[amsat-bb] Making the transponder sats as easy as the fm birds

[Greg D]

"subaudible" is only sub audible when you're dead on frequency if you're
using SSB.  For FM, where we are familiar with the technique, that's
fine.  But instead of a tone, you'd perhaps be better off running Single
Sideband AM (i.e. a sub audible tone of zero hertz); there was a
satellite recently that was in that sort of mode (I forget which bird),
and it was really interesting to work.

BUT, one huge problem with sending up a "beacon tone" for aligning
stations to, is that you're sending a 100% duty cycle carrier (though
perhaps reduced power) to a transponder that really hates having 100%
carriers run through it.  That's one of the big reasons why they don't
allow FM on the SSB / CW birds (the other being the extra bandwidth that
it takes).

Bottom line is that, yes, one can construct methods to aid in frequency
tracking.  But One True Rule software-assisted operation works really
well already, for those who can use it, and can be backed all the way
down to manual for those who can't.  And, manual operation of an SSB
station through a satellite is quite an interesting exercise.  I often
find it more satisfying than having to deal with starting up and fussing
with all the computer automation "help".  Just takes a bit of practice.

Greg  KO6TH


Eric Fort wrote:
> Computer control or actually a variation of such *IS* what I’m considering and proposing.  Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done.  Why however are we adjusting only one frequency?  It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
>
> AF6EP 
>
> Sent using SMTP.
>
>> On Apr 13, 2018, at 7:49 PM, Andy <w5acm at swbell.net> wrote:
>>
>> So VERY true!
>> Thanks Bruce,
>> ANDY w5acm
>>
>>
>> -----Original Message-----
>> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Bruce
>> Sent: Friday, April 13, 2018 9:40 PM
>> To: amsat-bb at amsat.org
>> Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
>>
>> Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
>>
>> 73...bruce
>>
>>> On 4/13/2018 8:41 PM, Eric Fort wrote:
>>> I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “.  Consider the following:
>>>
>>> As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
>>>
>>> Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
>>>
>>> We also know the frequency at the satellite of the various beacons 
>>> onboard. From this we can measure the doppler and work the other 
>>> direction
>>>
>>> If we transmit a subaudable tone of known frequency we should be able 
>>> to adjust the rx automatically by tracking the tone. (Acssb)
>>>
>>> Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
>>>
>>> Af6ep
>>>
>>> Sent using SMTP.
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>> -- 
>>
>> Bruce Paige, KK5DO
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> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions expressed
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> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb