Testing HT antenna SWR w/NanoVNA.

[TNFrank]

I got my NanoVNA H2 in today and was planning on doing a video on antenna swril with the antennas I have. I'd originally planned on doing a 401 node sweep of from 120MHz to 470MHz then see where each antenna worked best between that range. Now I'm thinking I should break each range up by Band(2M, 1.25M, MURS, 70cm, and GMRS)to get more accurate readings. Does that sound about right?

I'm curious to see which antennas are more limited to some frequencies and which word on a broader spectrum. Should be a fun experiment and make for an interesting video.  

[TerriKennedy]

6 hours ago, TNFrank said:

I got my NanoVNA H2 in today and was planning on doing a video on antenna swril with the antennas I have. I'd originally planned on doing a 401 node sweep of from 120MHz to 470MHz then see where each antenna worked best between that range. Now I'm thinking I should break each range up by Band(2M, 1.25M, MURS, 70cm, and GMRS)to get more accurate readings. Does that sound about right?

I'm curious to see which antennas are more limited to some frequencies and which word on a broader spectrum. Should be a fun experiment and make for an interesting video.  

This is a thankless task with handheld antennas. There's way too much interaction with the HT and your body to do any real-world analysis.

I set up a test rig for this, but decided that it wasn't worthwhile testing antennas beyond a "probably good / probably fake" check on their factory tuning.

My setup is a 36" diameter aluminum disc with a hole in the center with a mating SMA-M connector and  25' of RG316 coax. The disc is supported off the (concrete) floor with three 3" Teflon cubes (which I had laying around). These components are inside a shielded, un-powered building. The other end of the coax runs through a building penetration to a NanoVNA H4. The NanoVNA is connected to a laptop PC via a USB cable with ferrites at each end, and the laptop PC is running on battery power to avoid coupling AC line noise into the NanoVNA or antenna line.

This gives me nice, repeatable readings which have little to no relevance in the real world. 

[Lscott]

1 hour ago, TerriKennedy said:

This is a thankless task with handheld antennas. There's way too much interaction with the HT and your body to do any real-world analysis.

I set up a test rig for this, but decided that it wasn't worthwhile testing antennas beyond a "probably good / probably fake" check on their factory tuning.

My setup is a 36" diameter aluminum disc with a hole in the center with a mating SMA-M connector and  25' of RG316 coax. The disc is supported off the (concrete) floor with three 3" Teflon cubes (which I had laying around). These components are inside a shielded, un-powered building. The other end of the coax runs through a building penetration to a NanoVNA H4. The NanoVNA is connected to a laptop PC via a USB cable with ferrites at each end, and the laptop PC is running on battery power to avoid coupling AC line noise into the NanoVNA or antenna line.

This gives me nice, repeatable readings which have little to no relevance in the real world. 

When I tried testing HT antennas that was basically my experience too. There are far too many variables to control for to get good results.

As a general observation I found the VHF testing is very hit or miss. Generally the antennas are a helical design, thus far shorter than a 1/4 wave. There is way insufficient area for an effective ground using the radio chassis only, they really need to be held in the hand. The antennas are "tuned" to take that into account.

Whereas the UHF antennas are close to a real 1/4 wave and the metal chassis of the larger HT's come closer to a minimum size ground plane. I had fair luck testing them with a small sheet metal plate to simulate the ground plane.

Many of the older HT's used hybrid power amp sections. I had downloaded some datasheets to see what the spec's are. The surprising thing I saw was the max SWR rating. Some were as high as 20:1! 

M67798LRA.pdf M68732H.pdf

[MarkInTampa]

8 hours ago, TNFrank said:

I got my NanoVNA H2 in today and was planning on doing a video on antenna swril with the antennas I have. I'd originally planned on doing a 401 node sweep of from 120MHz to 470MHz then see where each antenna worked best between that range. Now I'm thinking I should break each range up by Band(2M, 1.25M, MURS, 70cm, and GMRS)to get more accurate readings. Does that sound about right?

I'm curious to see which antennas are more limited to some frequencies and which word on a broader spectrum. Should be a fun experiment and make for an interesting video.  

