[Namaste-dev] Re: Antenna Collecting

Michelle w5nyv at yahoo.com
Thu Jun 19 09:13:07 PDT 2008


Excellent!
Let's see if I can't answer some of the questions.
The polarization hasn't been communicated to me. My feeling is that we should choose a polarization for the terrestrial experiments with the understanding that it might change. I see a lot of papers on dual-polarization and polarization diversity for terrestrial applications. Is that related to the simultaneous polarization that you mentioned with respect to EME? 
The frequency plan is:
10MHz downlink (TDMA) from 3400MHz to 3410MHz
10MHz of uplink spectrum between 5650MHz and 5670MHz, with access either allocated or by random access - we're investigating both. 
The parts and projects I've been looking at, like the transverter project from the San Bernadino Microwave Society, have an IF that is compatible with 2m. I think that for a first step at the hardware that's the sort of architecture we'll be using, building, and buying - something with an IF stage that is most likely compatible with 2m or whatever intermediate frequency makes the most sense.
I've gotten a phone call or two on the frequency and drift requirements, and those need to fall out of the requirements effort as soon as possible. We don't know them yet, but there is some expressed concern that putting all the RF in the outdoor unit will require careful attention. 
 -Michelle W5NYV


----- Original Message ----
From: "Stan, W1LE" <stanw1le at verizon.net>
To: Namaste-dev at amsat.org
Sent: Wednesday, June 18, 2008 8:15:26 PM
Subject: [Namaste-dev] Antenna Collecting

Hello The Net:

I am in the process of collecting antennas for the ACP. Both uplink and 
downlink.
For actual operation I am planning 2 each antennas on a common AZ/EL 
positioner.
Both collimated. Emphasis on full duplex.

So far I have ;

2 each directtv type offset fed dishes are available with feed support 
but no feed for 3.4 GHz.
(directtv feeds are for 11 + GHz and are probably circularly polarized.
preamplifier at the feed is actually a block down converter, with a DRO 
as a LO,
so there may be frequency stability/accuracy issues.)

1 each Directive Systems, 45 element rear mounted loop yagi. Linearly 
polarized, horizontal or vertical.
Model:  945LY  and others.

See: http://www.directivesystems.com/

Initial plan is to use on 3456 MHz terrestrial comms, horizontal 
polarization.
Will eventually sweep the VSWR to see how it plays at 3400-3410 MHz.
No signal generator on this band, yet.

I also have on hand a gridded dish designed for the 5.7 GHz datacom 
band, linearly polarized
for the uplink (5668 MHz ?)  Initial plan is for 5760 MHz and a DEMI 
transverter to 2M IF
for terrestrial comms.


Other thoughts, to be resolved later, probably not part of the  
requirements definition.

1.  Are we planning circular polarization (LHCP or RHCP ?) or linear, 
horizontal or vertical or slant ?
Waveguide septum feeds for simultaneous RHCP and LHCP are being designed 
by EMEers
for use at 3400.0 MHz. There is a big international effort focusing in 
on EME at 3400.0 MHz  !!

2.  What are the frequencies planned ?  uplink 5668.0 MHz,  downlink 
where in 3400 to 3410 MHz
Will the ACP be compatible with a 2M IF  ?  or what IF ?
Or will the ACP have a direct RF input at 3.4 GHz ? and we need not 
worry about a transverter.

3. What frequency accuracy/drift  requirements  ?



Some pointers.....

Down East Microwave Inc, DEMI, makes a low noise preamplifier, coax in 
and out.
See:  http://www.downeastmicrowave.com/

DEMI also makes a transverter for 3456 MHz with a 144 MHz IF
I am exploring changing the LO to support someplace in the satellite 
band 3400 to 3410 MHz on RX for downlink.

DEMI also makes a 5760 MHz transverter for a 144 MHz IF,
I am slowly exploring how this could be used for 5668MHz with a 144 MHz 
IF for a TX uplink

DB6NT also makes transverters for 3400, 3456, 5760 and a TX only for 
5668 MHz, usually a 144 MHz IF.

W1GHZ has come up with a design for a simple transverter for 1296, 2304 
or 3456 MHz. Pcb's are available
See: http://www.w1ghz.org/
I am exploring how to change the LO so we can use it somewhere in the 
3400-3410 MHz satellite band for the downlink.
A possible solution may be to use a DEMI MICROLO pcb for the local 
oscillator.

AD6IW has a VCO/PLL used with a accurate 10 MHz OCXO reference for a 
possible LO.
Price: unknown at this time.
Phase noise issue needs to be evaluated/investigated.

www. keps.it  
offers some interesting concepts. A circularly polarized patch antenna 
for 2.4 GHz.
I like their low noise preamplifer, with block RX down converter, for 
2.4 GHz
placed at the round parabolic dish primary feed.
Technique has potential for 3.4 GHz.
Even a dual band patch feed has potential, formuse with 1 dish

Ebay does offer directtv antennas.

Stan, W1LE    FN41sr  Cape Cod




ZZZZz

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