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I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)
Joe, the same relays are used as the tiny low voltage Omron ones you use in your switch box.
I think those were $10-$20 each. They work alright but the isolation was poor. I have an old Transco relay that I made up a really crappy DC-DC to drive it from the USB port. My software supports it. I plan to mount that along with a couple of bias-t's and maybe a decent step attenuator. But then I think, I should really add some mixers and some better couplers and maybe a wide band amp...... Reality always steps in.
I've been meaning to try something like this, but haven't gotten around to it yet. I picked up an old HP 8711 K02 switching test set for that purpose, which is a essentially just a box with 4 N-connectors on the front and a couple of high-isolation RF relays inside. It's a big 19'' unit, so maybe not the most practical NanoVNA accessory, but it was cheaper than buying the relays separately (and as a bonus has two of those unobtainium HP probe power connectors as well).
The normal NanoVNA software doesn't support this measurement mode of course, but scikit-rf will do the 2-port corrections just fine.
The accuracy may be limited (apart from the switch repetability) by the unusal NanoVNA v2 architecture. The usual error model assumes that the load match on port 2 is the same for reflection and transmission measurements. But because there is only one receiver that is switched in for R and T measurements, this will not be the case, so the error correction will not be complete. It remains to be seen how bad this is in practice.
The author of the article uses a shielded box partition with a wall between them for isolation, so it could easily double the size of the nanoVNA, so the idea of an external add on for bench use makes more sense I think. See the second graphic below.
This would be a useful add on for the many of us with these small VNAs.
It could also be incorporated into a nanoVNA case. If it was permanently there, it would make sense to calibrate the vna for its presence permanently and add its presence to the FW. People could plug the calibration into the routines. Not very difficult. That would eliminate another source of error....
I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)
Joe, the same relays are used as the tiny low voltage Omron ones you use in your switch box.
I think those were $10-$20 each. They work alright but the isolation was poor. I have an old Transco relay that I made up a really crappy DC-DC to drive it from the USB port. My software supports it. I plan to mount that along with a couple of bias-t's and maybe a decent step attenuator. But then I think, I should really add some mixers and some better couplers and maybe a wide band amp...... Reality always steps in.The idea is that by reversing the two ports available with the very minimal differences possible, all four sets of S-parameters of a DUT become measurable.
(Thats what I meant by "four port" - I meant that the more VNA functionality is exploitable).
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There is a 3.3v version of the Omron relays.
I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)
The idea is that by reversing the two ports available with the very minimal differences possible, all four sets of S-parameters of a DUT become measurable.
If I could afford a 4-port or more, I think I would also invest in an ecal for it. The only time I have thought it may have been nice for home use was to look at some home made mixers and couplers. There was a 3-port 8753 for sale a while back with the test set built in. I've never seen one. They were asking around $5K. Sold fairly quickly.
If you wanted to use a transfer relay with the Nano, I would expect you could use a PC to drive it. No real need for firmware changes but the software would need to support it. Maybe the newer opensource software does.
To measure PCB trace impedance, better make through fixture for S21 measurements like shown here. Your S11 results show impossible - line impedance wandering between 25 and 200 Ohms. Do you know why?
The only real problem I saw when putting the plastic case that came with the V2+ together was the switches were not installed flat into the PCB. The would interfere with the holes. Quick touch of the iron. Worse part is having to align the spacers when placing the covers. They tend to move. Extra spacers and screw were included. I suspect people would loose them. I left off the rubber O-ring.
Flipper had printed a case for my original Nano. I added a slot for the development connector.
To measure PCB trace impedance, better make through fixture for S21 measurements like shown here. Your S11 results show impossible - line impedance wandering between 25 and 200 Ohms. Do you know why?
It's easier to use S11 for measuring impedance than to use S21. I have some of those PCBs shown in your link,and they aren't 50 ohms. They're close enough for many uses < 2 GHz, but I wouldn't use them for characterizing components.
If I could afford a 4-port or more, I think I would also invest in an ecal for it. The only time I have thought it may have been nice for home use was to look at some home made mixers and couplers. There was a 3-port 8753 for sale a while back with the test set built in. I've never seen one. They were asking around $5K. Sold fairly quickly.
If you wanted to use a transfer relay with the Nano, I would expect you could use a PC to drive it. No real need for firmware changes but the software would need to support it. Maybe the newer opensource software does.
I have a NanoVNA v2.2 with 2.8 inch screen size, can I buy a 4 inch TFT LCD for the NanoVNA and use it? after upgrading can I use the tact buttons?
I have a NanoVNA v2.2 with 2.8 inch screen size, can I buy a 4 inch TFT LCD for the NanoVNA and use it? after upgrading can I use the tact buttons?
I have designed a case for the NanoVNA V2. It has space for a 18650 cell, stores the stylus and has a lanyard attachment point. It is held together with 4 2.5mm countersunk screws on the bottom. Enjoy!
Edit: I just learnt that the 4 LED's on the bottom show the state of charge. Easiest would be to print the case (or at least the bottom half) out of translucent plastic. Another alternative may be to drill some holes into the side. Let's see what else we can come up with?