[Elecraft] K2 and FSK (summary)

[Jeff Stai]

hi Aki - absolutely right - for contest situations, it is especially 
useful to not have to worry about readjusting the radio when changing 
bands. But even for casual operating, its nice to be able to set the 
mode and go, without having to make adjustments.

This past weekend, I operated the CQWW RTTY contest at another 
operator's station. Since he was not a RTTY op, nor did he have SO2R 
capability, I hauled two FT1000Ds and a desktop computer to his QTH. I 
had wanted to operate high power, but after getting two monster rigs, 
keyboard, and monitor on his table, there was no way I was going to be 
able to deal effectively with his two non-auto-tune amps - so I went 
low power and did all right. But lugging those big radios was 
definitely non-optimal!

Later, I was thinking about the perfect portable set up for the 
future... how cool would it be to have two K2/100s with peaked and 
tweaked data filters, plus a KPA800 or KPA1500 amp with its SO2R 
ability (and auto-tune and it can sit under the desk)? I have always 
hesitated to use the K2 in RTTY contesting because you cannot zero the 
RIT by computer command, and because of no FSK (and also because you 
have to use non-standard tones to get within the filter bandwidth 
capability - with practice, I have gotten pretty good at tuning to pitch.)

The latest RTTY contesting software, with the ability to have multiple 
receive windows with different settings, has made it so that I hardly 
ever touch the RIT anymore. If we could get FSK, I would probably get 
past the tone issue... 

Looking at the schematics (RF sheet 1, left side), if I understand the 
circuit correctly, all it would take is injecting a voltage of the 
correct value and summing it with the thermistor voltage to create a 
170Hz shift (shifting the 8B value to the thermistor might even be 
easier). What I don't know is:

1. How precise this voltage would need to be;

2. Whether the same voltage would work for all bands.

Any insight on how "baked" this scheme is, before I start messing up 
my K2, will be very much appreciated!

thanks - jeff wk6i

ps: plan B: inject the two tones directly into the transmit audio. 
this sounds harder.


At 11:24 PM 9/25/2005, a.yoshida wrote:
>I appreciate your interesting posts.
>As Ron says AFSK is as clean as FSK if AF in level is set properly.
>
>Last week end I enjoyed CQ WW RTTY contest with QRP K2 (5W)
>One of major problem was that AF in level must be re-adjusted
>each time when I change Band. This is not in the case of FSK.
>I believe FSK is much simpler at least in operation.
>I have same problem (re-adjusting AF in level) when I change mode
>(RTTY to PSK31 etc)
>
>This is why I posted this question on the list.
>I hope Elecraft plans something new in this area.

--
Jeff Stai               jds at twistedoak.com
Twisted Oak Winery      http://www.twistedoak.com/