Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Tim, I have a two meter repeater that outputs 250 watts (approximately +54 dBm) into the duplexer. After the 93 dB of rejection that the duplexer provides for shear power reduction toward the receiver port, -39 dBm of transmitter power leaves the duplexer receiver port - headed toward the receiver. The repeater is a Motorola MICOR VHF equipped with a MICOR preamp. Bench sensitivity is -125 dBm for 12 dB SINAD. The duplexer is a stock Wacom WP-641. This repeater normally uses a tube type power amplifier to achieve the 250 watt level. Using the tube power amp, no desense occurs on the repeater. I also have a the stock 110 watt MICOR power amplifier (solid state) that can be switched in. The repeater has a slight amount of desense when running the solid state PA. Why? It's obviously not the shear amount of power, as it has been reduced over 3 dB. The culprit is /transmitter side-band noise/. The solid-state power amplifier provides no additional protection of the amount of transmitter side-band noise being produced by the exciter, in fact, being wide-band in nature, the solid-state unit amplifies the noise. The tube power amplifier, however, is a High Q (very narrow band - tuned to the exact transmit frequency) device only providing power gain on the 'desired' repeater output frequency, and reducing (or at least not amplifying) the transmitter side-band noise appearing on the receiver frequency. From your explanation below, I don't believe shear power is ruining your ability to duplex, but rater the amount of transmitter side-band noise reaching the receiver. To prove this, install a notch cavity in the transmit leg tuned to the receiver frequency. If your duplexer isn't capable of allowing the present radio equipment to properly duplex, either the duplexer needs replaced, or you can change the type of transmitter to something else - no, I'm not suggesting tube-type. General Electric built a VHF exciter that has 22 dB less transmitter side band noise (600 kHz from its primary carrier) than most multiplier counterparts (like your Motorola MICOR). Using it is like installing a 22 dB notch filter between the exciter (transmitter) and receiver where side-band noise is concerned. This exciter is the MASTR II PLL. To comment on the folks privately emailing you telling you a MICOR receiver cannot handle an off frequency carrier of -53 - they are full of it - period. The answer is HOW CLEAN the adjacent frequency signal is. If the adjacent carrier is full of noise, and that noise falls on the frequency the receiver is listening to - then no the receiver can't handle it, but that's a totally different thing ruining your lunch - comparing apples to oranges. Hope this helps... Kevin Custer Hi guys, Took some time away from the project... loosing too many hairs. Ok, I've gotten another receiver strip, and it has the specified sensitivity per Mot. Guess I want to bounce some ideas around with those of you who are more learned in the arts! With 250mW (+24dBm) into the transmit port... antenna port is a quality 50 ohm load, I see -72dBM at the receiver port. (pretty much what I expect.. 1.8dB loss through the xmit side, 100dB notch through the RX side. With it all hooked up receiving an input signal of about 0.7uV, application of the 250mw to the transmitter side will cause noise in the receiver, although not much. So, it appears that if I add an additional 30dB notch (another 'can'), the problem at high power may go away. If I compare what 50 watts with an additional can would be (-130dB) to what I get with 250mW current notch (100dB), then it looks like I just need to add an additional can. 50 w = +47dBm - 130dB future notch = -83dBm at receiver. 250mw = +24 - 100dB current notch = -76dBm With the current notch @ 50 watts, I see a receive signal of -53dBm. Some have said that the Micor can handle that, while others (off-line) have said no way. This setup appears to support the opinion that -53 is still way too much. Any comments and thoughts would be most appreciated! Thanks, Tim
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Kevin, Thanks for the info. I've used the PLL MastrII exciter on a couple of systems also. Now, since this duplexer is of the 'notch' variety, I already have about 100db of notch (on the TX side) that is tuned to the RX freq. Shouldn't this be enough? Tim
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
