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[aprssig] APRS Bandwidth

Steve Noskowicz noskosteve at yahoo.com
Wed Jun 24 05:56:52 UTC 2009

--- Stephen H. Smith wrote:

> For AFSK,  ...TX modulator & IF filters limit the bandwidth...
> Further, the better ... generators have limited transition rates...

a.k.a. bandwidth limits.

> The old time direct FSK RTTY setups from the 50s-60s
> actually diode-switched a small capacitor ...varactor diode

  Ah yes.  Modify the exciter and hook it up to a teletype machine.
Clackity-ckack, paper tape and all that.

>... commanding the synthesizer to two freqs 200 Hz apart.
> For direct FSK, most rigs have some sort of slew-rate
> limiting ... filtering.

What I'd hoped, but didn't know for sure.

Thanks, Steve.  I could surmise this, but I assume you *know* this.

73, Steve, K9DCI


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