Coil forms, Q, and instruments


Jim, N5IB
 

With too much free time for my own good, I did an experiment with 3D printing some spiral grooved coil forms.
I was curious if the PLA plastic material used to print would degrade the Q of the coil.
16 turns AWG24, about 1" diameter, about 1" long on a hollow, grooved PLA tube

Short answer, no noticeable Q degradation when I inserted a rod of the PLA material into the center of the coil.
The effective inductance of a coil wound on the form is a few percent lower than the "air wound" formulas predict.
prediction: 5.6 uH, measured: 4.8 uH
But that's to be expected because of the increased inter-winding capacitance due to the dielectric constant of the form's PLA material (about 3). We see the same effect with toroids when spreading/squeezing turns - changing the spacing changes the inter-winding capacitance.

Made a series trap with the test coil and a 200 pF dipped mica cap, and measured the 3 dB frequencies.
The interesting finding is that when I did the Q measurement with a $1000+ spectrum analyzer, I got Q=185.
The on a whim, repeated the measurement with a $65 Nano VNA , and got Q=180
Darn ! 2.7% low !

I think there is a lesson hiding here LOL

Jim, N5IB


Jim Sheldon
 

Ha Ha! Yup, for amateur use, spending 1000+ on a spectrum analyzer vs $65 on a Nano VNA or even maybe a bit more on a "Tiny" spectrum analyzer is pretty huge "overkill" LOL.

I have both the Nano VNA and the tiny Spectrum Analyzer and have gotten super good results from both of them. I sold my expensive spectrum analyzer. The only thing the two little ones don't have is a "tracking generator" and I never found the TG to be super necessary for most of my normal SA measurements.

Jim, W0EB

------ Original Message ------
From: "Jim, N5IB" <n5ib@juno.com>
To: main@4sqrp.groups.io
Sent: 7/22/2021 2:25:26 PM
Subject: [4SQRP] Coil forms, Q, and instruments

With too much free time for my own good, I did an experiment with 3D printing some spiral grooved coil forms.
I was curious if the PLA plastic material used to print would degrade the Q of the coil.
16 turns AWG24, about 1" diameter, about 1" long on a hollow, grooved PLA tube

Short answer, no noticeable Q degradation when I inserted a rod of the PLA material into the center of the coil.
The effective inductance of a coil wound on the form is a few percent lower than the "air wound" formulas predict.
prediction: 5.6 uH, measured: 4.8 uH
But that's to be expected because of the increased inter-winding capacitance due to the dielectric constant of the form's PLA material (about 3). We see the same effect with toroids when spreading/squeezing turns - changing the spacing changes the inter-winding capacitance.

Made a series trap with the test coil and a 200 pF dipped mica cap, and measured the 3 dB frequencies.
The interesting finding is that when I did the Q measurement with a $1000+ spectrum analyzer, I got Q=185.
The on a whim, repeated the measurement with a $65 Nano VNA , and got Q=180
Darn ! 2.7% low !

I think there is a lesson hiding here LOL

Jim, N5IB


davemrtn
 

Good experiment Jim, Thanks for sharing.


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/22/2021 2:25 PM, Jim, N5IB wrote:
With too much free time for my own good, I did an experiment with 3D printing some spiral grooved coil forms.
I was curious if the PLA plastic material used to print would degrade the Q of the coil.
16 turns AWG24, about 1" diameter, about 1" long on a hollow, grooved PLA tube

Short answer, no noticeable Q degradation when I inserted a rod of the PLA material into the center of the coil.
The effective inductance of a coil wound on the form is a few percent lower than the "air wound" formulas predict. 
prediction: 5.6 uH, measured: 4.8 uH
But that's to be expected because of the increased inter-winding capacitance due to the dielectric constant of the form's PLA material (about 3). We see the same effect with toroids when spreading/squeezing turns - changing the spacing changes the inter-winding capacitance.

Made a series trap with the test coil and a 200 pF dipped mica cap, and measured the 3 dB frequencies.
The interesting finding is that when I did the Q measurement with a $1000+ spectrum analyzer,  I got Q=185.
The on a whim, repeated the measurement with a $65 Nano VNA , and got Q=180
Darn !   2.7% low !

I think there is a lesson hiding here   LOL

Jim, N5IB








Kent Trimble, K9ZTV
 

Before buying any antenna analyzer you intend to use in the field, make sure the screen is legible in bright sunlight.  Many, advertised for the outdoors, are not.

