Repeater equipment having trouble RXing from members TXing to it...

[neosmith20]

Hello all,

So, i have a bridgecom (BCR-40U) repeater with a "XLT Communications GMRS Mobile Duplexer (50 Watt)" from buytwowayradios.com. I am using around 35-45ft of LMR-400 cable and that is going to a "Harvest BC-200U" antenna. The site that all of this is setup at puts my antenna up around 200ft from the ground. I originally had an ed fong antenna (DBJ - UHF) at the site, but was finding out that we were getting horrible signal reception to/from the site. I ended up changing that out to the bc200u antenna and thought that would take care of the issue.

Doing radio checks we are only getting around a 5 mile radius from the repeater site. It should be covering much much more area than that. I can not for the life of me figure out why the repeater equipment is having such a bad issue. I have made sure that the repeater is aligned and the duplexer was tuned before it was shipped to me. this is bugging the crap out of me and the club members are not too happy that this new setup isn't working very well.

I had tested the setup with another antenna that was at the site, from another gmrs repeater that was there at the time (it was in the process of being taken down before mine came in) and was getting amazing results, that's why i ended up trading out the ed fong antenna to the bc200u one. It only made a slight difference, if any.

I called bridgecom to try and get some help, i did what they suggested, but to no avail.

Does anyone have any ideas that could help fix this situation?

I have had nothing but theories about why this is happening, but everything i have tried doing to fix the situation so far has made no change.

[OffRoaderX]

I would focus the duplexer first - i've had those inexpensive ones fail on me..

Try removing the duplexer, and if possible put the repeater in base-station/simplex mode and see how well it transmits and receives.  

[Radioguy7268]

The most simple way to troubleshoot a repeater is to start with the basics. If you can, follow OffroaderX's suggestion and set up a simplex mobile radio (or temporarily reprogram the repeater as a simplex base - disable the repeat function). Connect the "base" radio directly to the antenna - forget about the duplexer for now. Get a helper to take a radio out to the current 5 mile edge of the system range.

Test the transmit function to a distant mobile. You should get the same range (assuming power level is the same as the repeater). If your range increases - need to look at the duplexer and cabling.

Now test receive function from that distant mobile. You should be able to receive from a similar distance as you could transmit to. If your receive range improves from what you saw with the repeater - you need to take a look at the duplexer and cabling.

I have seen more bad cables than I've seen bad duplexers.

Your story about the system working well with the other previous antenna makes me wonder if you were using the same duplexer and cables for that setup. Have you measured VSWR for the antenna system? Do you have the ability to sweep the antenna? That Harvest antenna is tunable - was it set for GMRS when you ordered it? What frequency was it supposed to be set to?

Don't just guess at what's wrong. Measure & test so that you know what is working and what seems to introduce trouble when you add it to the mix.

[Sshannon]

“Sweeping the antenna” means taking a series of SWR readings throughout the desired frequency range.  By doing this you can see the SWR for the antenna throughout the range and where the antenna has the lowest SWR. You say you have a NanoVNA so you have the tool for the job.  Be sure and calibrate the NanoVNA to that frequency range first, using a the no-load, short, and 50 ohm devices that came with the NanoVNA.  

 

[Radioguy7268]

5 hours ago, neosmith20 said:

after I tuned the repeater closer to the correct freq. and changed out the antenna i figured that it would work just fine.

It's nearly impossible to troubleshoot a system you've never seen from a thousand miles away, but please explain what you did to "tune the repeater closer to the correct freq." ??  There's not much tuning that I'm aware of with a Bridgecom repeater. Were you trying to bring the repeater closer to frequency center on transmit? Just how far had it drifted??

If the setup worked fine (repeater + duplexer) with one antenna system, and then you changed out to another antenna system - it would certainly seem that your new antenna system is suspect. However, I'm curious why you would have needed to "tune the repeater closer to the correct freq." if your range testing with the old antenna system was producing stellar results.

