[RTTY] Re: Back on the Air

[Richard Ferch]

On Tue, 30 Mar 2004 at 12:21:32 -0600,
Richard Kriss <<mailto:aa5vu%40arrl.net>aa5vu at arrl.net> said:


>I have been spoiled operation RTTY with a PK-232 in FSK. Going to a sound
>card implementation where you HAVE to operate in USB (not LSB or FSK) is
>really confusing.  I have no idea where to tune the VFO or how to spot
>stations. If I see a spot I put the rig on that frequency then try have to
>find them on the spectral display.
>
>If I want to spot new station and the radio display reads 14.085.00 USB but
>I had to work him  to the far left of the spectral display, what frequency
>should I use for the spot?  Life was easy when everyone was using AFSK-LSB
>or FSK. It is now more confusing.
>

Dick,

I bet you have trouble convincing some stations of your callsign!

As for frequencies to tune to or spot:

In FSK it's easy - the dial on your radio and the frequency of spots are 
the same.

In AFSK you have to add or subtract the audio frequency your sound card is 
using to/from the indicated dial frequency to match up with the spot 
frequency, depending on which sideband you are using.

Examples:

Tuning to a spotted frequency:

Radio in LSB
Spotted frequency 14085 kHz
Audio "mark" frequency 2125 Hz
Dial reading 14085 kHz + 2125 Hz = 14087.125 kHz. In LSB you tune your 
radio *above* the desired signal so that the signal will be in the *lower* 
sideband.

Radio in USB
Spotted frequency 14085 kHz
Audio "mark" frequency 2295 Hz
Dial reading 14085 kHz - 2295 Hz = 14082.705 kHz. In USB you tune your 
radio *below* the desired signal so that the signal will be in the *upper* 
sideband.

Conversely, if you want to send a spot:

Radio in LSB
Radio dial set to 14084.0 kHz
Audio "mark" frequency 1275 Hz
Frequency to spot: 14084 kHz - 1275 Hz, or about 14082.7 kHz. (*lower* 
sideband - the signal is *below* the dial frequency).

Radio in USB
Radio dial set to 14084.0 kHz
Audio "mark" frequency 1445 Hz
Frequency to spot: 14084 kHz + 1445 Hz, or about 14085.4 kHz. (*upper* 
sideband - the signal is *above* the dial frequency).

If you are using different audio frequencies, adjust the arithmetic 
accordingly.

A lot of software programs can do this arithmetic automatically for you 
provided you have your radio interfaced for computer control.

Does this help at all?

73,
Rich VE3IAY