Case for W6PQL 70MHz LPF


Milled aluminium case for my W6PQL 70MHz LPF.  Thirty-three threaded holes in all, M3/M4/M5. Connectors are Jyebao, bronze finish.  They seem just as good as Amphenol, maybe not quite in the league of Radiall, but entirely OK at these frequencies and 300W or so at 50MHz and 160W at 70MHz.  Don’t expect to have any cooling issues at those power levels.  The forward and reverse power sensors connect via 3nF 4.2mm feedthru caps.

Radiall R570153010 latching relay

Teardown of a RADIALL R570152010 12V latching coax relay.  I am trying to fit an auxiliary contact or position indicator to allow my sequencer to know the current state of the relay.  The relay has 80dB isolation and handles 500W at 1.3GHz.

The controller PCB is double-sided and contains protection diodes and (possibly) pulsed drivers, not checked that yet.

That projecting pin looks like it would operate an aux contact.  Perhaps I could use it to run a Hall sensor, or some contacts cannibalised from a small DC relay.




WA6KBL 10GHz feedhorn build for f/d 0.6 dish

I have an offset dish which has an f/d around 0.6, so I decided to make one of Jeffrey Pawlan WA6KBL’s linear dual-mode feedhorns as published in DUBUS 2016/1.  The design uses a stepped horn and an oval iris with direct WR90/WG16 flange connection.  The horn and round iris were turned from 65mm diameter aluminium bar, and the oval iris was milled from 10mm flat bar.

I used metric M2.5 capscrews to fix the three sections together, and tapped the waveguide mounts M4.

I found a 3/4 inch end mill in one of my dad’s old toolboxes, so I used it, not realising that he’d modified the grind, and that the sides were not parallel.  Took me three wrecked versions of the oval iris to realise what was wrong.  Simple enough to fix, I just milled out the waste in 0.5mm steps.

Although the joints appear to be perfect, I think I’ll need to add a bit of protection to prevent water ingress at the interfaces.

I will probably make a polyethylene cap for the end, although building foam was also recommended as a fill, to prevent any chance of condensation from diurnal pumping

Apart from the issues with that end mill, it was a nice straightforward project.  Next step is to measure the return loss and then make a mount to replace the LNA collar on the dish mount.  Might use a three-rod mount using aluminium tube or stainless steel rod.