Two new toys for testing antennas

[Brian.D]

Yes and no. It depends on how you use the NanoVNA. smac999 is correct in measuring power loss one needs to inject a signal of known power level and then measure at the opposite end of the cable. That would be correct way.

Now, if you had both devices you could do this. Place the NanoVNA at the radio end and put it in CW mode. This will give you a known value of +3dBM. Using the TinySA at the top of the mast you will get a value of less than +3dBM. That is your loss.

With the NanoVNA alone it is possible to test for cable loss. There are two methods. The first requires both ends of the cable to be hooked up to the NanoVNA. Kind hard to do with the other end of the cable sitting at the top of the mast.

The second method is to use the NanoVNA App program on your PC. But this still requires you to disconnect the cable at the top of the mast. However, if you have a spare antenna, or access to one, you can use that as a test to determine and extrapolate a close approximation.

To determine the loss, one would connect the NanoVNA to the free end of the cable. The NanoVNA will need to be calibrated for start 100MHz and stop 200MHz. Connect the NanoVNA USB to the PC and run the NanoVNA App. Do several sweeps then select the TDR (Time Domain Relectometer) function. This will tell you the length of the cable and on the display of the NanoVNA App there will be a total loss for the cable. You will need to divide it by half to get the correct value.

This video

This video explains how to do it. But remember, his coax is sitting on the floor. Yours is up the mast connected to an antenna. This is why I suggest you use a spare antenna like you have on the mast (does not have to be exact) for testing and determining if you can get a decent reading.

Good luck and as always, JMHO

[Jerry Woodward]

Thanks Brian for the detailed description. I was hoping to find an easy way to check without climbing the mast. Since everything seems to be working fine, I think I'll pass on this test for now.

[continuouswave]

Originally Posted by Jerry Woodward

Will one of these gadgets tell me how much of my signal I'm losing in my coax?

Not unless you remove the coaxial cable and connect both ends to the device.

[Beausoleil]

Just an FYI - the NanoVNA is an open source hardware design, so there are a few companies manufacturing it. It's available in several version - BNC connectors, SMA, N and I believe SO259 - and in two different screen sizes.

It's also available in with different upper-end capabilities, usually topping out at 900MHz or 1.5GHz. If you plan on doing any WiFi work, you'll need the version which goes up to 3GHz. Of course, that will only get you to IEEE 802.11b/g/n - no 11a or ac at 5GHz ;-)

[Cadence]

Probably a dumb question? Does it come with a dummy load for calibration. Sorry it has been a long time and that sticks in my mind.

[Brian.D]

Yes, it does. The NanoVNA uses the SOL (Short/Open/Load) calibration. It comes with cables and three SMA connectors that are Short, Open, and 50Ω Load. It also has a barrel connector. If you get the H4 model, it already has a case, but the H model does not. I purchased a case off eBay. It was 3D printed.