73,

Kent  K9ZTV



Virus-free. www.avg.com


davemrtn
 

ALso, I'd like to see your STL file for the spreaders.

David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/22/2021 2:25 PM, Jim, N5IB wrote:
With too much free time for my own good, I did an experiment with 3D printing some spiral grooved coil forms.
I was curious if the PLA plastic material used to print would degrade the Q of the coil.
16 turns AWG24, about 1" diameter, about 1" long on a hollow, grooved PLA tube

Short answer, no noticeable Q degradation when I inserted a rod of the PLA material into the center of the coil.
The effective inductance of a coil wound on the form is a few percent lower than the "air wound" formulas predict. 
prediction: 5.6 uH, measured: 4.8 uH
But that's to be expected because of the increased inter-winding capacitance due to the dielectric constant of the form's PLA material (about 3). We see the same effect with toroids when spreading/squeezing turns - changing the spacing changes the inter-winding capacitance.

Made a series trap with the test coil and a 200 pF dipped mica cap, and measured the 3 dB frequencies.
The interesting finding is that when I did the Q measurement with a $1000+ spectrum analyzer,  I got Q=185.
The on a whim, repeated the measurement with a $65 Nano VNA , and got Q=180
Darn !   2.7% low !

I think there is a lesson hiding here   LOL

Jim, N5IB








Jim, N5IB
 

Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB


Johnny AC0BQ
 

Gm Jim
You do amazing work with that printer.
These are really nice!
72
Johnny 

On Fri, Jul 23, 2021 at 7:49 AM Jim, N5IB <n5ib@...> wrote:
Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB





--
Check out the 4SQRP website at 4sqrp.com


Jim, N5IB
 

Thanks, Johnny,

Didn't notice the photo was blurry... here's a better one

Jim, N5IB


Ted
 

That's some nice work.  Do I see an antenna kit idea?    

Ted





On Fri, Jul 23, 2021 at 9:33, Jim, N5IB
<n5ib@...> wrote:
Thanks, Johnny,

Didn't notice the photo was blurry... here's a better one

Jim, N5IB







Bobby Drummond
 

They look great.  Love the ability to wind them with consistent spacing.  Great job, Jim!

Bobby - AK4JA

On Jul 23, 2021, at 12:12 PM, Ted via groups.io <k3rta@...> wrote:

That's some nice work.  Do I see an antenna kit idea?    

Ted





On Fri, Jul 23, 2021 at 9:33, Jim, N5IB
<n5ib@...> wrote:
Thanks, Johnny,

Didn't notice the photo was blurry... here's a better one

Jim, N5IB








WA4EFS
 

Hello Jim. Very nice work on the coil form. I test printed your .stl file and it came out perfectly.

If you don't mind my asking which CAD application do you use? Some time ago I attempted a similar project in FreeCAD. However, I encountered difficulties and set it aside.

73, -Lloyd (wa4efs)

-----Original Message-----
From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io] On Behalf Of Jim, N5IB
Sent: Friday, July 23, 2021 8:50 AM
To: main@4SQRP.groups.io
Subject: Re: [4SQRP] Coil forms, Q, and instruments

Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB


Jerry Brown
 

Does anyone see a roller inductor in the making???

They are hard to come by these days and the last one I bought was
for a club build project linked here....a LC matching network for 
end fed half wavelength verticals....


A QRP version would be nice!

72,
Jerry N4EO, ex-YI9EO


davemrtn
 

FreeCad is not as intuitive as AutoDesk Fusion 360, but I am unwilling to pay their exorbitant price for hobby use.

I have been designing things with FreeCad [on and off] for several months and becoming more comfortable using, not proficient, but very comfortable.

It does have a few quirks (bugs) you will discover along the way but nothing you won't find a work around for.

It is a bargain at 2 or 3 times the price !


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/23/2021 1:42 PM, WA4EFS wrote:
Hello Jim. Very nice work on the coil form. I test printed your .stl file and it came out perfectly.

If you don't mind my asking which CAD application do you use?  Some time ago I attempted a similar project in FreeCAD. However, I encountered difficulties and set it aside.

73, -Lloyd (wa4efs)

-----Original Message-----
From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io] On Behalf Of Jim, N5IB
Sent: Friday, July 23, 2021 8:50 AM
To: main@4SQRP.groups.io
Subject: Re: [4SQRP] Coil forms, Q, and instruments

Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion 

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB












Jim Sheldon
 

Dave,
Suggest you check again, Fusion 360 is still free for personal/non commercial use.  I have been using F360 for 3 years now, legally licensed for personal use and have not had to pay a penny for it.

