of an ANRITSU 2721B to keep the first mixer in the spectrum analyzer happy. I hook up a 10dBd Yagi to the duplexer and start looking for the noise floor to rise. Once I have found the site that is causing the increase in noise floor, then the hard part comes, getting the other site to cooperate in further testing. What we ultimately want is for the other site to completely shut down for the time it takes to test the sensitivity of the receiver that is experiencing the degradation. Since you mention that the degradation is intermittent, you may be able to monitor other signals and see a correlation between when the suspect transmitter keys, and an increase in the noise floor in your bandpass. If the problem is because of intermod, then it becomes a little more difficult as you have multiple culprits. The spectrum analyzer you use should have a noise floor of around -120 dBm @10 KHz bandwidth. The spectrum analyzer method is of course an excellent way to look for interference sources. However, a noise floor of -120 dBm @ 10 kHz RBW is a bit on the deaf side when you consider that your repeater RX will be almost 10 dB better than that. You might consider adding a preamp an additional pass cavity in front of the analyzer to maximize sensitivity if at first you don't find anything. Bob NO6B
Re: [Repeater-Builder] Duplexers
[EMAIL PROTECTED] wrote: I had them tuned because I had just bought them and didn't really trust that they were right. They were very far out so it's good that I got them tuned. I was having the same problem as now though very poor receive. Right now I have a radio on there for receive that was getting about 30 miles of coverage as an Echolink link node with home made antenna and now hooked up to the repeater using a big Tram Dualband antenna through the duplexer I am lucky if I am getting 3 miles. So I don't think the repeater's built in receiver is the problem which leads me to either desense or a bad antenna cable. Transmit is getting out very well and the swr is almost 1 to 1 so I think the cable is OK. I am running LMR 400 up the tower 95% of the way. I just have a short coax jumper that goes into the antenna. I am going to try to split them and see what I get. Thanks, Vern KI4ONW Before you do that. Have someone transmit a weak signal (or use an iso-T and transmit it in yourself, as someone else mentioned) into the repeater while you're at the site, listening to the receiver while the transmitter is on. Turn the transmitter off. If their signal gets better, you're fighting desense. It's that simple to find out. To find out exactly how bad it is, feeding a weak signal into the receiver with an iso-T and measuring the audio coming from the repeater receiver with a SINAD meter is the next level of knowing what's going on. (I've seen people do this by ear with practice and get close, but you need to see it on a meter first or have someone demonstrate to even try it. Hey... sometimes when you're starting out you don't have the gear, we understand...) Feed a weak signal (usually 12 dB SINAD for these tests, as a standard starting point) and then turn the transmitter on. The weak signal will disappear or be noisier if you have a desense problem, as mentione above. Increase the signal generator to the point where the weak signal is the same as before (usually 12 dB SINAD is used when you have a meter). The difference between where the signal generator was level-wise when you started, and where you end up, is how MUCH desense you're fighting, and how much more isolation you need in the overall system to make it work. Plus if gather numbers like this, folks here can tell you ballpark numbers to expect from your particular radio and setup. Also be forewarned, some antennas simply don't duplex well... it's difficult to explain, but you'll find antennas that throw all sorts of crap around when used in duplex operation, that are fine for simplex. I know nothing about the Tram antennas, but dual-band antennas for repeater operation, sets off warning bells for me. Use the best cables for interconnect you can possibly buy! Having nice double-shielded stuff built onto the duplexer by the manufacturer, only to run lossy/leaky crud from the repeater to the duplexer, is just asking for trouble. If you used your LMR 400 for that, good... it'll work in most cases, just fine. Many people do have problems with LMR 400 in duplexed service, other's don't. There's a long thread about it around here somewhere in the archives... If you can afford/get hardline - always do it. 1/2 will work fine at VHF unless you have an enormous run, and you might want 7/8 for UHF, depending on the length of your run. Keep an ear to the ground and scrounge hardline any which way you can. Hardline connectors too. They're not cheap. You can test your inside setup by replacing the antenna with a GOOD dummy load rated for the power you're pushing, and that is a solid 50 ohm load. (Don't use a cheap one for this. Find something big and stable. I found a 500W Bird load at a hamfest once for $12, best purchase that year.) See if the system desenses itself when not hooked to the outside antenna. If it does, you have something wrong right there in the repeater itself. Stop and figure that out. I could go on and on, but will stop and give the admonishment my elmers gave me... MEASURE IT... don't guess. Beg, borrow or steal test gear and get someone to show you how to use it. You can stumble into correct setups without it, but you can KNOW how well your repeater performs if you measure. - Receiver sensitivity -- put a very weak calibrated signal directly into the receiver and measure the 12 dB SINAD point. - Useable receiver sensitivity -- do the same test, but with an iso-T or directional coupler of known loss (measure that too!) and see how much more signal you need to have the same receiver performance through the duplexer, and final cabling. [If you have a pre-amp this becomes more important to see if the gain has driven the receiver into the noise floor at the site, and/or if you're overdriving the receiver with too much RF.] Those are good starting points, both with the transmitter on and off. Nate WY0X Nate WY0X
[Repeater-Builder] Duplexers
I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from the xmit cans and run to 2 seperate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through seperate cable, make a difference? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
Time for an isolated TEE test with a dummy load. Why did you have the duplexers tuned ? Was there a problem prior? You should be able to split the duplexer without any trouble - just mark things so you can go back as it was. Best luck and 73, Steve NU5D [EMAIL PROTECTED] wrote: I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from the xmit cans and run to 2 seperate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through seperate cable, make a difference? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
I would be quite surprised if you are NOT having desense with a Mastr II and a 6 can notch only duplexer at 600 khz Typically a 6 can reject only duplexer is not sufficient isolation at 600khz for 2 meters with a solid state PA.. Vertical separation or a pass/reject duplexer will be needed. 6 can notch only's were designed in a time where they were sufficient on Mastr Pro or similar tube PA's as they were significantly quieter in band noise off freq...Not so with a Mastr II or eq. these days... A 4 can Pass/reject is just barely enough and usually takes a dump if you try to run a Preamp.. on 100w or so repeaters... A 6 can pass/reject is the ticket if you want to really get the receiver working to it's fullest, or separate antennas can help.. There are isolation curves for antenna spacing at the repeater builder website... Typically the 6 can notch will make 65-80 db isolation.. from my experience you need at least 100db isolation on 2m probably more like 110 -120...Our TX/RX 6 can pass/reject is in the neighborhood of -127 db at 600khz on 2 meters You are on the right track Doug KD8B mailto:mung%40highwayusa.com[EMAIL PROTECTED] wrote: I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from the xmit cans and run to 2 seperate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through seperate cable, make a difference? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
I had them tuned because I had just bought them and didn't really trust that they were right. They were very far out so it's good that I got them tuned. I was having the same problem as now though very poor receive. Right now I have a radio on there for receive that was getting about 30 miles of coverage as an Echolink link node with home made antenna and now hooked up to the repeater using a big Tram Dualband antenna through the duplexer I am lucky if I am getting 3 miles. So I don't think the repeater's built in receiver is the problem which leads me to either desense or a bad antenna cable. Transmit is getting out very well and the swr is almost 1 to 1 so I think the cable is OK. I am running LMR 400 up the tower 95% of the way. I just have a short coax jumper that goes into the antenna. I am going to try to split them and see what I get. Thanks, Vern KI4ONW On Mon, 24 Sep 2007 12:50:48 -0500 Steve S. Bosshard (NU5D) [EMAIL PROTECTED] wrote: Time for an isolated TEE test with a dummy load. Why did you have the duplexers tuned ? Was there a problem prior? You should be able to split the duplexer without any trouble - just mark things so you can go back as it was. Best luck and 73, Steve NU5D [EMAIL PROTECTED] wrote: I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASRII repeater with a Decibal Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and seperate the recv cans from the xmit cans and run to 2 seperate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through seperate cable, make a difference? Thanks, Vern KI4ONW
