Category Archives: Uncategorized

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

Fusion360 stress simulation

I ran a quick test in Fusion360 to look at the stresses around holes in a 1 metre aluminium boom with a large hole in the top and a cross-hole, with one end of the boom fixed and 200N on the other end. Just testing the facility to see how it works.

Boom stress at 0-200N force. Red means bad times, likely to snap

Ideas for a 3.4 and 10GHz feedhorn

I’ve been trying out some ideas for a feedhorn that uses the dielectric-horn POTY approach with a 22mm circular guide for 10GHz suspended in the mouth of a 9cm horn. Quick video of the idea shows some issues, like it only works with the coax feed to the 10GHz horn when it is cross-polarized. Needs a lot more thought, but I needed to do this sketch to get it clear in my head. The outer tube is almost transparent in this rendering. It is 180mm long and 68mm OD. The open end of the 22mm tube will have an HB9PZK dielectric lens and the 68mm tube will have a thin dielectric plastic disk with a hole to support the 22mm tube. Hopeless like this though because of the cross-polarisation issue. More thought needed.

Lathe headstock spindle spider

I needed a spider to support long workpieces out of the back of the headstock spindle. I had a bit of EN8 round bar so I used that. Bored to 42mm to match the spindle ID, then counterbored to fit the spindle OD. I used a 1mm slitting saw to form a clamp and milled out pockets for a couple of M3 caphead bolts. Bored out a hole in the end of three M8 cap bolts and made brass inserts. Works a treat.

E-Field Active Antenna

This project is being implemented by the Goole Radio and Electronics Society. The antenna uses the modified PA0RDT Mini-Whip design. The PCB and component kit was put together as a kit by the late Dave Powis G4HUP and now sold by the UK Radio Astronomy Association. The kit only includes the electronics. I decided to make a proper enclosure, couplers and fittings to make a decent mechanical solution.

Standard post-mount base clamps and insulated offset mounts to fix to a shed or wooden post
The completed radome assembly mounted on a 32mm aluminium mast
Aluminium collar, PCB enclosure and radome mount
Radome cap with 22mm internal recess for the probe
Radome with cap
Probe support bush
PCB from UKRAA kit, assembled with a soldering iron and 0.3mm solder
PCB inside the collar. It will be potted to prevent moisture damage
Collar fitted to the mounting pole and radome. All sections will be filled with PU foam once tested
Brass end plug (tapped M4) soldered to the end of the 22mm copper tube
Base insulator and spacer with fixing screw – needs to be brass though!
Top cap fitted – I may need to shorten the probe, but best to start long
Exploded view of the larger probe. Standard probe is 100mm
Common mode choke enclosure
Adjustable mount in place (early version without the common mode choke)
Mounting plate, mast clamp and saddles
Mounting plate with angle adjuster
angle adjustment slot
Insulated gland at mast base for the coax connection to the screened, isolated common mode choke box