"Ralph Mowery" wrote in
:


"Owen Duffy" wrote in message
...
Dave Oldridge wrote in
:

...
I used to have an FT-221 tricked out with a hot front end. Solar
noise would run the S meter up to well over the S9 mark and you
could even see the galactic plane passing through the antenna
pattern. Needless to say, it heard well on terrestrial 2m SSB.

That is no mean feat!

I think ambient noise temperature at 144MHz for an antenna pointed at
cold sky is somewhere around 200K to 250K, when you add a pretty good
receiver at say 30K, you are talking 230K to 280K total system noise,
and the sun is probably around 800K with a low end 4 bay EME antenna
setup (Gain~22dBi), for a noise rise of 10*log((800+255)/255) or
16dB.

A single yagi of gain around 15dBi is much poorer, not only is the
sun noise reduced proportionately to the gain reduction, but the
ambient noise increases with higher gain in the side and back area of
the antenna, but it still should be possible to reliably 'see' the
sun with a very good receiver.

Ambient noise temperature for a beam at zero elevation here in
suburbia varies from 1000K to 6000K depending on the day and time...
so a very low temperature receiver is wasted for terrestrial
contacts.

Owen

Owen

I would like to see what mods are made to the 221 to do that and also
what kind of antenna system. I have a 221 I am using with a gasfet
preamp in the shack that should be less than 1 db of noise fugure and
about 20 db of gain. The antenna is a klm 22c and 75 feet of 9913
type of coax. I can just see some sun noise with the antenna aimed at
the sun. It sure does not deflect the smeter several sunits. The
antenna is on an azel mount. I am sure the system is working as I
compaired it to an Icom 706 and another antenna that is mounted on a
tower and I am getting about the differance in signal levels I would
expect at the horizon.

Well, the sun is much quieter nowadays than it was back then. When I had
the station at its peak, I was running a single 19-element boomer at 85
feet, with boudle shielded Belden COAX. The preamp I was using was a
mosfet, which, to the best of my measurement ability (none of the signal
generators at work could come close to measuring it) gave it a 1.2db
noise figure. Now there was probably also a 6db ground reflection gain
from measuring the solar noise at the horizon (sunset or sunrise) and, as
I say, it was a period when solar activity was high (6 meters was open to
Mexico city a lot).

--
Dave Oldridge+
ICQ 1800667