[amsat-bb] Why too much uplink power is bad/eggbeater antennas on xmit

[James Duffey]

I wonder what kind of feed line he issuing. RG8X or smaller can really eat the power up.

On Aug 3, 2015, at 7:17 AM, David <dwarnberg at verizon.net> wrote:

> Philip,
> 	I use M2 EggBeaters, both have preamps for receive... I use no more
> than 10 watts and am heard fine, if and only if the sat is on a low pass
> (i.e. less than 15 degrees above horizon) I may use 15 to 20 watts to be
> heard..  50 watts is way too much power and indicates another problem if
> they cannot be heard..
> 
> My 2 cents
> 
> David
> KK4QOE
> 
> -----Original Message-----
> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of Philip
> Jenkins
> Sent: Sunday, August 02, 2015 7:54 PM
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] Why too much uplink power is bad/eggbeater antennas on
> xmit
> 
> The discussion on uplink power fits right in with a conversation I had last
> weekend...
> 
> While I was not wearing my AMSAT badge at a hamfest on July 25, a married
> couple - both hams, both fairly recently licensed - recognized me from a
> previous hamfest when I was wearing that badge. Their question for me was to
> why they could hear  (a) satellite(s), but no one could hear them...
> 
> The satellite in question is SO-50 (and I did take a few minutes explaining
> the difference between linear birds and FM-only ones).
> 
> Before the OM joined us, his YL told me that her husband doesn't want to use
> antennas like the Elk or Arrow, even on a tripod. I then suggested to her
> that he consider a fixed elevation mount, so as to only have to track the
> azimuth.
> 
> Then the OM showed up. He doesn't even want to consider the fixed-elevation,
> because he'd still have to track . I suggested he leave the tracking to a
> computer...still not acceptable
> 
> He then explained that they spend a lot of time in a motorhome. For his
> antennas now, he is using eggbeaters. On the 440 receive side, he is
> thankfully using a pre-amp, so he can hear adequately,
> 
> For the transmit, he is using 50 watts into an eggbeater, and still can't be
> heard on the satellite. He told me one recommendation he was given was to
> increase the xmit power to 150 watts (*I visibly shuddered*) so as to
> overcome the non-directionality of the eggbeater. (And I explained why too
> much uplink power is bad for both FM and linear sats, in terms of bandwidth
> and power consumption on the satellite.)
> 
> On further questioning, he knew about the PL tone to turn-on SO-50, but
> didn't know about the different PL to actually access the satellite on each
> transmission. I explained to him that it is like terrestrial repeaters; no
> matter how much power you run, the repeater won't "hear" you unless you
> transmit the PL every time.
> 
> In a follow-up email the next day, I passed on the SO-50 operating guide
> (PDF) from the AMSAT website, and advised him to try programming his radio
> with the proper PL and frequencies for adjacent memories BEFORE consdering
> increasing transmit power.
> 
> I really think his problem is not using PLs, rather than inadequate power
> levels on an omni antenna.
> 
> My question is two-fold (I still need to follow-up with him). 1) For those
> of you successfully using eggbeaters for the uplink (and he is adamant about
> not using a yagi, despite my advice that the performance will suffer quite a
> bit with eggbeaters), what output power do you typically use? I think 50
> watts into an eggbeater is probably still too much power, considering 5
> watts into an Arrow is usually enough for successful communications.
> 
> 2) I know that various power levels are suggested for various gain antennas,
> but I'm wondering what the suggested EIRP is for successful - not ones which
> would hog the satellite  - uplinks.
> 
> Philip N4HF
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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
> are solely those of the author, and do not reflect the official views of AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb