Batboard

Anyone having trouble with the impedance on some of these new digital pair gain PLPA circuits? Our Astro Tac receivers are unable to compensate for the line loss. Normal PLPA twisted pair copper works well for us, but SBC has decided to install our new site audio lines with this digital pair gain circuit and we are dead in the water. We are getting around -16db in loss per circuit and the Astro Tac simply won't compensate for that level like our older Spectra Tac receivers would. The phone company is now telling us it is our gear, though they changed the first circuit to the older style analog and it worked fine. We are now getting the run around by SBC as they tell us it has to be our equipments fault.

If anyone out there has dealt with this before we would love to hear how you handled it and what circuit types work best with Astro Tac audio lines.

Thanks.

SBC Huh? I've heard those letters stand for, String Between Cans and that says it all!

For Standard Analog = Telco RT2002 Circuits

For the Older 12Kb Securenet = Telco RT3002 Circuits
Typically these Telco lines have -16 dBm losses end-to-end.
These circuits also require /\/\ T5091A Digital Voice Modems at each end of the Telco circuit for Securenet operation.

For Astro / Astro-Secure Digital = Telco T1 Digital Circuits
You feed 0 dBm In, you'll get 0 dBm Out, if you feed -10 dbm In, you'll get -10 dBm Out. In other words the T1 Telco circuit lines are Flat ... no line losses end-to-end.

I've also encountered New Telco T1 Circuit Pairs down in Ft. Lauderdale, FL that were not lmplemented and tested correctly by the local Telco for End-To-End Losses. Everytime the Telco C.O. would Loop the lines up ... on a "T-Bird" piece of test equipment, it would appeared to the C.O. Telco technician that everything was within electrical specifications. When we would cut the Telco Lines back into the circuit via a DACCs, the MSO would not link up with the remote tower sites.

This drove 3 of us /\/\ engineers nuts for a couple weeks till the local Telco sent out a Senior Field Technician (almost ready to retire) and it took him a hour to get the circuits up and operating correctly. We inquired what the signal level was before he changed the signal gain. He responded, "I measured the signal at -22 dBm. "Hey, What's a few 'dB' among friends?" The end results came back to bite the local Telco. As you understand in a Telco circuit there are line losses so the Telco installs audio repeaters to boost their levels every so many miles.

The original repeaters in the past would automatically adjust the dBm signal gain of each Telco circuit. Some where along the line, Telco infamous Purchasing Department decided to buy a less expensive version of these repeater circuit coils. On these less expensive repeater circuit coils the Telco Field Technucians are suppose to manually measure and set the dBm signal gain to the appropriate levels.

The end result drives us Radio People crazy and up a wall because when all the Telcos downsizing happened, they let their most valuable technical employees go into early retirement. We're left with the imept management and technical service contractors that can barely read or write let alone know anything about Telco hardware or electrical specifications. These people only know about computers, software and cellphones but do not ask these people how it operates or better yet, "How to Fix their own problems!" Duh!

Telco's new and improved Digital PLPA Circuits with built-in -16 dBm signal attenuation ... such a deal! Refer to line one of this reply.

Dan

Just to update, we found that our PLPA circuits that used to represent copper pair from A end to Z end, no longer automatically mean copper pair all the way through. SBC has been slowly updating circuits as they run through the central office to digital pair gain. Unfortunately our Astro Tacs cannot increase audio level enough to compensate. In order to restore proper op for our Astro Tacs SBC hemmed and hawed, tried to blame ceiling current, and attempted daily to close our tickets without resolution before finally breaking down and installing Wescom adaptors. That did the trick. So if you are using Astro Tac receivers on PLPA and begin having attenuation issues on your circuits, see if your phone company is "upgrading" your lines to digital somewhere in the path.

Dan562 wrote:Typically these Telco lines have -16 dBm losses end-to-end.

Dan- DAN - it's "16 dB losses end to end".

"dBm" is an ABSOLUTE POWER LEVEL MEASUREMENT and not a ratio. "dB" is a ratio like "10 dB of loss" or "20 dB of gain".

Thanks Dan for all your technical efforts BTW.

Jim