[amsat-bb] Question about PL/CTCSS on uplink

[Stefan Wagener]

I guess there might be a very simple answer:

On FM (one channel) satellites without the PL tone, any unwanted signal can
mess it up for everyone; on linear satellites any unwanted signal (uplink)
will mess up only a small portion (specific downlink frequency) and the
rest is still available. Bottom line PL tones on FM sats helps all of us.
No PL tones on linear sats will not be a significant problem.

My simple mind :-)

73 Stefan, VE4NSA

On Sat, Feb 3, 2018 at 9:11 PM, R.T.Liddy <k8bl at ameritech.net> wrote:

> The FM SATs decode discreet frequencies. The PL Tone goes up as 67 Hz
> and is detected only at that particular freq.
>
> The Linear SATs receive a wide bandpass and the incoming signals are
> beat against the SAT local oscillator and the resultant freq is the
> differential. Therefore, the resultant freqs are different based upon
> that differential. With multiple signals coming up to the SAT on their
> different freqs within the bandpass, which one would only have exactly
> 67 Hz? Tune across any HF Band with CW/SSB signals and you'll hear the
> result of multiple signals/freqs.
>
> Bob  K8BL
>
>
> > On 2/3/2018 09:45, Philip Jenkins wrote:
>
> > > I understand why FM satellites need an PL tone on uplink (to keep out
>
> > > land-mobile services, like taxi-cabs, etc), but why is a PL not
> required
>
> > > for the linear sats utilizing the same frequencies? A linear
> transponder is
>
> > > certainly capable of receiving/transmitting an FM signal (albeit not
>
> > > successfully demodulating that signal).
>
> > >
>
> > > This question came up at a satellite presentation I did, and I had
> never
>
> > > thought about it. ( Moreover, will radios even transmit a PL on SSB/CW
>
> > > transmissions?)
>
> > >
>
> > > Philip N4HF
>
> > > _______________________________________________
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