[aprssig] HT-220 HT's for APRS

Chris Kantarjiev cak at dimebank.com
Fri Jul 20 13:10:48 EDT 2007

I haven't tried HT-220, but did re-crystal several MT500s for this.
They have a t/r relay, so that aspect was pretty straightforward.
They have very low idle power consumption, which is good.

The bad: crystals are an issue. West Crystal in British Columbia
will happily make you new crystals for cheap (well, cheaper than
ICOM or Bomar). 

The MT500 doesn't just swap out a crystal, but an entire "crystal
element", which is a temperature compensated tunable oscillator.
There are several flavors of these, and one of the ones that is
needed for the 2m band is in short supply. New ones cost about $60.
KD8KZ and I figured out how to rewire the guts of the readily
available ($5) ones to work on 2m, but it wasn't much fun.

I think that the HT-220 uses something similar, but I'm not sure.
There's a lot of good info on the web (someone has pointed you
there already), unlike for the MT500 (we figured a lot out on
our own).

The external connector for a speaker/mic can be used to pick up some of 
the interesting signals, but I chose to connect to the PC board 
directly - mostly because it was a slightly smaller package and
because I could get to the audio before the volume control.

An interesting project, but not necessarily "economically viable".

73 de chris K6DBG

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