Batboard

I've got two MTS2000 900 MHZ portables (a model 1 and a model 2) that work absolutely sweet on the 25 MHZ repeater splits. Neither one will do talk around at 927 though (fail 001). After thoroughly searching the archives here, I have concluded that my issue involves the VCO crossover point. I have legitimate Motorola CPS and Tuner software, but see no ability to adjust the VCO setting. Both radio's have late firmware, so toolproofing would definitely be an issue. I can live with these radio's for repeater use only, but it sure would be nice to have talk around also. So, what's the concensus of the experts here? Is there a way to adjust the VCO crossover?

Thanks,
John
N1OTY

John, I'm not quite sure if the MTS software is the same as the MTX, but I had a similiar problem with my MTX9000. Check out this thread http://batboard.batlabs.com/viewtopic.php?f=3&t=52373 You're going to need LAB software. Follow the instructions, it worked great for me. Hope this helps.

Derek, N9UPW

Thanks for the response. Labtool will not work with these radio's. They are too new, so toolproofing would be a definite issue. The topic link you gave me was one that I had reviewed prior to posting. The key to my dilemna is whether there is another way to adjust the VCO without Lab software. I'm starting to think that it is not possible. Before giving up, however, I thought it might be useful to check here to determine if someone has solved this problem. For that matter, these two radio's are so good on 902, that I'm contemplating checking with Motorola to see if the Depot can make the adjustment for me.

John
N1OTY

One further piece of information that I learned from looking at the tuner software is that there is a menu entry for "TX VCO Crossover Frequency". Unfortunately, it is grayed out and not available. Now I am really curious. Checking the help files shows that TX VCO Crossover Frequency is supposed to be available to MTS 2000 radio's only, which these are. I think it is obvious that the software is designed to allow at least some of these radio's to have this setting adjusted. I've tried both of mine with the same results. This setting and a few others remain grayed out and unavailable.

Any thoughts before I call Big M and ask?

John
N1OTY

The 900 Mhz. band doesn't make use of VCO crossover frequencies, that's why the 'selection' is greyed out.

The only models that do use VCO crossover frequencies are the UHF and VHF models, due to the standard split arrangement these radios use, like 5 Mhz. on UHF, and .6 to over 10 Mhz. on VHF.

Standard splits on 900 are 39 Mhz, as well as 45 in many cases, and more recently, 25 mhz. splits for amateur use.

That's an interesting observation. I had assumed that the later 900 MHZ MTS2000's would also have VCO crossover points, since other 900 MHZ users reported adjusting this number in order to solve this problem. Most notably, it seems that MTX 9000 users have been able to adjust this number in lab software in order to solve this talkaround issue. I am not sure, but I believe that I read somewhere that folks were able to solve this talkaround issue on pre-toolproof MTS2000's by adjusting a so-called "fractional-n synthesizer" value. Any solution involving lab would be useless to me since all my MTS 2000's are subject to toolproofing. I did call M and asked them why that part of the menu was grayed out, but the CS rep couldn't explain. He did ask me why I wanted to adjust that value in the radio, so I told him about the error code and the failure to lock on transmit, but I did not tell him it was for the 902 ham band. I buy enough stuff out of M on my business account that they don't seem to give me a load of crap. He promised to get back to me, but it has been a few days. We'll see.

It really is too bad that these radio's I have will not do talkaround. They are without a doubt the absolute best handhelds I have used on 902 for repeater use. At least I have a Kenwood TK-481 that I can use for talkaround. It just doesn't hold a candle to these on the repeaters though.

Thanks for the reply.

John
N1OTY

John:

The fractional-N-synthesizer is one method of adjusting the radio to operate down in the 902 range, but it is a test and retest method, as one settign may allow transmission on 902, but cut off at 926, and vice versa.

You have to find the sweet spot that allows both TX and RX within the band segments you require most.

Lab will get these points once you dig into the software, but you must be careful as a single adjustment can cripple the radio, then you'll have to go back into the software are find where you made the mistake.

Always write down ALL the settings in the service section as you access them, to avoid any problems if you move the wrong softpot.

Never adjust the receive filters on any portable unless you have a calibrated service monitor...you'll kill the receiver in short order if the adjustment points are moved outside each listed frequency for the settings.