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.

[neosmith20]

31 minutes ago, Flameout said:

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

like i had posted on another comment, i programmed all of my handy radios and know there is no 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. The antenna at the site is up much much higher than the roads i was traveling on. again, she heard me clear as water, but nothing from her. stupidly odd for sure! 
Just to make sure that there were no pl codes used we used a variety of simplex channels and still nothing from her, but clear as day from me to her.

[neosmith20]

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.

 

3 hours ago, KAF6045 said:

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.

 

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.