spectra tac voter issue.

[efc]

Hi guys, got a situation which I think I know the answer to but just wanted extra input. Her it is:

1.2 site Spectra tac voter, one site local the other remote.
2. 13 db system,wide band. I set up both sites,-13 db tone and 0db audio,at 5khc dev. full quite.
3. When a unit is 800 feet away from the local site, the remote site votes and of course sounds worse,because of the distance.
4. When near the remote sit, the local votes up,and of course the local sounds worse.

5 Her is what I am thinking, since the receivers check out,levels are good, and this worked at one time,of course as usual they tell me it has been doing this for awhile,that I need a roofing filter at the local site, and that the newly repaired remote copper wire must have some kind of audio response issue.
What do you guys think?
As always, thanks for the great input.

[efc]

Got a follow up question to the original,are there any other ways to to test the freq. response to the phone line other than relying on the phone co.I am thinking maybe using a tone gen. from say 300 to 3khz and measuring the other end.

Thanks

[Bill_G]

I have a couple comments and a couple questions.

I normally set up Spectra-TACs with a -10db input for 3.3khz dev with the status tone being 13db below that. Your input may be too high, and thus too much noise is being applied to the SQM even with a fully quieted signal.

You can make your own "roofing filter" with a series .01uf cap and a 1200 ohm resistor across the phone line input to the SQM.

What model rcvrs are you using, and do they have adjustable equalization for their wireline (ala MTR2K)?

Do you use a TMS set to measure your levels, and if so, does it show dbrnc? That will give you the basic noise characteristics of a phone ckt. Otherwise, you'll need to sweep the lines with pink noise, and look at the response curve with an audio spectrum analyzer.

[efc]

Thanks Bill, lets see if I can answer these:

1. Remote site is a spectra tac Rx, which is down and I have had to set up a temp rx. with a ptg-10 for the 2175.We have new eqiup.to go in,but we are waiting on the cust.
2.Local rx is an MSR 2000.

3. I am using a Telephone test set,the name escapes me now,which is calibrated and works well.

4.The levels that I have used to set, was taught years ago by 2 retired radio techs who got the info out of the spectra tac voter manual.I have had succes for years now with this setup,I dont think the characteristics of the phone lines have changed, but who knows.Youcannot really do DC on the phone lines around here anymore, but still I dont think that is the issue.

5.sometime when the local site is voted, the remote site votes,which does not make sense because you can clearly hear that the sig. is bad. I did go by again today and check jumpers per the book and all seemed good.

Thanks again.

[Bill_G]

Voters work with high freq noise above 3k. When there is less noise in the upper band, you get inappropriate voting. You won't see the required noise with your tel test set because it's geared towards 1004. Your levels will look great at test tone, but you'll have no idea what the impulse noise level is.

You said the original Micor rcvr is down, and you have a temp rcvr in place along with a tone generator. Where are you getting the rx audio to send to the voter? If you are using a mobile and pulling off the spkr audio, it will have greater rolloff in the upper band, less high freq noise, and thus the problem you are experiencing. The telco may or may not be contributing to the problem as well.

The solution is to introduce some additional rolloff at the local rcvr input to see if that improves things. Again, a .01uf and a 1200 ohm resistor is a good starting place. You may have to adjust values by experimentation.

Hope that helps.

[efc]

Bill,thanks for the input.I do understand everything.The audio that I am pulling off is on the rear accessory connector.I wonder if it would behoove[spelling?] me to put into place the tac rx. that they will be receiving which is a Kenwood tkr 740,and the the pilot tone gen.Yea, I guess with less noise, that site will appear as a"quite" line, when actually that is not the best site to vote.

Thanks again for your help

[Bill_G]

You're welcome John. You can do it with mobiles like a Maxtrac. The gated audio out is rich enough to run a voter. You just need to roll your own line driver. Let us know how you resolve the problem.