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Re: An experiment 2.4 GHz SS Cordless vs Weak Signal



"Edward R. Cole" wrote:
> 
> > think we need to design a 2.4g beacon that we can put in our
> > yard to help keep 2.4g phones away.
> > W4SCO
>
> Here's an idea on how to make one:  Take a dead Drake convertor and
> move the LO up to 2402 MHz (ala the "Dead Duck" article in a recent
> Amsat Journal article).  That would give you maybe 0 to +5 dBm output.
> Run that into a 20 dB mmic amp and you have your 100 mw beacon.  Want
> more?  I believe DEMI has just announced a 10w amp for 2.3 GHz!  Run
> that when you are not on AO-40 and it should clear a nice circle
> around your neighborhood of such devices.  To be nice you should shut
> it off when AO-40 is visible so your fellow satellite operators
> aren't affected...but maybe it won't desense your preamp?

Ed:

Easy to build an illegal version.  To make it legal, it needs to send
at least a valid callsign of the beacon operator's license, and to make
it "ham friendly", should send a little more info such as 6-digit
Maidenhead Grid Square, elevation, power, and antenna type.  CW would
be the cheapest way to go.  For example,
    AL7EB/B BP40IQ 10 WATTS TO LOOP AT 50 FEET

Our local weak-signal group (Northern Lights Radio Society) is
interested in getting members to operate beacons on some of the
higher frequencies (or, if you prefer, lower microwave frequencies)
like 902/903, 2304, 3456 MHz.  Any suggestions on how to cause the
"Dead Drake" to generate CW, so it could send out a proper beacon
message instead of simply illegal QRM?  I could put together a
simple single-board computer interface using a ZWorld microprocessor
board, to generate the ON/OFF control for each Morse Code character,
but I'm not sure of the optimal way to actually modulate the RF
generator you described with the ON/OFF (dit/dah/space) data.  This
approach would allow you to go very simple or very sophisticated
(just send callsign or send other telemetry data also with appropriate
sensors added).  This seems to make more sense to me than setting up
the Drake at 144 MHz away from the desired frequency and dedicating
a 2 meter radio as a transverter IF rig.

The other "issue" in my mind is the selection of a good
omnidirectional antenna.  To accomplish Leslie's purpose, a
quarter-wave vertical groundplane should be easy to build and suit
the purpose, especially with a 10 Watt amp.  But for a weak-signal
beacon, we would definitely want a horizontally-polarized omni
antenna, since folks would be using their SSB/CW systems to listen
for the beaccon and they will be horizontally polarized.  M-squared
makes HOLoop antennas that serve the purpose, but only up to 432 MHz.
Any idea how to construct a good horizontal omni, or better yet, a
stacked pair (or two pair!) to give the signal a little more oomph?

Not that I'm trying to suggest that anyone on this list would
actually put up an illegal noise source instead of a legal beacon...

73 de KB0ZEV
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