开云体育

Hi -- I would like to use the NanoVNA for measuring and adjusting antennas in the field for relatively casual POTA and other portable ham radio activities (e.g. tuning the loading coil on a vertical; or tuning wire lengths on a dipole or EFHW; etc).

My antennas' feed points as well as my feed lines are all either UHF or BNC, and my radio has a UHF connector.

The problem is that the NanoVNA has SMA connectors and only an SMA calibration set. In order to measure my antennas and cables I need to use adapters.

Do I need to acquire or make BNC and UHF calibration sets for this kind of field antenna measurement? Or is calibration using the SMA cal set at all useful for this kind of amateur radio activity? I know it's not ideal but since I'm not looking for a high degree of precision I wonder how bad the error will be.

How can I measure the error due to the use of adaptors?


Thanks,

Connie

On Wed, Oct 12, 2022 at 09:26 AM, G8DQX list wrote:

the *Internet Archive *seems to have captured /The Radioboard/, to be found at
. Wait
for a calendar to show, and then the Archive has various captures at different
dates, so one can go back in time.

Thanks for checking, but as far as I can tell, none of the individual posts are archived

It has also captured the "didn't pay"

message to be found today.

The Crystal Set forum's most recent capture before things went south is at

<

These are after it went South. I think Namecheap.com is trying to sell the URL.

. (the equivalent for the website seems to be

.)

This looks like a page setup by the original founder of TheRadiboard, Dave Schmarder, a few
of the links work, others say account suspended or take you to the wayback machine.
I'm afraid all the info is gone only to be experimented, discovered, built and rewritten in the future.
Mikek

hello everyone!
I have such a problem: the screen of my nanovna v2 was broken. I ordered the same screen from aliexpress and got a big disappointment. The image on the screen is inverted and only half of the screen. I thought that transferring the display to the old board from the broken display would solve my problem, but no, I got exactly the same result. Perhaps someone has experience solving this problem. I ask for help.

Mike,

the *Internet Archive *seems to have captured /The Radioboard/, to be found at . Wait for a calendar to show, and then the Archive has various captures at different dates, so one can go back in time. It has also captured the "didn't pay" message to be found today.

The Crystal Set forum's most recent capture before things went south is at <>. (the equivalent for the website seems to be .)

HTH, 73, Stay Safe,

Robin, G8DQX

P.S: It's possible, likely even, that The Radioboard is awaiting revival on payment of a fee, if someone has the necessary cash.

My device is Nanovna-F and I couldn't make dfu work with it.

Even though this looks to be a solution to my problem, I am using Nanovna-F and I couldn't find dfu working with my device.

On Tue, Oct 11, 2022 at 02:14 PM, Brian Beezley wrote:

Mikek, I think this has gotten too far from the realm of NanoVNAs.

OK, no problem. Anyone that wants to email me about my last post, please do.
Thanks for the info about measuring Q of a cap, I'm building a circuit between forum exchanges, when
I get that working I'll pull out the 260A and see what I can find out about measuring cap Qs.
Thanks, Mikek
Just got your email 16 minutes ago.

Mikek, I think this has gotten too far from the realm of NanoVNAs. I have sent you several private messages to try to take this discussion off-line, but I've not received a reply. If you want to continue, send me an email. My address is shown where you downloaded the program.

Brian

On Mon, Oct 10, 2022 at 05:53 PM, Brian Beezley wrote:

our antivirus program is probably keeping you from opening the ZIP file. Send
the file to to assure yourself that
it's virus-free and then disable your antivirus program.

I finally got it to download and then opened.
Is the L that is displayed before accounting for distributed capacitance?
Do I add one wire diameter to my core diameter to get "Core Dia" (i.e. center to center)
Do I measure width from center of outer wire to center of the opposite outer wire?
If I do the above and the calculate measured L with distributed capacitance it comes close.
268uh displayed, 238.5uh calculated with distributed capacitance, 237.3uh measured.
True L x C/C+Cd = The measured L
Q is almost 24% higher than I measure.

However, If the Q of my 260A capacitor is 10,000, at 1MHz, that is 0.151Ω, add that to 0.958Ω from the program and we have 1.107Ω.
Q =XL / R(loss)-- 237uh coil at 1MHz is 1491XL / 1.107Ω = 1346Q, this is just below what I measured at about 1380Q.


I got 100pf cap from Digikey that was supposed to have a Q of 10,000, I added it to my minimum 37pf of the 260A,
and found Q dropped just a few points with the 10,000Q 100pf added, telling me my 260A cap is not very much better than the10,000Q fixed cap I added.