What connectors are you using on the LMR400 cable? Was that cable new or used? How hard would it be to swap out the cable? What condition are the duplexer jumper cables in?

Heliax is "better" than LMR400  - but for a 35-40 ft run, it should be marginal - especially when new. That Harvest antenna probably has an SO-239 UHF connector, and the DB404 would have had a Type N. Type N is "better" - but again it's not a night & day difference maker. What connections are on your duplexer? Do you have a surge protector or lightning arrestor in the mix?

For all the internet stories about duplexers going bad just sitting there, I haven't really ever seen it in the real world. Unless an elephant stepped on it, Zeus hit it with a lightning bolt, or Mike's Magic Golden screwdriver tried to field tune it, then it just kept on working. What I have seen is cheap cables with tin plated connectors deteriorating within a few years and causing all kinds of headaches that get attributed to a bad duplexer.

 

[OffRoaderX]

1 hour ago, Radioguy7268 said:

For all the internet stories about duplexers going bad just sitting there, I haven't really ever seen it in the real world. Unless an elephant stepped on it, Zeus hit it with a lightning bolt, or Mike's Magic Golden screwdriver tried to field tune it, then it just kept on working. 

I had a XLT Communications Mobile Duplexer (50 Watt) go bad just sitting there after using it for about 3 days.. Confirmed and replaced by the vendor.

[Radioguy7268]

I would be curious to know what component of a notch duplexer failed. Unless something cracked or corroded, there's just not much to go wrong inside a tuned cavity.

[Sshannon]

15 minutes ago, neosmith20 said:

So i took my repeater down today and hooked one of my handheld radios to the feedline and I'm thinking that there is a problem with the feedline. The antenna is new, so it has to be the feedline. When i transmitted out on simplex others could hear me, but when they transmitted back to me, i heard nothing.

I'm still going to check over the duplexer and repeater, but i think the problem has been found.

I will post with any updates i have.

I’m confused. Were you transmitting through the duplexer with your handheld?

Otherwise I’m not sure how an antenna and feed line allow transmission but block reception. 
Did you have a receive tone set and tone squelch turned on? 

[Radioguy7268]

How did the other user have their radio set up to respond to you? Normal function on a repeater channel is that the portable would listen on 462.xxx, but transmit on 467.xxx

If you go to Simplex, your portable is now transmitting and receiving on 462.xxx

Unless the other user switched their radio to simplex also - they would still be transmitting on 467.xxx and of course your portable that's listening on 462.xxx would not hear them.

As Sshannon mentioned above - there aren't many scenarios where an antenna line would be passing transmit, but blocking receive.

I'd put money on the distant user still transmitting on the high side of the split at 467.xxx

[KAF6045]

If it was a cable problem, I'd expect problems in both directions. Same for an antenna problem. However, a problem at the cable/antenna connection could result in a dead antenna, and high SWR putting a radiating signal on the OUTSIDE of the coax. (I managed to open squelch on a D-Star repeater located a few miles south of me using an Icom ID52 -- that was still set for SLO [100mW -- less than the GMRS/FRS 500mW channels]. So if you had a radiating coax it may still have put out enough signal to be heard, but not receive.)

My first approach -- start with an antenna analyzer that covers UHF range. And you probably won't like this -- start at the antenna itself, using something like a 1-3 foot coax from analyzer to antenna. Verify antenna SWR/resonance in the 462Mhz end (preferably your actual repeater output frequency; you aren't going to get both 462 and 467MHz to be resonant, and somewhat high SWR on the 467 receive shouldn't be deadly unless by some chance it is really obscene [historical meaning: out of sight ]).

If the antenna checks out, and with coax disconnected at both ends [disconnect ground end before you climb the tower, so you can do this while on the tower and have that end disconnected for the antenna test -- use the analyzer to determine open-ended cable length ("distance to fault" or similar check; you will need to know the cable velocity factor to compute electrical length vs physical length).