With 250mW (+24dBm) into the transmit port... antenna port is a quality 50 ohm load, I see -72dBM at the receiver port. (pretty much what I expect.. 1.8dB loss through the xmit side, 100dB notch through the RX side. Those numbers are fine. With it all hooked up receiving an input signal of about 0.7uV, application of the 250mw to the transmitter side will cause noise in the receiver, although not much. That's bad. With the amount of isolation you have (assuming you have the same amount of noise supression - did you confirm that?), you shouldn't need any more isolation. Whatever problem you have that's manifesting as desense is NOT due to insufficient carrier supression or noise supression (assuming they're symmetrical - again, you should measure the latter). How are you injecting the signal into the receiver while transmitting, by the way? Lossy tee or some other method? So, it appears that if I add an additional 30dB notch (another 'can'), the problem at high power may go away. Probably not. If I compare what 50 watts with an additional can would be (-130dB) to what I get with 250mW current notch (100dB), then it looks like I just need to add an additional can. Probably not. With the current notch @ 50 watts, I see a receive signal of -53dBm. Some have said that the Micor can handle that, while others (off-line) have said no way. The others are wrong, and if they they want to defend their position, I invite them to do it here on the list. -53 dBm 1 MHz away is not a problematic signal by any stretch of the imagination. Here's a simple sanity check for those that feel otherwise. I like using real-world examples as sanity checks. How many thousands of 2m repeaters are out there running 100 watts at 600 kHz offset without desense? Let's be generous and say they have 100 dB of isolation in the duplexer. +50 dBm TPO - 100 dB = -50 dBm transmit carrier hitting the receiver. No big deal. And that's on 2m. The offset on 2m is only 0.4% (0.6 MHz / 146 MHz), whereas on 6m, it's 1.9% (1 / 53 MHz), making isolation requirements that much more stringent on 2m. Now let's look at a 6m example. You have a 6m repeater on a 1 MHz split? Let's say it's on 53.99-, highest channel in the band, putting your receiver on 52.99. Some other ham is working simplex on 52.525, using 100 watts into a unity-gain antenna, and he's 40 miles away. His signal into your receiver, assuming unity gain on your end too, and line-of-sight, is -53 dBm (that's what the free-space path loss works out to: 103 dB for 40 miles on 6m, check my math). Would you expect this guy 40 miles away talking on 525 to desense your repeater? If so, then you should expect *every* ham who transmits on 525 (or potentially any other frequency within 1 MHz of your receiver) within a 40 mile radius of your repeater to cause you desense; those that are closer than 40 miles are just going to desense it even worse. Silly. Just plain silly. This setup appears to support the opinion that -53 is still way too much. No, it doesn't. You're drawing a conclusion from incomplete data. The only thing you know at this point is that what you have DOESN'T work, but what you DON'T KNOW is WHY it doesn't work. And I'm telling you, with the utmost certainty, that based on the numbers you've given, lack of carrier supression and/or noise supression in your duplexer at your operating frequencies is NOT the problem, you should be looking elsewhere. There are many potential causes of desense beyond just carrier supression and transmitter noise supression afforded by the duplexer at the Tx and Rx frequencies proper. To say that all of your problems will be solved by increasing either/both is not a valid conclusion to draw. Just a few of many possible issues that could be causing your desense problem: - lack of mid-band isolation - noisy components/connections in your duplexer, cabling, etc. - spurious transmitter - spurious LO - component breaking down/arcing when excited by RF - insufficient shielding (cabling, radio chassis/subassemblies, etc.) - bad test load or antenna - bad channel element or crystal - corroded/oxidized connector, contact, pin, etc. - cracked/broken/microscopically-intermittent connection, trace, conductor, etc. - bad/cold solder joint - other problem in exciter or receiver - loose, mis-installed, or otherwise faulty RF connector - bad RF cables (LMR, bare copper braid, etc.) - bad luck, bad karma, bad mojo, phase of the moon, alignment of the planets, etc. When you're duplexing, everything has to be damn near perfect otherwise you end up with desense. On 6m, you have a few things going for you, including a wide frequency split (percentage-wise), a high ambient noise floor (hides some sins/duplex noise), but otherwise, all of the same issues/caveats apply as they do on any other band when duplexing, noise is noise, dynamic range is dynamic range, whether you're on 50 MHz or 50 GHz.
