Re: [Repeater-Builder] Static on grounded feed line system.
A good gadget for doing this is a simple capacitor testerlike made by
Heathkit and many others. Set the capacitor tester for "ceramic and mica" and
"leakage test" and connect the antenna side of the Polyphaser to the
tester-the radio side should be disconnected. Now, turn up the test voltage
while watching the magic eye or whatever your tester uses as an indicator. The
commonly used gas tube or button in most arrestors will break down around 230
volts or so but arrestors are offered with buttons down to 90 volts and much
higher than 230. A typical capacitor tester is a very high resistance device in
the ceramic / mica leakage test mode and no damage to the gas cell is likely
but be careful not to test in the electrolytic mode---arrester cells are
designed to pass very high current for a couple of microseconds, usually
without damage, but I don't know just what one can stand more or less
continuously.
The series blocking capacitor used in some arrestors can also be tested with
the capacitor tester---just connect to the radio side of the arrester with the
antenna side shorted. I suggest that you use caution here though--I can't
remember a guaranteed voltage rating on the blocking cap. ---better look it up
before testing.
Scott, N6NXI
- Original Message -
From: Gary Schafer
To: Repeater-Builder@yahoogroups.com
Sent: Friday, April 04, 2008 1:26 PM
Subject: RE: [Repeater-Builder] Static on grounded feed line system.
You need a HI-pot tester to check the protection devices. You crank up the
voltage until they show a breakdown and see if it is breaking down at the
proper voltage for the device. It will not harm them at all as the current is
only a few micro amps..
Polyphaser used to market a small test set they called the FIST. They may
still have it?? It was a small automatic hi-pot tester with a meter that read
out in Kv. The voltage would rise to the breakdown point and stop. You read the
meter for the breakdown voltage.
73
Gary K4FMX
--
From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of
Radioman
Sent: Friday, April 04, 2008 8:49 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Static on grounded feed line system.
I replace the Polyphasers at the sites I'm responsible for every two years,
or sooner if a direct strike is suspected. Just because they pass RF OK doesn't
mean they're still doing the job efficiently. I believe it is cheap insurance
even it means replacing a half dozen or more at one site.
I have recently heard that there is a new series on the market which may not
require replacing except after a direct strike. I need to do more research on
those. Maybe someone here has info on those?
Harry, W0OZL
- Original Message -
From: Paul Plack
To: Repeater-Builder@yahoogroups.com
Sent: Friday, April 04, 2008 1:45 AM
Subject: RE: [Repeater-Builder] Static on grounded feed line system.
Sorry for being a few days behind on e-mail, but...don't those gas tubes
need replacing eventually? Maybe after 8 years, they've given all once too many
times to stay on the job.
RE: [Repeater-Builder] Static on grounded feed line system.
You need a HI-pot tester to check the protection devices. You crank up the voltage until they show a breakdown and see if it is breaking down at the proper voltage for the device. It will not harm them at all as the current is only a few micro amps.. Polyphaser used to market a small test set they called the FIST. They may still have it?? It was a small automatic hi-pot tester with a meter that read out in Kv. The voltage would rise to the breakdown point and stop. You read the meter for the breakdown voltage. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Radioman Sent: Friday, April 04, 2008 8:49 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Static on grounded feed line system. I replace the Polyphasers at the sites I'm responsible for every two years, or sooner if a direct strike is suspected. Just because they pass RF OK doesn't mean they're still doing the job efficiently. I believe it is cheap insurance even it means replacing a half dozen or more at one site. I have recently heard that there is a new series on the market which may not require replacing except after a direct strike. I need to do more research on those. Maybe someone here has info on those? Harry, W0OZL - Original Message - From: Paul Plack <mailto:[EMAIL PROTECTED]> To: Repeater-Builder@yahoogroups.com Sent: Friday, April 04, 2008 1:45 AM Subject: RE: [Repeater-Builder] Static on grounded feed line system. Sorry for being a few days behind on e-mail, but...don't those gas tubes need replacing eventually? Maybe after 8 years, they've given all once too many times to stay on the job.
RE: [Repeater-Builder] Static on grounded feed line system.
Harry, You don't see Polyphaser arrestors used much in commercial radio or cellular phone systems, because the gas tubes are soldered in place and not easily replaceable. I prefer to use Huber+Suhner devices, not only because the gas tubes are easily replaceable, but also because the devices are watertight and machined from stainless steel. Go here for info: These are available through commercial radio supply houses like Tessco, Talley, and Hutton. They are not cheap! 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Radioman Sent: Friday, April 04, 2008 5:49 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Static on grounded feed line system. I replace the Polyphasers at the sites I'm responsible for every two years, or sooner if a direct strike is suspected. Just because they pass RF OK doesn't mean they're still doing the job efficiently. I believe it is cheap insurance even it means replacing a half dozen or more at one site. I have recently heard that there is a new series on the market which may not require replacing except after a direct strike. I need to do more research on those. Maybe someone here has info on those? Harry, W0OZL
Re: [Repeater-Builder] Static on grounded feed line system.