If cable (fault) length is appropriate for the real cable -- no open or shorted fault in the middle -- reconnect cable to antenna and go back to ground level. Recheck SWR/resonance of the cable&antenna link. You might want to compute how many wavelengths of your target frequency fit the (electrical) length of the coax -- there can be "weird" behavior at certain multiples of quarter or half wave where SWR looks great (or terrible) because of interaction of reflected wave with forward wave. I'd have to dig up my ARRL handbooks to find the exact relationship.

Note: while I refer to SWR, actual Forward and Reflected power levels may be more indicative along with the ratio.

 

[gortex2]

I'd start with a cheap watt meter on a radio and feedline. As I say over and over thats the most important part of any system. 

[hfd376]

Thanks for posting your saga. It will be helpful for others in the future with their future repeater endeavors. Are there some amateur radio operators that you could reach out to? One or some them might have the level of test gear needed to troubleshoot and get the system where it should be. There is a YouTube video I'm following that has the same issue, is that yours?

 

 

 

 

 

 

 

 

[Sshannon]

8 hours ago, neosmith20 said:

So, a quick check with the nanovna on the duplexer showed that the notches for the high and low (467.650/462.650) where pretty much none existent. I tuned it back, as close as one could with a nanovna, but i will be calling buy two way radios tomorrow to see what can be done about the duplexer being out of tune yet again. if i have to send it back this would be the second time doing so. I believe there is a 1 year warranty on it, so it should be covered either way.

 

This still doesn't explain what the heck is going on with the feedline/antenna problem. That seems to be a separate issue. As easy as it won't be, I'll have to see what i can do to complete the tests that were suggested.

I don't have an antenna analyzer, but i am doing some research and am hoping that i can do some-most of those tests with the nanovna.

A NanoVNA is an antenna analyzer. Not a high end one perhaps, but capable of basic SWR measurements. Just be sure to calibrate it to the frequencies you’re interested in.

[Radioguy7268]

I'd also be checking  your antenna feedline for continuity. What you described with the ability to transmit, but not receive, could potentially be caused if you have a VERY slight gap between the coax and the connector - effectively creating  your own iso-tee. That's why people ring out their connectors when they're done installing them. With your adapters on each end, that possibility becomes a bit more likely.

[KAF6045]

12 hours ago, neosmith20 said:

I don't have an antenna analyzer, but i am doing some research and am hoping that i can do some-most of those tests with the nanovna.

Most VNA's do more than antenna analyzers. Though the manual https://nanovna.com/?page_id=64 isn't the most clear it appears to support setting cable velocity factor, and can detect short/open distance. You have to fiddle with stop frequency to adjust for "length".

[neosmith20]

1 hour ago, OffRoaderX said:

I would focus the duplexer first - i've had those inexpensive ones fail on me..

Try removing the duplexer, and if possible put the repeater in base-station/simplex mode and see how well it transmits and receives.  

Sadly I have been thinking that it was the duplexer as well.

I will see what I can do to accomplish your idea. I'm really hoping that it's not the duplexer, but if it is then i should be able to contact buy two way radios to see what they can offer for support.

Thanks for the help! I'll report back when i get that accomplished!

[neosmith20]

23 minutes ago, Radioguy7268 said:

The most simple way to troubleshoot a repeater is to start with the basics. If you can, follow OffroaderX's suggestion and set up a simplex mobile radio (or temporarily reprogram the repeater as a simplex base - disable the repeat function). Connect the "base" radio directly to the antenna - forget about the duplexer for now. Get a helper to take a radio out to the current 5 mile edge of the system range.

Test the transmit function to a distant mobile. You should get the same range (assuming power level is the same as the repeater). If your range increases - need to look at the duplexer and cabling.

Now test receive function from that distant mobile. You should be able to receive from a similar distance as you could transmit to. If your receive range improves from what you saw with the repeater - you need to take a look at the duplexer and cabling.

I have seen more bad cables than I've seen bad duplexers.

Your story about the system working well with the other previous antenna makes me wonder if you were using the same duplexer and cables for that setup. Have you measured VSWR for the antenna system? Do you have the ability to sweep the antenna? That Harvest antenna is tunable - was it set for GMRS when you ordered it? What frequency was it supposed to be set to?

