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Re: Hamsat FM



I respectfully disagree. For about $20 users can purchase a single frequency tone encoder for your radio, or build one for much less. Furthermore, once we let the genie out of the bottle of allowing FM on transponders, we'll never get it back in. Pretty soon the small percentage of the hams that don't understand the schedule or agreement will think FM is fine anywhere and anytime, and then the transponders will be useless. Once you go down that road there is no way back.

There are other issues as well. With FM on a transponder there is nothing holding users to one pair of frequencies. Without tuning for Doppler, or with crude 5 kHz steps and no AFC on the satellite to center things, the users would be all over the passband. Once you add multiple users, like would happen over Europe and the US, the downlink power would be split over a wide bandwidth as the various user uplinks diverge because of Doppler. Pretty soon instead of one fat hog that can hear himself on FM, you have lots of little squealing piggies sharing the one watt of downlink power over 30 kHz that can't hear anything coherent and have ruined the satellite for everyone. Over India, and probably the extreme north like where you are, the single FM users survives on VO-52 simply because there is no competition.

Allowing or encouraging FM on transponders is a dumbing down of AMSAT that I will not stand by to see happen. If the available FM satellites are not enough for your pleasures, step up to the SSB transponders, or support a satellite program that intends to build more FM birds, or convince the many educational or experimental groups to configure their sats for 2 way FM use when they are done with them (ie Saudisat series, Unisat series, Mozhayets series, future cubesats, etc....)

When Posat comes online again, I'll bet there will be no tone. Posat is bigger than your average FM sat like 27, 50, or 51 and has more power available. With it's big hairy downlink it will be like the heyday of it's predecessor UO-14, and we'll all forget about using FM on transponders.

Happy Thanksgiving for those celebrating today and 73 to all,

Drew KO4MA

-----Original Message-----
From: Mark Saurman <vo1one@gmail.com>
Sent: Nov 24, 2005 8:21 AM
To: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Hamsat FM

On 11/24/05, Andrew Glasbrenner <glasbrenner@mindspring.com> wrote:
> We all know FM works on transponders, MOST of us know it's not welcome because it hogs power. FM is 100% duty cycle, and steals downlink power from polite users on SSB and CW.
>
> Please leave FM to the FM satellites, and SSB and CW to the transponders.

It would be nice to see Hamsat allow FM mode for one day a week.  The
only satellite that does FM and does not require tone access right now
is AO-27, and that is on the air for only 6 minutes at a time.  For
those of us in northern latitudes like much of Europe, by the time
AO-27 gets up here, it switches to a minute of packet then shuts off.
Many in Europe still don't have tone boards in their radios and may
benefit from a sat which allows FM without tone guard.  The Indians
use FM on their bird; there's even mention about it on AMSAT-INDIA's
webpage.  If they could schedule just some time to allow FM users I'm
sure many will benefit from it and the SSB/CW crowd will still have
the vast majority of time on the satellite.

73,
Mark VO1ONE
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