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

Image of a brass and steel lantern chuck
click to open the video on Youtube

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 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

It would be hugely helpful if you have a Youtube login if you could subscribe to my channel

The RSGB recording includes the interview section by Jim Lee.

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

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

Finished 10 GHz feedhorn with Radiall SMA connector

The body is turned and bored from a bit of aluminium round bar

The flat area is too large on this one, I’ll make it narrower on subsequent versions so I don’t have to shorten those M2.5 screws

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.

One of the bearing bushes and mounting blocks being checked for fit

The original concept for the knuckle is here: and this is the story so far of the machining,

The 100 x 100 x 150 mm aluminium block
Facing the block, bit of unnecessary slow-mo trickery
Nice rainbow caustic
First stage of turning
Forming the boss on the first side
Turning on a mandrel to form the second boss
Knuckle finished and bored to take the pivot shaft
Pivot shaft machined to size, with flats for the grub screws and locked in place
Machining and tapping the bearing carriers. M10 spiral flute tap clearing the chips very nicely
I made a mandrel with a threaded hole to turn the bearings from a piece of an ancient slab of bronze that I remember my dad using in the 1960s as a soft anvil
Block fitted to the mandrel ready for OD machining and facing
Initial facing done and OD completed
Removing the semi-finished bush from the mandrel
One half of the first bush pressed into one of the the bearing carriers
Boring the completed carrier and pair of bushes to fit the shaft with a 5 micrometre clearance
Test fit of the first bearing carrier

Another batch of 122 GHz W2IMU f/d 0.8 feedhorns

Brass W2IMU dual-mode feedhorn for 122 GHz

I’ve just completed a batch of 24 of these W2IMU feedhorns for the 122 GHz band. Thread as usual is M8 x 0.5 mm. Horn ID is 4.03 mm, 27.1 degree internal flare, 2.00 mm reamed waveguide core, rear duplexer cavity for VK3CV boards, four M2 threaded holes, 4.00 mm reamed barrel, 3.98 mm spigot on the waveguide. This is the version 2 with a flat step as the end stop. Rather than relying on the 7.5 mm tapping drill to make the bottom of the threaded section, I now machine that using a centre-cutting M7 end mill. Part number for this version is DBN-122-IMU-0.7-02 and price to bona-fide 122 GHz experimenters is £14

The coupler body, internal thread M8 x 0.75, 14.85 mm diameter
Core of the horn, threaded M8 x 0.5, reamed to 2.00 mm internally
Rear cavity to fit over the chip on the VK3CV board. The barrel is adjusted for best TX and TX performance

CQWW 160 metre CW contest 2020

One of the main contests of the year for me is the CQ Worldwide 160 metre CW (Morse code) competition at the end of January. Here is a snapshot of the activity between 1810 kHz and 1900 kHz. The section around 1842 kHz is FT8, and there is a little WSPR traffic just above 1836.

I had enormous fun with a compromise antenna and only 5 watts from my FDM-DUO SDR, but I worked plenty of US stations as far as Texas and Ohio. Click the [ ] to show it full-screen