On Nov 25, 2013, at 6:09 PM, Bill Turner wrote:
> When you say above 250HJ1B, I believe the "1" should be a "2", correct? CW
> is "A1A".
Bill,
The first "A" in A1A designates it as a double sideband signal (on-off keyed
carrier systems like amateur CW has 2 symmetric keying sidebands), while the
"J" in J1B makes that an suppressed carrier (SSB) signal.
The middle digit of 1 and 2 has to do with whether there are subcarriers.
Steam RTTY and CW both don't use sub-carriers, so they are "1." Pactor 3 would
have a "2" in the middle digit because it uses between 2 and 18 subcarriers (as
it switches speeds).
The final "A" in A1A says that it is for aural (human) reception, while the "B"
in J1B says that it is for machine decoding.
So, A1A -- double sideband, no sub-carrier, human decoding. J1B -- SSB, no
sub-carrier, machine decoding.
You don't need to use SSB to generate the RTTY signal, you just have to make
sure that when the RF leaves your antenna, it looks sufficiently like an AFSK
(J1B) signal.
By the way, for the curious, the H in 250HJ1B is the decimal point for a
bandwidth in Hertz. For kiloHertz, you would use a K instead of an H, e.g.,
2K20 for 2.20 kHz.
There are always 3 digits in the bandwidth field. E.g., H050 (50 milli Hertz)
2H50 (2.5 Hertz), 400H (400 Hertz), 2K00 (2000 Hertz), 96K0 (96 kiloHertz).
73
Chen, W7AY
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