Just finished updating an R-4C with all five Sherwood mods including relay
selectable 1st IF filters. Wow, that's a job. I ended up using Don Buska's
blue LED replacements after alternating between the gells and the LEDs with
only the white diffuser to see what looks best. No comparison. The blue
LEDs with only the white diffuser look awfully impressive, especially in a
darkened shack. The LEDs will stay.
I have the QSK plans complete and initial testing looks promising. I am
routing my R-4C and T-4XC through an Ameritron QSK-5 PIN diode RF switch.
The QSK-5 was designed for amplifiers without their own internal QSK
circuit, but it can be adapted for use with classic "separates." No mods to
the rig except the Tx's bias line is controlled by the QSK-5 switch and is
easily reversible. No other complicated circuits needed. So, how do I
establish CW system timing? The latest generation of CW keyers now offer
lead-in and lead-out timing parameters on a dedicated PTT output line,
digitally adjustable in 1ms increments through software or paddle commands.
From initial tests, QSK is so fast that it sounds like full duplex. Since
the C line's VFOs run continuously without constant toggling Tx/Rx CW offset
shift as is the case of modern, synthesized rigs, QSK can be set blistering
fast since there's no synthesizer to settle before the switch occurs. The
mute line on the R-4C is disengaged, allowing the R-4C to listen to one's
own transmitted signal, greatly attenuated though the PIN diode switch in
the QSK-5 to serve as a sidetone.
It's amazing how much cooler the R-4C runs without that inefficient Class-A
audio amp burning up the air around it. Next change is to bring out a fixed
output audio line (capacitively-coupled to the high side of the Volume
control) for use with a Marantz audiophile-grade integrated audio amp.
I have the R-4C NB option, but just pulled it out of the circuit as the
system gain is about 6 dB less than without it -- even after adjusting the
gain pot on the NB. Is it common to run out of gain range on that pot? In
any case, I detest NBs anyway so I don't think I'll miss it.
When the QSK the project is complete, I'll post a block diagram on my
QRZ.com page. Folks who have always wanted to run super-fast QSK from the C
Lines now have an option that does not involve extensive and invasive
circuit changes.
Paul, W9AC
_______________________________________________
Drakelist mailing list
[email protected]
http://mailman.zerobeat.net/mailman/listinfo/drakelist
