[ARC5] R-23 Volume BFO/Volume control Question

[Brian A Clarke]

Hi Jim,

If your R-23 is original, that pot on the front is an RF gain control. It's
possible that if all the change in RF level is in the last 1/8th of a turn,
the series 360 k resistor may have gone high or open circuit. As there is dc
on the pot, it's best to leave it as a wirewound - which is not available
cheaply in audio taper. As you mention phone tip jacks, then it's not an
original FT-260 [or whatever the ARC equivalent is named].

You can change the BFO frequency by using a varicap diode whose bias is
altered from the front - but if you want the control for that to fit in the
bathtub at the front, you'll have to re-assign at least one pin. The varicap
diode needs to be across the trimmer inside the BFO box - but, do look up
how to connect varicap diodes across tuning caps; you need to provide
isolation from the variable dc bias you will be putting across the diode.

The R-23 uses 85 kHz IFs which are very narrow. Normally the BFO is set 500
to 750 Hz away from carrier. If you alter the BFO to listen 1.5 kHz away
from the carrier, you won't have much signal amplitude left - those skirts
can be very steep. However, you can overcouple the IFTs to give a wider
bandwidth - you move the small sticks in the tops of the IFTs. Decoding SSB
is best done at the last step in the detection chain. If you are planning to
use the R-23 to listen to the IF from the TCS, then SSB needs to be decoded
in the R-23.

73 de Brian, VK2GCE.