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Kevin - how did you get the MICOR 250 Watt VHF Amplifier to go down to 2-Meters? Or was it a factory 140-150 MHz range unit originally? I see plenty of the 100-watt (I think they're a TLD-1692) amps that are factory 2-Meter range PA decks (I have a few spares, in case I ever need them) but haven't ever seen a factory 140-150 range 1/4 KW PA. I know they do exist, and a few people have them. I just haven't found one, or found anyone who can move the 150-170 MHz range units down to 2-Meters. Thanks and 73, LJ -Original Message- From: Kevin Custer Sent: Jul 30, 2010 6:25 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Tim, I have a two meter repeater that outputs 250 watts (approximately +54 dBm) into the duplexer. After the 93 dB of rejection that the duplexer provides for shear power reduction toward the receiver port, -39 dBm of transmitter power leaves the duplexer receiver port - headed toward the receiver. The repeater is a Motorola MICOR VHF equipped with a MICOR preamp. Bench sensitivity is -125 dBm for 12 dB SINAD. The duplexer is a stock Wacom WP-641. This repeater normally uses a tube type power amplifier to achieve the 250 watt level. Using the tube power amp, no desense occurs on the repeater. I also have a the stock 110 watt MICOR power amplifier (solid state) that can be switched in. The repeater has a slight amount of desense when running the solid state PA. Why? It's obviously not the shear amount of power, as it has been reduced over 3 dB. The culprit is transmitter side-band noise. The solid-state power amplifier provides no additional protection of the amount of transmitter side-band noise being produced by the exciter, in fact, being wide-band in nature, the solid-state unit amplifies the noise. The tube power amplifier, however, is a High Q (very narrow band - tuned to the exact transmit frequency) device only providing power gain on the 'desired' repeater output frequency, and reducing (or at least not amplifying) the transmitter side-band noise appearing on the receiver frequency. From your explanation below, I don't believe shear power is ruining your ability to duplex, but rater the amount of transmitter side-band noise reaching the receiver. To prove this, install a notch cavity in the transmit leg tuned to the receiver frequency. If your duplexer isn't capable of allowing the present radio equipment to properly duplex, either the duplexer needs replaced, or you can change the type of transmitter to something else - no, I'm not suggesting tube-type. General Electric built a VHF exciter that has 22 dB less transmitter side band noise (600 kHz from its primary carrier) than most multiplier counterparts (like your Motorola MICOR). Using it is like installing a 22 dB notch filter between the exciter (transmitter) and receiver where side-band noise is concerned. This exciter is the MASTR II PLL. To comment on the folks privately emailing you telling you a MICOR receiver cannot handle an off frequency carrier of -53 - they are full of it - period. The answer is HOW CLEAN the adjacent frequency signal is. If the adjacent carrier is full of noise, and that noise falls on the frequency the receiver is listening to - then no the receiver can't handle it, but that's a totally different thing ruining your lunch - comparing apples to oranges. Hope this helps... Kevin Custer Hi guys, Took some time away from the project... loosing too many hairs. Ok, I've gotten another receiver strip, and it has the specified sensitivity per Mot. Guess I want to bounce some ideas around with those of you who are more learned in the arts! With 250mW (+24dBm) into the transmit port... antenna port is a quality 50 ohm load, I see -72dBM at the receiver port. (pretty much what I expect.. 1.8dB loss through the xmit side, 100dB notch through the RX side. With it all hooked up receiving an input signal of about 0.7uV, application of the 250mw to the transmitter side will cause noise in the receiver, although not much. So, it appears that if I add an additional 30dB notch (another 'can'), the problem at high power may go away. If I compare what 50 watts with an additional can would be (-130dB) to what I get with 250mW current notch (100dB), then it looks like I just need to add an additional can. 50 w = +47dBm - 130dB future notch = -83dBm at receiver. 250mw = +24 - 100dB current notch = -76dBm With the current notch @ 50 watts, I see a receive signal of -53dBm. Some have said that the Micor can handle that, while others (off-line) have said no way. This setup appears to support the opinion that -53 is still way too much. Any comments and thoughts would be most appreciated! Thanks, Tim
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Jeff, Thanks for the reality check... loved the real-world example of the mobile unit. At this point, I'm leaning towards the bad mojo/karma phase of the moon! Got a 'spare' set of low-band cans that need to be stored somewhere it's warm? :-) Thanks, Tim
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
Jeff, You did an excellent job of explaining the complex interrelationships among 2m repeaters. However, not all 6m repeaters have a 1 MHz split; my 6m repeater on Tranquillon Peak follows the California band plan and has a 500 kHz split. The duplexer has four cans about 12 in diameter and five feet tall. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jeff DePolo Sent: Friday, July 30, 2010 7:30 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Repeater transmit levels at the receiver? snip How many thousands of 2m repeaters are out there running 100 watts at 600 kHz offset without desense? Let's be generous and say they have 100 dB of isolation in the duplexer. +50 dBm TPO - 100 dB = -50 dBm transmit carrier hitting the receiver. No big deal. And that's on 2m. The offset on 2m is only 0.4% (0.6 MHz / 146 MHz), whereas on 6m, it's 1.9% (1 / 53 MHz), making isolation requirements that much more stringent on 2m. Now let's look at a 6m example. You have a 6m repeater on a 1 MHz split? Let's say it's on 53.99-, highest channel in the band, putting your receiver on 52.99. Some other ham is working simplex on 52.525, using 100 watts into a unity-gain antenna, and he's 40 miles away. His signal into your receiver, assuming unity gain on your end too, and line-of-sight, is -53 dBm (that's what the free-space path loss works out to: 103 dB for 40 miles on 6m, check my math). Would you expect this guy 40 miles away talking on 525 to desense your repeater? If so, then you should expect *every* ham who transmits on 525 (or potentially any other frequency within 1 MHz of your receiver) within a 40 mile radius of your repeater to cause you desense; those that are closer than 40 miles are just going to desense it even worse. snip --- Jeff WN3A
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Tim wrote: Hi Kevin, Thanks for the info. I've used the PLL MastrII exciter on a couple of systems also. Now, since this duplexer is of the 'notch' variety, I already have about 100db of notch (on the TX side) that is tuned to the RX freq. Shouldn't this be enough? Yes, 100 dB of duplexer isolation should be plenty - something is obviously a amiss. How dirty is the transmitter (spectral purity)?
