Email from owner of Dual Band Circular Polarized Satellite Yagi

 

Peter,

Hello and I hope all is well at Gulf Alpha Antennas. Thought you might
like an update as to my experience thus far with the dual band CP satellite
antenna that you built for me. I have had no more water infiltration
problems since I filled the T-matches with RF grease... SWR is nice and
flat. I was immediately (as soon as the antenna was installed) able to work
AO-51 / SO-50 / and AO-27 with 1 watt TX power and the use of an ARR 432 RX
pre-amp located inside the shack... RX sigs anywhere from just above the
noise to 20 db over 9 depending on the elevation of the pass, etc. The
antenna has no elevation control and is fixed at 12 degrees but the overhead
null is not noticeable until the satellite goes above 70 degrees... I can
live with that! The higher passes are not the best for DX anyway.

Desense has been a significant problem and has kept me from being able to
copy my own downlink on 432 while I TX on 144. I added a Diamond Diplexer
between the pre-amp and the 432 rig but it did not mitigate the problem
sufficiently (specs list 60 db isolation on the 432 port). It allowed me to
hear my 432 downlink on AO-51 when my TX power was limited to 1 watt but
even then it was clear that the 432 RX was being desensitized; however, the
AO-51 downlink is 10 - 20 db over 9 at times which was strong enough to
overcome the desensitization. I was completely unable to work CW on FO-29
because even at 1 watt on 144 TX, it wiped out the 432 downlink. I know
that a big part of the problem is that I am using an FT-817 for the 432
RX/TX rig.. and it has a barn door front end by design.. but it is what I
got! I ordered (and received a couple days ago) a 432 bandpass filter from
Cross Country Wireless which specs out at 63 db attenuation at 144 Mhz with
.5 db insertion loss at 432 - 435 Mhz. I placed that filter in line between
the antenna and the pre-amp inside the shack. With the 432 bandpass filter
in line, I have no detectable desense on 432 when I TX on 144 at the 20 watt
level. This has allowed me to work FO-29 with very good success on CW. I
have also had successful CW contacts on VO-52 and AO-7 (both using 432
uplinks at the 10-15 watt level via a little 432 brick in line with the
FT-817) as well as a few FM contacts on HO-68 (this is quite an
accomplishment due to the difficulty in getting into that busy and "uniquely
configured" bird.. I have not had a chance to try HO-68 on CW / SSB because
of its' "Commissioning Status").

The antenna appears to function very well and it has allowed me to get my
feet wet with the linear satellites on 144 / 432 with a single antenna and
no elevation rotor. I spent $55.00 on the Diplexer and $102.00 on the 432
bandpass filter (I also bought a Cross Country Wireless 144 bandpass filter
at $102) but I think desense would be an issue even with separate antennas
on 144 and 432 given my 432 rig. If I had a 432 only rig such as a Kenwood
TR-851A, I probably would not need the 432 filter. Also, I have not made
any SSB contacts yet because I can't find my downlink on SSB... but I think
that is just operator error and has nothing to do with the antenna!! I do
not have any detailed data about my operations thus far; however, the
anecdotal evidence is clear.. the antenna works very well! If any potential
customer is looking for someone to contact who has used this antenna, send
them my way.... I am very pleased.

Take care,

Guy B.
Maryland