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Re: Mode-S Antennas



The hard part is the oscillator.  I'm kicking around the idea of using
a Maxim MAX2751 VCO ($3.50 in one-seys, $1 in Qty) and some sort of PLL 
circuit-- the simple one in the Drake-- a fixed divider and a XOR phase 
comparator-- or more complex like a National LMX2326 and a PIC to program it 
(same parts count, and minimal difference in price-- and more flexible)...

If I/we can do that, the filters, amps and mixers are commercially 
available.  But, no it won't be a $25-$50 downconverter-- but it could be 
smaller and higher performance than the Drake.  Right at the back
of a Helix feed would be nice-- or in a dipole reflector feed for the 
Conifers...  Maybe send a TXCO high-stability freq reference (nice thing 
about PLLs) from the shack up one cable, and the signal down another.. lots 
of cool ideas here....

If I only had more time to work on things like this....:-)

Fred W0FMS

>From: Jon Ogden <na9d@mindspring.com>
>To: Gene Harlan <atvq@hampubs.com>, Steve Rubin <ser@tch.org>,   Art 
>Goldman <artg@home.com>
>CC: "Mark D. Fossum" <n0nsv@AMSAT.Org>, <amsat-bb@AMSAT.Org>
>Subject: Re: [amsat-bb] Mode-S Antennas
>Date: Mon, 12 Feb 2001 19:16:05 -0600
>
>on 2/12/01 3:30 PM, Gene Harlan at atvq@hampubs.com wrote:
>
> > Also, they sell Downconverter and mixer IC's that covers the 2.4 GHz 
>range.
> > Have not read yet, but I downloaded the PDF spec sheets. Seem to be 
>cheap
> > parts if they can be put together to make a new version of the Drake 
>2880???
>
>You know, this isn't a bad idea.  Perhaps one of us with a Drake should
>deadbug a design and publish it so that others could build them.  
>Certainly,
>the circuitry could be done for fairly minimal cost.  I'll admit I have
>opened my Drake up yet, but I can't imagine there is that much in there.
>With all the knowledge, I would think we all could put our brains together
>and reverse engineer a kit.
>
>73,
>
>Jon
>NA9D
>
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Member:  ARRL, AMSAT, DXCC, NRA
>
>http://www.qsl.net/ke9na
>
>"A life lived in fear is a life half lived."
>
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