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On 7/4/23 11:16 AM, WB2UAQ wrote:

Mike and Alan,
I measured the loss factor for PVC and it was about 0.005 or so at 1 kHz. I did more measurements at RF but will have to go back to old note books. I made a simple fixture to test a number of plastics. I rebuilt a coil that plugs into a BC-610 transmitter and from that sprung all kinds of questions about dielectrics. Many local guys are using 3D printers and using PLA, I think it is called. They printed out a plate of it for me to test. I would not say that all of this material is made equally and permitivity and loss factor are probably not well controlled. Won't be able to get back to this for awhile as it is Independence Day and a lot going on to take care of this week. Can only say right now that none of this plastic seemed to jump out as being a terrible dielectric. I also tested plate glass because back in the early days of radio capacitors for spark transmitters used what I think was regular glass available at that time.

PVC pipe has two potential problems as a coil form (based on experience of folks building tesla coils, so 100-500 kHz):
1) it's hygroscopic so the dielectric loss varies with the water content - nylon has the same problem, BTW.
2) most pipe is made from recycled material, and it can have metal fragments and other debris in it. The specs for pipe are about holding pressure and being "safe for drinking water", not dielectric properties.

Tesla coil folks solve #1 by drying it and then coating with something like lacquer, glyptal, or urethane

#2 is a bit trickier - it's not like you can take a 4 foot long piece of 6" pipe and throw it in the microwave and see if it arcs or has hot spots.

Mike and Alan,
I measured the loss factor for PVC and it was about 0.005 or so at 1 kHz. I did more measurements at RF but will have to go back to old note books. I made a simple fixture to test a number of plastics. I rebuilt a coil that plugs into a BC-610 transmitter and from that sprung all kinds of questions about dielectrics. Many local guys are using 3D printers and using PLA, I think it is called. They printed out a plate of it for me to test. I would not say that all of this material is made equally and permitivity and loss factor are probably not well controlled. Won't be able to get back to this for awhile as it is Independence Day and a lot going on to take care of this week. Can only say right now that none of this plastic seemed to jump out as being a terrible dielectric. I also tested plate glass because back in the early days of radio capacitors for spark transmitters used what I think was regular glass available at that time.
73

On Mon, Jul 3, 2023 at 11:24 PM, alan victor wrote:

Excellent Mike. So that is a Qul of 348. I spilt the difference between 6 and
8 ohms... lets say 7... From the appearance of your coil, that seems
reasonable. The material you wound the unit on has a loss tangent. Any idea
what it is? Nice if it were .0005 or better.... Suspect it is not.

It's PVC water pipe.

--
Mike

On 7/3/23 4:13 PM, WB2UAQ wrote:

Alan, How does the loss factor of the dielectric that the coil form is made from impact the magnetic circuit? I have heard others mention this but with no explanation.

Most coils have some parasitic C (it can be quite large). That C has a voltage on it, and a lossy dielectric leads to loss.

Hi Pete.

The inductor is supporting a propagating field. It is both magnetic and electric. You are correct, while the magnetic properties of a core are key to control loss, so are the dielectric properties, as this impacts the electric field. A good way to approach all lumped components is not to consider them as lumped, but as distributed. An L and C are actually transmission line components. Particularly as the frequency increases. So the dielectric loss as it affects a transmission line is really no different in its impact when it supports a coil on an insulating form. Loss in the dielectric contributes a resistive shunt component and reduces the inductor Q. As a rule of thumb, try to use a material whose loss tangent provides a Q value (1/loss tan) of 5 x the inductor alone.

You can change the setting in the menu to display R+jX instead of the default R +inductance/capacitance.

Roger

Alan, How does the loss factor of the dielectric that the coil form is made from impact the magnetic circuit? I have heard others mention this but with no explanation.
Thanks, Pete

Good evening!

I would very much appreciate recommendations on the best version of the NANOVNA that displays reactance values for the markers on the Smith chart, instead of inductance and capacitance.

Thank you very much!

