Scott,
I hear your point.. These are not HT's but 40 watt mobiles. I understand
how cheap HT's are and that's why I can't see spending much resources on the
conversion. But I'm always looking for new uses to implement PIC chips and
interfacing one to a synthesizer seemed like an inexpensive idea. PIC and
synthesizer cost together is barely 12 bucks.
Joe Loucka AG4QC
"Scott" wrote in message
...
Here's another idea...instead of making these radios to hand out to new
hams, maybe you could remove the transmit crystal and just replace the
receive crystal, lowering the conversion cost. You could hand these out
to NON-HAMS so they could listen in on the local repeater or simplex
channel. Maybe they would be interested in becoming hams. 2M HTs are so
cheap these days, just about any new ham can afford one with a lot of
bells and whistles built in.
Scott
N0EDV
Joel wrote:
The idea is we have a few dozen crystallized Maxon 4010's here and
figured we could get them converted to 2 meters to give to the new ham's
in the area. We would do the crystal route, but crystals seem to be in
the $12.50 or more range (If you can even find them) That means it would
be about 25 buck/channel. The price quickly makes conversion cost
prohibitive compared to a new 2 meter radio.
I reversed engineered the Maxon 3010 as they are synthesized and by
cutting diodes we have them working on 2 meters. Of course, having a
schematic for either radio would make things a lot easer.. (hint)..
Joe Loucka AG4QC
"Richard Hosking" wrote in message
...
If its for commercial use it would probably be easiest just to get the
crystals.
Otherwise designing a PLL system is possible - particularly if you want
to learn about them for your own education. But the work involved is not
trivial - probably not worth it for a few old radios. The other issue
will be how the radio achieves FM - if it does it swinging the crystal,
then this will impose another restriction on the PLL. While it is
possible to do (keep loop filter BW below min audio freq) I tried doing
this on a 2M design once - couldnt get it stable. Some radios phase
modulate one of the multipliers, which would avoid this issue.
R
Joel wrote:
I have a couple 6 channel public service radios that are in the 155Mhz
range. Some are synthesized and require cutting diodes to change the
frequency and that works out well.
But some are crystal controlled and with the cost and availability of
crystals it's cost prohibitive to re-crystal these radios. It looks like
these crystals are in the X9 mode so that puts them in the 16-16.5 MHz
range. I am considering building a VCO to inject a signal into the old
crystal socket to get around the crystal issue. Actually I figure a PIC
to program the PLL would be great. I'm just not sure what frequency to
inject into the old crystal socket. Should I build a 16mhz VCO or some
harmonic? Will injecting a signal into a crystal-less oscillator even
work? I'm going to use a ADF4110 PLL and a 16F89 PIC. Any suggestions
for the VCO? Schematic for a 16 MHz VCO?
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