From: Greg. (greger_at_rfelektronik.se)
Date: Sun Jun 01 2008 - 15:52:22 PDT
There's so little activity on the list so I might as well post some nonsense :-)
I've updated my system with 2-3GHz capability using an RF Bay mixer as downconverter.
The Icom R8500 is only 0-2000MHz but by injecting a 1000MHz signal into the mixer
the range is extended to 3000MHz (3.8GHz with the Advantest Spectrum Analyzer), I chose
precisely 1GHz as it was easiest to calculate the new frequency, not having to add or subtract MHz's...
The 1GHz signal generator is way overkill - if you have any convenient way to build a 1GHz
(+10 - +13dBm) signal source (temp.stabilized) please let me know, I would love to have the
signal generator free for other work in the lab.
Notes on the Dish:
http://www.gravitywell.org/station/Dsc_7450.jpg
It's a 3meter (10') mesh dish (originally for Ku-band) that came in 8 'cake-pieces' which made
it quite simple to handle, assembling it was no problem at all.
I had it shipped over 600miles for a neat sum, those large dishes are hard to find here in Sweden,
most that do appear are old military dishes of solid metal weighin ton's, so I just had to get this one...
The Feedhorn is from RAS and has a dual feed, 1420MHz and 1665MHz probes, however at the
next service when I remove it - it'll be modified also for 2.1-2.2GHz reception.
(Currently the 1665MHz line is down due to a faulty Line Amp. after the LNA, there's simply not
enough juice to pump it thru those 30m(100') of H1000 coax...)
At the moment I'm using separate coax for each feed, though in the future I'm thinking of using
coax relays, however I don't like mechanical stuff in my electronics gear, mechanics break :-)
There's a nice waterproof cabinet on the back to put the electronics in.
http://www.gravitywell.org/station/Dsc_6087.jpg
Notes on the 19" cabinet:
http://www.gravitywell.org/seti/Dsc_6895.jpg
Through the roof there are several coaxes, two for the dish, three HF antennas and two VHF/UHF antennas.
Using the block diagram you get to see exactly how it's all connected (well, the parts related to the dish anyway):
http://www.gravitywell.org/seti/block.png
The cabinet contains powersupplies for both coax-fed line amplifiers and also the radios, everything with mains
voltage is screened and filtered with dual layer copper plates, capacitors and varistors.
All dc is fed with coax, all analog (audio output) signals are also using coax cabling all the way to the computers,
trying to minimize interference as much as possible.
All microwave (dish) cabling is hardwire (2mm wall copper tubing with coax inside) with SMA/SMB connectors,
as is the R8500's IF output of 10.7MHz as the receiver hooked up to this may get inteference from AM stations far away.
The patch-panel lets me choose which antennas connect to which radios as I also like to play with HF/VHF.
Also this is where I connect the downconverter for 2-3GHz reception, I just remove the jumper and plug this unit in - voilá!
Besides the R-8500 there are also two computer controlled Icom PCR-1000 receivers, highly underestimated radios -
they are very sensitive and you can select 3/6/15/50khz filter for any mode which is great for data decoding amongst others.
They can both do FFT analysis or they can scan a wider range of freqs as the dish drifts, they also measure total power input.
Next is my Advantest R3361A Spectrum Analyzer 9kHz-2.8GHz (0.009-2600MHz or 200-2800MHz),
which also got integrated tracking generator so it's most useful in a wide range of applications.
If anyone know how to mod this one with an IF output please let me know - it would be most useful....
And in the bottom is the HP signal generator (0.250-1000MHz), +13dBm to -136dBm, which currently is set to 1GHz
for the above downconverter, need to replace this some day with a fixed 1GHz source...
There's space left alone, some day I hope to get a steerable dish with tracking, and it would be nice to have it all
in the same cabinet (yes it's got a 19" radial fan)...
Well, that's it for today, now I'll get back constructing cavity filters (it's fun) :-)
Greg.
Argus Station JO89sn
Sweden
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