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
On 7/30/2010 10:15 AM, Kevin Custer wrote: Tim wrote: Hi Kevin, Thanks for the info. I've used the PLL MastrII exciter on a couple of systems also. Now, since this duplexer is of the 'notch' variety, I already have about 100db of notch (on the TX side) that is tuned to the RX freq. Shouldn't this be enough? Yes, 100 dB of duplexer isolation should be plenty - something is obviously a amiss. How dirty is the transmitter (spectral purity)? I'd also look for other signal paths, leaky jumpers, ground loops, poor shielding... -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Larry - I didn't. The 250 watts is produced by a GE MASTR Pro/II 4EF5A1 capable of 330 watts continuous. The MICOR high-band tube amplifier, IMHO, is junk compared to the GE 4CX250R based VHF power amplifier. The 4EF5A1 is designed to operate from 144 to 174 MHz. without modification. Obtaining proper drive for it was the fun part. Read all about it here: http://www.kuggie.com/ahra/hmft.html Pictures of it here: http://www.kuggie.com/ahra/hmft.html Kevin Kevin - how did you get the MICOR 250 Watt VHF Amplifier to go down to 2-Meters? Or was it a factory 140-150 MHz range unit originally? I see plenty of the 100-watt (I think they're a TLD-1692) amps that are factory 2-Meter range PA decks (I have a few spares, in case I ever need them) but haven't ever seen a factory 140-150 range 1/4 KW PA. I know they do exist, and a few people have them. I just haven't found one, or found anyone who can move the 150-170 MHz range units down to 2-Meters. Thanks and 73, LJ
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi as do most european 6mtr repeaters, 500Kc split 73 Steve - Original Message - From: Eric Lemmon wb6...@verizon.net To: Repeater-Builder@yahoogroups.com Sent: Friday, July 30, 2010 3:57 PM Subject: RE: [Repeater-Builder] Repeater transmit levels at the receiver? Jeff, You did an excellent job of explaining the complex interrelationships among 2m repeaters. However, not all 6m repeaters have a 1 MHz split; my 6m repeater on Tranquillon Peak follows the California band plan and has a 500 kHz split. The duplexer has four cans about 12 in diameter and five feet tall. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jeff DePolo Sent: Friday, July 30, 2010 7:30 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Repeater transmit levels at the receiver? snip How many thousands of 2m repeaters are out there running 100 watts at 600 kHz offset without desense? Let's be generous and say they have 100 dB of isolation in the duplexer. +50 dBm TPO - 100 dB = -50 dBm transmit carrier hitting the receiver. No big deal. And that's on 2m. The offset on 2m is only 0.4% (0.6 MHz / 146 MHz), whereas on 6m, it's 1.9% (1 / 53 MHz), making isolation requirements that much more stringent on 2m. Now let's look at a 6m example. You have a 6m repeater on a 1 MHz split? Let's say it's on 53.99-, highest channel in the band, putting your receiver on 52.99. Some other ham is working simplex on 52.525, using 100 watts into a unity-gain antenna, and he's 40 miles away. His signal into your receiver, assuming unity gain on your end too, and line-of-sight, is -53 dBm (that's what the free-space path loss works out to: 103 dB for 40 miles on 6m, check my math). Would you expect this guy 40 miles away talking on 525 to desense your repeater? If so, then you should expect *every* ham who transmits on 525 (or potentially any other frequency within 1 MHz of your receiver) within a 40 mile radius of your repeater to cause you desense; those that are closer than 40 miles are just going to desense it even worse. snip --- Jeff WN3A Yahoo! Groups Links
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Tim it should be plenty, what about the notch on,the rx side, which I assume is tuned to reject the tx freq. Steve - Original Message - From: Tim tahr...@swtexas.net To: Repeater-Builder@yahoogroups.com Sent: Friday, July 30, 2010 4:42 PM Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Hi Kevin, Thanks for the info. I've used the PLL MastrII exciter on a couple of systems also. Now, since this duplexer is of the 'notch' variety, I already have about 100db of notch (on the TX side) that is tuned to the RX freq. Shouldn't this be enough? Tim Yahoo! Groups Links
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Steve, Both sides are exhibiting pretty much the same specs - about a 100dB notch (each side tuned to the opposite freq), and about 1.5dB attenuation at the desired freq. All cables are new RG142. Something's gotta be bad wrong if a 250mW input on the TX side will make noise. Using the Micor's exciter - about 270mW. Cannot see any spurs/noise within 80dB of the main carrier. Tim
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Kevin - Thanks for the clarification. I have one of those 1/4 KW VHF MICOR Repeaters in my garage, and wish I could get it to move down to 2-Meters. We have a local government agency that has one on 151 MHz, the sticker (the Motorola sticker that says ___ ua = ___ watts) on the inside of the cabinet says that it's doing 430 watts output! We always thought that one would be fun to move to 2-Meters on a simplex channel, but moving it there would be nearly impossible. LJ -Original Message- From: Kevin Custer Sent: Jul 30, 2010 8:38 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Larry - I didn't. The 250 watts is produced by a GE MASTR Pro/II 4EF5A1 capable of 330 watts continuous. The MICOR high-band tube amplifier, IMHO, is junk compared to the GE 4CX250R based VHF power amplifier. The 4EF5A1 is designed to operate from 144 to 174 MHz. without modification. Obtaining proper drive for it was the fun part. Read all about it here: http://www.kuggie.com/ahra/hmft.html Pictures of it here: http://www.kuggie.com/ahra/hmft.html Kevin Kevin - how did you get the MICOR 250 Watt VHF Amplifier to go down to 2-Meters? Or was it a factory 140-150 MHz range unit originally? I see plenty of the 100-watt (I think they're a TLD-1692) amps that are factory 2-Meter range PA decks (I have a few spares, in case I ever need them) but haven't ever seen a factory 140-150 range 1/4 KW PA. I know they do exist, and a few people have them. I just haven't found one, or found anyone who can move the 150-170 MHz range units down to 2-Meters. Thanks and 73, LJ
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Tim that should work fine, very strange. As a matter of interest how far apart are the tx and rx units and I take it all the covers and screening cans are fitted.. Steve
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Tim wrote: Using the Micor's exciter - about 270mW. Cannot see any spurs/noise within 80dB of the main carrier. I wonder Most of the MICOR exciters I have converted to 6M result in more than 270 mW of power - in fact, 400 to 600 mW is common. I wonder if something is amiss at the exciter, like a bad crystal or stage not peaked correctly generating noise. If you have a 6M hand-held or mobile rig capable of transmitting on your repeater output frequency, try substituting it for the MICOR and see what happens to your receiver with one of these transmitting instead. Kevin
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Actually, the output is about +26dBm, so it's closer to 400mW. I've also tried a VX-5 on low power, and got the same result. Tim On 7/30/2010 9:52 AM, Kevin Custer wrote: Tim wrote: Using the Micor's exciter - about 270mW. Cannot see any spurs/noise within 80dB of the main carrier. I wonder Most of the MICOR exciters I have converted to 6M result in more than 270 mW of power - in fact, 400 to 600 mW is common. I wonder if something is amiss at the exciter, like a bad crystal or stage not peaked correctly generating noise. If you have a 6M hand-held or mobile rig capable of transmitting on your repeater output frequency, try substituting it for the MICOR and see what happens to your receiver with one of these transmitting instead. Kevin
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Kev would it be feasable to use a sig gen cranked right up ? Steve - Original Message - From: Kevin Custer kug...@kuggie.com To: Repeater-Builder@yahoogroups.com Sent: Friday, July 30, 2010 5:52 PM Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Tim wrote: Using the Micor's exciter - about 270mW. Cannot see any spurs/noise within 80dB of the main carrier. I wonder Most of the MICOR exciters I have converted to 6M result in more than 270 mW of power - in fact, 400 to 600 mW is common. I wonder if something is amiss at the exciter, like a bad crystal or stage not peaked correctly generating noise. If you have a 6M hand-held or mobile rig capable of transmitting on your repeater output frequency, try substituting it for the MICOR and see what happens to your receiver with one of these transmitting instead. Kevin Yahoo! Groups Links
