MX w/DTMF?!

MarkHam2B · Post by **MarkHam2B** » Fri Nov 02, 2001 8:30 pm

Holy batwings! I didn't even think such a beast existed until I came across this:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dl ... 1291801128

Anyone know anything about this bad boy (frequencies, S model, cold war ready [kidding], etc.)?

Thanks in Advance,
Mark

Cowthief · Post by **Cowthief** » Fri Nov 02, 2001 8:46 pm

Hello.

Yes, DTMF, as well as IMTS, was an option on the MX3xx series.

This was simply an option, others were, marine 1watt/high switch, high sens front end (preamp), analog or digital scrambler, MODAT, PL/DPL, PAC-RT option, as well as there being a crystal and programmable models, a 5 crystal type I trunked model and the rubber-covered "military" models.
They came in low band, high band, UHF, and 800 MHZ, trunking and not.
The 2nd digit denoted the size of the radio, a MX320 is shorter than a MX350.

Thank You.

Elroy Jetson · Post by **Elroy Jetson** » Fri Nov 02, 2001 9:23 pm

An IMTS version MX, you say? I haven't seen THAT one yet but I've seen most of the rest. I still like those radios, if they're on the channels I want them to be on. It's my understanding that there were more different ways to configure an MX than any other portable radio in history. One of the oddest I ever saw was an SP version (of course) that had ten channels and they were all elements, it wasn't a synthesized radio. Twenty channel elements...and Motorola charged FIVE HUNDRED BUCKS PER CHANNEL (T/R pair of elements) back then. FIVE THOUSAND bucks just for the elements...plus the extra money for the SP engineering. That was probably a seven or eight thousand dollar radio! 360 size housing, of course...and low power. High power wouldn't fit!

When I was working on MXes routinely, I eventually got to the point where I could practically draw the whole schematic from memory, and was able to fix most of them in five minutes or less...or if it was a bad control flex (very common in retired government radios) I'd just save it for the modules. Those flexes were an incredible pain to unsolder without losing pads on the circuit board. Most common component failure: Bad TX/RX relay, oddly enough...

Elroy

EngineerZ · Post by **EngineerZ** » Mon Nov 05, 2001 7:05 pm

I have one of the high-split (162-174 MHz) high band synthesized (48 Chan) MX360 units. (Much like the ones up for auction on eBay.) The DTMF module is in the "frame" below the main board and connects the keypad on the front with a piece of flex. It's a pretty cool radio that could definitely double as a club. Hate to be the perp' on the receiving end of this baby!

Anyway... I'm getting ready to do a module-swap to convert this unit from the high-split down to the low-split (136-150.8 MHz) so I can run it on the 2-meter ham band. I bought a low-split MX350 (-s) specifically to supply the modules. Has anyone done this before? Any tips?

I noticed there are a few components on the main board (e.g. a few resistors, the VCO inductor-L4) that are different depending on the radio bandsplit. Do these components absolutley need to be changed as well or should I just swap modlules and see if I can get the VCO to lock and the radio to tune up?

--z

1 Adam 12 · Post by **1 Adam 12** » Tue Nov 06, 2001 5:02 am

Try switching the the modules out first, primarily the main ones, which are probably all marked with a 73, preselector, phase det, vco, pa's etc.. You may get some pretty good performance out of it, or may have to do even more. I haven't done one in a while but will pull my notes tonite and see what other steps on the board you may have to take. I also have some MX's with factory scan, VHF, UHF,800, a 96 channel unit, yes with two proms and a highly prized top 2 digit display, and I bet I haven't seen every possible model out there.

<font size=-1>[ This Message was edited by: 1 Adam 12 on 2001-11-06 08:04 ]</font>

<font size=-1>[ This Message was edited by: 1 ADAM 12 on 2001-11-06 08:15 ]</font>

willbartlett · Post by **willbartlett** » Tue Nov 06, 2001 10:17 am

Was there once a mt500 with some kind of 2 digit display or a synthesized model of this radio? I seem to remember seeing one once, but I cant tell if I actually did or if the neurons just aren't firing on all cylinders.
Will

1 Adam 12 · Post by **1 Adam 12** » Tue Nov 06, 2001 12:55 pm

I have heard rumours, and seen one photo, I understand that it was at least looked at. I also saw one that had what appeared to be a
internal board that looked to have a prom on it, but its like chasing ghosts. Another great radio, had one with scan in VHF, and for its time was one derrier kicking unit.

Elroy Jetson · Post by **Elroy Jetson** » Tue Nov 06, 2001 1:51 pm

If I remember correctly, there are NO frequency sensitive components on an MX main board. Any parts that change value from one radio to the next are engineering revisions or special options. All frequency sensitive components are in the modules. I'm pretty sure of it.

Elroy

Andy Brinkley · Post by **Andy Brinkley** » Tue Nov 06, 2001 6:41 pm

Elroy as usual you are correct. No freq sensitive components on the backplane. Main items to be swapped are: Preselector; VCO; RF Power Amp; you might can live with the RF Filter & detector modules as is. E-mail me direct if you need further.

1 Adam 12 · Post by **1 Adam 12** » Wed Nov 07, 2001 4:50 am

Yes, both Elroy and Andy are correct, but I'm glad you asked, because I went into the dungeon and found a whole box of stuff , that I didn't even remember I had. Only changes on the back, was SP or aftermarket board related, but I now remember some really fun stuff we did with these radios.
I thing I'm gonna have to start playing with them again.