[amsat-bb] SO-35 Portable 10/03/99

[Mike73@xxxxxxx]

Howdy all,

I had my first experience working SO-35 mode B today with my portable system. 
I made quite a few contacts. I thought I'd pass along a few observations.

First, the system used was a Yaesu FT-470 dual band HT with stock battery, a 
Diamond duplexer and Arrow antenna. The system generated ~20 watts ERP on the 
uplink. I usually run a receive preamp on AO-27 because it makes it much 
easier to hear, but didn't run one on SO-35. The downlink signals were superb 
without it!

The pass began at ~1520 UTC. This was a high elevation pass for me in 
Vermont. SO-35 reached 72 degree + elevation. I noticed three things during 
this pass.

1) My antenna was aligned (polarisation wise) almost identically with a 
typical AO-27 pass. 70cm antenna was almost vertical. (15 degree CCW from 
vertical). This gave me the best capture on the uplink.

2) Mode B has a lot higher antenna "fiddle factor" than Mode J. In Mode J 
(AO-27) you are receiving on the higher frequency. If you use an Arrow 
antenna, you have 7 elements which translates into a fairly sharp pattern. 
You need to keep the antenna pointed fairly well at the bird to hear it. This 
has the advantage of also keeping the 2M uplink aimed well at the same time. 
On SO-35, with the downlink being on 2M, I found the Arrow 3 el 2M section to 
be extremely broad. I could hear the bird well, but not necessarily get into 
it because my 70 cm uplink wasn't aligned well enough. I ended up relying 
more on my AZ/EL printout to guide me than I do with AO-27. 

Part of the problem was also that my receive S meter was full scale most of 
the time. Next time out I will insert my adjustable RF attenuator in the 
receive line to keep the S meter on scale. I bet this will aid in antenna 
alignment.

Uplink Doppler was easier than I thought it was going to be. I simply went by 
my watch and antenna alignment as to when to shift the uplink frequency based 
on where I was in the pass.

3) As I usually see with AO-27, I experienced 2 polarity shifts during the 
pass. They both seemed to be at ~ 30 degrees elevation, one as SO-35 
approached and the second as it went away. I usually see shifts on AO-27 at 
~15 degrees. I need to operate more passes of SO-35 to see if this holds true.

All in all, it was a great time! Next is to try 1/2 watt on the uplink (~4 
watts ERP). What a fun bird!

73,
Mike, N1JEZ
AMSAT #29649
Local area coordinator
"A closed mouth gathers no feet."   
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