Re: Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Agree on the MSTR PRO 4EF5A1. Had one in service on the amateur band (VHF HI) and it ran withoout a burp for 8 years. Would like to find another one to use with the MASTR II. David Jul 30, 2010 03:39:08 PM, Repeater-Builder@yahoogroups.com wrote: Larry - I didn't. The 250 watts is produced by a GE MASTR Pro/II 4EF5A1 capable of 330 watts continuous. The MICOR high-band tube amplifier, IMHO, is junk compared to the GE 4CX250R based VHF power amplifier. The 4EF5A1 is designed to operate from 144 to 174 MHz. without modification. Obtaining proper drive for it was the fun part. Read all about it here: http://www.kuggie.com/ahra/hmft.html Pictures of it here: http://www.kuggie.com/ahra/hmft.html Kevin Kevin - how did you get the MICOR 250 Watt VHF Amplifier to go down to 2-Meters? Or was it a factory 140-150 MHz range unit originally? I see plenty of the 100-watt (I think they're a TLD-1692) amps that are factory 2-Meter range PA decks (I have a few spares, in case I ever need them) but haven't ever seen a factory 140-150 range 1/4 KW PA. I know they do exist, and a few people have them. I just haven't found one, or found anyone who can move the 150-170 MHz range units down to 2-Meters. Thanks and 73, LJ
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
You did an excellent job of explaining the complex interrelationships among 2m repeaters. However, not all 6m repeaters have a 1 MHz split; my 6m repeater on Tranquillon Peak follows the California band plan and has a 500 kHz split. The duplexer has four cans about 12 in diameter and five feet tall. 73, Eric Lemmon WB6FLY Even at 500 kHz split, 100+ dB is more than enough isolation on channel center on 6m. Using simple frequency scaling (not to say that's truly the way to compare, but it gives a rough approximation), that would be like 1.4 MHz split on 2m with the same (100 dB) isolation. 500 kHz on 6m is about 0.9%, still more than twice as much as 0.4% on 2m with 600 kHz split. --- Jeff WN3A
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
At this point, I'm leaning towards the bad mojo/karma phase of the moon! Let's start out with the basics: 1. How much desense do you have? 2. How are you injecting the Rx signal, and what are you using for the signal source? 3. What are you using for a dummy load when doing the desense test? 4. Have you look at both the Tx and the Rx LO to confirm neither are spurious? 5. For the heck of it, have you tried using a totally different Tx and Rx (even just using ham mobile rigs, you have 100 dB of isolation which should make even ham rigs play without desense on the bench, though I'd never use them in production). 6. If do #5, and you still have desense, try flipping Tx and Rx frequencies and see if you still have desense, it might help point to a problem on one side of the duplexer versus the other (e.g. something on the Tx leg generating noise which ceases to be a problem when you're not passing high-level RF through that leg when you have the frequencies flipped). --- Jeff WN3A
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Steve wrote: Hi Kev would it be feasable to use a sig gen cranked right up ? Depends on how clean the signal generator is. I'd think it doesn't have enough smoke (output capability) to really be beneficial Many generators have a strong carrier (here we go again) adjacent from the desired carrier by few, several, many kHz/MHz. Also, depending on make/model, it may not be as clean (spurious emissions) as a tuned circuit (read MICOR exciter). I wonder how many of the -53 naysayers have or have used a Cushman CE-3? LOL! The folks that have looked at the output of one of these on a spectrum analyzer will get it. K
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Tim wrote: Actually, the output is about +26dBm, so it's closer to 400mW. Good - that's more like it. I've also tried a VX-5 on low power, and got the same result. Obviously, something is wrong with the operation of your duplexer or interconnecting cabling. I really don't think it's providing the isolation you believe it is... Can you explain in detail how you are determining the notch depth of the duplexer. Also, what exactly are you using for the components of the duplexer? If it's the coax stub type, which article have you followed? Thanks, Kevin
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi was just a thought, I use a Marconi 2015 with the synth unit and that is pretty clean, be interesting to see what Tim,s problem is Steve - Original Message - From: Kevin Custer kug...@kuggie.com To: Repeater-Builder@yahoogroups.com Sent: Friday, July 30, 2010 9:50 PM Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Steve wrote: Hi Kev would it be feasable to use a sig gen cranked right up ? Depends on how clean the signal generator is. I'd think it doesn't have enough smoke (output capability) to really be beneficial Many generators have a strong carrier (here we go again) adjacent from the desired carrier by few, several, many kHz/MHz. Also, depending on make/model, it may not be as clean (spurious emissions) as a tuned circuit (read MICOR exciter). I wonder how many of the -53 naysayers have or have used a Cushman CE-3? LOL! The folks that have looked at the output of one of these on a spectrum analyzer will get it. K Yahoo! Groups Links