I replace the Polyphasers at the sites I'm responsible for every two years, or sooner if a direct strike is suspected. Just because they pass RF OK doesn't mean they're still doing the job efficiently. I believe it is cheap insurance even it means replacing a half dozen or more at one site. I have recently heard that there is a new series on the market which may not require replacing except after a direct strike. I need to do more research on those. Maybe someone here has info on those? Harry, W0OZL - Original Message - From: Paul Plack To: Repeater-Builder@yahoogroups.com Sent: Friday, April 04, 2008 1:45 AM Subject: RE: [Repeater-Builder] Static on grounded feed line system. Sorry for being a few days behind on e-mail, but...don't those gas tubes need replacing eventually? Maybe after 8 years, they've given all once too many times to stay on the job.
RE: [Repeater-Builder] Static on grounded feed line system.
Sorry for being a few days behind on e-mail, but...don't those gas tubes need replacing eventually? Maybe after 8 years, they've given all once too many times to stay on the job. 73, Paul, AE4KR _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of wa5luy Sent: Tuesday, April 01, 2008 8:25 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Static on grounded feed line system. Our repeaters are located on a 200 foot self supporting tower at the top of a 1200 foot mountain. Anytime there is a storm with in 50 miles we get a lot of pulsing static on the 2 meter repeater which is a Micor. This is not noticeable on the 440 repeater. We hear this when the receiver is open from a signal and when the repeater identifies with the receiver squelched. The antenna is a DB 224 fed with 7/8 hard line. The tower is self supporting. All this was installed by a professional tower company. The tower is about 8 years old and appears to be well grounded. The 7/8 hard lines outer shields are grounded to the base of the tower then continues 30 feet to the inside of the building. There are gas tube protectors between the feed lines and duplexers. My question is grounding the outer shield to the tower a good practice? Also any other suggestions as to where to look for this problem.
Re: Re: [Repeater-Builder] Static on grounded feed line system.
Curt, I've also found some low noise pre-amps that have little tuning and are wide band can be zapped by static and lightning. The transistors used are for low level signals of course and can have problems dealing with sources like lightning. Lightning energy has the RF properties of pretty flat DC to 1 MHz and then roll off at a 20 db/decade rate. So as you go higher in freq the less energy. Also as with any wide band signal the energy is spread over wide range. I can see you inserting a band pass cavity or filter will remove much of this energy reducing the affect on a pre-amp. 73, ron, n9ee/r >From: Curt Seaton <[EMAIL PROTECTED]> >Date: 2008/04/01 Tue PM 09:51:21 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: [Repeater-Builder] Static on grounded feed line system. > >Something else to consider is what we experienced on our two and 440 >repeaters. Our 440 has a stationmaster type of antenna into the >duplexer into a preamp then into the Micor repeater. Most of the >electrical storms we had caused me to go to the site to replace the >preamp transistor. After many trips, I installed a single bandpass type >low insertion loss cavity between the duplexer and the preamp. That was >3 years ago... Then I found out that most all duplexers don't really >offer broadband selectivity, they do their main job of notching out the >appropriate frequencies to allow the repeater to do it's job, but then >several MHz away, the signals start slowly coming back in. Remember >lightning is quite broadband and strong. Our two meter repeater had a >bandpass in it's path also. It is my suggestion that in addition to the >all the appropriate grounding of the feedline that you may consider a >real band pass type of cavity (may be easier than to use a shorted stub >and more broadband) which has two independent loops in the cavity. >Sharpness is NOT needed here, so go for the lowest insertion loss and >let the loops do their static/lightning rejection... > >Good luck > >Curt W1FSM > >wa5luy wrote: >> Our repeaters are located on a 200 foot self supporting tower at the >> top of a 1200 foot mountain. Anytime there is a storm with in 50 miles >> we get a lot of pulsing static on the 2 meter repeater which is a >> Micor. This is not noticeable on the 440 repeater. We hear this when >> the receiver is open from a signal and when the repeater identifies >> with the receiver squelched. >> >> >> >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
Re: [Repeater-Builder] Static on grounded feed line system.
Something else to consider is what we experienced on our two and 440 repeaters. Our 440 has a stationmaster type of antenna into the duplexer into a preamp then into the Micor repeater. Most of the electrical storms we had caused me to go to the site to replace the preamp transistor. After many trips, I installed a single bandpass type low insertion loss cavity between the duplexer and the preamp. That was 3 years ago... Then I found out that most all duplexers don't really offer broadband selectivity, they do their main job of notching out the appropriate frequencies to allow the repeater to do it's job, but then several MHz away, the signals start slowly coming back in. Remember lightning is quite broadband and strong. Our two meter repeater had a bandpass in it's path also. It is my suggestion that in addition to the all the appropriate grounding of the feedline that you may consider a real band pass type of cavity (may be easier than to use a shorted stub and more broadband) which has two independent loops in the cavity. Sharpness is NOT needed here, so go for the lowest insertion loss and let the loops do their static/lightning rejection... Good luck Curt W1FSM wa5luy wrote: > Our repeaters are located on a 200 foot self supporting tower at the > top of a 1200 foot mountain. Anytime there is a storm with in 50 miles > we get a lot of pulsing static on the 2 meter repeater which is a > Micor. This is not noticeable on the 440 repeater. We hear this when > the receiver is open from a signal and when the repeater identifies > with the receiver squelched. > > > >
Re: [Repeater-Builder] Static on grounded feed line system.
To WN3A..I'd like to tune in to this interesting conversation. What frequency stub are you referring to? Please be a little more specific on which side of DC ground arrestor. Thanks, Gary K2UQ **Create a Home Theater Like the Pros. Watch the video on AOL Home. (http://home.aol.com/diy/home-improvement-eric-stromer?video=15&ncid=aolhom000301)
RE: [Repeater-Builder] Static on grounded feed line system.
> My question is grounding the outer shield to the tower a good > practice? Most definately. There should be a ground kit at the top of the run ABOVE the hoisting grip (if one is used), one at the bottom of the run before it makes a horizontal bend, and at the entrance bus bar. If the cable is longer than 200' there will be additional hosting grips along the length (typically at no more than 200' intervals), and there should be a ground kit about 10' ABOVE each hoisting grip. > Also any other suggestions as to where to look for this problem. What kind of duplexer are you using? If it is a type that doesn't provide a DC short through the coupling loops, you might want to add a shorted quarterwave stub before your existing gas discharge tube arrestor. --- Jeff WN3A
Re: [Repeater-Builder] Static on grounded feed line system.
> At 4/1/2008 07:25, you wrote: > > >> Our repeaters are located on a 200 foot self supporting tower at the >> top of a 1200 foot mountain. Anytime there is a storm with in 50 miles >> we get a lot of pulsing static on the 2 meter repeater which is a >> Micor. This is not noticeable on the 440 repeater. We hear this when >> the receiver is open from a signal and when the repeater identifies >> with the receiver squelched. Try this: http://www.repeater-builder.com/antenna/static.html Kevin
Re: [Repeater-Builder] Static on grounded feed line system.
According to Motorola R-56 standards a 200 foot tower requires the coax to be grounded at the top and the bottom using a coax ground kit. If the run from the tower to the building entrance is greater than 20 feet the coax should be grounded at the entrance to the building as well. The coax inside the building should be fitted with surge suppresors (polyphasers or equivalent) within 2 feet of the entrance port. The polyphasers and all equipment grounds should be connected to a single point ground at the entrance panel. If there is a "halo" ground it should connect to the single point ground bus. It is recommended today that the halo ground NOT be a complete loop but be open for about 1 foot at the opposite end of the halo loop. Non equipment items (door frames, cable tray, cabinets, metal louvers, doors, etc) should be connected to the halo or the single point ground bus which ever is the shortest run. Motorola's R-56 manual is an excellent standard and tutorial on the professional way to properly ground and bond a communications site. I worked for Motorola for 18 years installing communications buildings and equipment. If you have any questions about grounding I will try to help. Bill - WA0CBW **Create a Home Theater Like the Pros. Watch the video on AOL Home. (http://home.aol.com/diy/home-improvement-eric-stromer?video=15&ncid=aolhom000301)
Re: [Repeater-Builder] Static on grounded feed line system.
At 4/1/2008 07:25, you wrote: >Our repeaters are located on a 200 foot self supporting tower at the >top of a 1200 foot mountain. Anytime there is a storm with in 50 miles >we get a lot of pulsing static on the 2 meter repeater which is a >Micor. This is not noticeable on the 440 repeater. We hear this when >the receiver is open from a signal and when the repeater identifies >with the receiver squelched. > >The antenna is a DB 224 fed with 7/8 hard line. What type of feedline are you using between the 7/8 & antenna? (I assume it's not directly connected) Bob NO6B
[Repeater-Builder] Static on grounded feed line system.
Our repeaters are located on a 200 foot self supporting tower at the top of a 1200 foot mountain. Anytime there is a storm with in 50 miles we get a lot of pulsing static on the 2 meter repeater which is a Micor. This is not noticeable on the 440 repeater. We hear this when the receiver is open from a signal and when the repeater identifies with the receiver squelched. The antenna is a DB 224 fed with 7/8 hard line. The tower is self supporting. All this was installed by a professional tower company. The tower is about 8 years old and appears to be well grounded. The 7/8 hard lines outer shields are grounded to the base of the tower then continues 30 feet to the inside of the building. There are gas tube protectors between the feed lines and duplexers. My question is grounding the outer shield to the tower a good practice? Also any other suggestions as to where to look for this problem.
