[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

RE: Newbies! Low cost U/S stations.



As put up before (EasyOn 40) I'm writing a magazine article to awaken my
friends.
I'm also giving memo's and talking to local clubs. Here's my thrust, I hope
its of
interest.
==================
Setting a target of Low Cost on to AO-40 begs the question; “How much ON?”
If it is to have a strong signal and hear the satellites base-band noise at
max range
then the task is difficult. If it is an introduction, an appetite wetting
then it’s
surprisingly easy.

I tackled this. Step one was to hear and decode the telemetry. There has to
be some
starting point and I chose a reasonable SSB receiver, a reasonable Pentium
computer,
12V supply and a standard junk-box or swap-meet visit for the connectors,
coax and
sundry. Throughout I have used what I felt where the most available to me.
Often
buying something from an individual meant getting a Bank Draught at $25
extra which
made some lower cost alternatives dearer than commercial - where my VISA
made the
purchase easy.

Step 1.	Drake converted but 122MHz IF	$150	US$65
	Ant. “Paper" antenna - 22T helix	$10	US$5
	Az/El	Clamps, Rope, Vice or ??	$0	US$0
	Software down loaded free of charge!
I have used this both to decode the beacon and to raise my enthusiasm.
My IC-PCR100 makes it easier but there are plenty of good designs for VHF
converters
(NZART’s Break In, May/June 2001 – “A Kiss VHF converter”) which, with a
surplus xtal,
will bring that 122MHz down into the average HF receiver’s tuning range. Say
$10, US$5.
(Xtals. Before synthesizer gear became the norm in aircraft, the “real” gear
used stacks
of crystals – round 64 MHz. They drifted and had to be replaced every few
months. I got
a draw full for nothing from an avionics crowd.)
Total	$170	US$80

Step 2 is the DEM LNA kitset at $124 (US$51). Make your own case or spend
the extra $$
and get the whole thing. I used surplus connectors and my own enclosure. I’m
working on
using an “N” type barrel connector for the input – saves space and an
adapter with losses.
This will enable reception of the beacon at max range – 65,000 km.
Total now	$194	US$131.

Now I’m hearing stations and drooling!

Step 3 is 70cm uplink. That’s going to cost me about $500 for a second hand
unit. I don’t
know US prices for an equivalent but I feel it’s got to be about US$250
somewhere. Antenna
could be a home made helix (say $20 US$15?) but I’ll actually use a 20 year
old 10 el Xed
Yagi I have sitting around.
Total up to $700	US$330

Step 4 is a dish. Now I need to pay some attention to pointing but I do not
have to have
advanced Az/El rotators. It’s the Armstrong method like I used for
Oscar-6/7 – and they
moved a lot faster across the sky. Mind you I was younger and didn’t mind
running outside
to peak the beam!
Again I’ll use a “paper” helix design in a 4” x 2” can base. I’ll obtain a
light reflector
like they use in big warehouses. They are about 2’ (600mm) and should give
me 21-db gain.
How do I cost this? If I have to buy everything I’ll allocate $40 including
the can of fish
fillets from the supermarket! Or, how about a surplus Sky TV dish – 800mm (2
’8”) for $65.
I’ll add on $100	US$45.

That gives me a stepped total expenditure of $800 (US$375) and I can have
pull out earlier
if I don’t enjoy the challenge. This set up puts me in the running for good
contacts and
excitement.

There are plenty of alternatives along the way. Some will find more
economical ways of
achieving the end and we can all find more expensive ways as well.

I guess the major saving in getting on to AO-40 is the rotator system. The
learning and
satisfaction leaves the mode A etc. systems for dead!
Aerials are a cinch. Surplus gear and kits abound (thanks to folk like Bob
Seydler, Mark
Fossum and David, G0MRF) not forgetting the excellent software being
written. The
satellite’s going great! AO-40 is EASY, just don’t be frightened by the
numbers and range.

I neglected the one piece of test gear I am finding essential. A 2.4GHz
signal source.
Made mine for $2 – the cost of the 78L05. Apart from an old tin I used as
the case and a
strip of brass from my scrap pile, everything came off an old 486 board.

How does that stack up with you guys in the US? Apart from some starting
problems locating
sources, everything has been reasonably straightforward. Lots of learning. I
was surprised
how easy it is to get good results on SHF.

See you on AO-40.

Terry,  ZL3QL.

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home