[aprssig] FT-107M and HF APRS

[Stephen H. Smith]

Norm McMillan wrote on 10/30/2004, 6:36 PM:

 > Unfortunately I'm now faced with the FT-107M not transmitting on the
 > WARC bands! I'm wondering if this is a *feature* which can be
 > circumvented somehow.

This radio is an old ham-bands-only type design from the late '70s/early 
'80s that predates the continuous-coverage 0-30.0 MHz design of modern 
radios.   Modern continuous-coverage designs are inherently capable of 
transmitting through their entire range; the TX ability is arbitrarily 
locked out in software, and can usually be re-enabled by cutting a diode 
or PC board trace.

Older ham-bands-only radios would require extensive HARDWARE mods that 
would involve: removing one existing band from the bandswitch (probably 
40M or 20M), adding new tuned circuits and a new band-segment oscillator 
crystal to place a new 10 MHz band in it's place, and finally wire 
jumpers to cause the correct PA low-pass filter to be activated when the 
new band is selected.

Unless you are lucky and the radio has a "WWV" position at 10 MHz 
instead of 15 MHz.  [ Many of these older radios received WWV at 15 MHz 
since they could use the same front-end preselector tuned circuits as 
the 14 MHz band. ]  It might then be a fairly trivial process to defeat 
a "receive-only" interlock.  Since the VFO tuning range on most of these 
classic "ham-bands-only" rigs had a 500 KHz tuning range, a "10 MHz" WWV 
band would probably tune 10.0 to 10.5 and would easily cover the 10.1 to 
10.15 30M band.



Stephen H. Smith                   wa8lmf (at) aol.com

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