Maxtrac 40 watt 2 channel has Noise in transmission

[Daniel Watson]

Brrrrrrrrrr I have a really agravating noise in the background during transmissions. Sounds like a motor running and somewhat intermittment. I have changed power supplies and mics to no avail. I have not tried running it off a battery because I have never had this before on other Maxtracs???? Help

[wx4cbh]

It wouldn't be DPL on the Tx freq, would it? Just a thought. The intermittency means that if it is DPL, it's not operating properly. TX RF getting into the wrong places internally will cause these kinds of noises, too. Have you removed and checked/cleaned the mating surfaces of the various covers? Is the solder joint on the PA good? Geez, this could go on forever. I hate not being able to actually experience the problem and to "lay hands upon."

[Monty]

Hello:

We will assume you have a good Antenna and Cable
within your set up. This too can cause triouble.

Unfortunitely, there are just too many items that
could casue the motor-boating sound, and is generaly
due to a poor ground somewhere.

If you want a few places to check, here is what i would
due first:

1. Check the Coupling Nut on the Antenna Jack ! That is
always been a little of a troubled spot !

2. Make Sure the 2 Screws that hold the power connector
to the chassis is secure. DO NOT overtighten these !, Just
make ssure they are secure.

3 Sometimes the On/Off Volume Control may cause poor
Tx / Audio perfomance.

4. Make sure all the screws that secure the Rx-Tx Board and Logic
Board are secured.

5. Maker sure the Shields are there, and clean and free of debrie.

If the above does not work, post the results, and I am sure
someone will add there input as well....

Outside of that, you may need to have the radio set up
on a Work Bench, and do some hunting around by tapping
on varies areas of the radio to see where the Noise gets
better or worse while tapping on a suspected area....

Monty

[kcbooboo]

While you're inside the radio, it might be worth pulling the logic board up just a bit to clean the contacts that go to the RF board. The VCO control voltage pin could be dirty causing all sorts of strange things. Many of these radios are also sensitive to vibration from nearby fans, or even something vibrating on the same bench that the radio is on. I had one in service on a repeater and the fan vibration modulated the radio something fierce. Worth checking into.

I also have a 2ch MaxTrac or Radius that has what I'd call "wind noise" in the tx audio. Could be a defective capacitor in the power supply somewhere but I've swapped everything possible and the problem persists.

Bob M.

[Daniel Watson]

Well, followed the advice. Cleaned contacts, moved logic board to clean pins, removed shields to inspect. I am thinking when I used contacct cleaner on the ground of the power supply connection that 99% of the noise went away. Those pins corrode teribbly and someone suggested possible bad ground. I think this to be correct.

[phrawg]

Look at the output freq on a svc monitor and see if the line
it generates on the scope is stable. If it wobbles around
then check out the vco steering voltage line with a scope and
see if it does the same. If so troubleshoot the ckt.
That wobbling vco voltage can produce some strange sounds.
Phrawg