Jim, W0EB


On Jul 23, 2021, at 4:37 PM, davemrtn <davemrtn@...> wrote:



FreeCad is not as intuitive as AutoDesk Fusion 360, but I am unwilling to pay their exorbitant price for hobby use.

I have been designing things with FreeCad [on and off] for several months and becoming more comfortable using, not proficient, but very comfortable.

It does have a few quirks (bugs) you will discover along the way but nothing you won't find a work around for.

It is a bargain at 2 or 3 times the price !


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/23/2021 1:42 PM, WA4EFS wrote:
Hello Jim. Very nice work on the coil form. I test printed your .stl file and it came out perfectly.

If you don't mind my asking which CAD application do you use?  Some time ago I attempted a similar project in FreeCAD. However, I encountered difficulties and set it aside.

73, -Lloyd (wa4efs)

-----Original Message-----
From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io] On Behalf Of Jim, N5IB
Sent: Friday, July 23, 2021 8:50 AM
To: main@4SQRP.groups.io
Subject: Re: [4SQRP] Coil forms, Q, and instruments

Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion 

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB












Jim, N5IB
 

Hi Lloyd,

I'm CPU limited and can't run the better CAD packages like Fusion360.
So I've been using TinkerCad on-line, and it's been sufficient for most things I've needed.
With Ultimaker Cura 4.6.2 as the slicer

One day, with a better CPU, I'll move up.

Jim, N5IB


Jim Sheldon
 

Jim G's work inspired me to work on a 40/20 meter trap doublet/dipole/inverted vee with 3D printed trap coil forms and insulators.  I have the traps coil forms done and the end/trap center insulators done and I really got lucky.  A 20 meter trap should have 4.7 uH worth of inductance with a 27pF capacitor to resonate at 14.100 MHz and TOTALLY by accident, my initial print of the coil form wound with 16 turns of #20 wire just so happened to come out to just a bit over 4.7uH when I measured it.

I worked on the design (I used AudoDesk's (free for personal/non-commercial use) Fusion 360 as my CAD program.  F360 gives a bit more finesse when making threaded cylinders than TinkerCad does. 

Taking Jim's advice, I also added blockers to the inside of the coil form so the insulator will slide tightly inside and allow you to wind the coil first and pick which 90 degree point gives you the best coil positioning.

Here's a couple of pictures of the lot.

Jim Sheldon, W0EB  -- 3D printing is a super 2nd hobby to HamRadio --









cornhusker
 

I hope you can post the STL files!   This looks great!
73 de K0NEB 



On Fri, Jul 23, 2021 at 8:01 PM, Jim Sheldon
<w0eb@...> wrote:
Jim G's work inspired me to work on a 40/20 meter trap doublet/dipole/inverted vee with 3D printed trap coil forms and insulators.  I have the traps coil forms done and the end/trap center insulators done and I really got lucky.  A 20 meter trap should have 4.7 uH worth of inductance with a 27pF capacitor to resonate at 14.100 MHz and TOTALLY by accident, my initial print of the coil form wound with 16 turns of #20 wire just so happened to come out to just a bit over 4.7uH when I measured it.

I worked on the design (I used AudoDesk's (free for personal/non-commercial use) Fusion 360 as my CAD program.  F360 gives a bit more finesse when making threaded cylinders than TinkerCad does. 

Taking Jim's advice, I also added blockers to the inside of the coil form so the insulator will slide tightly inside and allow you to wind the coil first and pick which 90 degree point gives you the best coil positioning.

Here's a couple of pictures of the lot.

Jim Sheldon, W0EB  -- 3D printing is a super 2nd hobby to HamRadio --









Jim Sheldon
 

I will Joe.  I have a couple more things before I post the complete package.  I still need to design a center insulator to take a BNC connector and one to take an SO-239 before I post the files.

I’ll work on those tomorrow after breakfast and hopefully have a zipfile with all the .stl and I’ll include the .f3d files for those who can use them.