Don't just guess at what's wrong. Measure & test so that you know what is working and what seems to introduce trouble when you add it to the mix.

When i tried out that other antenna (the one being decommissioned) the difference was the cable and of course the antenna itself. The cable, i believe, was heliax, not sure what diameter, and the antenna was an "Andrew DB408-B." Other than that, i was using the same duplexer and of course the same bridgecom repeater as i'm currently using. It could be the cable, not sure how it could, but that's always a possibility!

When i hooked the currently used antenna up to a swr meter i am showing 1.00 - 1.02 and 99.99% transmit power. That's tested with the meter being from the duplexer to the meter to the antenna with the lmr400 cable i have setup at the site.

The antenna i am using now was already tuned for gmrs from the person i got it from. he was running a repeater in the mountains for a little over a year and didn't have any problems. He's a member of the club and thought that it would fix the problem i was having after the first install, so he was nice enough to donate it to me.

I'm not sure what you mean by "Do you have the ability to sweep the antenna?" Please school me on what that means.

I'm trying hard not to guess what is wrong, after I tuned the repeater closer to the correct freq. and changed out the antenna i figured that it would work just fine. I did test the setup at my house before it was all installed at the site and everything ran just fine. Of course that was inside, with lower output power and just testing. So, i figured that i could install it at the site and everything would be good.

I have an sdr and a NanoVNA i could use to do testing, if any of those would help the cause... but, i am thinking that it's the duplexer. I'm really trying to save myself from having to send the repeater back to bridgecom a second time, in 6 months, for them to look over it and tell me that everything is fine.

[neosmith20]

On 6/25/2022 at 5:56 AM, Radioguy7268 said:

It's nearly impossible to troubleshoot a system you've never seen from a thousand miles away, but please explain what you did to "tune the repeater closer to the correct freq." ??  There's not much tuning that I'm aware of with a Bridgecom repeater. Were you trying to bring the repeater closer to frequency center on transmit? Just how far had it drifted??

If the setup worked fine (repeater + duplexer) with one antenna system, and then you changed out to another antenna system - it would certainly seem that your new antenna system is suspect. However, I'm curious why you would have needed to "tune the repeater closer to the correct freq." if your range testing with the old antenna system was producing stellar results.

What connectors are you using on the LMR400 cable? Was that cable new or used? How hard would it be to swap out the cable? What condition are the duplexer jumper cables in?

Heliax is "better" than LMR400  - but for a 35-40 ft run, it should be marginal - especially when new. That Harvest antenna probably has an SO-239 UHF connector, and the DB404 would have had a Type N. Type N is "better" - but again it's not a night & day difference maker. What connections are on your duplexer? Do you have a surge protector or lightning arrestor in the mix?

For all the internet stories about duplexers going bad just sitting there, I haven't really ever seen it in the real world. Unless an elephant stepped on it, Zeus hit it with a lightning bolt, or Mike's Magic Golden screwdriver tried to field tune it, then it just kept on working. What I have seen is cheap cables with tin plated connectors deteriorating within a few years and causing all kinds of headaches that get attributed to a bad duplexer.

 

So, with the bridgecom repeater there is a temperature crystal in there that you can, software wise, adjust to bring the freq. back to center. With it being so hot it threw it out of center and was on the minus side of the actual freq... My thought was that since the duplexer was notched to a specific freq. that if the freq. wasn't centered correctly by the repeater, it wouldn't be correctly filtering the signals.

The setup wasn't working very well either with the ed fong antenna, the first antenna used with the setup, that's why we thought that if we switch out the antenna... it would fix the problem. When i used the db408-b it was like nothing was wrong with the setup and was getting great signal in places that previously had no signal or people couldn't hit the repeater from.

The antenna, and duplexer connections are 239, but i am using adapters to n-connectors.

