432 MHz EME Array Elevation Plate
Upside-down Dishes and Rotary Clamps
Inverted 1.2 metre dish with 10 GHz waveguide feed connected. The 5.7 GHz horn is fitted so a 3 degree elevation change brings that band into play. Having the feed at the top with the dish inverted keeps the rain out of the horn and removes any risk of hitting your head on the arm when standing on the roof rack. Bracing bars are 10 mm carbon fibre tube with quick-detach fittings epoxied into the ends. Elevation strut is a cheap 12 volt mechanical actuator.
The rotator fits on a mast section that tilts over so the dish can be worked on for band changes. It rests on a trestle or “mast scissors” when luffed over. This is the 3.4 GHz setup with a commercial C band scalar choke on a 9cm feedhorn I made for Tony
Rear view of the dish with two ODUs for 5.7 and 10 GHz
Another implementation of the rotary mast clamp. This one has a side entry for use on narrow lane verges. It also has a ground-mounted tilt plate and rotator. The fishing-rod stand allows you to lower the mast but it remains supported above ground for adjustments and band changes.
The second version of the clamp. The brass nuts fit on to captive clamps with 3/4 inch spigots to allow rapid removal of the clamp from the roof rack.
Close-up of the mast clamp with the gate open, showing the rollers and the knurled locking nut
The first prototype clamp
The 2.4 metre mesh dish on Tony’s van-mounted 60ft pneumatic mast
Elevation mechanism I made for the 2.4 metre mesh dish. The arm at the right is for the counterbalance weights
Porthole feedthrough in the mesh surface to allow shorter feeders to be used. Brass insert in the Delrin bush is for the quick-detach carbon fibre feedpoint support rods. Designed to be dismantled while standing on the van roof on a stormy winter night in pitch darkness with horizontal sleet on a Yorkshire Dales hilltop at 54 degrees North.
The Great Seal Bug Project
I had a call from the Radio Society of Great Britain. BBC Television were looking for someone to make a replica of the Great Seal Bug found in the US Ambassador’s residence in Moscow in 1952. It had been there for SEVEN YEARS. I made some Youtube videos about the initial stages of the project under the code name Project Swordfish, but then after the programme was broadcast, I was able to create a series of videos about the whole project.
It’s a story of spycraft, cutting edge tech, celebrities, gulags, sharaskas and some extremely clever PsyOps work. This was one of the first really clever bugging operations, known as JUNE, although GUNMAN, Buran, EASY CHAIR, SATYR and many others were to follow.
Lantern chuck DRAWINGS
I made a video on Youtube about making a lantern chuck which I needed to grip a batch of M5 cap screws so I could machine a domed end to the threaded shaft, then polish them. A few folks have asked for the drawings. If I made another of these, I’d probably make the brass collar 10mm longer and the openings 15mm longer, and maybe make the collets slightly smaller. I don’t have a drawing of the insides of the shaft, it is just a simple magnetic hex-socket fitting as used to hold screwdriver bits, in a hole reamed to be a sliding fit. I milled a slot in the side and fitted a dog-point grub screw to prevent rotation, then used another grub screw in an M6 tapped hole at the rear end to fix the position of the bit-holder. Finally, I made a pointed locking grub screw to clamp the other grubs screw in place. Details are on https://youtube.com/ and drawings are here. I can send the DXF on request, I can’t upload it here
Microwaves and Machining
I gave a talk to the Radio Society of Great Britain Convention on Oct 9th 2021 via Youtube. The recorded section is on my Youtube page at https://youtu.be/7GINqOnwxCc
It would be hugely helpful if you have a Youtube login if you could subscribe to my channel https://youtube.com/MachiningandMicrowaves
The RSGB recording includes the interview section by Jim Lee. https://www.youtube.com/watch?v=9_78oR9SZRc
The series of videos about making a rotary mast clamp for VHF/UHF/Microwave portable contest operating is also on my Youtube channel. Latest episode is the final assembly https://www.youtube.com/watch?v=sNpHqtuJ-Ik
10 GHz Dielectric lens Feedhorn
I’m working on a simple, waterproof, reproducible design for a 10 GHz dish feed for folks who are taking part in the group buy project to build F6BVA 10 GHz to UHF transverters. This uses a probe launch into a round waveguide machined from solid aluminium. The lens is made from Rexolite 1422, which is a free-machining cross-linked polystyrene with well-defined relative permittivity and a loss tangent of about 0.0004. This one is designed for a rather flat offset dish I have with equivalent f/d about 0.75, but I will be doing some for more common offset dishes
432 MHz Moonbounce array elevation mechanism
I’m working on an elevation pivot plate for a large 70cm moonbounce array for a friend. The design uses a 40 x 30cm plate with clamps and alignment blocks to carry GRP and aluminium tubes to support the array and LNA/phasing harness. This is the first stage, making the knuckle and pivot pin and bearing bushes/carriers. The bodies are aluminium, the shaft is 316 stainless steel and the bushes are phosphor bronze. It will have dust caps and grease nipples. The bushes are in two parts with a 1mm grease groove between them
So far, it is looking OK. More to follow.
The original concept for the knuckle is here: http://www.g4dbn.uk/?p=1618 and this is the story so far of the machining,
Tilt plate proposal
Aluminium 75 x 100 x 150 mm
20mm stainless shaft with milled flats
50mm stub mast
DB0MU 10 GHz beacon from JO31
DB0MU/b is a tremendous signal this evening in IO93NR on 10 GHz. Peaking 65 dB over noise in 12 Hz bins. 591 km/367 miles
And here is a spur from PI7ALK on 10368.0916 at the bottom of the band!