Re: [Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
I've been told that stainless steel is alot weaker that the original tower bolts. 73, Joe, K1ike Chuck Kelsey [EMAIL PROTECTED] wrote: That's why I pitch the cheap, plated bolts that come with the tower sections and use stainless steel ones instead. The zinc plated ones would be rusty about a year later. Chuck WB2EDV - Original Message - From: Frank R. Vondra [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, August 23, 2005 9:56 PM Subject: [Repeater-Builder] Re: Induced RF on tower - May cause desense, too? We experienced a similar situation with an VHF repeater two years ago. The culprit was traced down to rusty bolts on the Rohn 25 tower. Tapping on the tower legs with a large hammer would make the problem go away for a short period of time, but it would return in a few weeks or days. Finding and replacing the bolts cured the problem. Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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] Re: Induced RF on tower - May cause desense, too?
Yes you need to keep that in mind. I know the bolts that are on my tower came with grade 5. keep that in mine. I don't know if SS comes in grade 5. - Original Message - From: Joe [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Wednesday, August 24, 2005 7:57 AM Subject: Re: [Repeater-Builder] Re: Induced RF on tower - May cause desense, too? I've been told that stainless steel is alot weaker that the original tower bolts. 73, Joe, K1ike Chuck Kelsey [EMAIL PROTECTED] wrote: That's why I pitch the cheap, plated bolts that come with the tower sections and use stainless steel ones instead. The zinc plated ones would be rusty about a year later. Chuck WB2EDV - Original Message - From: Frank R. Vondra [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, August 23, 2005 9:56 PM Subject: [Repeater-Builder] Re: Induced RF on tower - May cause desense, too? We experienced a similar situation with an VHF repeater two years ago. The culprit was traced down to rusty bolts on the Rohn 25 tower. Tapping on the tower legs with a large hammer would make the problem go away for a short period of time, but it would return in a few weeks or days. Finding and replacing the bolts cured the problem. Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
I've wondered if induced signals into the tower may be causing a problem with the 2M repeater I have been working with lately. I've not seen a spark from induced signals yet, but suspect something is resonant and being re-radiated causing a problem. The 2M repeater was running on a brand new Celwave PD-340-3. I've tried several other antennass and have the same problem. The repeater is a pair of GM-300's back to back, running around 35 W out of XMIT, going into 8 inch 4 cav duplexer by Wacom. Into the dummy load, no desense, no duplex noise (I use superflex for all jumpers and Heliax to the antenna). The antenna was top mounted at 150 feet of Rohn 25G. Normally, the repeater would work fine. No problems until early morning or at night. Mainly in early morning hours, the repeater would desense itself up to 20 dB, make all kinds of garbage noises like popping and crackling, it almost sounded like someone was on the tower taking two screwdrivers and rubbing them together next to the antenna! Yet nothing on the tower is loose, and shaking the guy wires when the repeater is actually acting normal doesn't cause noise. I have even heard video buzz coming out of the receiver. When I kill the transmitter, all noise goes away and the receive signal is quiet. There is a Ch 6 TV tower about 15 miles from me. There are two pagers 152.480 and 158.700 about 1 mile from me. Other than that, the tower is in a remote area far away from saturated RF generators. Like I said, the repeater works fine duplexed to the same antenna most of the time, just under certain conditions (like enhanced tropo) does it mess up. I can't find out what's doing it. I finally wound up using dual antennas, dropping the TX antenna down 30 feet from the RX, and it works like a charm. Could the tower have induced currents and signals coming in and energizing something causing a mix? The separation is 600 KHz and I don't know of any strong AM stations on that frequency except for a 640 KHz station 5 watts and 30 miles away. Guess I'll have to keep running dual antennas until I figure out what's wrong? 73, KC4FWC Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
Duplexer generated possibly... Reads like arc type pitting inside the duplexer. Take a slow speed drill and run the duplexer tune shafts up and down through their range a number of times. Hopefully the plunger finger stock will knock off or polish off/down the pit/arc spot enough. Don't know if Wacom uses threaded tune shafts like Telewave and others... but you get the idea. After you've used the plunger finger stock as a cleaner, retune and try the duplexer and see if the problem goes away... been there done that... Two or three things cause it... one is no lightning or disharge protection on the antenna. The most common problem is often traced back to extended cavitiy plunger movement (tune up and mechanical vibration) at high power into non perfect conditions... but not exclusive to... good luck, skipp www.radiowrench.com/sonic kc4fwc [EMAIL PROTECTED] wrote: I've wondered if induced signals into the tower may be causing a problem with the 2M repeater I have been working with lately. I've not seen a spark from induced signals yet, but suspect something is resonant and being re-radiated causing a problem. The 2M repeater was running on a brand new Celwave PD-340-3. I've tried several other antennass and have the same problem. The repeater is a pair of GM-300's back to back, running around 35 W out of XMIT, going into 8 inch 4 cav duplexer by Wacom. Into the dummy load, no desense, no duplex