K2 PTT

[Steve L.-3]

My SO2R contesting setup just replaced an FT847 and
SB220 amp (2nd station) with the K2/100.

My setup is a single PC running Writelog with CW
keying and Radio A/B selection coming from the LPT
port. A homebrew bit of hardware does the keying and
PTT generation for both radios. My previous setup
controlled the HW PTT input of the radio, the radio's
'STBY' output driving the SB220's T-R relay, but the
K2 doesn't have a HW PTT input in CW mode.

I connect the PC's sound card outputs to each radio's
microphone input (transformer coupled) for sending SSB
voice. My microphone plugs into the PC's sound card
MIC IN.

I had trouble with the K2's lack of PTT on CW because
that's how I did T-R on the SB220. On Don W3FPR's
advice, I've changed the station slightly so the HW
PTT output now drives the SB220's T-R relay directly.
Writelog allows me to program a delay between PTT
assertion and sending code to allow for the dinosaur
relays to clunk over. The K2 works fine in QSK mode
since the amp's T-R is handled externally.

This works perfectly for CW but for SSB the VOX simply
isn't very good and trips in and out when being driven
by the PC (with gain set to 3 and compression set to
3). I set Writelog to assert PTT via the CAT port for
SSB, this works perfectly! Is this the 'KY' command
I'm hearing about? Writelog does it for me.

However, when I use my microphone instead of the PC's
sound card output, CAT port PTT is NOT asserted so the
SB220's relay doesn't activate... so I ALSO connected
the K2's Amp Drive output to the SB220's T-R
(buffered) so when the K2's VOX is tripped the SB220
is held in Transmit mode.

Now, it's seamless. I can send anything at anytime at
any speed and the relays stay in the correct mode,
even when sending slow CW or fast CW or whatever. I
don't have a key or keyer connected to the K2 in this
configuration but it would work just like the SSB VOX
and assert the amp output drive.

Of course, the key and PTT are optoisolator buffered
for ground-break, this makes a huge difference in
eliminating RFI in a QRO SO2R station.... and all the
audio is transformer coupled too.

So, I was plenty worried about the lack of HW PTT for
real contesting applications, but this simple fix
cleared it all up.

I think I'll make a little audio summing circuit for
lack of SSB transmit monitoring. It won't tell me if
my SSB TX signal is clean but it WILL let me hear
what's being transmitted in case I get confused which
I do all the time.

I'm so happy I can use my K2 for QRP field activities
(just did the FYBO FD event) and then slide it into a
real contest setting and use it QRO. Very cool!

Of course, none of this crap is needed if you have a
QSK amplifier, but I don't run QSK during SO2R
contesting because I'm listening on the other radio
while transmitting on the first, I want the
transmitting radio to be very quiet (I turn the
sidetone way down).

The DX contest is this coming weekend, the K2/100 will
get a serious shakedown cruise!

73, Steve N4SL Snohomish, WA USA

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around
http://mail.yahoo.com 
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com