EMRFD Message Archive 3489
Message Date From Subject 3489 2009-08-20 06:59:14 timshoppa The best QSK - how to replicate I get to use some of my friend's fancy-pants modern transceivers every so often. And I also have a Ten-Tec with pretty good QSK. Most of them have pretty good QSK - sometimes it takes me a little while to get used to relay chatter.
But far and away the best QSK system I ever had is the most primitive. My HW-16 with HG-10 VFO. Even though sold as a "transceiver", it is really an independent transmitter and receiver in the same box. What's amazing about QSK on the HW-16 is that when I use it (I fire it up every so often - most often in winter for ragchewing on 80M and 40M at nights) I honestly feel like I can hear the band even when my key is down.
I think that the HW-16 is supposed to have this lousy neon-bulb sidetone oscillator, and it's supposed to do complete muting of the receiver on transmit, at least that's the way I see the schematics and the description in the heath manual.
I think that in between the sidetone oscillator of my HW-16 being disabled or nonfunctional, and the incomplete muting of the receiver in transmit, the resulting effect (perhaps entirely nonintentional) of hearing my CW signal just as it would sound to an independent receiver, is the best most useful and most enjoyable QSK I have ever heard.
In my homebrew solid-state setup, I'm trying to emulate the HW-16's behavior. So far I've got a good homebrew multi-band solid state receiver. Rather than have different knobs for transmit and receive VFO's (this is such a pain and nonoptimal result of the HW-16 + HG-10 combination) I plan to have one master VFO and maybe a RIT (more likely a XIT). I already have a receive synthesizer that takes the master VFO and makes the LO for receive; clearly I can put a second output on the synth for transmit LO. Then I mix it with the keyed transmit BFO (EMRFD has the good idea of running the transmit BFO all the time at a harmonic of the actual BFO, then dividing down to the actual BFO when the key is down), filter, amplify, and send to the antenna. In the end what I'll end up with is independent transmitters and receivers controlled from the same VFO.
Unlike the HW-16, my receiver has AGC. I would like the receiver to work, mostly but not entirely muted, when my key is down. And then when I key up to go back (way less than a dit time) to receive I want the receiver to be back pretty much where it was before I did a key-down. What I do need to figure out, is how to hold to not pump the AGC voltages just because my transmitter came on. If anyone has done something like this using the Hybrid Cascode (which I note does have some sort of mute input) I'm interested.
3495 2009-08-23 13:22:05 Johan H. Bodin Re: The best QSK - how to replicate Tim,
I don't have the HyCas schematic at hand but I believe there is a
"memory capacitor" somewhere in the AGC circuit. Maybe it is possible to
uses an SPDT analog switch, for example 4053 or, if the voltage levels
allow, a 74HC4053, to disconnect that capacitor immediately at key-down
and connect the circuit to a fixed voltage level that corresponds to
minimum gain. A short time after key-up, switch back to the capacitor,
which is holding the pre-TX AGC level.
Just an idea...
> I would like the receiver to work, mostly but not entirely muted, when my key is down. And then when I key up to go back (way less than a dit time) to receive I want the receiver to be back pretty much where it was before I did a key-down. What I do need to figure out, is how to hold to not pump the AGC voltages just because my transmitter came on. If anyone has done something like this using the Hybrid Cascode (which I note does have some sort of mute input) I'm interested.