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I recently finished building some Sat antenna polarity switches. (2M and 70CM)
They switch between Horz, Vert, RH or LH polarization.



I think all is OK but how would I use a nanovna to confirm that they are within spec? I am still a naonvna beginner and have not tried to measure anything like this before.

TIA
Glenn VE9GJ

On 8/11/22 12:13 PM, Glenn VE9GJ wrote:

?I recently finished building some Sat antenna polarity switches. (2M and 70CM)
They switch between Horz, Vert, RH or LH polarization.
I think all is OK but how would I use a nanovna to confirm that they are within spec? I am still a naonvna beginner and have not tried to measure anything like this before.
TIA

This unit takes a single feedline from the Tx/Rx to two antenna ports. In linear pol, it should be a straight feed through one of the two antenna ports, with the other port terminated (or open, I couldn't find a schematic).
So it's kind of like doing it with an ohmmeter.

Let's call the outputs H and V.

First test, CH0 of VNA to Tx/Rx port. LOad on H, Ch1 connected to V.
Set the switch to V-pol, you should see |S21| nearly 0dB loss, and |S11| as a "good match". Disconnect the load on H. You should see no change. Put the load back on.

Now select RCP - you should see S21 decrease by about 3dB (because half the power goes to each output), and there will be some phase shift. Record that number.

Select LCP, Should see the same S21 as RCP, but the phase will be different, record that number.

Put the load on V, and Ch1 on H output.
Select H pol - should see low loss, good match
Select V pol - should see no power, but good match (looking into the load)

Select RCP, should see S21 go down by 3 dB, and the phase shift should be either identical to what you measured on the other port, or be 90 degrees different (it depends if you're driving a crossed yagi that's offset by lambda/4 or if it isn't)

Select LCP, see S21 same as for RCP, but the phase shift is flipped or the other 90 degrees relative to what you measured last time.

On 2022-08-11 21:25, Jim Lux wrote:

On 8/11/22 12:13 PM, Glenn VE9GJ wrote:

?I recently finished building some Sat antenna polarity switches. (2M and 70CM)
They switch between Horz, Vert, RH or LH polarization.
I think all is OK but how would I use a nanovna to confirm that they are within spec? I am still a naonvna beginner and have not tried to measure anything like this before.
TIA

This unit takes a single feedline from the Tx/Rx to two antenna ports.
In linear pol, it should be a straight feed through one of the two
antenna ports, with the other port terminated (or open, I couldn't
find a schematic).
So it's kind of like doing it with an ohmmeter.
Let's call the outputs H and V.
First test, CH0 of VNA to Tx/Rx port. LOad on H, Ch1 connected to V.
Set the switch to V-pol, you should see |S21| nearly 0dB loss, and
|S11| as a "good match". Disconnect the load on H. You should see no
change. Put the load back on.
Now select RCP - you should see S21 decrease by about 3dB (because
half the power goes to each output), and there will be some phase
shift. Record that number.
Select LCP, Should see the same S21 as RCP, but the phase will be
different, record that number.
Put the load on V, and Ch1 on H output.
Select H pol - should see low loss, good match
Select V pol - should see no power, but good match (looking into the load)
Select RCP, should see S21 go down by 3 dB, and the phase shift should
be either identical to what you measured on the other port, or be 90
degrees different (it depends if you're driving a crossed yagi that's
offset by lambda/4 or if it isn't)
Select LCP, see S21 same as for RCP, but the phase shift is flipped or
the other 90 degrees relative to what you measured last time.

Thanks for the great explanation Jim! I think I understand what to do now as your instructions make sense to me.

73
Glenn VE9GJ

So this switch actually has BOTH antennas connected ALL the time for ALL modes, so the nominal 3 dB loss from the input to each antenna is present at all times. Be sure to terminate the antenna connector not being measured for good results. Their assumption is that the crossed antennas are mounted in an X with respect to the horizon rather than a plus (+). On the website you linked they have VNA measurements for each mode and both antennas. If the driven elements are located at the same point on the boom, the feedlines should be the same length, but the length isn't critical. If they are offset (which is common), you will need to adjust the feed line to one of the antennas so the phase matches the at the switch antenna connectors.

Hi Dave
Thanks for the input. Yes you are correct, this switch does have both "antennas" configured as an X and they are both always connected.
The switch is based on the work of I8CVS. I should have included the link in y original post.


The antennas I am using are the Wimo X-quad so both antennas are offset by zero degrees.


This is very much a learning exercise for myself. I will need to obtain some more BNC to sma jumpers or adaptors to do some more testing.
I also started using nanovna-saver and getting some crashes but that will be a separate post.

73
Glenn VE9GJ

Glenn:

I reviewed the antenna that you linked to (WMO-18011) and I am pretty sure that it isn't compatible with the polarization switch that you linked to. The antenna has an unusual feed element that gives H and V output directly, without having to phase the driving elements to achieve H or V linear polarization. This polarization switch with this antenna will produce +45 degree, -45 degree, RHCP and LHCP.

Yes, you simply rotate the Antenne by 45 degrees and it will worked fine.

Regards

Matthias

www.dd1us.de


-------- Ursprüngliche Nachricht --------
Von: "Dave W6OQ via groups.io" <david.hostetler@...>
Datum: 12.08.22 23:43 (GMT+01:00)
An: [email protected]
Betreff: Re: [nanovna-users] Testing X polarity Antenna switch

Glenn:

I reviewed the antenna that you linked to (WMO-18011) and I am pretty sure that it isn't compatible with the polarization switch that you linked to. The antenna has an unusual feed element that gives H and V output directly, without having to phase the driving elements to achieve H or V linear polarization. This polarization switch with this antenna will produce +45 degree, -45 degree, RHCP and LHCP.

Well I considered that rotating it 45 degrees would fix it, but is it simple enough? The antenna boom is square and I am not sure how that will be easily attached to the mast or other mount system.

I am not at home at the moment to investigate the antenna. I should have paid more attention when selecting antennas. All the parasitic elements are in and X config but now that you mention it the driven elememt may not be X. I do have the wimo rhcp harness if the relays won't work. Rotating the boom 90 degs should not be difficult.
Thanks
Glenn VE9GJ

It needs to be rotated 45 degrees, not 90, to work with the polarity switch you have. If all you want is circular polarization, you don't need to rotate it, just use the phasing harness.