Jim


On Jul 23, 2021, at 8:53 PM, cornhusker via groups.io <cornhusker@...> wrote:

I hope you can post the STL files!   This looks great!
73 de K0NEB 



On Fri, Jul 23, 2021 at 8:01 PM, Jim Sheldon
<w0eb@...> wrote:
Jim G's work inspired me to work on a 40/20 meter trap doublet/dipole/inverted vee with 3D printed trap coil forms and insulators.  I have the traps coil forms done and the end/trap center insulators done and I really got lucky.  A 20 meter trap should have 4.7 uH worth of inductance with a 27pF capacitor to resonate at 14.100 MHz and TOTALLY by accident, my initial print of the coil form wound with 16 turns of #20 wire just so happened to come out to just a bit over 4.7uH when I measured it.

I worked on the design (I used AudoDesk's (free for personal/non-commercial use) Fusion 360 as my CAD program.  F360 gives a bit more finesse when making threaded cylinders than TinkerCad does. 

Taking Jim's advice, I also added blockers to the inside of the coil form so the insulator will slide tightly inside and allow you to wind the coil first and pick which 90 degree point gives you the best coil positioning.

Here's a couple of pictures of the lot.

Jim Sheldon, W0EB  -- 3D printing is a super 2nd hobby to HamRadio --

<Img_7973.jpg>


<Img_7974.jpg>


<Img_7976.jpg>



<Img_7973.jpg>
<Img_7974.jpg>
<Img_7976.jpg>


davemrtn
 

Jim,  I had the original hobbyist version and Autodesk said my "free trial" was over !

I tried to sign up again for hobbyist license and couldn't find a means to do it.

Points would be appreciated.

In the mean time, I am getting better at using FreeCad.


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/23/2021 4:41 PM, Jim Sheldon wrote:
Dave,
Suggest you check again, Fusion 360 is still free for personal/non commercial use.  I have been using F360 for 3 years now, legally licensed for personal use and have not had to pay a penny for it.

Jim, W0EB


On Jul 23, 2021, at 4:37 PM, davemrtn <davemrtn@...> wrote:



FreeCad is not as intuitive as AutoDesk Fusion 360, but I am unwilling to pay their exorbitant price for hobby use.

I have been designing things with FreeCad [on and off] for several months and becoming more comfortable using, not proficient, but very comfortable.

It does have a few quirks (bugs) you will discover along the way but nothing you won't find a work around for.

It is a bargain at 2 or 3 times the price !


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/23/2021 1:42 PM, WA4EFS wrote:
Hello Jim. Very nice work on the coil form. I test printed your .stl file and it came out perfectly.

If you don't mind my asking which CAD application do you use?  Some time ago I attempted a similar project in FreeCAD. However, I encountered difficulties and set it aside.

73, -Lloyd (wa4efs)

-----Original Message-----
From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io] On Behalf Of Jim, N5IB
Sent: Friday, July 23, 2021 8:50 AM
To: main@4SQRP.groups.io
Subject: Re: [4SQRP] Coil forms, Q, and instruments

Hi David,

Here's the STL file, attached, and a photo.
It's such a thin tube it needs a "brim" for buildplate adhesion

There's a tiny hole at each end to pass the wire through to secure the turns.
I plan to make another with multiple holes to accommodate different turn counts.

Jim, N5IB












davemrtn
 

Jim, what material are you printing with, PETG ???

I wouldn't use PLA, but ABS would last longer than PLA, but I think PETG might last the longest ??


David Martin - NA1MH - Mountain Home, Ar. -----------------------------------------
Wherever I go, there He is.


On 7/23/2021 8:01 PM, Jim Sheldon wrote:
Jim G's work inspired me to work on a 40/20 meter trap doublet/dipole/inverted vee with 3D printed trap coil forms and insulators.  I have the traps coil forms done and the end/trap center insulators done and I really got lucky.  A 20 meter trap should have 4.7 uH worth of inductance with a 27pF capacitor to resonate at 14.100 MHz and TOTALLY by accident, my initial print of the coil form wound with 16 turns of #20 wire just so happened to come out to just a bit over 4.7uH when I measured it.

I worked on the design (I used AudoDesk's (free for personal/non-commercial use) Fusion 360 as my CAD program.  F360 gives a bit more finesse when making threaded cylinders than TinkerCad does. 

Taking Jim's advice, I also added blockers to the inside of the coil form so the insulator will slide tightly inside and allow you to wind the coil first and pick which 90 degree point gives you the best coil positioning.

Here's a couple of pictures of the lot.

Jim Sheldon, W0EB  -- 3D printing is a super 2nd hobby to HamRadio --