My 10GHz QSO Log
WBFM and NB Activities

22 June, 2008
Sunday 22nd June '08 saw my first QSO on 10GHz SSB. I am so pleased, it has been a long time in the construction and
planning. The distance of 95km from Mobbs Hill Lookout, Carlingford (inner west Sydney) QF56mf to Mt Gibraltar QF55fm,
SW of Sydney. It is a line of sight path. VK1BL, Ted at Mt Gibraltar was using a DEMI transverter with a 3W amp (it wasnt
needed) into a 700x 600 (round figs) offset dish. I was also using a DEMI xverter but with no amp. (20mW TX out) and initially
an offset dish then moved to Jack's (VK2TRF) pennyfed prime focus 60cm dish.
VK1BL 's signal was just so, so strong, whilst disconnecting the UT141 coax from the horn feeding the offset dish, I could still
receive Ted's signal easily with no antenna connected to the coax !!!!! amazing! a tribute to both the power Ted was transmitting
and the hot receiver in my DEMI transverter.
Moving the transverter to the prime focus dish, Ted gave me a 59+ signal and I gave him a 59+++ he was right off the end of
the scale. With a 20dB attenuator in the path of my sys brought Ted's received signal down to a readable 5x9+20 or so and
my signal down to a 5x4-5. The 20dB atten brought my TX level down to 0.2mW at the antenna.
I am looking forward to increasing the path distance and improving my offset dish feed which was far from optimum as
demonstrated when we moved to the second dish. At Ted's end of the link helping out was Owen, VK1OD and at my end
Jack VK2TRF, my regular "partner in crime" haha when it comes to uWave hilltopping activities.

Click on images below for full size pics
Left - The 2 dishes; Centre - Me transmitting on Jack's dish; Right - Ted and his setup at Mt Gibraltar

Cheers
Dave, VK2TDN

12 July, 2008
Dave, VK2CQ came over home to help me out with a WBFM experiment. I wanted to try the Gunn Osc. transmitter out
over a distance greater than across the room. We went out onto my street and Dave took the Satellite LNC and scanning
RX whilst I proceeded to walk down the street and talk to him using the Gunn TX. The Gunn had a 18dB gain horn on it
and the LNC was straight out of the box, ie. no additional antenna.
It was a great success as my signal could easily be heard over the 200m+ that we got between us. It was interesting to
experiment with the reflections off cars moving up and down the street between us and also off the various buildings.

Cheers
Dave, VK2TDN

08 Nov, 2008
Saturday 8th November '08. Jack, VK2TRF and myself did some short hop hilltop experiments.There were several objectives
for the days' outting. Firstly Jack had taken delivery of his 10gig xverter from Khune (DB6NT) and wanted to test it onair.
The Spring Fieldday was the coming weekend and we both wanted to make sure all gear was working ok. Finally, we wanted
to do some trials with different antennae and insersion of attenuators in the feedline to the antenna and see what it took to
loose the signal at the receiving station.
Since the June test with VK1BL, I removed the 18dB gain feedhorn from the offset dish and replaced it with a modified LNC.
Removing the cct board and the 12GHz probes from the metalwork, I made a probe using a long pinned SMA bulkhead socket.
The length of the probe (6mm) is an ideal monopole probe for 10.3 GHz. This came about after talking to a couple of USA
10gig'ers and seeing some of their pics of horn feeds. The conclusion was that my higher gain hornfeed was under-illuminating
the dish and significantly reducing its efficiency.

Now for the tests, we started with 17-18dB gain horns at each end, Jack with 40mW and me with 20mW. The path was 23km
(18.75 miles for the non-metric amongst us ;) ) line of sight path with a freespace pathloss of 140.0 dB. .....
Ohhh just a side note on freespace pathloss, basic formula is ....
log distance (km) x 20 + 112.7 = loss in dB ... 112.7dB = loss for 1 km, add 6dB loss each time path doubles
example ... log 23 = 1.3617 x 20 = 27.234 + 112.7 = 139.9 dB (140.0)
23km = 140dB loss; 46km = 146dB loss; 92km = 152dB loss; 184km = 158dB loss .... etc

The FM signals between us were full scale and starting with that, Jack added 10dB of attenuation in the antenna line which
dropped the received signal to just below full scale. Skipping 20dB and going to 30dB of attenuation dropped the signal to
~ half scale (~ S5) and still a good readable copy. With 40dB of attenuation the signal became unreadable on FM. We both
switched to SSB and although there was no signal strength, Jack's signal was quite readable. Finally, going to 50dB lost
the signal totally.
Jack removed all the attenuators and restored full signal strength. I removed my horn antenna and was suprised to find that
I could still hear a signal from Jack. I touched the centre pin of the SMA plug with a small screwdriver and he became virtually
full quietening. He went to 200mW output and I could easily read his audio without touching the SMA connector, and touching it
with my finger made his signal full quietening!!
I next tried a 400mm (18") dish with a penny feed, should be ~ 25dB gain, and Jack's 40mW signal was as expected better than
the 18dB horn ... nice to know the dish was working!. We both then switched to larger dish antennae, Jack used his pennyfed 2ft
dish and I used my 700x600mm offset fed dish. He then proceded to once again insert attenuation into the transmission line with
40mW of output. This time he was still quite readable with 50dB of attenuation inline and his signal was finally lost at 60dB of
insertion loss !!. 40mW (16dBm) - 50dB = 0.4uW (-34dBm) WOW

Click for larger image
The pic above shows the xverter mounted nead the feedpoint of the dish which keeps the losses
in the UT141 feedline to a minimum. On the back of the dish is the Icom IC290H 2m allmode
xceiver that I have modified to give 8VDC up the coax for the xverter switching
Cheers
Dave, VK2TDN

15 Nov, 2008
I am pleased to report that my trip to Mt Canobolas for the spring fieldday was a success. Mainly referring to the extension
of my 10GHz SSB distance now at 216km from Mt Canobolas to Mt Coree. Thanks Ted, VK1BL for having a 10gig station
active. Once the dishes at each end were aligned Ted's signal was very strong at 5 x S8-S9+10. He has 3W into a ~ 35dB
gain offset dish. My signal to him was a 5 x 2 with my 20mW into a ~35dB gain offset dish.

Whilst on Canobolas, I did beam east to listen for a possible scatter signal from Jack, VK2TRF who was beaming west from
Top Ryde with 5W and a 33dB gain dish. Unfortunately nothing heard. Maybe the huge amounts of cloud and rain over the
Blue Mtns between us did too much scattering.

Time to complete my 1.2 W and 3W amplifiers and then see how far we have to travel to find a 300 + km path that is pretty
much LOS. Could be difficult!!
The other goal for this summer is 10gig rain scatter between Sydney and Canberra .. roll on the BIG thunderstorm cells half
way between us
Click for larger images
Left to right... Dish, Front view; Xverter and feed closeup; Dish, side view; View towards Mt Coree, 216km that way
The 2 other radios in the back of the car, a FT90 FM dual band for working repeaters and a FT897D for 2m and 70cm SSB

Cheers
Dave, VK2TDN



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Page created 08 July 2008
Page updated 14 Dec 2008
Dave, VK2TDN