RE: [Repeater-Builder] Duplexers
Vern, Did this problem exist before you had the duplexer tuned? Was anything at all done to your repeater system just before the problem was noticed? A band reject (notch) duplexer may be incapable of performing even satisfactorily at 2m. Please advise the model number of your duplexer, so we can understand your situation. Are all of your cables double-shielded? It might be a good idea to perform a noise-floor test using an iso-tee and a service monitor. Some helpful information about investigating desense problems can be found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-02.pdf 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Monday, September 24, 2007 7:02 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers I am having some receive problems on my repeater and I am thinking that it might be desense. I am on 2M running a MASTRII repeater with a Decibel Products band reject 6 can duplexer. While I can key the repeater from a pretty good distance the audio that makes it through the repeater drops off pretty quickly. I just had the duplexers tuned and they are tuned very well. So on to my question. If I were to take and separate the recv cans from the xmit cans and run to 2 separate antennas would that mess up the duplexer tuning? will 20' of vertical seperation plus the cans and the fact that I would be running through separate cable, make a difference? Thanks, Vern KI4ONW
Re: [Repeater-Builder] Duplexers
Decibel did make a 6 cavity notch duplexer - 4 full sized cavities - that would work nicely on a 110 Watt M2 station @ 600 kHz. Isolated TEE test into a dummy load - how bad is the receiver desense ? If you don't have some test equipment - signal gen, dummy load, and a TEE fitting with the side pin cut away (makes 60 dB lossy coupling, there abouts) you probably will need to find someone who does locally that can help. 73, Steve NU5D Eric Lemmon wrote: Vern, Did this problem exist before you had the duplexer tuned? Was anything at all done to your repeater system just before the problem was noticed? A band reject (notch) duplexer may be incapable of performing even satisfactorily at 2m. Please advise the model number of your duplexer, so we can understand your situation. Are all of your cables double-shielded? It might be a good idea to perform a noise-floor test using an iso-tee and a service monitor. Some helpful information about investigating desense problems can be found here: www.repeater-builder.com/ge/datafile-bulletin/df-10002-02.pdf 73, Eric Lemmon WB6FLY
RE: [Repeater-Builder] Duplexers
Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff True but only if everything (tx out, cable and duplexer) is matched Z. If duplexer in and tx output are not exactly the same then adding or subtracting cable lengths can change the vswr the tx sees. I have seen this in real life, I do not have a network anylizer so I can not be sure what was happening but to make the tx happy some cable was added until the reflected power was minimized and the desense went away like magic. I think the manual that came with my Wacom duplexer talks about this phenomena. tom
Re: [Repeater-Builder] Duplexers
IIRC the Bird manual had a chart in the back for making up 1/2 wavelength coax lines (Bird + coax = 1/2 wl). If this combination is inserted on the input side of the duplexer then the measurement should be fairly correct. Other lengths could give other readings. My guess would be a cable problem. Milt N3LTQ - Original Message - From: Eric Lemmon [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, August 25, 2007 1:38 AM Subject: RE: [Repeater-Builder] Duplexers My statement regarding tuning did not explicitly refer to the actual tuning of the duplexer, but to the matching of the TX and duplexer in combination. This can be proven if two Birds are used, one between the TX and the duplexer input and the other between the duplexer output and the antenna. In the majority of cases I have witnessed, adding a Bird between the TX and the duplexer will cause the forward power shown on the other Bird to change significantly. To avoid the misunderstanding, perhaps I should have used the term impedance match. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Friday, August 24, 2007 9:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff Yahoo! Groups Links
RE: [Repeater-Builder] Duplexers
Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff True but only if everything (tx out, cable and duplexer) is matched Z. No, NOT true. The VSWR always remains the same, only the impedance at the transmitter end of the interconnect cable going to the duplexer changes. If duplexer in and tx output are not exactly the same then adding or subtracting cable lengths can change the vswr the tx sees. No, it will not. I have seen this in real life, I do not have a network anylizer so I can not be sure what was happening but to make the tx happy some cable was added until the reflected power was minimized and the desense went away like magic. Yes, you were changing the Z the transmitter sees. You were NOT changing the VSWR. The two are not the same. Re-read follow up posts from the last week or so for further clarification. --- Jeff
RE: [Repeater-Builder] Duplexers
At 8/29/2007 06:40 PM, you wrote: If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re-reflected power. This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. The tuner would be adjusted so as to create a conjugate impedance of the antenna at the end of the feeding coax, thus eliminating the mismatch. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. Bob NO6B Hi Bob, Please read again what I wrote. I am not sure that you are following how the meters are in the circuit. Remember that whatever you do at the transmitter end of a transmission line has no affect on what is going on in the line itself. The only thing that will change the swr on the line is what you do at the load. 73 Gary K4FMX OK, after talking to a senior RF engineer at lunch here at work I think I understand what's going on. The part that threw me was having the matching circuit in the middle of the feedline the fact that any reflected power from the load MUST be totally re-reflected back by the matching circuit, otherwise there would be power reflected back to the TX, which by definition does not occur in this example. Because of the multiple re-reflections between the matching circuit load resulting in multiple waves back forth within that coax section, typical single-wave thinking doesn't apply. I guess it's a useful way to illustrate why coax gets lossier if you use a tuner far from the antenna. Bob NO6B
Re: RE: [Repeater-Builder] Duplexers
Bob, It is better to have someone so one can set down and talk to. This e-mail is great for bringing the world together, but face to face is much better except for most of the ugly Hams I hang out with. The problem with a tuner is the feedline losses, but better than no tuner at all unless got resonant antennas. On HF this is harder to do if one moves about. Putting the tuner at the antenna is a solution, but then get into remote application. Some tuners are automatic and tune whenever they see higher than say 1.5:1 SWR. 73, ron, n9ee/r From: Bob Dengler [EMAIL PROTECTED] Date: 2007/08/30 Thu PM 12:53:11 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers OK, after talking to a senior RF engineer at lunch here at work I think I understand what's going on. The part that threw me was having the matching circuit in the middle of the feedline the fact that any reflected power from the load MUST be totally re-reflected back by the matching circuit, otherwise there would be power reflected back to the TX, which by definition does not occur in this example. Because of the multiple re-reflections between the matching circuit load resulting in multiple waves back forth within that coax section, typical single-wave thinking doesn't apply. I guess it's a useful way to illustrate why coax gets lossier if you use a tuner far from the antenna. Bob NO6B Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: [Repeater-Builder] Duplexers
