Batboard

This will take you back....


I have a pair of "Blue dot" Motorola Radius P10 radios laying around that are perfectly good transmitting units.. Just never had a use for them, until now.

At this point in time there is nothing I can locate about these radios, I think they were made long before I was even born. Here is what I'd like to do, however. Want to tweak their frequencies a bit if possible... One I'd like to move to 144.390 for a *VERY* compact APRS tracking module. Now, I tore the radio down and observed there are 2 crystals soldered onto the board. Blue dot is 154.5700 megacycle, they're simplex radios so TX and RX are the same. Observing the P/N on the crystals gives me the following:

(One has a blue dot, one has a purple dot.. ??)

Blue Crystal is P/N KXN6331
Purple Crystal is P/N KXN6330

Now, google searching those part numbers gives me a reference page containing a table that read the following: (http://www.icmfg.com/channelelements.html)

"(138-174) Radius" For both crystal part numbers.


So, here is my question... That means that with adjustment of pots, this radio could potentially (ha ha!) easily (bite my tongue, nothing is that easy!) move down frequency to the APRS? So long as it transmits quality audio and can at least give indication of broken squelch, I don't care about anything else. Now the only problem is, I can't find a diagram of the radio and there is 10 pots with screw adjustments...... Ruh Roh!! Think it'd actually be possible to get one on a 145.170rx/144.570tx too? I know, pushing my luck!

Anyone ever screwed with one of these junkers?

You're correct, nothing is THAT easy. You'll need to get someone (like ICM) to make the correct crystals for your frequencies, and then align the radio. You can't change channel just by adjusting the coils (if thats what you were thinking).

And I have no experience with them, so I dont know how low the current coil/slug combination will let you go.

If the radio series was made in versions to cover that wide range doesn't mean that your unit will do it. Chances are that the boards vary with range and a 13 mHz change on a crystal-controlled radio is a LOT to ask for unless you change some other components in addition to the crystals. Now, if you can get hold hold of an old VHF Mitrek (I know, it's not a portable) I can give you the 144.39 elements you'd need for APRS and that will definitely work.

One of Xtals is Rx the other Tx. I picked up my pair at Costco in the early 90's. Besides making the P10's as 'dot' radios they were also available put on your frequency. If memory serves me they were rated about 151-159 in your split so moving these to Ham would be an ambitious project. Good part is the Blue dot are very usable as they were re-allocated to the license free MURS and replacement batteries for those are probably the cheapest available for a 2 way.

So my assumption that I was a little too ambition was correct once again!

Well my interest was making an aprs setup about the size of a card deck, but neglected to consider power source for the three items. This little radio chassis is pretty tiny and would've been great, but all things considered suppose there are other HT's much better suited. It was just so tiny! haha.

Did notice in testing, both of my batteries are dead. Don't charge anymore dead. However I managed to supply power to both radios and one appears to still work perfectly fine, the other however doesn't seem to do much. When powered on the squelch function no longer works as well as xmit. So that one is pretty useless.

Thanks anyway everyone! Better luck on my next over ambitious project!

Just as a note for anyone interested the rf board bandsplits for the P10/P50/HT10 series are:

30-34
34-39
39-44
44-50

136-150.8
150.8-162
162-174

403-416
416-424
450-470

Regards,

Allen