The cable was bought brand new, as well as all of the connectors for the cable. I chose to use n connectors on the cable as that would have been easier for me to install at the site.

As for the surge protector, the repeater is protected by a server rack surge protector and I have the lightening arrestor, but have not been able to install it quite yet.

As for the duplexer not going bad... when i tested the one i have right after it was shipped to me, the first time, i found that it was not in tune. I then sent it back to buy two way radios and they were nice enough to get it set back to the correct freq... They also hot glued the tuning screws so that they wouldn't move during shipping back to me.

[neosmith20]

On 6/25/2022 at 2:25 AM, Sshannon said:

“Sweeping the antenna” means taking a series of SWR readings throughout the desired frequency range.  By doing this you can see the SWR for the antenna throughout the range and where the antenna has the lowest SWR. You say you have a NanoVNA so you have the tool for the job.  Be sure and calibrate the NanoVNA to that frequency range first, using a the no-load, short, and 50 ohm devices that came with the NanoVNA.  

 

I will have to give that a try and see what i find.
of course, i always re-calibrate it... every time i start it up and before i do anything. just in case.

[neosmith20]

On 6/25/2022 at 7:52 AM, OffRoaderX said:

I had a XLT Communications Mobile Duplexer (50 Watt) go bad just sitting there after using it for about 3 days.. Confirmed and replaced by the vendor.

What brand of duplexers have you found to be the best and cause less of a headache for you?

[KAF6045]

32 minutes ago, neosmith20 said:

The antenna, and duplexer connections are 239, but i am using adapters to n-connectors.

The cable was bought brand new, as well as all of the connectors for the cable. I chose to use n connectors on the cable as that would have been easier for me to install at the site.

Just out of curiosity, did you ever work out what effect the insertion losses on those N<>UHF adapters are? They shouldn't be too bad, but deliberately going from UHF to N at one end, just to convert back from N to UHF at the other, just because N was easier to route???

 

[neosmith20]

1 hour ago, KAF6045 said:

Just out of curiosity, did you ever work out what effect the insertion losses on those N<>UHF adapters are? They shouldn't be too bad, but deliberately going from UHF to N at one end, just to convert back from N to UHF at the other, just because N was easier to route???

 

I never planned on using a duplexer or anything that had 239 connections on them. My original plan and setup was two antennas, which had n connectors as well as the tx/rx for the repeater. So, i bought a bunch of n connectors, a few to see how they worked & how to install them on to the cable, and a few to make a couple of test cables. Then of course used some for the original setup. The antennas ended up not being spaced apart in a way that could not cause desensitization. So, a duplexer was looked at. I got a super cheap chinese duplexer from a member, but it never would tune properly and had problem after problem with it. During that time I also was trying to updated the firmware of the repeater and one of the radios locked up, thus the reason i had to send the repeater to bridgecom. While i was working on getting the money up for a new duplexer we ended up loosing the site we were at and i had to scramble to find a new one. Once i got the repeater back from bridgecom, and finally got up enough donations from members, i was able to get the (current) duplexer installed on the repeater and then setup at the new site (current location). After having troubles getting a good rx signal from members to the repeater it sat for a month or so while i tried to figure out how to get the ed fong antenna up higher. I ended up getting the current antenna from one of the members and was able to get that antenna up way higher than what i had the ed fong one at. This brings me to around a couple of weeks ago when, after the install of the new antenna, i was still hearing from members that they were having a hard time hitting the repeater. They would hit it, but then 1-3 seconds later it would just courtesy tone out, even when they were still talking. So to me, it sounded like people were kerchunking the repeater, but it was members trying to use it.

I have no clue what the losses on the adapters are, they were never tested. I never had a problem, for the short time i had the repeater up, at the first location. So, they were never tested.

Plus, hanging 17 stories up, it's not easy to solder a connection and not knowing exactly how much cable was going to be used... i couldn't just cut the cable add the connectors and send one side of the cable up. So, that was another reason i kept using the n connectors and just added the adapters to the duplexer and antenna.