I usually do a sweep of 430MHz to 470MHz (70cm and GMRS) and 140MHz to 155MHz (2m and MURS), the bands I'm most interested in and document it with VNASaver. I've never actually used the interface on the VNA itself (small screen, bad eyes) when I can use the computer to do it all on a 27" monitor.

 

[SteveShannon]

1 minute ago, MarkInTampa said:

I've never actually used the interface on the VNA itself (small screen, bad eyes) when I can use the computer to do it all on a 27" monitor.

This!  Nano VNASaver is just so much easier to use and gets you more easily viewed results.

[Lscott]

8 hours ago, TNFrank said:

I got my NanoVNA H2 in today and was planning on doing a video on antenna swril with the antennas I have. I'd originally planned on doing a 401 node sweep of from 120MHz to 470MHz then see where each antenna worked best between that range. Now I'm thinking I should break each range up by Band(2M, 1.25M, MURS, 70cm, and GMRS)to get more accurate readings. Does that sound about right?

I'm curious to see which antennas are more limited to some frequencies and which word on a broader spectrum. Should be a fun experiment and make for an interesting video.  

I would go ahead and try it!

Even if the results are a bit "screwy" there is some benefit if comparing different antennas on the same test setup. 

[Lscott]

24 minutes ago, MarkInTampa said:

I usually do a sweep of 430MHz to 470MHz (70cm and GMRS) and 140MHz to 155MHz (2m and MURS), the bands I'm most interested in and document it with VNASaver. I've never actually used the interface on the VNA itself (small screen, bad eyes) when I can use the computer to do it all on a 27" monitor.

 

What antenna was this? The results look VERY good!

This is my 20 plus year old Comet Dual band SWR scan. They don't make this model any more. They should. I have one new in the green shipping sleeve. Look at the top center photo, the green sleeve on the left side.

https://forums.mygmrs.com/gallery/image/469-antenna-collectionjpg/

https://forums.mygmrs.com/gallery/image/471-mobile-mount-with-antenna-rear-view/?context=new

This is why I really hate to give it up.

https://forums.mygmrs.com/gallery/image/282-ca-2x4mb-scansjpg/?context=new

 

 

[MarkInTampa]

51 minutes ago, Lscott said:

What antenna was this? The results look VERY good!

 

Comet GP-6NC dual band GMRS/MURS. SWR is as close to perfect out of the box as you can get on GMRS, pretty dang good on 70cm, decent on 2m but sucks on MURS (151.8MHz and 154.6MHz) - what it advertised for but still usable. I'd rather have 2m than MURS anyway.

 

 

[TNFrank]

I'll have to look up NanoVNA Saver. Also, I know ground plane plays a big part in the efficiency of the antenna and it hit or miss with an HT. I just wanted to get an idea of where each antennas "sweet spots" were so I'd have a better idea of which one to use for what. Plus I think it'd be a fun video for my channel. 

[MarkInTampa]

2 minutes ago, TNFrank said:

I'll have to look up NanoVNA Saver. Also, I know ground plane plays a big part in the efficiency of the antenna and it hit or miss with an HT. I just wanted to get an idea of where each antennas "sweet spots" were so I'd have a better idea of which one to use for what. Plus I think it'd be a fun video for my channel. 

Do a search on YouTube for VNASaver. There are a bunch of videos on how to use it and have you up and running in under 10 minutes.

[Lscott]

18 minutes ago, MarkInTampa said:

Comet GP-6NC dual band GMRS/MURS. SWR is as close to perfect out of the box as you can get on GMRS, pretty dang good on 70cm, decent on 2m but sucks on MURS (151.8MHz and 154.6MHz) - what it advertised for but still usable. I'd rather have 2m than MURS anyway.

 

 

Thanks for the antenna type update. Little big for mobile use.  Also rather expensive too. 

I haven't noticed hardly any MURS traffic by me. Anyway by the time you feed in the legal limit of 2 watts, no one uses their modified 50 watt 2M rig do they, and get maybe 1 to 1.5 watts at the antenna it still isn't going to go far.