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Bob Dengler Sent: Thursday, August 30, 2007 12:53 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers At 8/29/2007 06:40 PM, you wrote: If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re- reflected power. This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. The tuner would be adjusted so as to create a conjugate impedance of the antenna at the end of the feeding coax, thus eliminating the mismatch. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. Bob NO6B Hi Bob, Please read again what I wrote. I am not sure that you are following how the meters are in the circuit. Remember that whatever you do at the transmitter end of a transmission line has no affect on what is going on in the line itself. The only thing that will change the swr on the line is what you do at the load. 73 Gary K4FMX OK, after talking to a senior RF engineer at lunch here at work I think I understand what's going on. The part that threw me was having the matching circuit in the middle of the feedline the fact that any reflected power from the load MUST be totally re-reflected back by the matching circuit, otherwise there would be power reflected back to the TX, which by definition does not occur in this example. Because of the multiple re-reflections between the matching circuit load resulting in multiple waves back forth within that coax section, typical single-wave thinking doesn't apply. I guess it's a useful way to illustrate why coax gets lossier if you use a tuner far from the antenna. Bob NO6B Yes coax is lossier with reflected power on it. The part of the power that gets reflected from the antenna back toward the transmitter gets attenuated a second time by whatever lose the cable has to begin with. Then when that portion of the power gets re-reflected at the transmitter end and is on its way back to the antenna again it suffers attenuation a 3rd time by the coax so all the re-reflected power does not make it back to the antenna. Then a portion of the re-reflected power gets reflected again back toward the transmitter along with the new wave of power. This repeats itself again and again adding to the loss but after a few round trips of bouncing up and down the feed line most of it gets radiated and some has gotten attenuated to a miniscule amount. Of course this process is continuously repeated as power is constantly applied from the transmitter. But my reason for using the first wattmeter and the tuner was to have a nearly perfect flat load on the transmitter so that one could see the true power coming out of the transmitter. The second wattmeter after the tuner will then show the higher power which would be the sum of the forward and re-reflected power so it could be seen that reflected power does indeed get re-reflected at the transmitter (in this case at the tuner)and makes its way back to the antenna. In common applications with just a single wattmeter and no tuner involved where there is reflected power on the line the wattmeter in the forward position will show the forward power plus the re-reflected power. To find power out of the transmitter you would subtract the reflected power shown in the reverse position from the indicated forward power on the meter. This works over a wide range of impedances with a bird wattmeter. 73 Gary K4FMX
Re: RE: [Repeater-Builder] Duplexers
Jeff, I have Reflections II. Walt does good job explaining transmission lines. The only problem I had was all the complaining he did about other authors and articles. Some was good, but seemed to get carried away times, hi. I think the book is $19.95. One of the Ham mag has it, think CQ or World Radio...def not QST. 73, ron, n9ee/r From: Jeff DePolo [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 05:11:42 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers As a side note for this discussion, I think Jeff's doing a great job of explaining how transmission line theory works... I try... For those that want to dive in a lot further (e.g. Do the math), the ARRL Antenna Book has a whole section dedicated to this topic, and it's written well enough that a mathematical dolt like myself can still follow the concepts and not scratch my head at the math. Another good, readily-available book is Reflections by Walt Maxwell W2DU. My copy is old; he put out an updated edition Reflections II later. It's a good read, but has one drawback (to me anyway). A lot of what he discusses relates to pi matching networks common in tube HF rigs. You have to keep in mind that a lot of the myths he dispels don't always translate directly to the world of VHF/UHF solid state amplifiers, but theory behind what he preaches is dead nuts on. --- Jeff Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: [Repeater-Builder] Duplexers
It doesn t matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. I don't buy into this. In order for reflected power to not be absorbed by the TX, it would have to appear totally reactive. Not necessarily true. If there exists a conjugate match at the transmitter, the reflected power will be re-reflected back to the load. The problem, though, is most of our solid state repeater amps may exhibit other problems due to the mis-matched load Z (efficiency drops, PA goes into oscillation, whatever). This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. There won't be any reflected power if the matching is done *at the antenna*. If the matching is done at the source end of the line (via a transmatch or similiar device), which is what I believe the topic of discussion was, then there will be reflected power (and likewise VSWR) on the feedline if the load (antenna) Z does not match the cable's characteristic Z. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. If placed along a length of transmission line that has a VSWR other than 1:1, a directional wattmeter (Bird or similiar) will show the sum of forward+reflected with the slug rotated to the forward direction due to the reflected power being re-reflected at the source end. --- Jeff
RE: [Repeater-Builder] Duplexers
-Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Tuesday, August 28, 2007 10:54 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers At 8/27/2007 20:52, you wrote: Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? It doesn t matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. I don't buy into this. In order for reflected power to not be absorbed by the TX, it would have to appear totally reactive. Although I've never measured one, I don't believe that's the case. If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re-reflected power. This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. The tuner would be adjusted so as to create a conjugate impedance of the antenna at the end of the feeding coax, thus eliminating the mismatch. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. Bob NO6B Hi Bob, Please read again what I wrote. I am not sure that you are following how the meters are in the circuit. Remember that whatever you do at the transmitter end of a transmission line has no affect on what is going on in the line itself. The only thing that will change the swr on the line is what you do at the load. 73 Gary K4FMX
RE: RE: [Repeater-Builder] Duplexers
Your typical swr meter does not measure voltage on the line. It is measuring a combination of voltage and current. By just measuring voltage it is impossible to tell which is forward and which is reflected. By using a slotted line you can find voltage min and max but you must have a line that is at least 1/4 wavelength long. This is impractical at HF frequencies and cumbersome at VHF. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Ron Wright Sent: Wednesday, August 29, 2007 9:00 AM To: Repeater-Builder@yahoogroups.com Subject: Re: RE: [Repeater-Builder] Duplexers I think he quote needs little correction...âWhen you are using a VSWR meter you are measuring voltageS, not just one voltage, hi. You are measuring voltage ratios. The SWR reading due to losses changes when one moves closer or farther away from the end of a feedline. The power going out is attenuated, then the load reflects a portion of this back and gets attenuated again and the reflected is measured. Moving closer increases the power to the load and also increases the reflected read at the source showing a higher SWR. Lengthing the cable does the opposite. This is why one can have say 500 ft of RG58 at 450 MHz completly open at the load end and the swr might read 1.5:1 at the source. Also for long feedlines with antennas can give deceptive readings at the source. SWR at the load is much more real. 73, ron, n9ee/r From: R. K. Brumback [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 12:25:59 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers Quote from Jesse: âWhen you are using a VSWR meter you are measuringvoltage, if you move the meter to a different spot on the cable, the voltage isdifferent, therefore it gives you a different reading.