Mikek

On Mon, Oct 10, 2022 at 05:53 PM, Brian Beezley wrote:

Measuring large coils can be difficult because they couple to everything,
including the Q meter enclosure and your body. See README.TXT for a simple way
to overcome this problem.

Yes, If I get within two feet of my coil at resonance, I can see the Q start to drop.
I use about 10" of styrofoam to get the coil away from the Q meter, probably not far enough, but
it's the best I can do.
There is a low loss ferrite available that if wound right will get you a Q over 1200 through the BCB.

And into the high 1400s If with contra wound.
Mikek

I'm sure you're right, Jim. I think most experimenters grab whatever is at hand and press it into service as a coil form. No telling what its characteristics really are. At one time or another I've used beverage bottles and cardboard boxes. I did find the dielectric constant and dissipation factor for a particular cardboard material. It's on the bottom of the dielectric list for a good reason. I expect it too attracts water.

My favorite writeup on wet coils:



I think this kind of loss would be easy to measure with a NanoVNA.

Brian

On 10/11/22 7:21 AM, Brian Beezley wrote:

After much searching, I was able to locate D-2852, the ASTM standard for the styrene pipe coupling. As expected from the application, it does not contain any electrical specs. Here's the description of its composition:
5.1 Materials—The pipe and fittings shall be made of styrene-rubber (SR) plastics meeting the following requirements:
5.1.1 The SR plastics compound shall contain at least 50 % styrene plastics, combined with rubbers to a minimum rubber content of 5 %, and compounding materials such as antioxidants and lubricants, and may contain up to 15 % acrylonitrile combined in the styrene plastics or rubbers, or both. The rubbers shall be of the polybutadiene or butadiene-styrene type, or both, with a maximum styrene content of 25 % or nitrile type. The combined styrene plastics and rubber content shall be not less than 90 %. No fillers may be used.
It sounds like a form of ABS, acrylonitrile butadiene styrene. Here are the dielectric constant and dissipation factor for ABS and PVC, both at 1 MHz:
ABS 3.20 .008
PVC 2.88 .016
The higher dielectric constant of ABS pretty much negates its loss advantage. See the two models for a coil using a 4.5" pipe coupling below.
Brian

pipe and tubing will have wild variations in EM properties. Not specified, so therefore not controlled.

I used to build a lot of HV gear using plastic pipe in various forms. One problem is that seemingly pristine PVC pipe might actually have all sorts of inclusions and other materials - if you cut off the outside on a lathe (e.g. to turn grooves) you might find that the nice white pipe is grey or black inside. And that might be from carbon black (a cheap additive that makes it UV resistant, among other things). PVC is also pretty hydrophilic so it picks up atmospheric moisture, which also increases the loss and epsilon.

Hi Brian,
Those Qs are higher than anything I have made, However, I would like to see a real world case on PVC that has a higher Q than
my so called styrene coupler.
Can you run my coil? Dimensions are, 6.5" in diameter, Coil length is 3.3125", wall thickness 0.138", it is 37 turns,
23" leads (total), (Wire diameter is 0.067", TPI is 11.)
Thanks, Mikek

After much searching, I was able to locate D-2852, the ASTM standard for the styrene pipe coupling. As expected from the application, it does not contain any electrical specs. Here's the description of its composition:

5.1 Materials—The pipe and fittings shall be made of styrene-rubber (SR) plastics meeting the following requirements:

5.1.1 The SR plastics compound shall contain at least 50 % styrene plastics, combined with rubbers to a minimum rubber content of 5 %, and compounding materials such as antioxidants and lubricants, and may contain up to 15 % acrylonitrile combined in the styrene plastics or rubbers, or both. The rubbers shall be of the polybutadiene or butadiene-styrene type, or both, with a maximum styrene content of 25 % or nitrile type. The combined styrene plastics and rubber content shall be not less than 90 %. No fillers may be used.

It sounds like a form of ABS, acrylonitrile butadiene styrene. Here are the dielectric constant and dissipation factor for ABS and PVC, both at 1 MHz:

ABS 3.20 .008
PVC 2.88 .016

The higher dielectric constant of ABS pretty much negates its loss advantage. See the two models for a coil using a 4.5" pipe coupling below.

Brian

Well, with the H version, the solder on the LCD's ribbon cable can sometimes crack and cause the white screen. I had this on one of my units.
You need to VERY carefully run a thin wire under the metal LCD frame to cut the double-sided tape BUT only at each side of the display - otherwise you will cut the ribbon cable!
You can then touch up the soldering connections.

There are photos of the H4's LCD cable on the forum's photo gallery to give you an idea.

As for the H4, I've never seen this - the the H4 uses a ribbon connector so make sure the tabs on the connector are pushed in properly.

