[amsat-bb] AO-85 vs SO-50 for newbies with modest equipment

[Daniel Estévez]

Hi Felix,

I'm also having a bit of trouble working AO-85. My equipment for FM sats
is an arrow antenna, FT-817ND for RX and FT-2DE for TX.

With this I can work SO-50 without any problems. Whenever more that a
couple of degree's over the horizon, I can hear it well and I hit the
transponder perfectly. In fact, the UHF downlink helps a bit in pointing
the antenna, and I would usually point it by ear, having just a mental
picture of the pass. If you can hear well the downlink, then you can get
in well, because your uplink has wider beam and much more power.

However, with AO-85 it's a bit hit and miss for me. I find it a bit
difficult and random to hit the transponder, and I think it would be
almost impossible for me to work it half-duplex. I will often retry and
tweak things if not hearing myself on the downlink properly. The
downlink of AO-85 is very strong, and it can be heard with the antenna
all over the place, even pointing into the ground sometimes. So you have
to know well where the satellite is before transmitting, and listen
yourself and tweak the antenna as you transmit.

Several people report, and my experiences agree with them, that the
receiver on AO-85 is a bit deaf for some unknown reason (this has
nothing to do with the 70cm band) and that it's 5kHz low in frequency
from the published specs. Thus, I will start a pass on 436.165 and work
up from that as the pass progresses, being at about 436.175 at midpass
and 436.185 at LOS.

Regarding working full-duplex, if you're going to get a single radio to
do full-duplex, check very carefully that it won't suffer from
desensing. This can be very critical, especially when working V/U. If
you already have a UV-5R, I would probably get a second of those, or
perhaps another handheld with better sensitivity to use as RX if you
want to invest a bit more money. Of course, you'll need a duplexer to
use the elk with two radios.

73 and looking forward to working you on the birds,

Dani M0HXM/EA4GPZ.