noise (I use superflex for all jumpers and Heliax to the antenna). The antenna was top mounted at 150 feet of Rohn 25G. Normally, the repeater would work fine. No problems until early morning or at night. Mainly in early morning hours, the repeater would desense itself up to 20 dB, make all kinds of garbage noises like popping and crackling, it almost sounded like someone was on the tower taking two screwdrivers and rubbing them together next to the antenna! Yet nothing on the tower is loose, and shaking the guy wires when the repeater is actually acting normal doesn't cause noise. I have even heard video buzz coming out of the receiver. When I kill the transmitter, all noise goes away and the receive signal is quiet. There is a Ch 6 TV tower about 15 miles from me. There are two pagers 152.480 and 158.700 about 1 mile from me. Other than that, the tower is in a remote area far away from saturated RF generators. Like I said, the repeater works fine duplexed to the same antenna most of the time, just under certain conditions (like enhanced tropo) does it mess up. I can't find out what's doing it. I finally wound up using dual antennas, dropping the TX antenna down 30 feet from the RX, and it works like a charm. Could the tower have induced currents and signals coming in and energizing something causing a mix? The separation is 600 KHz and I don't know of any strong AM stations on that frequency except for a 640 KHz station 5 watts and 30 miles away. Guess I'll have to keep running dual antennas until I figure out what's wrong? 73, KC4FWC Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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] Re: Induced RF on tower - May cause desense, too?
VERY interesting. I have a VHF repeater that is doing the same thing (intermittent bouts of noise that sounds like a bad connection / micro-arc). I've been blaming it on the very old Phelps Dodge PD220 antenna... which it may well be in my case. What I am curious about here is that in both cases (the originator of this thread and my mystery system) it is fine into a dummy load, only acting up on the antenna. Do you still suspect the duplexer? Perhaps slightly different impedance of the antenna vs. the dummy load is enough to cause the problem to occur? I have a replacement for the antenna, but if that doesn't cure it I will have to start looking for new suspects! Paul N1BUG On Tuesday 23 August 2005 12:20 pm, skipp025 wrote: Duplexer generated possibly... Reads like arc type pitting inside the duplexer. Take a slow speed drill and run the duplexer tune shafts up and down through their range a number of times. Hopefully the plunger finger stock will knock off or polish off/down the pit/arc spot enough. Don't know if Wacom uses threaded tune shafts like Telewave and others... but you get the idea. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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] Re: Induced RF on tower - May cause desense, too?
At 8/23/2005 09:20 AM, you wrote: Duplexer generated possibly... Not likely: of XMIT, going into 8 inch 4 cav duplexer by Wacom. Into the dummy load, no desense, no duplex noise (I use superflex for all jumpers and Heliax to the antenna). The antenna was top mounted at 150 Works fine on a dummy load, so the problem is after the duplexer. Using Superflex jumpers, so no copper-braided coax problem. tower taking two screwdrivers and rubbing them together next to the antenna! Yet nothing on the tower is loose, and shaking the guy wires when the repeater is actually acting normal doesn't cause noise. I have even heard video buzz coming out of the receiver. Got any security cameras at the site? Wouldn't explain the scratchies but I've had problems with those too. 38th harmonic of 15.75 kHz horizontal sync = 598.5 kHz, mixes with output to land on input. Also check other antennas near yours. I've had nearby Stationmasters with internally broken elements cause major scratchies on my 2 meter system. Just send someone up the tower to shake each nearby stick individually while listening for the noise. Bob NO6B Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
I've had the same problem caused by an old station master. We swapped it out and the new antenna fixed the problem I thought the original post mentioned the unit worked fine on the same antenna split... which is not really a true test... but it leads me toward the plunger arcing test/tune first. Testing the antenna with strong wind moving it around quite a bit would be the best first choice for checking the station master. skipp Paul Kelley [EMAIL PROTECTED] wrote: VERY interesting. I have a VHF repeater that is doing the same thing (intermittent bouts of noise that sounds like a bad connection / micro-arc). I've been blaming it on the very old Phelps Dodge PD220 antenna... which it may well be in my case. What I am curious about here is that in both cases (the originator of this thread and my mystery system) it is fine into a dummy load, only acting up on the antenna. Do you still suspect the duplexer? Perhaps slightly different impedance of the antenna vs. the dummy load is enough to cause the problem to occur? I have a replacement for the antenna, but if that doesn't cure it I will have to start looking for new suspects! Paul N1BUG On Tuesday 23 August 2005 12:20 pm, skipp025 wrote: Duplexer generated possibly... Reads like arc type pitting inside the duplexer. Take a slow speed drill and run the duplexer tune shafts up and down through their range a number of times. Hopefully the plunger finger stock will knock off or polish off/down the pit/arc spot enough. Don't know if Wacom uses threaded tune shafts like Telewave and others... but you get the idea. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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] Re: Induced RF on tower - May cause desense, too?
In my case, what worries me is the problem seems to be worse in a gentle breeze than a strong wind. About half the time shaking the antenna seems to produce the problem and the other half it doesn't. It is nearly always breezy at the site which leads to a certain ambiguity on that test. I guess I will see what happens when I swap out the antenna. The original post did say it worked OK on split antennas, but also mentioned it worked OK into a dummy load (I assume he meant connected at the antenna port of the duplexer, but I don't think that was specifically stated). Paul N1BUG On Tuesday 23 August 2005 02:28 pm, skipp025 wrote: I've had the same problem caused by an old station master. We swapped it out and the new antenna fixed the problem I thought the original post mentioned the unit worked fine on the same antenna split... which is not really a true test... but it leads me toward the plunger arcing test/tune first. Testing the antenna with strong wind moving it around quite a bit would be the best first choice for checking the station master. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
If it's a regular event in a light wind, I'd go after the antenna first. You'd be able to test for the antenna problem without the transmitter on. The reactance back from the antenna might also contribute toward problems in a duplexer. I've got one really cranky UHF duplexer that's pretty much unusable in a specific section of the band. Any reflected power from even a good antenna caused the attached repeater system to growl with intermod about 40% of the time. As you rotate the tune plunger through it's range, you can feel and hear the finger stock hit the pitted section. I got the duplexer from FLorida in one of those great Ebay Deals we all hear about... I assume the duplexer has seen more than one nearby high energy discharge in it's day. cheers, skipp Paul Kelley [EMAIL PROTECTED] wrote: In my case, what worries me is the problem seems to be worse in a gentle breeze than a strong wind. About half the time shaking the antenna seems to produce the problem and the other half it doesn't. It is nearly always breezy at the site which leads to a certain ambiguity on that test. I guess I will see what happens when I swap out the antenna. The original post did say it worked OK on split antennas, but also mentioned it worked OK into a dummy load (I assume he meant connected at the antenna port of the duplexer, but I don't think that was specifically stated). Paul N1BUG On Tuesday 23 August 2005 02:28 pm, skipp025 wrote: I've had the same problem caused by an old station master. We swapped it out and the new antenna fixed the problem I thought the original post mentioned the unit worked fine on the same antenna split... which is not really a true test... but it leads me toward the plunger arcing test/tune first. Testing the antenna with strong wind moving it around quite a bit would be the best first choice for checking the station master. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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] Re: Induced RF on tower - May cause desense, too?
That's why I pitch the cheap, plated bolts that come with the tower sections and use stainless steel ones instead. The zinc plated ones would be rusty about a year later. Chuck WB2EDV - Original Message - From: Frank R. Vondra [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Tuesday, August 23, 2005 9:56 PM Subject: [Repeater-Builder] Re: Induced RF on tower - May cause desense, too? We experienced a similar situation with an VHF repeater two years ago. The culprit was traced down to rusty bolts on the Rohn 25 tower. Tapping on the tower legs with a large hammer would make the problem go away for a short period of time, but it would return in a few weeks or days. Finding and replacing the bolts cured the problem. Yahoo! Groups Links Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
We experienced a similar situation with an VHF repeater two years ago. The culprit was traced down to rusty bolts on the Rohn 25 tower. Tapping on the tower legs with a large hammer would make the problem go away for a short period of time, but it would return in a few weeks or days. Finding and replacing the bolts cured the problem. Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
[Repeater-Builder] Re: Induced RF on tower - May cause desense, too?
Yes the repeater does work well with split antennas, no problems now except for reduced TX coverage and a nice null towards the tower opposite from the side mount.. Yes the dummy load was connected to the antenna port of the duplexer, simulating the antenna. I am believing the antenna is near a perfect 50 ohm match because the VWSR is excellent and of course the PD-340-3 is made for the 140-150 band. I even have an isolator in line with the transmitter to reduce the chances if stray signals coming back down the antenna line and mixing with components in the PA. I also don't think it's the duplexer making noise because it's nearly new, or at least it was one of the last models made by Wacom (so what, several years old?) When running full power and injecting a signal through a Bird directional coupler, I can wiggle and shake all duplexer interconnect cables, bang the plungers around and beat the dummy load and not get any duplex noise. I had the antenna on the ground laying on some plastic saw horses. Dumped 100 watts into the thing and wiggled all the phasing harness outputs and nothing. Took the old PD-220-2 Stationmaster and did the same thing, flopped it back and forth a dozen times, not and squeak or crack. Nothing loose on the tower. Isolators on all other transmitters at the site.. Only does it when conditions are right. Beats me. Mysterious garbage floating in the air. Thanks for replies, 73, KC4FWC The original post did say it worked OK on split antennas, but also mentioned it worked OK into a dummy load (I assume he meant connected at the antenna port of the duplexer, but I don't think that was specifically stated). Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * 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/
