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Re: Link budgets??



Tony, Jerry, et al:

Some alternative thinking about S-band IF:
Looking in the long term at doing more dsp at the antenna, using some of the
chipsets available from Maxim and Analog Devices, I realize that it is possible to
be free of the traditional v/u band IF's for the microwave gear.

Backing up to an evolutionary approach, I'm seriously thinking about some low UHF
IF OUTSIDE the amateur bands, which has a couple of advantages:
     freedom from conflict with vhf or uhf uplink (important since ao-40 supports
any combination)
     ability to choose relatively "quiet" frequencies

I've got a Drake 2880 modified for 2m, and that will be my first setup.  I'm
looking at taking another drake, leaving in the original crystal, and taking the IF
where it is, modifying the front end to improve 2.4 GHz performance.  This actually
simplifies the drake mods.  As I recall, this is about 3 to 400 mhz IF for 2.4 Ghz,
so I'll transvert in the shack (homebrew or modified DEM 2m-24mhz xverter) down to
an HF IF, since I have an extra HF rig available which was nicely designed for
transverters (Icom 751).

This solves the dilemma I ran into, no matter whether I used 2m or 70cm as the IF,
I could see some kind of conflict between my own uplink and what I was trying to
receive.

To simplify things, I'm also planning to use the Drake as the IF for the X-band
downconverte; this simplifies feedlines/control, and allows much better image
suppression at X-band than a 70cm IF, which is what I currently have.

For S-band uplink, I'll probably go up on 2m, based on what I have, and the
assumption that I won't need 2m up if I'm going up on S-band and the further
(possibly bad) assumption that if I'm going up on S-band I won't be needing to
listen to the V-band downlink.

Also considering the S-band uplink as the IF for C-band, but that's WAY down the
road.

Some wild ideas for thought, for what it's worth.
73,
Jim
wb4gcs@amsat.org


Tony Langdon wrote:

 > Hello Jerry!
 >
 > 24 Nov 00 12:07, you wrote to All:
 >
 >  JP> Any thoughts on S Band Converter output frequency? Choices seem to be
 >  JP> 2 meters or 70 cm. If there really is some problem with 70 cm
 >  JP> transmitter then 70cm might be the uplink band and therefore the
 >  JP> Converter should downlink from 13cm to 2 meters??
 >
 > My IF choices are likely to be dictated by available equipment.  I'd envisage
 > using 2m for my S band IF and may have to go to 10m for my L band, or transvert
 > via 2m and hope I can keep the two IFs far enough apart, before final
 > conversion to 1269 MHz.
 >
 > Converting from 2400 to 28 MHz would be nice (the HF box is by far the best Rx
 > here), but might be tricky, so will probably settle for 144 IF.
 >
 > Pity I can't open up the HF box for general coverage Tx, would have made
 > transverter operation a lot more flexible. :-(
 >
 > Tony, VK3JED
 >
 > .. (c) 1994 Elmer Fudd.  All wights weserwved. Hehehehe. . . .
 > --
 > |Fidonet:  Tony Langdon 3:633/284.18
 > |Internet: tlang@freeway.apana.org.au
 > |
 > | Standard disclaimer: The views of this user are strictly his own.
 >
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