[ARC5] Reversibly modifying 1415kc IFTs - Dial 'tracking'

[Bill Cromwell]

Hi Brian,

Ian has already told us that his radio was for use on a single frequency 
so that would not be a problem for him. If we change the frequency of 
operation the VFO, RF amp, and mixer input do have to 'track' but that 
can be worked out. We wouldn't be modifying the radio if the desired 
frequency is already included in it's coverage. A "logging scale" can be 
fabricated and fitted over the existing dial or a logging scale with 
numbers representing the actual frequency of operation could be made 
with only a little more effort. Logging scales with tuning charts are 
just as "accurate" and repeatable as any of the mechanical dials that 
have the operating frequency numbers on them in place of the 0 - 100 
numbers. My experience has been that 0-100 logging scales with a tuning 
chart curve are more reliable than dials with the logging scales printed 
with other numbers like 3.500 - 4.000. Boiled down to essentials the 
3500 - 4000 example is really just a logging scale with the tuning chart 
printed on the dial. It takes a lot of of fussy work to make that 3500 - 
4000 tuning chart printed right on the logging dial as accurate across 
it's range as the 0-100 scale.

My radios with 0-100 logging scales can be preset or reset to a specific 
frequency with "deadly" accuracy. The pretty ones with scales like .190 
to .550 not so much. The 'pretty' scales are repeatable but we then have 
to rely on our notes about where to actually set them - no different 
than consulting an X-Y graph generated from a few points in a spread sheet.

Of course we could hack into the radios and add an electronic dial - but 
why not just build a whole new radio if we are going to that much trouble?

73,

Bill  KU8H



On 03/25/2015 07:58 PM, Brian wrote:
> Hello Ian,
>
> Great idea.
>
> If you changed the oscillator frequency in a Command receiver to 
> produce the 1750 kHz, what did you do about tuning dial tracking?
> Have you tried raising the BFO frequency the same way?
>
> 73 de Brian, VK2GCE.
>