â This now makes more sense to me as I once saw a feed line demonstrationwith voltage and current sleds showing the difference at different points alongthe line. At some places the voltage was null (as with any sine wave). I donâtsee how this could happen at the antenna port of a transmitter unless it wasmicrowave as the cabling from the tuner to the output connector is not near ½ wave. Also to Alan, I appreciate your sympathy for us âlittle peopleâbut I do find this very interesting. And as you can see, the experts sometimesneed a tune up. Randy W4CPT -Original Message- From: [EMAIL PROTECTED]:Repeater- [EMAIL PROTECTED] OnBehalf Of Jesse Lloyd Sent: Monday, August 27, 2007 12:48 PM To:Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder]Duplexers The length of coaxdoesn't effect impedance. Trimming the coax effects what is read on theVSWR meter because what is actually happening is that there is an interferencepattern created when you have a mismatch on the end of feedline. This patternis sinusoidal and changes in voltage and current along the line, in 1/2 waveperiods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter youare measuring voltage, if you move the meter to a different spot on the cable,the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating thereflected power into its heatsink. If you put it at a voltage null, Iwould suspect that the SWR would not get dissipated by the transmitter as muchas if you put it at a voltage peak. The standing waves are still there,there is still a mismatch, you will get the same power out, but its just notgoing to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using itin a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohmcable put it on the end of 50 ohm cable you will get a match with a 112.5 ohmload. You make an interesting point though, why does the cabling of duplexer's needto be a certain length. I would suspect that its because they are loopedand make an inductor. This then is part of the LC filtering, and changing thelength effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback [EMAIL PROTECTED]wrote: I have heardthis point argued for years. Does trimming the coax affect theSWR? If the length of coax has an affect on impedance, then howcould it not affect power out? We strive to maintain 50 ohms at the tail of alldevices to match the end load. GE puts matching networks in their Mastr II's. Ihave taken a MFJ-259 and soldered a PL259 only at one end and then startedtrimming the coax down and watched the impedance change significantly with eachcut. Duplexers come with precise lengths of cabling. I have heard thattrimming coax only fools the meter. Not being
Re: RE: [Repeater-Builder] Duplexers
Gary, Transforming from a load to 50 Ohm resistive depends on the load impedance. Same for other impedances. Going from a load to another resistive load will always be a the ratio of N:50. So 50 Ohm coax could transform say a 75 OHM load to a 75:50 or 50:75 ratio. 75 Ohm load with 1/4 wave 50 Ohm coax to 33 Ohms, but not anything. At 1/2 wave back to 75 Ohm. In between would be R with j component, inductive or capacitive depending on length. A Smith Chart shows this. So converting the load to what you want would normally require a different cable impedance. The wiring harnesses used in multi-element antennas like the DB224 4 bay dipole antenna use cable type to convert each antenna load to a 50 Ohm input. In this case there are actually 3 harnesses, one for each of 2 dipole sets and then a 3rd to take these two to one input. I think 92 or 62 Ohm cable is used, but not sure. 73, ron, n9ee/r From: Gary Schafer [EMAIL PROTECTED] Date: 2007/08/27 Mon PM 10:52:11 CDT To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers   From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 9:39PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder]Duplexers  If your coax is the sameimpedance as your transmitter, but different than your load, can it still be atransformer though? Is it possible to transform a load that isn't 50 ohmsto 50 ohms using 50 ohm coax?  Yes italways acts as a transformer when the load impedance is not the same as thecoax impedance. You cannot transform any impedance to 50 ohms with a 50 ohm cable. You can transformto something above or below the 50 ohm cable impedance. Thereason changing the length of the coax to a transmitter helps sometimes, eventhough the transformation of impedance is not to 50 ohms, is that thetransmitter may see an impedance that it is happier with than what the originaltransformed impedance was. Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of theinterference pattern caused by standing waves. Even still there is apoint where the voltage is at a minimum on the line. What happens if thatpoint is at the transmitters output... does it help keep the heat down in thetransmitter due to high SWR?  It doesnâtmatter where the min and max are on the line. The same amount of reflectedpower will be seen at any point. Reflected power does NOT get back into thetransmitter. It gets re-reflected back towards the antenna when it reaches thetransmitter circuits. If youhave a 100 watt transmitter with 10 watts reflected from the load yourwattmeter will read 110 watts forward and 10 watts reflected. The extra 10watts forward power comes from the 10 watts that is reflected from the load andre-reflected at the transmitter. The re-reflected power adds to the original100 watts forward power for a total of 110 watts forward power. All of the 100watts eventually gets radiated by the antenna. This is of course disregardingany line loss which would lower the reflected power indication by the amount ofline loss. Line loss would also claim a portion of the re-reflected power too. If youhave two watt meters and an antenna matching device you can put one wattmeter betweenthe transmitter and the matching device and tune it for minimum reflected poweron the first meter. Then with a second meter between the tuner and themismatched load you can see the second wattmeter that is reading the reflectedpower. The second wattmeter will have a higher forward power reading than thefirst due to the added re-reflected power.  With amismatched load the transmitter may run hotter because it is under oroverloaded due to the non 50 ohm load that it is seeing but it is notdissipating any of the reflected power. Many solid state transmitters aresensitive to reactive loads and may draw more current because of this.  73 Gary K4FMX On 8/27/07, GarySchafer [EMAIL PROTECTED]wrote: VSWR (voltage standingwave ratio) will be the same at any point on a transmission  line. Theimaginary standing wave does not move as the forward and reflected power does.The voltage standing wave ratio is the ratio of the forward voltage to thereflected voltage at a given point on the line. As you move up or down the linethe forward voltage will change and so will the reflected voltage but the ratioor difference between the two will work out to the same value. Thus the termstanding wave. The wave appears to stand still on the line as itoscillates up and down in a sin wave manor.  As Jeff has said theimpedance shown to the transmitter will be different with different lengths oftransmission line only if the load is not a perfect 50 ohms assuming a 50 ohmline. With a load that does not match the line the line operates as animpedance transformer. Think about what a quarter wave length line looks likewith
RE: [Repeater-Builder] Duplexers
If your coax is the same impedance as your transmitter, but different than your load, can it still be a transformer though? It will ALWAYS act as a transformer when the cable's Z does not match the LOAD Z. The SOURCE device (transmitter) plays NO part in the transformation that happens. The Z at the source end of the line is a function of only three things: the load Z (antenna, duplexer, whatever), the cable's characteristic Z, and the cable's electrical length (in degrees/wavelengths/radians/whatever). Cable loss also plays into it, as its effect is to always bring the load Z closer to the cable's characteristic Z as cable loss goes up, but let's leave that out for the sake of simplicity. The source device's impedance does not factor into the equation at all when it comes to determining what the resultant Z is at the source end of the line. Any mismatch that occurs at that end of the line (the source/transmitter end) does NOT affect the VSWR on the line, nor does it change the Z at the source end of the line. It's very important to not put the cart before the horse here. While it may seem to be contrary to instinct, the device that is sourcing the power is NOT what determinates what happens on the transmission line with respect Z and VSWR, it's the LOAD mismatch that sets up the standing waves and the resulting Z's along the length of the line. It is for this reason that your transmitter CANNOT detune your duplexer, and for the same reason, you can't tune (change the Z) of your antenna from the far end of the cable. Is it possible to transform a load that isn't 50 ohms to 50 ohms using 50 ohm coax? NO. Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? NO. VSWR on a transmission line doesn't directly manifest as heat in a transmitter. The whole notion of high VSWR creating heat in a transmitter is likely based on a drop in efficiency in SOME transmitters when they are not properly matched to the feedline. You can have a very high VSWR on the feedline, and provided the transmitter is matched to the Z at the source end of the line, the efficiency will not suffer, and there will be nother ill effects (including heating) that occur within the transmitter. A PROPER MATCH DOES NOT OCCUR WHEN THE TRANSMITTER'S SOURCE Z IS THE SAME AS THE CABLE'S CHARACTERISTIC Z EXCEPT WHEN THE LOAD Z ALSO MATCHES THE CABLE'S CHARACTERISTIC Z. Or, rewritten, if the load Z (antenna) is not 50+j0, a 50 ohm transmitter delivering power into a 50 ohm transmission line will NEVER be matched. (Didn't mean to shout, but it's important to understand and accept that fact.) Sidebar: VSWR is a conveniently-simplistic scalar value, but it doesn't tell you anything about the specific impedance at a particular point along the line, nor what the ratio and phase relationships are between voltage and current. You can calculate VSWR based on a specific Z, but you can't do the reverse, except in the case of a true 1:1 VSWR. All Corvettes are Chevys, but not all Chevys are Corvettes. You get the idea. Many hams like to talk in terms of VSWR as it's a nice easy number to deal with, and the lower the number, the better. But that oversimplification seems to also translate into a relaxation in the attention paid to the theory behind what's really going on along the transmission line, at the source-to-line interface, and at the line-to-load interface. When it really comes down to the nuts and bolts of designing and building matching networks, you don't care about the VSWR value, you need to know, think, and design based on complex impedances. Back in the good ol' days when your rig running 6146's had a pi matching network on its output, you could tune the transmitter into some not-so-good loads, often in excess of 3:1 VSWR, without any problem. Why? The pi network did its job, matching the high-Z (and somewhat reactive) output Z of the tubes to the whatever-Z existed at the end of the antenna feedline. You could get efficiency just as good at a 3:1 VSWR as you could at 1:1 because the output of the matching network provided a conjugate match. --- Jeff
Re: [Repeater-Builder] Duplexers
Jeff DePolo wrote: NO. VSWR on a transmission line doesn't directly manifest as heat in a transmitter. The whole notion of high VSWR creating heat in a transmitter is likely based on a drop in efficiency in SOME transmitters when they are not properly matched to the feedline. Or worse, a transmitter that when feeding anything other than its design Z starts throwing spurs. In that case, it's output filters (if it has any!) may be eating all that spur power... because folks set power AFTER the final low-pass filter. I could see that being another possible way you'd get transmitter heating if things were mismatched. It wouldn't be as significant as the whole PA getting inefficient, though. Jeff also already mentioned (and set aside for purposes of this discussion) transmitters that have built-in directional couplers and loads that are mounted to a common heatsink with the PA transistors. Moto likes to do this on most of their continuous-duty PA's. That can cause heating too, if reflected power is high, but it's not relevant to the discussion at hand, because it's not the transmitter heating up, it's the load hanging off of the directional coupler. Nate WY0X
RE: [Repeater-Builder] Duplexers
At 8/27/2007 20:52, you wrote: Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? It doesn t matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. I don't buy into this. In order for reflected power to not be absorbed by the TX, it would have to appear totally reactive. Although I've never measured one, I don't believe that's the case. If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re-reflected power. This doesn't sound right either, as there should be no reflected power at the antenna if it's been matched further down the line. The tuner would be adjusted so as to create a conjugate impedance of the antenna at the end of the feeding coax, thus eliminating the mismatch. My guess is that the higher power reading on the wattmeter is due to the weird impedances it's seeing on both its input output. Bob NO6B
RE: [Repeater-Builder] Duplexers
I have heard this point argued for years. “Does trimming the coax affect the SWR?” If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II’s. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo Sent: Saturday, August 25, 2007 12:30 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding)-. --- Jeff - Jeff DePolo - HYPERLINK mailto:jd1%40broadsci.com[EMAIL PROTECTED] Broadcast Sciences LLC, Valley Forge PA v: 610.917.3000 f: 610.917.3030 No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
Re: [Repeater-Builder] Duplexers
The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. If you put it at a voltage null, I would suspect that the SWR would not get dissipated by the transmitter as much as if you put it at a voltage peak. The standing waves are still there, there is still a mismatch, you will get the same power out, but its just not going to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback [EMAIL PROTECTED] wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT -Original Message- *From:* Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] ups.com] *On Behalf Of *Jeff DePolo *Sent:* Saturday, August 25, 2007 12:30 AM *To:* Repeater-Builder@yahoogroups.com *Subject:* RE: [Repeater-Builder] Duplexers When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff - Jeff DePolo - [EMAIL PROTECTED] jd1%40broadsci.com Broadcast Sciences LLC, Valley Forge PA v: 610.917.3000 f: 610.917.3030 No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
RE: [Repeater-Builder] Duplexers
One can also use 1/4- and 1/2- λ stubs of coaxial cable of the same impedance as matching networks in conjunction with a Tee connector. Shorting or Opening the end of the matching stub also makes a difference, based upon the length being employed. I believe that VSWR is *one* reason that cabling on a duplexer must be a function of length, based upon a fraction of the characteristic frequency. But not being a duplexer person I'm not all that familiar with the precise engineering behind their interconnecting cabling. Mark - N9WYS From: Repeater-Builder@yahoogroups.com On Behalf Of Jesse Lloyd --- snip --- The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] Duplexers
Quote from Jesse: When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefore it gives you a different reading. This now makes more sense to me as I once saw a feed line demonstration with voltage and current sleds showing the difference at different points along the line. At some places the voltage was null (as with any sine wave). I dont see how this could happen at the antenna port of a transmitter unless it was microwave as the cabling from the tuner to the output connector is not near ½ wave. Also to Alan, I appreciate your sympathy for us little people but I do find this very interesting. And as you can see, the experts sometimes need a tune up. Randy W4CPT -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 12:48 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. If you put it at a voltage null, I would suspect that the SWR would not get dissipated by the transmitter as much as if you put it at a voltage peak. The standing waves are still there, there is still a mismatch, you will get the same power out, but its just not going to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback HYPERLINK mailto:[EMAIL PROTECTED][EMAIL PROTECTED] wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT -Original Message- From: HYPERLINK mailto:Repeater-Builder@yahoogroups.com[EMAIL PROTECTED] [mailto:HYPERLINK mailto:Repeater-; [EMAIL PROTECTED] HYPERLINK http://ups.com; \nups.com] On Behalf Of Jeff DePolo Sent: Saturday, August 25, 2007 12:30 AM To: HYPERLINK mailto:Repeater-Builder@yahoogroups.com[EMAIL PROTECTED] Subject: RE: [Repeater-Builder] Duplexers When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding)-. --- Jeff - Jeff DePolo - HYPERLINK mailto:jd1%40broadsci.com; [EMAIL PROTECTED] Broadcast Sciences LLC, Valley Forge PA v: 610.917.3000 f: 610.917.3030 No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database
RE: [Repeater-Builder] Duplexers
Randy, the null repeats at - IIRC - odd ½-λ intervals. so if the cable was cut to a length equal to an odd multiple of ½ of the wavelength (1/2, 3/2, 5/2, etc.) you would see the null at the transmitter end repetitively. Regarding your reference to microwave, it doesn't matter what the frequency range is - it could be HF, VHF, UHF of SHF. so you could make this occur as long as your cable was cut to ½ wavelength. This only becomes difficult at HF frequencies, where ½ of a wavelength might be, for example, 40 meters long for the 80m band. But when you get to VHF your cable is now considerably more manageable, such as for 2m - only 1 meter long, or approximately a bit over 3'. I also think I remember that voltage and current are at opposites along the cable - where voltage is lowest, current is highest. and vice versa. I'm not in radio as a profession, so I don't work with this stuff on a day-to-day basis - therefore my memory may be a bit foggy regarding this phenomenon. Now putting on my flame-proof underwear. ;-) 73 de Mark - N9WYS _ From: Repeater-Builder@yahoogroups.com On Behalf Of R. K. Brumback Quote from Jesse: When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefore it gives you a different reading. This now makes more sense to me as I once saw a feed line demonstration with voltage and current sleds showing the difference at different points along the line. At some places the voltage was null (as with any sine wave). I don't see how this could happen at the antenna port of a transmitter unless it was microwave as the cabling from the tuner to the output connector is not near ½ wave. Also to Alan, I appreciate your sympathy for us little people but I do find this very interesting. And as you can see, the experts sometimes need a tune up. Randy W4CPT -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 12:48 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. If you put it at a voltage null, I would suspect that the SWR would not get dissipated by the transmitter as much as if you put it at a voltage peak. The standing waves are still there, there is still a mismatch, you will get the same power out, but its just not going to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] org wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.484 / Virus Database: 269.12.6 - Release Date: 8/24/2007 12:00 AM
