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Trbo rptr receive threashold chatter

Posted: Thu Dec 07, 2017 4:41 am
by Bill_G
In the Trbo repeater channel settings is a receive threashold setting. According to the help docs, if that level is qualified, it disables the station.
How quickly does that enable/disable take effect?
Does it effect calls in progress?
What do you think happens when the interference causes that detector to chatter many times a minute?

Re: Trbo rptr receive threashold chatter

Posted: Sun Jan 14, 2018 1:15 pm
by FatBoy
My experience is that it will not disable a call in progress. Also, I have never seen it activate many times per minute in rapid succession, so I have idea about the disable "hangtime" of that setting. Have you thought of lowering the threshold. selecting a different frequency, or reducing the priority of that frequency (if Cap Plus or LCP)? FB.

Re: Trbo rptr receive threashold chatter

Posted: Mon Jan 15, 2018 8:16 am
by Bill_G
Thanks FB. Unfortunately, they cannot escape the noise causing the chatter because it's across the band. It's a five site VHF IPSC with two of the sites nearly deaf from local desense on the order of 20db or more. I raised the programmed threashold to -80, or something redunkulas, forcing the station to ignore cochannel activity. Their license has exclusive use for a 50 mile radius. So, monitoring isn't necessary. Raising the threashold seemed to give their mobiles better opportunity to access the site, and the complaints stopped.

Re: Trbo rptr receive threashold chatter

Posted: Mon Jan 15, 2018 1:12 pm
by Astro Spectra
I set the threshold to -45dBm (as high as it will go) because the protection mechanism is wrong.

You're supposed to listen before transmission to avoid co-channel but in a two frequency system the repeater receiver is not listening to the transmitter frequency (and can't because of the duplexer) so the feature is pointless.

Re: Trbo rptr receive threashold chatter

Posted: Fri Jan 19, 2018 2:43 pm
by motorola_otaku
Bill_G wrote:It's a five site VHF IPSC with two of the sites nearly deaf from local desense on the order of 20db or more.

Just curious, is it colo'd with AT&T? I tried to run a 2 meter repeater on an AT&T colo site once and the noise floor was so bad I eventually had to take it down. I think there was another thread posted by a user here with the same issue.

Re: Trbo rptr receive threashold chatter

Posted: Sun Jan 21, 2018 4:36 am
by Bill_G
motorola_otaku wrote:
Bill_G wrote:It's a five site VHF IPSC with two of the sites nearly deaf from local desense on the order of 20db or more.

Just curious, is it colo'd with AT&T? I tried to run a 2 meter repeater on an AT&T colo site once and the noise floor was so bad I eventually had to take it down. I think there was another thread posted by a user here with the same issue.


Both sites are colo'd with multiple cellular providers including AT&T Cingular. They are in separate shelters, but on the towers.

Over the years, I've noticed the increased VHF noise floor coincided with cell carriers. The urban VHF noise floor is now at least -110dbm almost anywhere you build. If the rooftop suddenly sprouts a bunch of PTP wireless ethernet links, your footprint shrinks as the floor rises above -90dbm from all the unshielded CAT5 cable. If some lazy tech decides the mast you put up for the VHF base is an excellent place for his access point serving all the wireless cameras he put up to cover the yard, you can kiss the VHF receiver goodbye.

It's but slowly rising over time.