[amsat-bb] What on earth (or in space...) is going on?
scott23192 at gmail.com
Mon Dec 28 15:03:40 UTC 2015
I would certainly be interested in learning how to utilize the higher frequencies without spending a fortune.
In that spirit, sure would appreciate it if the mentions of known-good hardware from Amazon & eBay could include links to the particular items.
Montpelier, VA USA
----- Original Message -----
From: Mike Seguin
To: amsat-bb at amsat.org
Sent: Monday, December 28, 2015 05:58
Subject: Re: [amsat-bb] What on earth (or in space...) is going on?
I have a GPS locked 10 GHz beacon on Mt Mansfield here in Vermont and I
use the exact setup to monitor it.
I use an old DSS dish and a $7 LNB plus a FunCube. IF frequency is about
617 MHz for the 10,368.320 beacon.
I just looked on eBay and the LNB I use is there for $6.95 plus free
On 12/28/2015 5:00 AM, Tom Clark wrote:
> A related thread has been running on QRZ.com where I just posted this
>> 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
>> 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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