[neosmith20]

So i took my repeater down today and hooked one of my handheld radios to the feedline and I'm thinking that there is a problem with the feedline. The antenna is new, so it has to be the feedline. When i transmitted out on simplex others could hear me, but when they transmitted back to me, i heard nothing.

I'm still going to check over the duplexer and repeater, but i think the problem has been found.

I will post with any updates i have.

[Flameout]

3 hours ago, neosmith20 said:

So i took my repeater down today and hooked one of my handheld radios to the feedline and I'm thinking that there is a problem with the feedline. The antenna is new, so it has to be the feedline. When i transmitted out on simplex others could hear me, but when they transmitted back to me, i heard nothing.

I'm still going to check over the duplexer and repeater, but i think the problem has been found.

I will post with any updates i have.

I'm pretty new at all of this and I am probably way off here, but I was not hearing any audio on my HT even though the power bar was showing I was receiving a strong signal. It ended up being that I had somehow had Rx-DCS on. Turned it off and all was good again

[neosmith20]

3 hours ago, Sshannon said:

I’m confused. Were you transmitting through the duplexer with your handheld?

Otherwise I’m not sure how an antenna and feed line allow transmission but block reception. 
Did you have a receive tone set and tone squelch turned on? 

sorry if i wasn't clear enough.
I took both the repeater and duplexer, which is attached physically to the repeater, down to connected directly to my handheld. both me and my g/f were on simplex with no pl tones/codes used.

[neosmith20]

1 hour ago, Radioguy7268 said:

How did the other user have their radio set up to respond to you? Normal function on a repeater channel is that the portable would listen on 462.xxx, but transmit on 467.xxx

If you go to Simplex, your portable is now transmitting and receiving on 462.xxx

Unless the other user switched their radio to simplex also - they would still be transmitting on 467.xxx and of course your portable that's listening on 462.xxx would not hear them.

As Sshannon mentioned above - there aren't many scenarios where an antenna line would be passing transmit, but blocking receive.

I'd put money on the distant user still transmitting on the high side of the split at 467.xxx

like it was stated i/we used simplex. so both me and my g/f were on 462.xxx, none of the repeater freq.s were used. i just wanted to test what someone said above, but first eliminating the repeater and duplexer. if that test went fine then it would point me to something wrong with the repeater or duplexer, but since i couldn't, for some odd reason rx her signal to me, that kinda of told me that it had to be either the feedline or the antenna. since the antenna is brand new, that lead me to believe it had to be the feedline.

"I'd put money on the distant user still transmitting on the high side of the split at 467.xxx"
The city i live in, we are the only people that use .650, there is one other repeater in the area and it is confirmed that he uses a different freq... as he's an old member where we setup his info on his repeater. Since then he moved on from the club, but never changed his freq. We were the first club to bring a gmrs repeater to the area and from what i can tell, there are no others that could even be close to being in the same freq. Denver would be the closest, but we have a mountainous area that is blocking us from them.

"If you go to Simplex, your portable is now transmitting and receiving on 462.xxx

Unless the other user switched their radio to simplex also - they would still be transmitting on 467.xxx and of course your portable that's listening on 462.xxx would not hear them."
I understand fully about repeater freq.s and simplex freq.s. I had her on the phone making sure that she was on simplex. I'm also the one that programmed the handy radios, so i know they dont have any codes on the simplex freq.s. I also verified this by using my mobile radio that i know 1000% has no codes programmed on any of the simplex freq.s. I was chatting with her on the way to the site and it worked just fine, until i got to a point where there was just too many things in the way while traveling. The antenna at the site though is up much much higher. It's stupidly weird that i could tx clear as day to her, but heard nothing from her. i even had her go outside, where i have hit me repeater clearly before, and still i got nothing from her. I even had her change channels to different simplex freq.s and it was the same on the all of the ones we tested... i could hit her nice and clear, but nothing from her.

The repeater was receiving, but at a very very limited range (5 miles tops is what we found). It should be receiving much further than what it is, especially being up as high as it is.