Re: [amsat-bb] mode A

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

At 09:14 AM 10/21/02 -0700, Bob V Johnson wrote:
>Hello	
>Jess, W4MVB raised the issue of our mode A satellites.  Which essentially
>is pitiful.  Since the demise of RS10, 12, the unreliability of RS15 and
>ao7, we have nothing.  Granted they are unsophisticated and perhaps at
>the low end of the satellite food chain.  They are (were) fun.  I cut my
>teeth, worked WAS on mode A, and meet a lot interesting people there. 
>This has been beaten to death on the BB before.  I know there is a lot of
>interest in this, in addition to our more bells and whistles satellites.
>73...Bob...W7LRD
>Seattle

Bob, Jess, Mode-A Ops:

Yes the mode-A situation has gotten slim.  I think Jess made some good
comments about receiving setups.  Many HF radios are not very low-noise or
sensitive on 10m.  A preamp would definitely help many of them.  It need
only be a 1 to 1.5 dBNF to work well.  ARR makes some nice JFET models
(P28VDA).

Regarding 10m antennas, I'll bet most are fixed in horizontal and not
elevated, so probably picking signals off higher lobes of the pattern.  I
would guess a turnstye would work well...same problem as omni antennas used
on 2m or 70cm for Leos.  

K7OE's "Texas Potato Masher" is one I would look at.  In fact, I NEC4WIN
modeled his 2m rectangular loop "turnstyle" design for 28.8 MHz (1 MHz Bw).
 I rotated the design to a "diamond-loop" configuration so it could be
supported by a single 35-foot mast and two horizontal wooden cross-booms.
The wire-loops were squeezed slighly narrower to reach the design impedance
of 100-ohms (so two loops at right angles and phased together with
90-degree delayline on one loop, match a 50-ohm coax).  The height is
appropriate to placing crossed-radials at ground level.  I never got around
to building the "critter"...but I named it "the Monster Masher"!  Pattern
comes out the same as K5OE's VHF design having slightly better gain at the
horizon and circular polarity overhead.  Might make a nice "cloud-warmer"
for 10m operation, too!

Maybe with the resurrection of AO-7 its time to roll it out again.

BTW the Amsat team under Mike, N1JEZ, are attempting to get AO-7 under good
command control so it will be reliable.  I think I read that there are some
mode-A birds under construction by other organizations, for the future.

Ed - AL7EB


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