Thanks for those notes, Geoff. It did cross my mind that I would probably
need some home to site link to avoid continuous transmission and switch
between the amplifier front end filters or complete amplifier/TRF. For a
start this would be an additional challenge for the battery supply and
reliability of the system and I would avoid unattended transmissions. I
would use high gain, directional antennas at each end of the microwave link
to keep tx power down and avoid QRM in that band. I would provide good
filters to avoid bc QRM and I note your comment about core-generated IMD.
Initially I was considering only pointing at North America with one aerial
to get the hang of it and that should avoid most night time Eu bc QRM.
As to modulating a microwave signal with as much as 7.2MHz, I don't know
either, but I'm hoping I can purchase the microwave bits as off the shelf
products, so, that will be part of my search.
I wondered if there might be front end parts of Elecraft products that would
do some of the work and I would look at amplifiers off the shelf to
interface to the Beverage.
Thanks, again, Geoff and seasons greetings to you and all on reflector.
David
G3UNA
David,
My XYL and I have been away, so my apology for being slow to make a
comment.
If your remote Beverages are to be used on 160m, 80m and 40m, and a remote
TRF is used on each band to provide selectivity and gain, then unless
their outputs are combined before up-conversion then obviously you would
require a home-to-remote site link to band-switch the TRFs.
Of course I have no idea as to the level of BC signal(s) etc your
Beverages would present to the TRFs, but as you know the size and mix of
all Iron/ Ferrite cores used in the system (including the combiner's) must
be chosen with care to prevent "Core Generated IMD" becoming a "problem".
Another difficulty which might arise in an up-conversion scheme is the
generation of intermodulation products, either by the up-converting mixer
or by any subsequent stage. This makes me wonder whether it would be
better to run the 160m, 80m and 40m TRFs continuously, and view their
combined outputs as "Baseband". Then use this "Baseband" signal to Angle
Modulate (FM or PM) the microwave transmitter at the remote site. At the
home site the recovered baseband from a FM/PM receiver would be the 160m,
80m and 40m bands. Of course a home-to-remote link would not be required.
Here I must put my hand up, because it has been a -long- time since I
designed any microwave kit, and I cannot recall if a "Baseband" extending
to 7.2 MHz is feasible.
Best wishes to you, David, to all on the "List", and to everbody at
Elecraft for the New Year when it comes!!
73,
Geoff
LX2AO
On December 22, 2012 at 2:40 PM, David Cutter wrote:
I want to place Beverages at remote sites (for rx only), for 160m (useable
on 80 and 40m), but it's not viable to use a K0 at each site. Is there a
way to use a simpler system: perhaps a TRF on each band, up-converted to,
say, 2.3/2.4GHz then down-converted to each band for my K3 at home. The
transmit antenna will be at home and listen in diversity mode.
I can see various issues like image and sensitivity cropping up, but I
just wonder if this has been done. It would be nice if there was a lower
cost K series simple remote receiver available.
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