Original VA3TO 10GHz Portable Station


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Front | Back | Transition | Feedhorn





Equipment details:

Dish: 36" prime focus. f/d = 0.36, focal length = 12.76"
Feed: Homebrew Shepherd's Crook made from 3/4" copper pipe.
Feedhorn: Homebrew VE4MA style w/ Scalar Ring made from a 2" copper pipe cap.
Transition: Homebrew SMA to circular waveguide made from 3/4" copper pipe per W1GHZ article.
Transverter: DB6NT/Khune MKU 10 G3.
LNA: Downeast Microwave W5LUA design 3-2 ULNA kit. 22dB Gain/ 1.1dB NF.
PA: Downeast Microwave 3-3 PACK kit. 23dB Gain/ 2.5 Watts.

Sequencer: W6PQL 4 event sequencer kit w/ W6PQL latching relay driver kit.
I.F. Rig: Yaesu FT-817.


Accomplishments to date:

Distance: 315km - VA3TO in EN93SG to WW8M in EN72XF.

10 GHz VUCC: 6 Grids from EN93SG.



With the ultimate goal of getting on 10GHz EME in my sights, I thought it would be good to get some experience on the band using a terrestrial station so over the winter of 2012/13 I built up a portable rover station. I acquired a DB6NT transverter, ordered DEMI's 3cm PA and VLNA kits, ordered a W6PQL sequencer kit and one of his latching relay driver kits for the SMA relay that I bought off eBay. I considered several approaches for feeding the dish then settled on fabricating a circular waveguide Shepherds Crook out of readily available 3/4" copper pipe and fittings. At the time I couldn't find any details on constructing a Shepherds Crook but as I saw it, the geometry is defined by the requirement to have the mouth of the feed at the focal point of the dish, and to ensure that the feed is truly centered. The SMA to waveguide transition was made after reading W1GHZ's QEX article Understanding Circular Waveguide - Experimentally.


I soldered a brass disk onto the end of a short piece of 3/4" copper pipe then drilled it and mounted the SMA connector. The length and diameter of the probe and distance from the backshort are critical so I followed those dimensions closely. The transition is mated to the Shepherds crook on the back side of the dish using a slotted pipe coupler and a hose clamp. This allows me to rotate the SMA transition to adjust for skewing of the horizontally polarized signal through the bends of the Shepherds crook. The coupler protrudes through a thick aluminum disk in the centre of the dish and secures the Shepherds crook on the front side in the same manner. This also allows me to adjust the focal point of the feed by sliding the complete assembly in or out. The feedhorn is essentially the opening of the 3/4" circular waveguide along with an adjustable VE4MA design Kumar scalar ring.

The project was completed by spring so I arranged to run a test across the parking lot of a local high school with VE3MSC for my very first 10GHz contact. The test revealed an intermittent problem with the sequencer which was subsequently diagnosed and repaired, otherwise all seemed well.

My first forray into microwave contesting was the 2013 ARRL 10GHz & up contest in August and September (2 weekends). Conditions were not very favourable with little to no enhancement and heavy rain on the second weekend. Participation around Lakes Ontario and Erie was down and I was limited on operating time for both weekends but managed to make 31 contacts for 4900 points. Not a contending score however I did attain my first 10GHz VUCC while operating from EN93SG near the abandoned observatory in Ayre, Ontario (main picture above) which was redeeming.





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