Re: WR90-SMA transition update

Robin Szemeti - G1YFG

Thanks for the detailed info, I am a big fan of WD40 for aluminium. It is useless as a lubricant in most situations, but as a cutting fluid for aluminium, it works quite well!

You clearly have the old Bridgeport running well. My CNC router does not have the stability to achieve anything like that sort of surface finish, sadly, even though it cuts aluminium quite nicely otherwise.

On Thu, 10 Sep 2020 at 07:54, Neil Smith G4DBN <neil@...> wrote:
I ran a load of simulations in OpenEMS, but I’ll file the probe to length and measure the actual length, then see how repeatable it is. Without a trimming screw, I’ll have to file them all to get them on frequency I’m sure.
I’ll publish the OpenEMS model when I publish the drawings
Neil G4DBN

On 10 Sep 2020, at 06:27, Alex May M1BSX <alexmay@...> wrote:

A thing of beauty! :-)

Very intrigued as to how it was milled and whether you're using an empirical approach to determine the length of the "probe" ? 

73s Alex (M1BSX)

Alexander R. May

On Thu, 10 Sep 2020, 00:01 Neil Smith G4DBN, <neil@...> wrote:

This pic is my first try at machining an SMA coax to WR90 waveguide transition.  Milled it from a lump of 1 3/4 inch aluminium square bar on my ancient Bridgeport.    It needs a bit of trimming to get it bang on frequency as I left the pin a little long. Now I'm waiting for a load of Radiall SMAs to arrive from Mouser.

Neil G4DBN

I modelled it in OpenEMS with a three-inch length of WR90 mated with the oval cavity. Return loss (black) and through loss (red) look promising, I need to check the real thing once I have the probe filed to resonance.

Fusion 360 CAD image


Robin Szemeti - G1YFG

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