RE: [Repeater-Builder] Duplexers
The length of coax doesn't effect impedance. That statement is misleading, if not totally wrong. If there is anything other than a perfect match at the load (in other words, if the VSWR on the line is not a perfect 1:1), the coax behaves as a transformer. The resulting Z, as measured at the source end of the line (i.e. the transmitter end) WILL vary depending on the length of the coax. Don't confuse Z with VSWR. The two are related, but you can't use them interchangably. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. No, that's not right. Reflected power doesn't get dissipated into the heatsink, unless the transmitter happens to have an isolator on its output, in which case most of the reflected power ends up in the reject load which sometimes is mounted to the same heatsink as the devices, but that's really stretching... A mismatch between the transmitter and the load can result in lots of things. It may cause the amplifier's efficiency to degrade as the devices are no longer able to transfer power to the load efficiently, but that's only one possibility. In some cases, it might actually cause the transmitter to make more power, sometimes at higher or lower efficiency, depending on many factors related to the design of the amplifier itself. If the matching network (if one xists) was adjusted to properly match the PA to the mis-matched load, all of the power (minus transmission line losses) will ultimately get to the antenna. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. Coax itself doesn't affect the power output. The LOAD IMPEDANCE that terminates the transmitter, and how the transmitter is (or isn't) matched to that load is what affects the power output in real-world transmitters. Varying the length of the coax MAY result in a change in the transmitter's power output when the VSWR is not 1:1 because the coax acts as a transformer. It transforms the antenna's mis-matched feedpoint Z to some other Z at the far (transmitter) end. Since a perfect 50+j0 match is practically impossible to achieve, coax (or any other form of transmission line) will virtually ALWAYS act as a transformer except at exact half-wavelength multiples. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. If you're talking about the cables within the duplexer harness, the reason is to properly repeat and transform impedances. The simplest example I can give you is to consider what happens at the antenna tee of a duplexer. At the transmit frequency, one side of the tee feeds the transmit side of the duplexer which presents a good match. Looking toward the opposite side of the tee, the receive side of the duplexer typically presents a SHORT at the transmit frequency (typical of a pass/reject cavity). By offsetting that SHORT by a 1/4 wavelength section of cable going to the tee, the SHORT gets transformed to an OPEN, therefore no power can flow in that undesired direction. Maybe it's time for somebody to do a Smith Chart 101 article. No, I'm not volunteering myself :-) --- Jeff
RE: [Repeater-Builder] Duplexers
I have heard this point argued for years. Does trimming the coax affect the SWR? The answer is NO!! If the length of coax has an affect on impedance, then how could it not affect power out? Changing the length of the line changes IMPEDANCE at the source end (assuming the VSWR isn't 1:1). Changling the length of the line DOES NOT change the VSWR on the line. Both of these statements ignore feedline losses, which are negligible when we're talking about adding or subtracting a few inches or a few feet of cable at HF/VHF/UHF frequencies for the kinds of cable we normally deal with. The more cable loss, the lower the VSWR will be at the source end. Likewise, the longer the cable, the closer the Z at the source end will be to the cable's characteristic impedance. We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Everything you just said above is right. I think what has you confused is that you're thinking that Z and VSWR are interchangable. They aren't. Z changes with coax length. VSWR does not. --- Jeff
Re: [Repeater-Builder] Duplexers
As a side note for this discussion, I think Jeff's doing a great job of explaining how transmission line theory works... For those that want to dive in a lot further (e.g. Do the math), the ARRL Antenna Book has a whole section dedicated to this topic, and it's written well enough that a mathematical dolt like myself can still follow the concepts and not scratch my head at the math. Too bad the book is something like $70 bucks... I won my copy as a door prize at a hamfest or I'd have never bought one... the book is definitely worth the price of admission and the CD along with it contains some useful tools that just add to the value... Nate WY0X
RE: [Repeater-Builder] Duplexers
As a side note for this discussion, I think Jeff's doing a great job of explaining how transmission line theory works... I try... For those that want to dive in a lot further (e.g. Do the math), the ARRL Antenna Book has a whole section dedicated to this topic, and it's written well enough that a mathematical dolt like myself can still follow the concepts and not scratch my head at the math. Another good, readily-available book is Reflections by Walt Maxwell W2DU. My copy is old; he put out an updated edition Reflections II later. It's a good read, but has one drawback (to me anyway). A lot of what he discusses relates to pi matching networks common in tube HF rigs. You have to keep in mind that a lot of the myths he dispels don't always translate directly to the world of VHF/UHF solid state amplifiers, but theory behind what he preaches is dead nuts on. --- Jeff
RE: [Repeater-Builder] Duplexers
VSWR (voltage standing wave ratio) will be the same at any point on a transmission line. The imaginary standing wave does not move as the forward and reflected power does. The voltage standing wave ratio is the ratio of the forward voltage to the reflected voltage at a given point on the line. As you move up or down the line the forward voltage will change and so will the reflected voltage but the ratio or difference between the two will work out to the same value. Thus the term standing wave. The wave appears to stand still on the line as it oscillates up and down in a sin wave manor. As Jeff has said the impedance shown to the transmitter will be different with different lengths of transmission line only if the load is not a perfect 50 ohms assuming a 50 ohm line. With a load that does not match the line the line operates as an impedance transformer. Think about what a quarter wave length line looks like with a short on one end. It transforms that short to a high impedance or open at the other end. If one end is open the other end will look like a short to the transmitter. With a load impedance that is not 50 ohms what is seen at the transmitter is something between an open and a short depending on how far from 50 ohms the load is. In other words the load impedance gets transformed to something else. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 11:48 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. If you put it at a voltage null, I would suspect that the SWR would not get dissipated by the transmitter as much as if you put it at a voltage peak. The standing waves are still there, there is still a mismatch, you will get the same power out, but its just not going to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, R. K. Brumback [EMAIL PROTECTED] wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] ups.com] On Behalf Of Jeff DePolo Sent: Saturday, August 25, 2007 12:30 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Duplexers When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff - Jeff
Re: [Repeater-Builder] Duplexers
