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GB3XGH:
10GHz
From David Wrigley, G6GXK
06 October 2006 21:04
The Manchester 10GHz
beacon is finally operating under test conditions at a
temporary location. When the licence finally arrives it will be
moved about
4.5Km to a site with a new antenna with a better pattern and slightly
better
takeoff all round - and less interference with my home transverter.
North
is presently a badly obscured direction from here.
In the present situation
it is likely to be switched on and off over the
immediate future as modifications take place - so don't start
to dismantle
your receiver if you fail to hear it. Currently the problems are
mainly to
do with concerns over temperature of the heatsinks - however a
few fans seem
to have fixed the problem! Also mains switching surges can be
heard as
variations in the tone. It looks like a better PSU is indicated.
The set-up uses a mixer
stage and only partial lock to GPS. The final signal
may therefore be a few hertz out from the nominal. This will be
fixed
shortly when the DDS clock is derived directly from the GPS.
The present scheme is
similar to a normal transverter in that it uses a
mixer/ LO +filter to get to the final freq. This was due to the
unsuitability of the DDS to provide a clean enough signal after
multiplying
to 10368MHz.
LO is 106.52MHz x 96
= 10225.92MHz locked to GPS
IF from a DDS a la G4JNT (unlocked 10MHz OCXO ref) 71.445 x2 =142.89MHz
The "out of band" IF is deliberate and intended to avoid
interference with
my 2m IF. The LO level is 20mW and the IF power level is 10mW
as they go up
to the beacon mast assy.
The output signal is
as follows:
1. Morse 10368.810MHz
using an amplitude ramped on off keying "G6GXK
IO83VO" followed by a continuous tone until the end of the
minute.
2. Morse FSK 10368.810MHz
shifted to 10368.8106MHz "G6GXK IO83VO" followed
by a continuous tone to end of minute and then repeated
Antenna is omni and the
new PA is giving out a considerable increase in
power over the old 200mW beacon. PA is rated at 8W but is currently
under-driven on advice from UKuG beacon licensing liaison people.
Reports sought and will
be very welcome whatever they are - good or bad!
Please let me know - where you are and whether you can hear it.
I will use these reports
to consider whether to increase the height of the
antenna.
There is microwave life
in Manchester after all.......... :-)
David Wrigley, G6GXK
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