Re: Anyone got any spare WG15 / WR112 waveguide


Thanks Andy, and I will take your advice...

I build stuff, and experiment, even though I don't always know what I am doing.
Eventually I get there, well most of the time...

So I am looking for WG14 (WR137), but will take WG15 (WR112) if anyone has any to spare.
I have some WG16, but not enough to waste, so may need some more of anyone has some to spare.

I built a filter using WG17 just because I had some, and used dimensions for this QEX article:

I realised later that the WG17 was for a 5.7GHz filter.

Anyway, the filter did eventually tune down to 2.3GHz, but I had to add some concentric tubes to the face opposite the tuning screws.
The filter looks like this:

The tuning screws and nuts came from some surplus Nokia filters the at I have.

This was a useful project to try out my nanovna v2 plus 4, the passband looks like this:

The filter is too narrow for my application, and it's too lossy.
As you say - it would be nice to get a filter that covers 2300 - 2420 with a good transition band.
Actually, I don't need to worry about image rejection, as I have a 7 pole filter on the 13cm side of the mixer.

The evanescent mode filter is intended to be placed between my G4DDK VLNA (at feed point) and the RF stage (mga86576) in my transverter.
This is part of an effort to reduce wifi qrm which I can see on 2320, and of course much worse on 2400.
I'm sure that the RF stage in the transverter is being overloaded, and tests using a pipecap filter proved that was the case, and the qrm could be eliminated.

In addition to the above, I changed the RF stage in the transverter to a PHA-83w, and this has almost eliminated the problem with out adding any extra filtering.
No qrm on 2320, 2300, 2304, 2301, and greatly reduced on 2400 (was S9 on K3S meter). I can now receive JA's again on 2400 EME.

Almost there, but would like to build another filter using the right waveguide this time.

Thanks and 73
Howard, G4CCH

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