If your coax is the same impedance as your transmitter, but different than your load, can it still be a transformer though? Is it possible to transform a load that isn't 50 ohms to 50 ohms using 50 ohm coax? Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? On 8/27/07, Gary Schafer [EMAIL PROTECTED] wrote: VSWR (voltage standing wave ratio) will be the same at any point on a transmission line. The imaginary standing wave does not move as the forward and reflected power does. The voltage standing wave ratio is the ratio of the forward voltage to the reflected voltage at a given point on the line. As you move up or down the line the forward voltage will change and so will the reflected voltage but the ratio or difference between the two will work out to the same value. Thus the term standing wave. The wave appears to stand still on the line as it oscillates up and down in a sin wave manor. As Jeff has said the impedance shown to the transmitter will be different with different lengths of transmission line only if the load is not a perfect 50 ohms assuming a 50 ohm line. With a load that does not match the line the line operates as an impedance transformer. Think about what a quarter wave length line looks like with a short on one end. It transforms that short to a high impedance or open at the other end. If one end is open the other end will look like a short to the transmitter. With a load impedance that is not 50 ohms what is seen at the transmitter is something between an open and a short depending on how far from 50 ohms the load is. In other words the load impedance gets transformed to something else. 73 Gary K4FMX -- *From:* Repeater-Builder@yahoogroups.com [mailto: [EMAIL PROTECTED] *On Behalf Of *Jesse Lloyd *Sent:* Monday, August 27, 2007 11:48 AM *To:* Repeater-Builder@yahoogroups.com *Subject:* Re: [Repeater-Builder] Duplexers The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up and down too. When you are using a VSWR meter you are measuring voltage, if you move the meter to a different spot on the cable, the voltage is different, therefor it gives you a different reading. Now if you put a voltage null at your transmitter, what would happen? Normally with high SWR your transmitter will get hot because its dissipating the reflected power into its heatsink. If you put it at a voltage null, I would suspect that the SWR would not get dissipated by the transmitter as much as if you put it at a voltage peak. The standing waves are still there, there is still a mismatch, you will get the same power out, but its just not going to hurt your transmitter as much because of the heat. The only time coax length makes a difference to power out is if your using it in a matching stub, or a matching section ie. if you take 1/4 wave of 75 ohm cable put it on the end of 50 ohm cable you will get a match with a 112.5 ohm load. You make an interesting point though, why does the cabling of duplexer's need to be a certain length. I would suspect that its because they are looped and make an inductor. This then is part of the LC filtering, and changing the length effects L. But I could be wrong on that. Jesse On 8/27/07, *R. K. Brumback* [EMAIL PROTECTED] wrote: I have heard this point argued for years. Does trimming the coax affect the SWR? If the length of coax has an affect on impedance, then how could it not affect power out? We strive to maintain 50 ohms at the tail of all devices to match the end load. GE puts matching networks in their Mastr II's. I have taken a MFJ-259 and soldered a PL259 only at one end and then started trimming the coax down and watched the impedance change significantly with each cut. Duplexers come with precise lengths of cabling. I have heard that trimming coax only fools the meter. Not being an engineer with millions worth of equipment I can only make a SWAG (scientific wild ass guess) as to whether coax length makes a difference in power out. Randy W4CPT -Original Message- *From:* Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] ups.com] *On Behalf Of *Jeff DePolo *Sent:* Saturday, August 25, 2007 12:30 AM *To:* Repeater-Builder@yahoogroups.com *Subject:* RE: [Repeater-Builder] Duplexers
RE: [Repeater-Builder] Duplexers
_ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 9:39 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers If your coax is the same impedance as your transmitter, but different than your load, can it still be a transformer though? Is it possible to transform a load that isn't 50 ohms to 50 ohms using 50 ohm coax? Yes it always acts as a transformer when the load impedance is not the same as the coax impedance. You can not transform any impedance to 50 ohms with a 50 ohm cable. You can transform to something above or below the 50 ohm cable impedance. The reason changing the length of the coax to a transmitter helps sometimes, even though the transformation of impedance is not to 50 ohms, is that the transmitter may see an impedance that it is happier with than what the original transformed impedance was. Yes your right VSWR is the ratio between Vmax and Vmin, node and anodes, of the interference pattern caused by standing waves. Even still there is a point where the voltage is at a minimum on the line. What happens if that point is at the transmitters output... does it help keep the heat down in the transmitter due to high SWR? It doesn't matter where the min and max are on the line. The same amount of reflected power will be seen at any point. Reflected power does NOT get back into the transmitter. It gets re-reflected back towards the antenna when it reaches the transmitter circuits. If you have a 100 watt transmitter with 10 watts reflected from the load your wattmeter will read 110 watts forward and 10 watts reflected. The extra 10 watts forward power comes from the 10 watts that is reflected from the load and re-reflected at the transmitter. The re-reflected power adds to the original 100 watts forward power for a total of 110 watts forward power. All of the 100 watts eventually gets radiated by the antenna. This is of course disregarding any line loss which would lower the reflected power indication by the amount of line loss. Line loss would also claim a portion of the re-reflected power too. If you have two watt meters and an antenna matching device you can put one wattmeter between the transmitter and the matching device and tune it for minimum reflected power on the first meter. Then with a second meter between the tuner and the mismatched load you can see the second wattmeter that is reading the reflected power. The second wattmeter will have a higher forward power reading than the first due to the added re-reflected power. With a mismatched load the transmitter may run hotter because it is under or overloaded due to the non 50 ohm load that it is seeing but it is not dissipating any of the reflected power. Many solid state transmitters are sensitive to reactive loads and may draw more current because of this. 73 Gary K4FMX On 8/27/07, Gary Schafer [EMAIL PROTECTED] wrote: VSWR (voltage standing wave ratio) will be the same at any point on a transmission line. The imaginary standing wave does not move as the forward and reflected power does. The voltage standing wave ratio is the ratio of the forward voltage to the reflected voltage at a given point on the line. As you move up or down the line the forward voltage will change and so will the reflected voltage but the ratio or difference between the two will work out to the same value. Thus the term standing wave. The wave appears to stand still on the line as it oscillates up and down in a sin wave manor. As Jeff has said the impedance shown to the transmitter will be different with different lengths of transmission line only if the load is not a perfect 50 ohms assuming a 50 ohm line. With a load that does not match the line the line operates as an impedance transformer. Think about what a quarter wave length line looks like with a short on one end. It transforms that short to a high impedance or open at the other end. If one end is open the other end will look like a short to the transmitter. With a load impedance that is not 50 ohms what is seen at the transmitter is something between an open and a short depending on how far from 50 ohms the load is. In other words the load impedance gets transformed to something else. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Jesse Lloyd Sent: Monday, August 27, 2007 11:48 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Duplexers The length of coax doesn't effect impedance. Trimming the coax effects what is read on the VSWR meter because what is actually happening is that there is an interference pattern created when you have a mismatch on the end of feedline. This pattern is sinusoidal and changes in voltage and current along the line, in 1/2 wave periods. You will find max voltage peaks and min voltage peaks. Also current will go up
RE: [Repeater-Builder] Duplexers
Ya you should be able to trim your coax so the transmitter sees 50 ohms, which should be every 1/2 wave. All this does it protect the transmitter, the standing waves are still there, they just gets dissipated/radiated by the coax. No, no, no, no, no (thumping head on desk). If the VSWR on the line between the transmitter and the duplexer is anything other than 1:1, THERE DOES NOT EXIST a point along that line where the impedence is 50+j0. Line losses go up with VSWR, but coax doesn't radiate unless there are currents flowing on the shield, and those aren't a function of VSWR on the line. --- Jeff
RE: [Repeater-Builder] Duplexers
Jeff you have just made two statements that are the exect opposit of each other. If changing the length of cable makes a differance, then the swr as seen by the transmitter must change. Re-read what I said. Changing the cable length changes the *Z*, but it doesn't change the *VSWR*. As you vary the cable length, the Z changes in a cyclical fashion, but always remains at a constant VSWR. For any given VSWR, there are an infinite number of complex Z's that will produce that VSWR. As some transmitters can not be tuned for impedance mismatch, adding lengths of line may change the impedance where the transmitter will produce the maximan ammout of power out. Yes. But it doesn't change the VSWR. If say the duplexer is setup for a 50 ohm load and the transmitter wants to load into a 60 ohm load, then changing the length of cable between the duplexer and transmitter may let the transmitter see 60 ohms instead of 50 ohms. Not if the cables your using are also 50 ohms. If the duplexer presents a 50 ohms like you said, you can use whatever cable lengths you want and the resulting Z as seen by the transmitter will always be 50 ohms. Transmission lines only act as transformers when their characteristic Z is different than the termination Z. --- Jeff - Jeff DePolo - [EMAIL PROTECTED] Broadcast Sciences LLC, Valley Forge PA v: 610.917.3000 f: 610.917.3030
RE: [Repeater-Builder] Duplexers
--- Jeff DePolo [EMAIL PROTECTED] wrote: When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff Jeff you have just made two statements that are the exect opposit of each other. If changing the length of cable makes a differance, then the swr as seen by the transmitter must change. As some transmitters can not be tuned for impedance mismatch, adding lengths of line may change the impedance where the transmitter will produce the maximan ammout of power out. If say the duplexer is setup for a 50 ohm load and the transmitter wants to load into a 60 ohm load, then changing the length of cable between the duplexer and transmitter may let the transmitter see 60 ohms instead of 50 ohms. The swr will not really change on the line as a whole, but at a given point it may match the impedance of the transmitter for maximum power transfer. Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/
Re: [Repeater-Builder] Duplexers
Ya you should be able to trim your coax so the transmitter sees 50 ohms, which should be every 1/2 wave. All this does it protect the transmitter, the standing waves are still there, they just gets dissipated/radiated by the coax. Also with cans usually, if I have enough time on my hands, I tune them one way (higher frequency = cans marked TX), then the other (lower frequency = cans marked TX). Almost every time you'll get a different outcome. Which way you tune them in the end depends on your situation, weather your putting out lots of TX power and need the isolation, or if you care about receive sensitivity. I find that usually one side of the duplexer will have a better insertion loss than the other, while the other will have better null than the other. The one with better insertion loss I usually put on the RX side (I can simply bump the TX power by a dB to compensate for the extra loss). This of course only applies to cans where you can not set the insertion loss. For cans that you can change the insertion loss you can spend hours on fiddleing. If you take your transmitter and put it into a dummy load what's its TX power? Also no one mentioned this (I think), but check you cables and connectors, I had one that was bad, produced a bunch of swr, cans were fine. Jesse On 8/25/07, Ralph Mowery [EMAIL PROTECTED] wrote: --- Jeff DePolo [EMAIL PROTECTED] jeff%40depolo.net wrote: When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. Adding a wattmeter or any other length of cable between the transmitter and the duplexer Tx input port has no effect on the tuning of the duplexer. It may change the load Z the transmitter sees, which may make the transmitter happier (or sadder) depending on the resulting Z, but in no way does it alter the tuning of the duplexer itself. Adding or removing cable lengths between the transmitter and duplexer also does not change the VSWR as seen by the transmitter (minimal cable loss effects notwithstanding). --- Jeff Jeff you have just made two statements that are the exect opposit of each other. If changing the length of cable makes a differance, then the swr as seen by the transmitter must change. As some transmitters can not be tuned for impedance mismatch, adding lengths of line may change the impedance where the transmitter will produce the maximan ammout of power out. If say the duplexer is setup for a 50 ohm load and the transmitter wants to load into a 60 ohm load, then changing the length of cable between the duplexer and transmitter may let the transmitter see 60 ohms instead of 50 ohms. The swr will not really change on the line as a whole, but at a given point it may match the impedance of the transmitter for maximum power transfer. __ Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/
[Repeater-Builder] Duplexers
Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP
Re: [Repeater-Builder] Duplexers
Generally the duplexer only makes a slight contribution to the reflected power. How doe the reflected power between the transmitter and antenna, without the duplexer in line look? Steve NU5D dallasreact112 wrote: Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP Yahoo! Groups Links
Re: [Repeater-Builder] Duplexers
If the duplexer is correctly tuned, there will be NO measurable SWR into it. If you have 25/60 watts, it is way off frequency. - Original Message - From: dallasreact112 To: Repeater-Builder@yahoogroups.com Sent: Friday, August 24, 2007 7:16 PM Subject: [Repeater-Builder] Duplexers Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP
Re: [Repeater-Builder] Duplexers
From the Dup. to the Ant. is ok. But the Dup. is out of tune or no good. Might even be a bad jumper on the Dup. dallasreact112 [EMAIL PROTECTED] wrote: Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP Yahoo! Groups Links
Re: [Repeater-Builder] Duplexers
Bernie, A typical VSWR for a duplexer would be 1.5:1 or less, more like less. Will not be 1:1 most times, but low. A lot lower than your 65/25W which is more like a 4.5:1 VSWR. Really sounds as the duplexer is out of tune or has an internal problem. Wonder if you tuned these from another band such as 150-160 down to 144-148. Did you keep the upper freq on the same side and the lower on the new lower??? Often one should keep the same even if the upper/lower is say tx/rx and the new is upper/lower rx/tx. Not always, but have seen a problem if one tries to reverse the cavity sides, make upper side the lower freq just because one says tx and the other rx and try to keep on same side, but reverse the upper/lower. This is getting confusing, hi. 73, ron, n9ee/r From: dallasreact112 [EMAIL PROTECTED] Date: 2007/08/24 Fri PM 07:16:22 CDT To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
RE: [Repeater-Builder] Duplexers
Bernie, When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. But, really, you need not worry about what the SWR is, if the forward power to the antenna is appropriate. Let's say you have a 4-can duplexer, which might have about 1.5 dB insertion loss. If your power amp delivers exactly 100 watts into a dummy load when connected directly at the TX output, you should expect about 70 watts going to the antenna when the duplexer is in the circuit. A 6-can duplexer might have about 2.2 dB insertion loss, and you should see about 59 watts going to the antenna. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of dallasreact112 Sent: Friday, August 24, 2007 5:16 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Duplexers Anyone one know what to expect SWR wise with a duplexer? I have a DB products 2 meter duplexer on an amateur repeater. Measuring with a Bird wattmeter between the duplexer and antenna I read 50W forward and a couple watts reverse. That is ok. But when I check between the transmitter and the TX port on the duplexer I get a about 60 W forward and 25W reverse power. Is there a rule fo thumb for a known good SWR value thru a duplexer? Should a good duplexer introduce any significant SWR? Thanks Bernie Parker K5BP
RE: [Repeater-Builder] Duplexers
--- Eric Lemmon [EMAIL PROTECTED] wrote: Bernie, When you put the Bird between the TX and the duplexer, you have changed the length of the jumper cable, which upset the tuning. But, really, you need not worry about what the SWR is, if the forward power to the antenna is appropriate. Let's say you have a 4-can duplexer, which might have about 1.5 dB insertion loss. If your power amp delivers exactly 100 watts into a dummy load when connected directly at the TX output, you should expect about 70 watts going to the antenna when the duplexer is in the circuit. A 6-can duplexer might have about 2.2 dB insertion loss, and you should see about 59 watts going to the antenna. 73, Eric Lemmon WB6FLY When the wattmeter is inserted it will not upset the tuning of the duplexer enough to reflect that kind of power. About all it could do is upset the tuning of the transmitter so that it will not put out the same ammount of forward power. This should not have much effect of the reflected power. One thing that could be (but not likely) is the transmitter is producing spurs and harmonices the duplexer is not letting pass to the antenna and is being reflected back. Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it's updated for today's economy) at Yahoo! Games. http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow
