Batboard

I have had several GTXs for some time and though they are easy to get into 902-928, I have never really liked them. I recently bought a MTX9K on E bay and after doing the VCO crossover mod, it locks on both repeater and talkaround frequencies. The receive sensitivity is not as good as the GTX but everything else I like much better. I cannot get the power out and deviation right on talkaround with the GTX. It only gives you one test freq for that and if you adjust everything so it is right there, you only get a little over a watt of power on talkaround and less than 1 khz of deviation. The MTX, on the other hand, has the same power and deviation on both ends of the band.. If anyone knows the secret to getting the GTX to work across the whole band, please let me know. I also have a MTS2K but it will be my last because of the tool proof issue. I am going to attempt a hardware hack to get it to do talkaround. It may end up in the waste can but oh well. What have been your experiences?

I own three MTS2000 900MHz. One is a model III made in late 1998, the other a model II made in mid 1993, and the third a model I made in early 2000. The later radios seem to have better performance in the ham band. Both of them have rated power and decent sensitivity in the 926 portion of the band. Forget getting them to do the entire band, the VCO is not broadbanded enough. I did no software mod to any of the radios other than hacking the ODB file to type in the freqs. In fact, the MTS2000 made in 98 works with decent RX up to about 960MHz (we have a local MUZAK service on a few 956 and 959 freqs and the VCO locks there in both TX and RX) the model I doesn't like those freqs though.

My experience has been that the earlier Jedi's were not as broadbanded as the later RF boards. Maybe someone at Motorola wanted a 33cm radio, who knows.

As a note, be very careful soldering on the RF board or anything inside. If you lack a hot air station, you WILL easily hose up the boards, even if all you are trying to do is remove one of the shields. These are multi-layer boards and you will have a guaranteed paperweight if you are not careful.

I don't much care for the GTX either, but they do have much broader band coverage in the 33cm band. Though our local coordinating body at least operates in the 20th century and realizes most commercial gear won't work well below 925 and has a new bandplan with repeater outputs on 927 and inputs on 902.

I know what you mean about the RF board on the MTS2K. I was trying to remove the shield from the VCO with hot air and only succeeded in blowing several chip parts off the board. Ended up using a Dremel tool to remove the top. I haven't had time to replace the chip parts and see if I can coax the VCO into working on talk around. This one may end up as ballast. I did remove the first filter from the front end. I believe that will restore some receive sensitivity though it isn't a good fix. I am going to see if I can get the existing filters to move down a little on the MTX9K. I hear the Kenwood TK481 is the real hot ticket. Would love to get my hands on one.

I've played with quite a few MTS2ks in the Model II variant, and as long as you don't want to receive below 926, they are pretty good to go. I've had the occaisional one that won't get a VCO lock, but all in all not too bad. I've never owned a GTX, but I've fingered them a bit, and don't really care for them...

-Head

John G wrote:I recently bought a MTX9K on E bay and after doing the VCO crossover mod, it locks on both repeater and talkaround frequencies.

Please tell me more about the VCO crossover mod. I would like to do it on my MTX9000's!

Thanks,

John

There was a topic here about a while back. Someone said they had done it, so I tried it. In lab you look for the VCO crossover point. I forget what it is called. I do remember that you change it to 6000. Mine does T/A just fine now.