Tom

Excellent Mike. So that is a Qul of 348. I spilt the difference between 6 and 8 ohms... lets say 7... From the appearance of your coil, that seems
reasonable. The material you wound the unit on has a loss tangent. Any idea what it is? Nice if it were .0005 or better.... Suspect it is not.

On Mon, Jul 3, 2023 at 03:27 PM, alan victor wrote:

If difficulty in finding the paper from EDN and the figures, here is a pdf
abbreviated and a test case circuit screen capture. If you are careful in
fixture construction depending on operating frequency, unloaded Q of 350 or
more is easy to obtain. You really need to take care in any Q measurement to
prevent series R losses from accumulating unless you can accurately de-embed
the "stray" R value(s).

Alan

OK I had a go at this with my NanoVNA and got the attached result, which if I follow your calculation correctly equates to Rq = 8.05 ohms.

Coil64 estimates 5.9 ohms which, given the less than ideal test jig I'm using, is not too far off.

Mike


--
Mike

Return it and get a refund. Then go to R & L Electronics and purchase a genuine one. Problem solved!!! PS... This is the very best advise ANYBODY can give you!!!

Alan

I found the article from your earlier link and will give it a go, thanks.

In the meantime I repeated my measurement with NanoVNA-App calibrated for 6401points and got a slightly lower value of 13.6 ohms at resonance.

--
Mike

On Monday 03 July 2023 08:20:00 am DougVL wrote:

I occasionally see them for sale at hamfests. I have gotten a few that way, but I shouldn't have - I haven't used any yet. Not even the big, (relatively) heavy old U.S. military one.
If you look for one that way, be sure that any that you find still has its set of plug-in coils.

I had the thought to get one some time back, and started looking on ebay. It's amazing how many of these units do NOT have any of the coils with them! I know of one guy who took on one of those and proceeded to try and make his own coils, but I'm not feeling that ambitious these days...

I wonder where all of those coils go?

--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin

Mike,

the article is in this file /g/Test-Equipment-Design-Construction/files/Q-factor%20%28Q%20is%20the%20inverse%20of%20dissipation%20factor%20DF%29./Method%20simplifies%20testing%20high-Q%20devices;%20Alan%20Victor,%20EDN%20Feb%202002.pdf. [It's no longer available on the EDN website with the all-important diagrams!]

HTH, 73, happy (or otherwise) measuring,

Robin, G8DQX

If difficulty in finding the paper from EDN and the figures, here is a pdf abbreviated and a test case circuit screen capture. If you are careful in fixture construction depending on operating frequency, unloaded Q of 350 or more is easy to obtain. You really need to take care in any Q measurement to prevent series R losses from accumulating unless you can accurately de-embed the "stray" R value(s).

Alan

I occasionally see them for sale at hamfests. I have gotten a few that way, but I shouldn't have - I haven't used any yet. Not even the big, (relatively) heavy old U.S. military one.
If you look for one that way, be sure that any that you find still has its set of plug-in coils.
--
Doug, K8RFT

I am using nanoVNA-H
The product was purchased on Ali Express, and I thought it was genuine, but it was fake.

First of all, I am a Windows 10-64bit user.

What did you do to solve the problem
1. Install stm32080 driver - Failed to solve
2. firmware upgreade or downgreade - 2 out of 5 bricks (0.9.2 << became a brick, 0.9.3 failed to connect to usb, current version 1.2 but failed to connect to usb)
3. Cypress usb installation - failed
4. FTDI usb installation - failed

Is there any way to connect the fake product to the pc? Tried on win7, linux, and macos, but failed.

Unfortunately, if it's not genuine, can't it be connected to the pc?

i want help

On Mon, Jul 3, 2023 at 12:23 AM, alan victor wrote:

Hi Mike,

Please see message # 23812. This documents one approach.

Alan

Thanks Alan I'll have a look at that.
--
Mike

Mike
15 ohms is not too far from what a long inductor made with small gauge wire could have. Q of about 143.
Pete

Mike, Scratch that idea about the scales because it doesn't work the same at 4 MHz where the Z should be about +j503 ohms.