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On Sep 9, 2020, at 21:25, Bob Albert via groups.io <bob91343@...> wrote:

? First decide the frequency range of interest. Then program it either as start and stop, or center and span. Then set up for Smith chart and SWR display.
The Smith chart will plot the impedance of the antenna. The marker, which is controlled by the rocker switch, can be moved to any frequency point and the resultant impedance will be displayed. If the impedance is anywhere near 50 Ohms you will see the SWR at all frequencies in the range.
Antennas are complex devices and characterizing them is partly art and partly science. Most people think in terms of 50 Ohms as a standard, and the Smith chart is set up for that. If your antenna impedance is much different from 50 Ohms, say by a factor of three or more, it won't work well with a 50 Ohm system. The alternative is either to change the antenna to bring it closer to 50 Ohms or transform its impedance to something near that value.
Random wire antennas may do well enough for receiving but for transmitting it's a different story. A transmitter will not perform properly if its load is far from its design value. There are losses when mismatch is great, and these sometimes can cause problems such as arcing or favoring undesired frequencies.
There is, of course, no substitute for a good understanding of the principles. There are many books on the subject, and not all of them are good. Just because it's been printed and bound, don't assume it's correct.
I am a great fan of resonant antennas, and they have worked well for me. I routinely plot SWR across the appropriate band for each antenna and thus see if anything has changed much. I almost never use an 'antenna tuner'.
Bob K6DDX
On Wednesday, September 9, 2020, 07:00:10 PM PDT, Darrell Carothers <rescuemedic1@...> wrote:

Doubting the accuracy of my NanoVNA H4. Is there a way for a non electronics minded person to verify the accuracy of my H4? I am a beginner with the NanoVNA. I have calibrated the unit per recommendations. After calibration the open, short and load show where they should be.
I have used the helpful recommendations from members in this group. I am trying to analyze a random wire antenna that shows no resonant areas. I have a lot of noise and do not hear a lot of stations. I did make one contact last weekend, my only QSO, from Arlington Texas to Jinks OK on 7.280.00 LSB.
Thoughts, suggestions, solutions?
The antenna is a random wire 9:1, 135’ element, 35’ counterpoise, about 40’ up in the tops of trees with leaves. Line was placed with a drone. I would like to learn to use the NanoVNA in and out for my benefit.

Thanks
Darrell

Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar errors are due to my IPhone auto correct feature.

On Sep 9, 2020, at 21:04, David Eckhardt <davearea51a@...> wrote:

?I can assure you the NANOVNA's agree quite well with equivalent
measurements using the HP 8753C VNA - FAR more expensive!! It's a good
instrument.

Dave - W?LEV

On Thu, Sep 10, 2020 at 2:00 AM Darrell Carothers <rescuemedic1@...>
wrote:

Doubting the accuracy of my NanoVNA H4. Is there a way for a non
electronics minded person to verify the accuracy of my H4? I am a beginner
with the NanoVNA. I have calibrated the unit per recommendations. After
calibration the open, short and load show where they should be.
I have used the helpful recommendations from members in this group. I am
trying to analyze a random wire antenna that shows no resonant areas. I
have a lot of noise and do not hear a lot of stations. I did make one
contact last weekend, my only QSO, from Arlington Texas to Jinks OK on
7.280.00 LSB.
Thoughts, suggestions, solutions?
The antenna is a random wire 9:1, 135’ element, 35’ counterpoise, about
40’ up in the tops of trees with leaves. Line was placed with a drone. I
would like to learn to use the NanoVNA in and out for my benefit.

Thanks
Darrell

Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar
errors are due to my IPhone auto correct feature.

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

On Sep 10, 2020, at 06:39, DougVL <K8RFTradio@...> wrote:

?On Wed, Sep 9, 2020 at 10:00 PM, Darrell Carothers wrote:

The antenna is a random wire 9:1, 135’ element, 35’ counterpoise, about
40’ up in the tops of trees

135 feet is very close to 1/2 wavelength for 80 meters, and a full wavelength. A 1/2 wavelength (and multiples of 1/2 wave) antenna has an impedance in the range of 3,000 to 5,000 ohms. As was mentioned earlier, you would need a higher-ratio unun transformer. 49:1 is common and would bring 5,000 ohms down to 100 ohms.
As was also mentioned, your sweep settings may need to be changed. The NanoVNA does not make a "continuous" sweep of frequency, it takes 101 individual measurements across the programmed range. If you set it to scan from 3 to 30 mHz, it scans 27 mHz in 101 samples, so the readings are about 270 kHz apart. That means, if I got my math right, that you'd only get ONE reading in the whole 80 meter band. If you're new to the NanoVNA and left the scan set to 50 kHz to 900 mHz, you're not likely to get any usable, useful reading for an HF antenna.
The point about trouble from leaves (especially when wet with rain) may also contribute to your trouble. A non-resonant antenna, and an end-fed half wave in particular, with an impedance of thousands of ohms requires a much higher voltage (and lower current) than a 50 ohm antenna. Any contact with leaves or branches could cause transmit power to "leak" off into the trees, and would reduce received signal levels too - IF the antenna wire is not insulated.

Do you have anything to tell you your SWR? If you are using an antenna tuner or matching system, can it handle a 100:1 transformation? Not many can. Well, come to think of it, your 9:1 unun would bring the 'thousands' of ohms impedance down into the hundreds .

If you could make your antenna a bit longer or shorter, it might make a big difference, but that's not easy now that it's up in the trees. By the way, the type of lead-in wire or cable also can make a difference. What is your lead-in wire, and how long is it? Is your counterpoise on the ground? How far is the counterpoise from the antenna? If you are using a 2-conductor wire or cable, like coax, from radio to antenna, and your co-ax ends at the counterpoise on the ground, the wire going up to the antenna is also antenna and adds to the antenna length.

And, as was already mentioned, a random wire is not supposed to be resonant, so there's no particular indication on the NanoVNA to look for, other than impedance.

I use a random wire about 270 feet long, strung through/over several trees. It's about 30 feet high, and made of THHN insulated wire. I've made about some qso's with it (and an autotuner), but it's not my main antenna and is used more for just band monitoring, receiving only. It does work well for that. Main antenna is a resonant vertical.

Maybe your main problem is the poor band conditions. Can you -hear- many strong signals?

Doug, K8RFT