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Hello Pierre,
Yes, what the others have said, your hand changes the loading on half the antenna, both with HT and Nano.
If your goal is max range mountain-topping, you can easily make a much better antenna than a short "rubber duck."
Here is a portable, adjustable VHF/UHF dipole I made years ago with TV rabbit-ears:

You can also easily make 3-5 element yagi wiith PVC pipe and aluminum tape. Model it in MMANA-GAL first.
73, --KV5R

On Mon, Mar 1, 2021 at 10:00 AM, Donald S Brant Jr wrote:

All: Unless one is building a tuned circuit like a tuning stub or a series
matching section, and in the typical use case of an untuned feeder for a
non-resonant dipole, the exact impedance and velocity factor are mostly
irrelevant. 73, Don N2VGU

I'm probably one of those rare birds who actually uses twin-lead VF and Zo.

There's about a 30 foot run of coax from where my doublet's window-line terminates on an outside wall of the house to the FT-1000D (w/its antenna tuner) at the operating position inside.

If the SWR on the coax is high, there can be significant loss. So I "tune" the twin-lead length to give me a good match (although not a perfect match) to 50 ohms on the bands I'm interested in. Still, on 18.1 MHz, there's about 2.5 dB of loss (1.3 dB in the 118 feet of 554 window line, and about 1.2 dB in the RG-142). (It's a 43' doublet at 80 feet, thus the long run of twin-lead.)

I first started doing this using Excel to find the best lengths of ladder-line for various bands. Now I use SimSmith, which really simplifies the process.

I've attached a plot from SimSmith showing simulated SWR and Loss on the various bands. The simulated SWR matches the measured SWR pretty well.

I've even used the doublet on 30 (albeit rarely) where the SWR is high. With 100 watts (on FT-8) the RG-142 coax starts to get warm. Never a good sign, but it does get out.

73,

- Jeff, k6jca

The coax braid/ground is connected. I should elaborate that I see higher
than normal readings when testing many different antennas. I just tried
flashing back to the 0.7 firmware and get the same results. If I use a 50
ohm dummy load I see a 1:1 SWR, so that is working as expected.

On Tue, Mar 2, 2021 at 2:44 PM Dragan Milivojevic <d.milivojevic@...>
wrote:

Ground is connected?

On Tue, 2 Mar 2021 at 19:43, Matt Trull <Oxyacetylene@...> wrote:

I have one of the original type NanoVNA. The connectors are on the end,
not the side. Anyway, I upgraded the firmware several months ago to the

0.8

version. Ever since then the SWR measurements always read high. For
example, I am getting a measurement of 4:1 on a vertical antenna in VHF
range, but my Bird meter shows a 2:1 for the same antenna. I have tried
calibrating multiple times. Any ideas?

Ground is connected?

I have one of the original type NanoVNA. The connectors are on the end, not the side. Anyway, I upgraded the firmware several months ago to the 0.8 version. Ever since then the SWR measurements always read high. For example, I am getting a measurement of 4:1 on a vertical antenna in VHF range, but my Bird meter shows a 2:1 for the same antenna. I have tried calibrating multiple times. Any ideas?

I us a 13 buck case from Harbor freight.Mine holds 4 cables (sma) and adapters for PL-259 and SO- as well.6 calibration plugs.Neat

I also added a tiger tail radial to my ICOM HT.
Lesson well learned. Make sure you cover the exposed end of the wire before use.
I was too eager to check for signal improvement, keyed down the PTT and that Tiger tail burnt a chunk of my hand. The exposed end of wire was laying across my hand and gave me my one and ONLY encounter with a RF burn. It took 3 days to heal.

As previously mentioned, the problem is because of the lack of a 'ground plane' or return circuit to the nanovna (or HT).

Search the web for "tiger tail" or "rat tail" and ht or handheld radio. There are many results about adding a 1/4 wave counterpoise wire to the HT. Some have measured and posted the results of tests, which were quite good.
QRP "walkabout" or pedestrian mobile HF operators often use what they call a "drag wire" counterpoise, which trails along behind them on the ground.
I made one for my UV5R HT, using some #28 silicone covered, very flexible wire that is also quite limp. It seems to have helped a lot. I intend to operate battery portable, and bought this BNTECHGO brand wire from Amazon for making small, lightweight counterpoises and maybe (shorter) antenna wires.
At first, after reading about the 'tiger tail' counterpoise, I tried a leftover piece of very thin magnet wire, but it was too stiff and inconvenient. The limp silicone wire is much better, although a little bulkier (but still tiny).
To connect it to the HT, I stripped the end for about 3/4 inch and bent it into a circle. Then adjusted the circle diameter to fit easily over the threaded antenna connector on the top of my HT. After soldering the little loop, i place it over the threaded SMA post on the radio, then screw on the antenna. That clamps the counterpoise wire in place. That last bit, with the antenna base being wider than an SMA cable connector, would be the difficulty with this method with the nanovna.
A simple way would be to connect a 1/4 wave wire to an alligator clip, and attach the clip to the SMA connector shell. I've done this, both for a multiband HT antenna, and for a mobile antenna. It works. (Moving the counterpoise will still affect the nanovna readings, but much less.) Hand position will not have such a large effect, either.

And it's cheap and easy to try!

--
Doug, K8RFT

They sell ready made sun shield or sun hoods for smartphones, tablets and laptops.
The design is three sided with the fourth left open for screen inputs. Made in multiple sizes and places like Amazon sell them for about $10.

I had the same problem, and after trying many times, finally added a NanoVNA-F to my test instrument collection. It's much better outdoors, but still not perfect. And it's more expensive.
Indoors, I usually pull out the small -H because it's handier, and my indoor workspace/hamshack "bench" is small and crowded.
--
Doug, K8RFT

Hi Roger,

Setting the sweep points to 101 fixed the issue.

Thank you for all the tips!

Max

My prefered way is to look at the smith chart. When wiggling the connector/cable, the smith chart "goes wild" with a bad connector/connection. a good connector shows a stable image.
You could also use time domain function ("transform" on V2 devices). That will show cable anomalies as a function of the position. A great way to spot bad connector transitions or damaged cables.

Enviado desde mi teléfono Huawei

-------- Mensaje original --------
De: David Eckhardt <davearea51a@...>
Fecha: mar., 2 mar. 2021 2:26
Para: NANO VNA <[email protected]>
Asunto: Re: [nanovna-users] 450-OHM WINDOW LINE........OR IS IT?

Good point and an argument for using the guitar pick style of stylus.

DaveD

I would think that any solution would still have to allow access to the touch screen.
Ed

You are so correct, Don! I really don't care what the impedance or Vp is.
Just parallel wire transmission line with low loss pretty much independent
of SWR. You hit the nail on the head.

Dave - W ?LEV

On Mon, Mar 1, 2021 at 6:01 PM Donald S Brant Jr <dsbrantjr@...>
wrote:

All: Unless one is building a tuned circuit like a tuning stub or a series
matching section, and in the typical use case of an untuned feeder for a
non-resonant dipole, the exact impedance and velocity factor are mostly
irrelevant. 73, Don N2VGU

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

Speaking of which - I saw a Hack-a-day article a few years ago where someone actually removed to top polarized surface of an LCD screen (very carefully) and made what looked like glasses out of the material.
Since the display panel no longer had the top polarizing layer - no one could read the display without wearing/looking-through the polarized material.
It was touted as a privacy project.
Look here:

One easy way of determining which end of a cable is bad is to connect the center connector to a wire and drag it across a portable radio's antenna. The good end will produce a lot more static.

On 3/1/21 10:33 AM, Roger Need via groups.io wrote:

There is a Japanese Web magazine, published in English, that had a 3 part series on testing "rubber duck" and other antennas on portable radios (HT's). They did SWR and field strength tests (Tx and Rx) using a modified Icom handheld radio as a test jig. I think members of this group will find the results interesting.....

Part1
Part2
Part3

Roger

interesting, but I'm not sure I buy his antenna test fixture:

1) in practice people hold the ht (or it's next to your body with a mic/headset)

2) he has no choke on the coax, so the coax is "part of the circuit"

It could well be that the "match" is better (or worse) than he has shown.


This whole "measure performance of antennas on mobile devices" is a really, really tricky thing. (As Apple found with the iPhone 4, with the? feedpoint shorted by your hand).

I'd measure them on a feedthrough connector in the middle of a *big* conductive plate(cardboard + aluminum foil. Something that is at least a wavelength in *radius* - so for a 2m HT antenna, you're looking at a 12 foot diameter circle.

or on a plate that's at least radius > height of antenna

On Mon, Mar 1, 2021 at 10:12 AM, John Brent - VA7WPN wrote:

Can I change the tone? or does anyone even know what the tone generated is? IT
would help a LOT with using it as a tone generator.

When you put the NanoVNA in CW mode it generates a square wave at that frequency. So you have a fundamental and harmonics of that frequency.

I don't know what you mean by using the NanoVNA as a "tone generator". If you mean generating an AM signal like 455 kHz. with a modulation tone of say 1000 Hz. you need a different device. I suggest the TinySa which has the same 2.8" case style but can operate as a spectrum analyzer or signal generator with CW, AM and FM capability.

Roger