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

Philip Jenkins n4hf.philip at gmail.com
Sun Aug 2 23:53:58 UTC 2015

The discussion on uplink power fits right in with a conversation I had last

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

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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