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
I think they use that spec trace on the opening of the tv show Fraser _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer Sent: Friday, July 30, 2010 4:51 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Repeater transmit levels at the receiver? Steve wrote: Hi Kev would it be feasable to use a sig gen cranked right up ? Depends on how clean the signal generator is. I'd think it doesn't have enough smoke (output capability) to really be beneficial Many generators have a strong carrier (here we go again) adjacent from the desired carrier by few, several, many kHz/MHz. Also, depending on make/model, it may not be as clean (spurious emissions) as a tuned circuit (read MICOR exciter). I wonder how many of the -53 naysayers have or have used a Cushman CE-3? LOL! The folks that have looked at the output of one of these on a spectrum analyzer will get it. K
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
I wonder how many of the -53 naysayers have or have used a Cushman CE-3? LOL! The folks that have looked at the output of one of these on a spectrum analyzer will get it. K Where I come from, we call that a comb generator, not a signal generator... Ya gotta know the limitations of your test equipment. I recently went several rounds via telephone with a friend of mine who was trying to troubleshoot an apparent desense problem on the bench involving a Mastr II and a 6-cavity DB Products duplexer that I had tuned up for him on the VNA. Long story short, it turned out that when he was doing the desense test using his service monitor (R2600?) as the dummy load and signal source simultaneously that the sig gen would go spurious and result in apparent desense. When he finally did a lossy tee test using an external dummy load, no desense, and likewise when hooked up to the antenna at the site, no desense. --- Jeff WN3A
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
Sounds like someone has been watching The EnforcerMr Eastwood.every man has got to know his limitations? Soory could not resist!! D On 30/07/2010 22:35:35, Jeff DePolo (j...@broadsci.com) wrote: I wonder how many of the -53 naysayers have or have used a Cushman CE-3? LOL! The folks that have looked at the output of one of these on a spectrum analyzer will get it. K Where I come from, we call that a comb generator, not a signal generator... Ya gotta know the limitations of your test equipment. I recently went several rounds via telephone with a friend of mine who was trying to troubleshoot an apparent desense problem on the bench involving a Mastr II and a 6-cavity DB Products duplexer that I had tuned up for him on the VNA. Long story short, it turned out that when he was doing the desense test using his service monitor (R2600?) as the dummy load and signal source simultaneously that the sig gen would go spurious and result in apparent desense. When he finally did a lossy tee test using an external dummy load, no desense, and likewise when hooked up to the antenna at the site, no desense. --- Jeff WN3A Yahoo! Groups Links
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi Kevin, Yes, the original used RG-58.. couldn't see using it. Figured it would give me desense! As far as the amount of notch, I was surprised that the total was more than each one added, but with 50 watts coming out of the antenna port, I see -55dBm at the RX port. - kinda made me think the original measurements were ok. I cut them to 35 each. (visible coax showing between each end of the PL-259). Not exactly to length. Might affect performance a bit. Tim
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Tim wrote: Hi Kevin, Yes, the original used RG-58.. couldn't see using it. Figured it would give me desense! As far as the amount of notch, I was surprised that the total was more than each one added, Don't be - it's common for the apparent notch to be deeper than the measured addition of individual cavities - added together. Don't be fooled, the depth was there the whole time (no black magic here), it just wasn't all being realized in the test set-up. Proper interconnect cable lengths can do a bunch for notch depths. but with 50 watts coming out of the antenna port, I see -55dBm at the RX port. - kinda made me think the original measurements were ok. What you see coming out the RX port depends on several factors: How good the match of the attached equipment is - at the frequency being tested, and the phase angle of the connecting cable. Other factors play a part too, but these two play the bigger part. I cut them to 35 each. (visible coax showing between each end of the PL-259). Not exactly to length. Might affect performance a bit. I wouldn't have chosen UHF connectors for building the duplexer. IMHO, their construction leaves a lot to be desired when trying to optimize a duplexer for maximum performance, unless you take their inherent flaws into consideration when using them. Wacom built a good duplexer which uses UHF connectors, but they actually used those properties to their advantage. 35 inches, plus the amount inside the connector results in approximately 37-1/2 inches of interconnecting cable. From my calculations, I have extrapolated your optimum notch depth to appear on 54.44 MHz. I believe, with RG-142 coax, that a length longer than 38 inches will be needed, depending on your exact frequency. From your photo, I believe some of your problem to be the UHF connector and how you have it mounted. A solid ground all around the connector is important to achieve a low impedance (low inductive reactance) connection. I have always preferred the Utah Cap approach for building the Heliax duplexer. It allows you to realize most/all of the potential of the stub. The thicker the copper (within reason) the better. Also - it looks like you might be using only one connector per stub. If this is true, and you are using a UHF tee connector with the stub - it won't work as expected. The electrical length of the tee will throw the whole thing off - this might be your biggest problem with your design/construction. Kevin
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
Hi guys, Took some time away from the project... loosing too many hairs. Ok, I've gotten another receiver strip, and it has the specified sensitivity per Mot. Guess I want to bounce some ideas around with those of you who are more learned in the arts! With 250mW (+24dBm) into the transmit port... antenna port is a quality 50 ohm load, I see -72dBM at the receiver port. (pretty much what I expect.. 1.8dB loss through the xmit side, 100dB notch through the RX side. With it all hooked up receiving an input signal of about 0.7uV, application of the 250mw to the transmitter side will cause noise in the receiver, although not much. So, it appears that if I add an additional 30dB notch (another 'can'), the problem at high power may go away. If I compare what 50 watts with an additional can would be (-130dB) to what I get with 250mW current notch (100dB), then it looks like I just need to add an additional can. 50 w = +47dBm - 130dB future notch = -83dBm at receiver. 250mw = +24 - 100dB current notch = -76dBm With the current notch @ 50 watts, I see a receive signal of -53dBm. Some have said that the Micor can handle that, while others (off-line) have said no way. This setup appears to support the opinion that -53 is still way too much. Any comments and thoughts would be most appreciated! Thanks, Tim
Re: [Repeater-Builder] Repeater transmit levels at the receiver?
On 7/23/2010 10:34 AM, tahrens301 wrote: Hi folks, Still working on the hardline duplexer for 6 meters, and have some data I'd like to run by you guys. Running 80 watts out of a Micor tx into the TX bank of cavities. With test equipment, get about 100dB notch. (shows 50 watts into dummy load as well).. have about 1.5 - 2dB loss through them. Ok, now I hook the spectrum analyzer up to the receiver port, and I see about -55dBm. 50 watts = +47dBm, minus the 100dB notch = -53dBm that is pretty close to what I'm seeing at the rx antenna port. This should be good enough. You probably want the TX freq well below -30 dBm or so.TX noise should be notched to at least 10 db below the noise floor at the RX frequency. IF the TX is a Micor or MASTRII of any stripe, 100 dB at teh RX frequency ought to be fine with margin. Question is: Should this good enough for a low band micor receiver? Thanks, Tim W5FN -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
RE: [Repeater-Builder] Repeater transmit levels at the receiver?
Ok, now I hook the spectrum analyzer up to the receiver port, and I see about -55dBm. 50 watts = +47dBm, minus the 100dB notch = -53dBm that is pretty close to what I'm seeing at the rx antenna port. Question is: Should this good enough for a low band micor receiver? Thanks, Tim W5FN Yes, should be good enough for even 500 kHz split. However, at close tx-rx offsets, transmitter noise is often more of an issue than carrier supression, so test your duplexer backwards to make sure you have the same isolation in the other direction. And don't forget the noise foor on 6m is usually pretty high, so even if you have a trace of desense on the bench using a dummy load and lossy tee, you may not even notice it in the field. --- Jeff WN3A
