Mike asked me to make a stronger rotator attachment plate for his telescopic mast. The top section is thick walled GRP with 40mm OD. I made a collar and a central pin to fit inside the tube, and fitted the usual 12mm plate with 119mm PCD 8.4mm holes to fit Yaesu or Kenpro rotators. The collar was put in the freezer and the plate in the oven, then they were aligned and pressed swiftly into position to make a string shrink fitted join.

The completed assembly was fixed in place with gap-filling Loctite.

A friend asked me to reproduce a missing element of a commercial UHF LPDA. The thread was #8-32 UNF and trying to find suitable slotted pan-head stainless screws was a nightmare, so I had to use a Philips head instead.

A local friend asked me to make up a joining spigot to fix two 40mm Delrin tubes together. Nice simple job. I made it a very tight hammer-in fit and knurled part of the 20mm sections to help prevent any rotation or creep.

A friend asked if I could machine the ends of a soft copper tube around 70mm diameter to be flat and square, and to an exact length. Not easy to hold in the lathe, so I made up some expanding mandrels from engineering plastic.

I made a silver steel shaft with an M12 threads on one end and drilled a centre. The other end mounts in a 12mm ER40 collet and there is a bracing tube so tightening the nut forces the the tapered plugs into the split mandrels and they open and press very tightly against the inside of the copper tube. The mandrels when uncompressed are a tight fit in the tube.

Using this technique allows full access to both ends and the whole outside of the tube for machining and polishing.

The simple approach to attach an Octagon LNB to a circular waveguide is to saw off the ridged scalar horn and push the cut end into a split 22mm pipe, but I decided to do it the long way. I made up a conical plug from brass to fit against the cone of the horn, then bored a tapered hole inside the plug to match the 17.5mm ID of the Octagon to the 20.2mm ID of 22mm water pipe waveguide. Probably totally unnecessary, but I had fun doing it.

First step was a CAD design

A friend asked me to make up a heatspreader for a 500W load resistor and fit it and a 7-16 DIN socket to a giant heatsink weighing about 15 lbs

The load and coax will be soldered to the spreader, and high performance conductive paste will be used between the spreader and the heatsink.

Two friends have asked me to assemble dual-band 2.4GHz/10.4GHz patch/horn antenna feeds, known aa a POTY (for Patch of the Year).

The first one I made was from 1.5mm brass sheet, and I made it on the lathe and milling machine, but for these, a group buy was arranged on the UKMicrowaves group to get them cut on a CNC laser. The cuts are very slightly oversize, by about 0.2mm, but the edges are very clean and only needed minimal fettling to remove the inevitable pip at the start/finish of each cut. I had to open up the centre holes using a deburring tool to make the fit perfect. I also had to mark up and drill/ream the hole for the socket. I made a custom collet for the previous one, it supports the reflector at exactly 90 degrees. It is relieved near the solder joint.

It was a lot of effort and actually it would have taken about the same amount of time to machine them from scratch, but for folks without a machine shop, they are excellent.

The Radiall N socket my friend supplied is not the usual small-format N with 4.1mm PTFE sleeve over a 1.27mm gold-plated brass pin. It has a solder spill. I had to cut it back a little and solder in a suitable extension pin. Again, a lot of work for no benefit.

In addition the N socket and the TNC supplier by the other friend for hit POTY both have a 1.5mm raised boss behind the socket.

The N connectors I use are like this:

On the 0.9mm laser-cut material, that means the boss would intrude into the space between the element and reflector. I made up a precision washer to ensure the boss was flush with the reflector surface.

I soldered the reflector to the tube at the right spacing from the machined top edge of the tube (6mm+0.9mm+3mm) using 183C tin-lead solder paste, which makes a neat joint,

I used a 3mm U-shaped spacer to fix the driven element in place and clamped it, then soldered it. to the tube. Then I stuffed paper towel into the tube and soaked it with water to prevent the existing joints from melting, then soldered the N connector and spacer to the rear of the reflector.

After a good cleaning with isopropyl alcohol then hot water and detergent, I fitted the 10GHz dielectric lens and connected the 2,3GHz port to an HP directional coupler, signal generator and spectrum analyser

So far, I have not been able to get the correct double-dip response. I can get a very deep single dip to -33dB (!) but even doing asymmetric bends or dielectric slips, I can’t split the dips. At max RL, the axial ratio is pretty much that of a linear feed, and with it much flatter, the axial ratio is still around 6dB. I am making another of the original patter with 1.5mm brass parts and machining them on the lather and mill, with a good small-format N socket with 4.1mm PTFE over 1.27mm brass pin so see if I can find what is going on. Then I need to make another with these TNCs…

For the Goole Radio and Electronics Society entry in the RSGB SSB Field Day contest, we needed to fit some 3m extension scaffold poles on top of a pair of SCAM12s to support our doublet. I made up some 40mm spigots which are a push fit into the poles, and fitted a locking bolt, and made the SCAM spigot as a sliding fit at -0.15mm as usual. Made from aluminium extruded bar stock.

I made up some M8 threaded lockbolts by turning down some M10 bolts to 8mm diameter and cutting an M8 thread on the lathe.

This is just a test of my signal generator at 15kHz as displayed on Spectrum Lab.

The tailstock DRO is now completed. The last element was a block to bolt to the existing end clamp, to hold another rare-earth 12mm magnet which keeps the end of the scale firmly attached to the tab on the quill. See part 1 and part 2 for details