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Re: FO29/RS13 compared to UO14 - Why?



Thanks to all for your comments. Based upon people's indication of how their
S meters are behaving, I'd say I have a problem in my antenna system.
Several commented that their S meters were strongly indicating for FO29 and
UO14 which is definitely not my experience.

Can anyone recommend a quantitive method for testing the antenna system with
the preamps? my local 70 cm repeaters give me an S9 signal with the
satellite antennas.

Jim, KD7GND

----- Original Message -----
From: "Jon Ogden" <na9d@mindspring.com>
To: "jim" <jmadden@seanet.com>; <amsat-bb-digest@AMSAT.Org>
Sent: Wednesday, September 20, 2000 12:48 PM
Subject: Re: [amsat-bb] FO29/RS13 compared to UO14 - Why?


> Jim,
>
> As other users have pointed out, FM birds put their full downlink power on
> one frequency instead of across a full passband.  Additionally, SSB
readings
> on an S-meter are generally lower because it is an amplitude modulated
> signal.  The highest meter reading and therefore, the largest signal
occurs
> on a voice peak.  Your S-meter on your radio is probably not fast enough
to
> catch the voice peak so you get a more "average" reading than you do with
> the constant carrier of an FM signal.
>
> Secondly, there is also the fact that with a linear transponder bird, the
> whole goal is to conserve the birds power.  The downlink signal on a
linear
> bird is directly proportional to the uplink signal.  In other words, if I
> run 150 watts into my 22 elements on the uplink and get the strongest
signal
> at the bird, I will get the largest percentage of power delivered to the
> downlink.  Say the bird has a total output power of 10 Watts.  If there
are
> 10 users on the bird and the bird hears each of us at the same level, we
> each will get about 1 watt on our respective downlinks.  Say however, I
have
> 10 times the power level of everyone else at the bird.  I will then take
10
> times more power on my downlink than everyone else.  Therefore, I will get
> well over a watt on the downlink and everyone else will get significantly
> less than a watt.
>
> So good satellite users keep their transmitter power as LOW AS POSSIBLE so
> as to maximize the total transponder power available to other users.  P3D
> will limit you and even give you voice feedback when you start pushing the
> AGC of the transponder.  FO-29 doesn't have this.
>
> There is no need to be heard 59 through the satellite.  Most people run
> enough power so they can comfortably hear themselves and the other person.
> Satellites are a WEAK signal mode.  This is why it is SO essential to have
> really good ears when working the birds.  It's more important to HEAR
well.
>
> Now, I question how well your preamps are working at the mast.  Just last
> night, I was listening to FO-29 (I can't get into the bird because my 2m
> beam is hosed right now).  With my new preamps on (>20 dB gain on 432), I
> was getting a 59 + 10dB signal from FO-29.  Without the preamp (just using
> the internal preamps on the 847), I was getting about 53.  I receive FO-29
> as well as I do UO-14.
>
> I think your issue with receiving FO-29 better could be that something is
> amiss with your preamps or that the people you hear are just keeping their
> transmitter power low so that they don't overload the bird.
>
> 73,
>
> Jon
> NA9D
>
> ----- Original Message -----
> From: "jim" <jmadden@seanet.com>
> To: <amsat-bb-digest@AMSAT.Org>
> Sent: Wednesday, September 20, 2000 9:03 AM
> Subject: [amsat-bb] FO29/RS13 compared to UO14 - Why?
>
>
> > I've been playing with satellites for a few months now with my Yaesu 847
> and
> > autotracked M2 antennas.
> >
> > My question is why do I get such fantastic reception of UO14, but FO29
> > signals are down in the static most of the time.  Does UO14 have
> > considerably more power? both satellites are  leo. Both satellites use
70
> cm
> > for the downlink. They do use different modulation methods but would
that
> be
> > a problem?
> >
> > I'm using preamps mounted on the antennas with low loss coax. What do I
> need
> > to do to improve reception of FO29?
> >
> > thanks. Jim
> > kd7gnd
> >
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
>

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