Re: Wimo 13cms aerial VSWR


SAM JEWELL
 

Ed,
Hardly a recommendation....I use an HP 5753C and S parameter test set. The price was good!
Calibration is done at the end of the test cable using professional SOT calibration and a good test cable.
I purposely said that the cheapies didn’t allow ‘measurement’ at 2.3GHz, but the indications can still be useful.
It’s all down to how good the directivity is of whatever the ‘device’ is that is discriminating the direction of signal ‘flow’.
It goes without saying that when the VNA is not directly connected to the antenna feedpoint, and a coax cable is used, then it is necessary to calibrate at the antenna end of the connecting cable, using a good, known, cal kit SOT set.

I find it useful to test with various good quality Attenuators at the end of the cable. The attenuators are terminated in a short (or open) to minimise fringing effects. 3 and 6dB attenuators should read close to twice their attenuation. 10dB and higher will probably show increasing error.  Calibrated mismatches are harder to find but can be made, but will need calibrating with a known, good  VNA.

I hope that helps?

73 de Sam

On Friday, November 15, 2019, 4:17 pm, Ed G3VPF <g3vpf@...> wrote:

Sorry to start a new thread but Groups.io rejected my attempts to reply to the old thread!

Many thanks for the replies so far. Once the weather improves I will set things up on the lawn and have a play with the various ideas. Currently bitterly cold with horizontal drizzle - not ideal for playing with aerials.

Sam - which VNA's are OK on 13cms? At present only test gear I have is the directional coupler  built into the transverter. Had a quick look on the internet but only found two that claimed to work at 2.3GHz, of which only the Mini-VNA was reasonably priced.

Ed
 G3VPF IO80RQ

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