MT1000 Poor Receiving Range

Stage 2 · Post by **Stage 2** » Fri Mar 02, 2007 1:47 pm

I have 2 MT1000's with matching frequencies on certain channels. The freq's in question are in the UHF ham bands. One of them does not receive nearly as well as the other. Both transmit identically well to the point that People I talk to cannot distinguish one radio from the other with regards to transmit quality. I am guessing that this rules out the possible bad solder connection on the antenna connection that sometimes happens with these. I had also popped the 2 plugs off the bottom of the control borad to verify that the radio with the problem is indeed the correct bandsplit which in this case is 438 to 470 Mhz. I'm still learning this stuff. Any ideas? Thanks

PETNRDX · Post by **PETNRDX** » Fri Mar 02, 2007 4:09 pm

The reciever coils L9 thru L13 are set at the factory for a 30 mhz wide rx window.
But, coils L1 and L2 are adjusted for an 8 mhz window.
This sort of "optimizes" the radio for a specific split.
So, if one radio happend to be tuned for a slightly different range, the Rx sensitivity can be several dB different.
I have experienced the issue you described, and is pretty easy to fix, if you have access to a service monitor or any UHF signal generator.

Stage 2 · Post by **Stage 2** » Sun Mar 04, 2007 9:19 am

Thank you for the tip. I don't have access to a service monitor,but, I know someone who does. I will have this checked out.

PETNRDX · Post by **PETNRDX** » Sun Mar 04, 2007 12:47 pm

Its certainly an easy thing to check and fix.
L1 and L2 are along the edge of the circuit board, nearer to the top.
The others are around the middle of the board (center of the board).
I usually just generate a weak signal into the Rx on a freq clossest to the center freq range I wan to use, and peak those two coils.
If it does not make several dB difference within a turn or two, there is likely some other problem.
Hint: remember the coil position before you start, and return it to the original position if it does not help.
And while you have the radio apart, re-solder the antenna connection and accessory plug connections.

57Shasta · Post by **57Shasta** » Sun Mar 04, 2007 7:59 pm

Before you start tweeking on the coils, take some compressed air and blow out the dendrites that form in the preselector coils. MT1000/HT600 UHF had a problem with this, but not as bad as a 800 Mostar.

Stage 2 · Post by **Stage 2** » Mon Mar 05, 2007 10:00 am

Thank you both for sending along more info. I will try the compressed air trick before having the coils tweeked.