Batboard

I have a low band Syntor X9000. It is programmed with mostly public safety 42 MHz freqs. I usually scan about 4-6 channels.

Recently it began a wierd problem while scanning. The first thing I noticed what that I was recieving traffic from a channel that I did not have in my scan list (the channel is in the radio, just not in the scan list) and what makes it even wierder is that the traffic was coming across a channel that i am scanning, but the signal level was extremely weak.

I hope I have not throughly confused anyone so far.

Let me try to explain further.

I was recieving traffic coming across 42.700 MHz. The transmission is actually being made on 42.600 I have 42.600 programmed in the radio, but i do not have it in the scan list.

After I noticed this, sometime later I noticed a similar problem with one 2 of the channels I was scanning. I was recieving a transmission on 42.500, which is in my scan list, but as soon as the radio would check my priority channel of 43.160 it would lock onto that channel and I would still be able to hear that transmission being made on 42.500, but the signal strength was very degraded.

I have searched here on the board and did not find anyone posting any problems similar to mine, but after reading a couple of old threads:

http://batboard.batlabs.com/viewtopic.p ... ight=x9000

http://batboard.batlabs.com/viewtopic.p ... ight=x9000

I am thinking this could be an "extender" malfunction of some kind. I havent programmed this radio in quite some time, but If i remember correctly I have the "extender" function enabled for every channel in the radio. I do not have a button on the control head assigned as "extender" where I can turn it on and off.

I have another x9000 programmed with some of the same freqs and it does have the "extender" button on the control head ("extender" is always enabled on this radio) and it has never done any crazy stuff like this other one is doing.

I am going to try and disable the "extender" function and see if that has any effect on it. I just thought I'd post here first and see if there was anyone who has seen any problems similar to this before???

All help is appreciated!!

Wes

Okay, since the channels are close together, here goes a few ideas...

I would check the output of the VCO to make sure it's clean. If it gets noisy, then you would have crap that the other channels could get mixed against and end up coming through your receiver.

I was going to say fractured IF crystal filter but since I'm lazy and didn't consult the manual, I will keep that as my second answer.

I still think it's a noisy VCO. Check the output with your service monitor spectrum analyzer and see if it's clean.

I would also be willing to guess that your local area, like most areas on low band is not using PL. Either that, or if you are, due to historical reasons, the PL codes are all the same throughout the area and that's why you can hear your other traffic when you are not on that channel.

Bottom line: With parts availability being what it is, you should just replace the entire front end and VCO of your radio and solve the problem in one shot. You will spend more time trying to fix it than what it's worth.

George

George,

Thanks for the tips...and BTW, you are right, all of the PL's are the same.....

Wes

What does the control head display have on it when you are receiving 42.6?

If you are using operator select scanning, double check your scan list. Press and hold the SCAN button until the light blinks, then press the RCL button one time for each scan mode in your radio (when it is done it will loop back to where it started). Maybe someone messed with your scan list. Press HOME when you are done looking.

Try using the other radio in the same places and way you used the old radio (just substitute the drawers and reprogram it). I don't suppose your area has just started using something like broadband Internet over power lines? There is always at least a small chance your receiver is really working and hearing weak mixing products. A Rx preamp is standard in these radios and they have a sensitive front end. Using the second radio in the same environment will tell you if your radio is having problems or actually working.

The extender receiver goes through a SAW filter to a blanking gate. It does not go to a discriminator and get demodulated into audio. I doubt the extender could be the cause of your problem. Checking the VCO for noise is important because it also generates your Tx signal. In the event it is a noisy VCO your radio could also be sending interference. A very nasty thing for a 110 watt transmitter to do! Even if your IF filter is damaged, I think it would be hard pressed to demodulate frequencies that are a full 100 KHz too high (Rx at 42.7 minus 42.6 = 100 KHz off frequency). It will be easy for you to bench the radio with a generator or service monitor putting out a 42.6 MHz signal with the correct PL. If your scan catches it on 42.7 MHz, you will have reproduced the problem in the shop where you can track it down. If you need repair parts, it is always easier to use donor radios. You can also look for the older Syntor X low band radio drawers if you need a donor. Everything except the personality board and common circuits board can be swapped out into the Syntor X 9000 low band.

Mike, Thanks for the input.

I guess I should clarify and add a couple of things.

This problem is intermittant, and does not occur all the time.

When this problem occurs, I can take radio off scan and i am still hearing the wrong transmission on the wrong freq (selected channel).

These 2 radios are always used in the same area and the second radio works prefectly.

When I am recieving 42.600, the control head displays 42.500.
I am sure no one has messed with the scan list. I only have them set up for user selectable scanning and I have checked the scan list and it set up correctly.

The extender can be tuned to a particular sampling area within the band and comes from the factory tuned to what they think is right for the channels ordered. In the old days you were given suggested frequencies to tune the extender to, based on your channels, and you were to avoid tuning it too close to the frequencies you were receiving on. I never tried tuning the extender into an active area of the band or too near to the desired channel, to see what would happen. For 42 and 46 MHz channels, I would think about 49 MHz would be a good frequency area to tune the extender to. The extender sensitivity isn't that high. The instructions are in the manual.

Might not hurt to refresh the programming in the radio, either.

The VCO module from a low band Syntor X is the same and low band drawers are pretty cheap these days, it wouldn't hurt to try that.

Cheap lowband drawers?? Do tell where! The last few Syntor X lowband drawers on ebay were in the $150-$250 range at the cheapest..