>Newsgroups: rec.radio.amateur.misc
>Path: news.unomaha.edu!unlinfo.unl.edu!wupost!cs.utexas.edu!uunet!psinntp!digex!sgreene
>From: sgreene@access.digex.com (Stephan Greene)
>Subject: Summary - Getting onto the Hamsats
>Message-ID: <1992Mar20.165707.3374@access.digex.com>
>Keywords:  Satellites, OSCAR, AMSAT
>Organization: Express Access Public Access UNIX, Greenbelt, Maryland USA
>Date: Fri, 20 Mar 1992 16:57:07 GMT
>Lines: 249

On Wednesday, 11 March 1992, I posted a message to rec.radio.amateur.misc asking for suggestions and advice on 
equipment for using the amateur satellites.  This article is a 
summary of the responses I received, as well as some related 
e-mail and news articles.

A big thank-you to those who responded directly to my 
posting or posted a related article:

	mbutts@mentorg.com  or mbutts@qcktrn.com (Mike Butts), KC7IT
	psmith@mozart.convex.com (Presley Smith), N5VGC
	rwa@cs.athabascau.ca (Ross Alexander), VE6PDQ
	gary@ke4zv.uucp (Gary Coffman), KE4ZV
	Andy MacAllister, WA5ZIB (via CompuServe's Internet gateway)
	Don_R._Moberly.El_Segundo@xerox.COM, WB6LFC

Here's the consensus opinions (any misrepresentations or 
misquotes are my own - so flame me, not the nice folks who contributed!)


Antennas:
------------

For AO-13, the consensus is get to get KLMs, Telex/Hy-Gains, or 
roll-your own,  Nobody liked the Cushcraft satellite antennas - 
they appear to have problems in wet weather.  Bigger is also 
better, if you have the space.  Several people mentioned the 
KLM  22C and 40CX pair as excellent performers (again - you 
need the room for those long booms!)  KE4ZV stated his pair of 
KLMs (the big ones!) lets him work AO-13 with 3 to 30 watts 
(hardline feed and rigorous attention to routing the feedlines a
nd cables properly to maintain the antenna patterns helps, too.).  
Others mentioned the KLM 14C/18C pair as good performers - 
but you need more power on the uplink.  

Telex/Hy-Gain antennas were recommended by several people 
as a less expensive alternative to KLMs that work almost as 
well.  There's also M2 (started by an engineer from KLM).  
While no one who responded uses them, the information I 
received from a call to their factory in California suggests 
they are comparable to slightly better than the KLMs in 
performance, and about the same in cost.  Dave, WB6LFC, said homebrewing antennas is also feasible - it takes work, 
but attention to detail results in top-notch performance 
for very little money.  Finally, Ross, VE6PDQ, reported good 
results using a pair of Cushcraft 215WBs on receive.

Problems encountered with AO-13 antennas include routing 
cables and feedlines off the back of the antennas 
(to preserve antenna patterns), use of fiberglass cross 
booms, mounting preamps as close to the feedpoint as 
possible, and long antenna booms drooping.  (Gary, KE4ZV, 
recommends using a rope to brace the boom or stiffening 
booms and fiberglass masts internally with foam-in-a-can 
insulation.)

On antenna rotators, it appears the Alliance UD-100 is no 
longer made, though it should still show up at hamfests.  
People with long-boom antennas report the Alliance 
rotator is too weak to move a big array anyway, and 
recommended Yaesu's elevation-only rotator or their 
Model 5400 azimuth-elevation unit.

Antennas for the low-altitude satellites appear to be much 
less critical.  J-poles were most frequently mentioned 
(the design from the AMSAT Journal?), but dipoles, ground-
planes, and yagis are also in use.  Several people work 
RS-10 quite well with antennas in the attic.  Best results 
are with steerable antennas, but the high operator 
workload during a pass (unless the satellite is just 
grazing your access circle) almost demands computer 
control of the rotators.


Preamps:
-----------

You need a preamp for AO-13.  (I can hear the downlink 
after a fashion on a Ringo fed with cheap coax and a 
10 dB preamp in the shack, but it's not communications 
quality reception!)  Only two people mentioned a specific 
brand name (Advanced Receiver Research and the unit 
included with the Ten-Tec 2510), so I assume almost 
any GAsFET preamp in the 20dB gain class is adequate.  
THE PREAMP MUST (almost always) BE MOUNTED AT THE 
ANTENNA (check the discussion in Chapter 9 of the 
Satellite Experimenter's Handbook and you'll see why!).  
KE4ZV recommends mounting the preamp AT the antenna 
feedpoint, if your elevation rotator can handle the 
unbalanced load.

While no one mentioned it (maybe it's obvious), if the 
antenna is used to transmit (say Mode J) as well as 
receive (on Mode B, for example), the preamp MUST 
either include RF-sensed switching, or be switched 
out of the line before you transmit.  TRANSMITTING 
INTO AN UNPROTECTED PREAMP WILL DESTROY IT INSTANTLY!

Preamps also seem to help on RS-10 (especially with 
older HF rigs) and on the Pacsats.  It seems to be a 
case of "try it, and get a preamp if it looks like it 
would help").


Rigs:
------

Three radios were mentioned by name - Yaesu FT736 
(and it's predecessor, the 726 with satellite module), 
Kenwood TR751 (a mobile-capable 2 meter multimode), 
and Ten-Tec's 2510.  The Ten-Tec unit is out of production.  
The few units left are selling for about $300-350.  I'm 
sure other multi-mode radios, and setups with converters 
and transverters work well, too - it's just that no one 
mentioned any by name.