Good luck

Excel does allow you to curve fit and then find an extrapolated value. It will provide you with the curve fitted formula.

Your antivirus program is probably keeping you from opening the ZIP file. Send the file to to assure yourself that it's virus-free and then disable your antivirus program.

The pipe coupling datasheet has a standard listed for the styrene, but I was unable to find it for free. However, it is listed as a withdrawn standard. That may explain why styrene couplers are now hard to find. I wonder if it like ABS, which has styrene in the name. PVC and ABS have similar loss.

The capacitance measurement procedure uses a coil, but its Q is irrelevant. Read the instructions and you'll see what they're up to.

The example coil with Q > 2000 used a single 660/46 Litz wire. Form wall should have been 4.95", but styrofoam has such low loss that it makes no difference. I ran a model with a 6.67" PVC pipe coupler, the largest size available. Q was something like 1880, which isn't all that bad. Optimum Q occurs near 9.3". The program will find that value automatically if you let it vary coil diameter.

Measuring large coils can be difficult because they couple to everything, including the Q meter enclosure and your body. See README.TXT for a simple way to overcome this problem.

Brian

On Mon, Oct 10, 2022 at 03:25 PM, Brian Beezley wrote:

1. Use this program to calculate coil inductance and Q. It models skin effect,
proximity effect, and more subtle effects for both solid and Litz wire:

I can open the above page but the Coil.Zip keeps say connection reset while loading.

3. Evidently the styrene pipe couplings popular with crystal set builders use
PVC Type 1. This is not a particularly low-loss dielectric. See the attached
data sheet.

I think that would depend on the crystal set builder. I was active on the now *defunct
'The Radioboard' crystal radio section, stryene was discussed , it is well known
in the crystal radio community that PVC is lossy.
You can tell the difference in the feel, styrene is harder than PVC.
It has more ring to it (like bell), PVC has a damped thud. I doubt you would get a
Q of 1400 with PVC. It is much harder to find a source for Styrene couplers now than it was 5 years ago.
I recently went on a search for a friend and found some, I gave him him the site,
he called and they said they don't carry them anymore. So it may be difficult to find them now.
You can also tell styrene from PVC by a burn test, flame and smell.

4. If you have a Q meter, it's easy to measure capacitor Q. See the Boonton
260A or HP 4342A manual for instructions. These Q meter utilities contain the
instructions and will do the calculations:

I'll look it to that, but, are you actually measuring the capacitor Q, and not the capacitor and inductor Q.
I suspect it's both.

6. Q > 2000 is readily achievable with Litz wire at 1 MHz. The design shown
below uses a 9.9" OD styrofoam cake form.

As I said, a couple people did it on the older Rap n Tap crystal radio forum, using double and triple
660/46 litz wire.

Thanks, Mikek

*Sadly, the fairly new administrator got covid, had real issues and didn't pay the
server fee and we lost years of information. It was very active and productive group.

1. Use this program to calculate coil inductance and Q. It models skin effect, proximity effect, and more subtle effects for both solid and Litz wire:



Results agree well with measurements made with an HP 4342A Q meter. Use the program to verify that Q measurements made with a NanoVNA are not grossly off.

2. Silver plating annealed copper increases Q about 4%. This is usually not worth the trouble.

3. Evidently the styrene pipe couplings popular with crystal set builders use PVC Type 1. This is not a particularly low-loss dielectric. See the attached data sheet.

4. If you have a Q meter, it's easy to measure capacitor Q. See the Boonton 260A or HP 4342A manual for instructions. These Q meter utilities contain the instructions and will do the calculations:



5. The 3-D coil is a novel idea. However, the inner windings contribute much less inductance because of their smaller diameter. I get similar Q at 1 MHz by having the coil program automatically optimize the design of a conventional solenoid of #24 wire.

6. Q > 2000 is readily achievable with Litz wire at 1 MHz. The design shown below uses a 9.9" OD styrofoam cake form.

Brian

On Mon, Oct 10, 2022 at 12:53 PM, Bert W wrote:

From my point of view it will be better to use thick silver-plated copper wire
for high-Q inductors.

That is true in some circumstances, it depends on the inductor in question and the frequency.
For a 240uh air core inductor at BCB frequencies, I doubt silver would beat litz, because of skin effect.
In copper at 1MHz, the resistance is 6.7 times the DC resistance. It is similar in silver.
But it all comes down to the diameters. 660/43 litz is about 0.065", if you went with a
silver wire 0.065", because of skin effect, 37% of the current flows in the wires outer 0.026".
This causes the AC resistance to be higher that the DC resistance.
These pages has some explanation.


Mikek