[RTTY] 300 baud RTTY

[Kok Chen]

On Jun 5, 2011, at 7:28 PM, Ktfrog007 at aol.com wrote:

> I'd like to try a  QSO with you, but doubt if I'd see anything but garbage.

If you are using 170 Hz shift, try to open up the receiver passband to about 170 + ( 300/2 )*3*2 or so, i.e., about 1 kHz.  That will let through the third harmonic of the keying sidebands (the 300/2 number is the fundamental of the keying sideband) on each side of the two FSK carriers.

Any passband that is narrower than 470 Hz (letting though just the fundamental of the keying sideband on each side of the two carriers) will incur data errors.  470 Hz will work; but with that, you are already losing SNR by removing too much of the keying sidebands.

If you use 200 Hz shift, add 30 Hz to the above numbers.

For transmission, use AFSK instead of FSK, unless you know for sure that the FSK modulator in the rig can handle 300 baud transmissions.

Needless to say, to avoid QRMing others, leave a lot of space from the other stations.  Don't rely on the rule of thumb that you have been using with 45.45 baud RTTY.  All that wide keying sideband will be transmitted into the ether.

73
Chen, W7AY