¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. Nanovna-Users
  2. Topics

backyard antenna ranges

 

I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in the context of a backyard antenna range.? One of the tricky things about doing antenna measurements has always been the whole "calibration" thing, or the need to remote control a source (or receiver).


Hey, the NanoVNA does half that work for you!? It's in the back yard, so it's probably not going to be doing very much for your 160meter full size yagi, but for VHF and UHF, or for "near field" systems with small loop antennas, it should work quite nicely.? If you wanted to evaluate the antenna on a walkie talkie, it would be great.

The current crop of VNAs doesn't do WiFi bands, but I think it's useful to think about it.? (these days, running patterns of 2.45 GHz antennas is a standard thing in undergrad antenna classes - but they get to use the fancy Keysight box, provided at attractive prices to universities)


What I'm thinking is using a deliberately non-matched "probe", the radiation pattern of which you can determine? by modeling.? Or build 3 and do a three cornered hat measurement.? It could be as simple as a (very) short dipole with a good choke.
 

Jim, I've usually used a capacitive probe for the purpose at home. That
means a very short probe above an image plane or a very short dipole as a
function of the wavelength of the highest frequency desired. It works well
as a pretty much frequency insensitive receiving antenna.

And, I believe the latest version of the NANO V2's end at 6 GHz.

You have hit a need directly on the head. If you don't, I will - given a
little time to decompress from my CMC ventures....

There are available PC printed LPDA's available with published antenna
factors that cover up to 3 GHz for less t6han $15. i have two. These are
about as good for the amateur as the expensive LPDAs used professionally in
accredited labs.

DO IT for the good of the NANO bunch!!!!

With encouragement:

Dave - W?LEV

Dave - W?LEV

On Tue, Feb 2, 2021 at 10:40 PM Jim Lux <jim@...> wrote:

I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in
the context of a backyard antenna range. One of the tricky things about
doing antenna measurements has always been the whole "calibration"
thing, or the need to remote control a source (or receiver).


Hey, the NanoVNA does half that work for you! It's in the back yard, so
it's probably not going to be doing very much for your 160meter full
size yagi, but for VHF and UHF, or for "near field" systems with small
loop antennas, it should work quite nicely. If you wanted to evaluate
the antenna on a walkie talkie, it would be great.

The current crop of VNAs doesn't do WiFi bands, but I think it's useful
to think about it. (these days, running patterns of 2.45 GHz antennas
is a standard thing in undergrad antenna classes - but they get to use
the fancy Keysight box, provided at attractive prices to universities)


What I'm thinking is using a deliberately non-matched "probe", the
radiation pattern of which you can determine by modeling. Or build 3
and do a three cornered hat measurement. It could be as simple as a
(very) short dipole with a good choke.








--
*Dave - W?LEV*
*Just Let Darwin Work*
 

I'm having lots of trouble with my local area coverage. Neither my
multiband HF vertical (a CHA-250B with its base mounted about 14ft above
ground) nor my G5RV dipole in roughly NVIS mount with 100w can be heard on
10m or 40m by friends about 2-6 miles away. My main interest is about a
500-1000 mi radius around my QTH. Now trying a KISS-SSB counterpoise and
also my ATAS-120a autotune stick that goes with my FT-991a. VHF isn't a
problem. Any suggestions?

Chuck
K4TZO

On Tue, Feb 2, 2021 at 5:40 PM Jim Lux <jim@...> wrote:

I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in
the context of a backyard antenna range. One of the tricky things about
doing antenna measurements has always been the whole "calibration"
thing, or the need to remote control a source (or receiver).


Hey, the NanoVNA does half that work for you! It's in the back yard, so
it's probably not going to be doing very much for your 160meter full
size yagi, but for VHF and UHF, or for "near field" systems with small
loop antennas, it should work quite nicely. If you wanted to evaluate
the antenna on a walkie talkie, it would be great.

The current crop of VNAs doesn't do WiFi bands, but I think it's useful
to think about it. (these days, running patterns of 2.45 GHz antennas
is a standard thing in undergrad antenna classes - but they get to use
the fancy Keysight box, provided at attractive prices to universities)


What I'm thinking is using a deliberately non-matched "probe", the
radiation pattern of which you can determine by modeling. Or build 3
and do a three cornered hat measurement. It could be as simple as a
(very) short dipole with a good choke.
 

Last winter I did a lot of UHF antenna debugging for a wireless microphone installation project in my small basement by using the through mode of the VNA and measuring the loss/gain between the antenna under test and a dipole antenna a few wavelengths away.

I built a number of discone variants and log periodic arrays for the 500Mhz range and found it easy to weed out the ones that were a waste of time. I ended up with some nice tiny discones and A4 size log periodics for the final installation...

Of course I did not get absolute measurement quality results and I had to experiment a bit to confirm that I wasn't seeing reflected paths from nearby objects, but the results were useful enough to build several prototypes and pretest the final versions before taking ithem outside.

I've also found the same general idea very useful in measuring the relative coupling between my various ham antennas so that I can decide if I need to worry about protecting receivers on a given antenna from transmitters on others....

M
 

"I've also found the same general idea very useful in measuring the relative coupling between my various ham antennas so that I can decide if I need to worry about protecting receivers on a given antenna from transmitters on others...."

That's a very usable idea! Thanks
 

On 2/3/21 11:50 AM, Dave W6OQ wrote:
"I've also found the same general idea very useful in measuring the relative coupling between my various ham antennas so that I can decide if I need to worry about protecting receivers on a given antenna from transmitters on others...."

That's a very usable idea! Thanks
Oddly, I was just about to measure the port to port isolation on a RCS-8V, to see if it's safe to leave the NanoVNA connected to one port, and the 100W transceiver to the other.? +50 dBm on one port, probably want to keep power on the other ports <0dBm, so we'll find out if the measurement floor is low enough for the measurement.
 

Jim,
Nice idea. I had been thinking of this myself. I am working on a discone antenna and given it's wide-band and omnidirectional response thought that it would serve well as a receiving antenna for measuring antenna pattern and gain. I'll be sure to let the group know how it works out.

Mark Walter
 

That sounds great Mario! I'd love to see some write-up of what you found worked, and what didn't... anything that would make it easier for us also to get good test antennas.
 

There's really no more to it than I've said. I use a long coax cable to connect a reference dipole antenna a few wavelengths away to one VNA connector and the antenna to the other. It usually is easiest to connect the antenna under test to S1 so you can observe the match as well.

For a reference dipole I use a tiny rabbit ears that came with my RTL-SDR because it can be adjusted to be resonant at most VHF/UHF frequencies (it came with two sets of elements). It also has a ferrite isolator installed on the cable. Make sure it's oriented correctly and away from other objects and correctly adjusted for the frequency by adjusting the elements for maximum signal at the frequency of interest.

My extension cables are made of RG316 and were bought premade from Amazon. The loss is much lower than RG174.

I use microphone stands, stage lighting stands and camera tripods to support the antennas (whatever works) - sometimes I use small sections of PVC water pipe to extend them to keep the antennas away from the stands.

The results are excellent out-of-doors, but indoors I have to do some trial and error to find measurement locations for both antennas not affected by reflections, but usually find one fairly easily.

The results are only broadly useful, but I compare the performance with another reference dipole in the same location and it's usually good enough to save a lot of time before going to play in the back yard.

Make sure, of course to calibrate the S1 port at the antenna itself first. I usually do a local (short) cable calibration "through", but I probably should experiment with calibrating out the remote antenna. For my purposes, manual comparison with reference is usually enough...

M

1 - 9 of 9