And dont forget how you can take most old 10' dishs and disassemble it into 4 sections and make FOUR vrey high gain antennas. Just mount the feed to fully illuminate your quarter section of the dish and you have adequate gain in 1/4th teh space. Lots of fun with microwafves..

I thought I had photos, but cannot find them. I did find this old portable briefcase 1m dish system I put together for AO40:

http://www.aprs.org/ao40ant.html

Bob, Wb4APR

On Mon, Dec 28, 2015 at 5:00 AM, Tom Clark [email protected] wrote:

A related thread has been running on QRZ.com where I just posted this comment:

To all those who have been bewailing the fact that the microwave

...

technology needed to use the P4B digital GEO satellite let me
offer a couplke of comments. I preface this by saying I am a part
of both the AMSAT and VT "factions:".

All of you are making the mistake in believing that the 10 GHz
downlink will be complicated and expensive. Au contraire!

How many of you have a 20 to 40 inch dish you use to watch TV?
Well, the downlink that DirectTV uses is well up in the microwave
spectrum in Ka band, at about 12 GHz. Many of the other TV
satellites operate at ~11 GHz. Hams in several parts of the world
have found that the feed used in these dishes (called an LNB)
consists of a good feed (designed to work with the small offset
dishes) coupled to a HEMT Low-Noise Amplifier (don't believe the
advertising -- the Noise figure is closer to 1 Db and not the 0.1
dB the vendors claim). The LNA feeds a crystal-controlled down
converter which, off the shelf, makes the IF come out around 700
Mhz. I can go on Amazon, Ebay or Alibaba today and purchase a dish
plus a full LNB plus some dish mounting hardware plus 100 ft of
low-loss (foam) 75 ohm coax and have it delivered to my house for
less than $100.

The ~700 MHz IF can plug into a $200-300 RX SDR which converts the
~10 MHz wide downlink into usable signal channels. Instead of
tuning an analog frequency dial, you will select an appropriate
channel to listen to your buddies. Or you can feed the SDR into
your local VHF/UHF LAN where you can user your existing HT. If you
are a skeptic about using the TVRO hardware in the amateur world,
I'll note that just such hardware has successfully copied the DL
10GHz EME beacon in San Diego using a DVB Dongle+a laptop as the
receiver.

What I described was the downlink side. The ~6 GHz uplink will
require the addition of a 1-5W PA, a small (probably array of
patches) with the TX side of an SDR and an upconverter from
whatever IF your SDR can generate to 6 GHz. The C-band TX should
cost under $500-$600 with the bulk of the cost in the SDR and TX PA.

If you add up the RX and TX hardware, the tariff is less than the
price of an FT-1200 or KX-3, i.e. under $1000. We are working hard
to meet this goal since it meets FEMA requirements for portable
first responder "Go Boxes" to cover the need during major
disasters (Katrina, tsunamis, earthquakes) for reliable
communications in the first 24-96 hours. The ARRL and FEMA have an
agreement to have a hundred such "Go Boxes" (which also includes
suitable portable radios to augment whatever local resources exist).

For those of you who want to use "conventional" modes our current
plans call for a ~100 kHz wide LINEAR C/X-band transponder. I note
(with pride) that I have figured out how we can have a LINEAR
transponder built on RX software running the "main" payload and
getting a LINEAR ANALOG output from a hard-limiting digital PA.
Using the linear transponder will require you to have a bit
antenna/TX power, but it will be there as a challenge!

For all the nay-sayers please realize that AMSAT is trying to make
a miracle happen. We need financial, moral and technical support.
The "Space Biz" of today is radically different from what it was
when NASA and ESA were launching their own rockets and when AMSAT
was able to get sympathy for a bunch of "Space Cadets".

73 de Tom, K3IO (ex W3IWI)

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