Power output required is a function of the satellite, 
your antennas, and how badly you want to communicate.  
[QRP on the satellites is just like QRP on HF - you need 
good antennas and feedline, you have to pick optimal 
passes, and skilled operators at both ends are needed.  
Given the apparent "calmer" operating style on AO-13, 
QRP is probably easier there than on 20 meters!]

Anyway -about power for AO-13.  3-30 watts will 
work if you have top-notch antennas (KE4ZV).  
KC7IT uses 50-100 watts (Ten Tec 2510, Mirage D1010 
amplifier, KLM 14C/18C fed with 50 feet of 9913).  
Both KE4ZV and KC7IT use Mirage D1010 amplifiers 
on 70 cm when they need a little extra power.  
For an "optimum station", WA5ZIB recommends 
60 watts on 70 cm and 80 watts on 2 meters for 
AO-13, assuming good antennas (Telex/Hy-Gain or 
better) and feedlines, and 20 watts to a 5' dish for Mode L.  
Andy emphasized that you can get by and have lots 
of fun with much less!

For Mode A, WA5ZIB said 6 watts to the AO-13 2 meter 
antenna will work well.  People using omnis report 
success with the Pacsats running 50-70 watts to a 
J-Pole (N5VGC).  Several people said they (or someone 
they know) have no trouble using RS-10 at lower 
power (10-25 watts) with simple, omnidirectional 
antennas.  Again, it's a case of "try it and see if it works."

There was unanimous consensus that the receiving 
quipment (antenna, preamp, feedline, and receiver) 
is more important than the transmit equipment.  
Running more power "to hear yourself" is frowned 
upon, to say the least!  It's also important to be able 
to vary uplink power to adjust to specific conditions.  
Both the Ten Tec 2510 and the Yaesu 736 have 
continuously variable power output  (I guess the 
rest of us just have to fiddle with the drive controls 
on our rigs!).


Accessories and Other Stuff:
----------------------------------

You need a PSK modem to use the Pacsats.  PacCom 
makes fully assembled units, either already integrated 
with their own TNC, or as a board you install in your 
TNC-2 clone.  They make similar 9600 bps units for 
accessing UO-22.  The downlink receiver (on 70 cm) 
should be capable of being tuned by the PSK modem's
AFC lines.  Newer radios can use the up/down lines from 
the microphone jack or an accessory connection on the 
rear panel.  Older radios must be modified, or be tuned 
manually.  N5VGC told me he sees about 20KHz of doppler 
on an AO-16 pass, and that without automatic tuning, 
operator workload is too high to do much else besides 
tune the receiver!

Just about any radio suitable for packet on 2 meters 
will work for  AO-16, WO18, and LU-19.  To run 9600 
bps on UO-22, modifications to bypass the microphone 
and speaker's audio processing circuits are required.  
I've seen some reports on rec.radio.packet and in the 
various Hamsat columns that differences between 
UO14 and UO-22's transmitters make UO-22 more 
difficult to copy.  (I'll worry about that problem 
later - I'll start with AO-16 and LU-19 first!)

No one mentioned computers - again, it must be 
obvious (also, we're "talking" using computers!).  
They're handy, and you need one IN THE SHACK when 
working the Pacsats or for automated, real-time 
control of antenna rotators (useful for low altitude satellites).  

Other operator aids mentioned, or I thought of on my 
own:  If your radio can't slave uplink and downlink 
tuning (Ten Tec 2510 and Yaesu 736 can), you need 
something to help convert between uplink and downlink 
frequencies (and account for doppler shift and calibration 
errors on the radios' frequency readouts).  A cardboard 
slide scale or dial will work.  I'm thinking of programming 
my HP48 to do the conversion for me.  You need something 
like this to know where to tune on the uplink to hear 
a given downlink frequency.

Software to track satellites and predict passes.  There 
are many programs that work.  Price ranges from free 
to $70 for state-of-the-art QuickTrack or InstantTrack 
(available from AMSAT).  Special software is also needed 
to use the Pacsats, and to interpret telemetry data.  This 
software is also available from the usual ham sources, and 
from AMSAT (BTW, software sales support the 
amateur satellite program!)

Polarity switchers optimize antenna performance by 
allowing switching antenna feeds from RHCP to LHCP as 
the need arises.  They are a very useful add-on, but  
don't appear essential.  

Equipment to measure power output, SWR, transmit
 frequency - all useful (see - satellites are not that 
different from HF!).


Conclusion:
---------------

Finally, there's AMSAT!  They're the people who build 
and run several of the satellites (AO-10, AO-13, AO-16), 
and have a hand in many of the others!  They're also 
beginning development of the replacement for 
Oscar 13 (known as Phase 3-D).  ANYONE INTERESTED IN THE 
AMATEUR SATELLITES SHOULD BECOME AN AMSAT MEMBER.  
Its' the closest place I've found to one-stop-shopping 
for information on the satellites (this newsgroup is number 
two, at least until I get onto the satellites myself!).  
You can reach AMSAT at:

	AMSAT
	PO Box 27
	Washington, DC  20044
	(301)589-6062

I know there are several AMSAT members in this 
newsgroup (who even have satellite experience.  I'm 
still working on it!) - so you can always ask here!


Again, thanks to everyone who answered my query!  
You've helped a great deal.   I'll look for you on the birds!

73, Steve          (AMSAT Member 21876)

		packet::   KA1LM@N4WJN.VA or KA1LM@WA3ZNW.MD
		Internet:  sgreene@access.digex.com