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For Dave, AA7EE, and anyone else interested. I added about 3 mins at the end of this
video showing that a toroid inductor in free space, vertically mounted on a PCB or
horizontally mounted on a PCB has the same value.
Now the nits are going for the 3rd and 4th digit, but fluctuations occur in the
process of moving the toroid around and the spacing of the leads, thus the
stray capacitance across the toroid causes a very minor change in the total.
I will come back, after I finish this and ADC-40 (I'm doing the transmitter
on the side), and do a complete video on toroids and why they are your
friend.? Once you get over the fear of winding the critters, you will use
them everywhere.? Well, almost.....
<>?? is the video by AA7FO for your entertainment.
Watch the whole thingy and add a like to help an old man down on his luck.? :-)
And trying to get to a polished presentation sometime in the future.
ciao,
--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
PA,CA,CO,WI,NE,ID,IL,NC,LA
DXCC W,VE,JA,PY,ZL
|
On Fri, Apr 11, 2025 at 12:09 AM, chuck adams wrote:
For Dave, AA7EE, and anyone else interested. I added about 3 mins at the end of this
video showing that a toroid inductor in free space, vertically mounted on a PCB or
horizontally mounted on a PCB has the same value.
That was instructive Chuck. I knew about the self-shielding properties of toroids, but didn't realize the fields around them are that tightly restricted. On the PCB's I've seen that have horizontally mounted toroids, the ground plane on the other side is largely removed. I guess the designers are just playing it safe. In the past, I have spaced my horizontal VFO toroids above the copper substrate with an extra nylon washer, but it looks as if a single shoulder washer is enough. You are proving the value of measuring and verifying these things for ourselves instead of making assumptions.
?
Dave
AA7EE
|
All,
Not to get into a dispute with Chuck and others, but my experience
is that if you mount a toroid tight to the copper surface of PCB
material, it will indeed change the inductance of the toroid, but
more importantly, will cause small circulating currents to be
created in the copper substrate under the toroid, leading to
frequency instability, especially if said toroid is in a VFO or LO.?
I always mount them between shouldered washers with a nylon screw to
hold them down.? Early 2N2 style rigs confirmed the information
above.
72/73,
Jim, K8IQY
On 4/11/2025 1:00 PM,
davidgeorgerichards via groups.io wrote:
toggle quoted message
Show quoted text
On Fri, Apr 11, 2025 at 12:09 AM, chuck adams wrote:
For Dave, AA7EE, and anyone else interested. I added
about 3 mins at the end of this
video showing that a toroid inductor in free space, vertically
mounted on a PCB or
horizontally mounted on a PCB has the same value.
That was instructive Chuck. I knew about the self-shielding
properties of toroids, but didn't realize the fields around them
are that tightly restricted. On the PCB's I've seen
that have horizontally mounted toroids, the ground plane on the
other side is largely removed. I guess the designers are just
playing it safe. In the past, I have spaced my horizontal VFO
toroids above the copper substrate with an extra nylon washer,
but it looks as if a single shoulder washer is enough. You are
proving the value of measuring and verifying these things for
ourselves instead of making assumptions.
?
Dave
AA7EE
|
Jim,
I do not consider it a dispute.? I was using an L/C meter to test for effects.
Since the L/C meter evaluates at a much lower frequency, there is room for
more experiments.? I would have to sit down and look at the skin effect to
see the difference between 1oz, 2oz and 3oz coatings.? This is an area
for lots of experimentation.
I've seen a lot of places where a nylon screw and nut with washer were used
to mount a toroid.? I know it helps in a rough environment for reducing
microphonics in a cheap way.? Some hams I've seen use a hot glue gun to
lock down parts for the same reason.
This is the kind of area where you need a graduate student in a lab
to spend a few hundred hours taking data from DC to daylight to
determine all the ins and outs.
As soon as I finish the current projects, I have a microvoltmeter
design to build and I can do some more testing.? From DC to 100MHz
in fact.
Thanks for the feedback and I stand corrected.
toggle quoted message
Show quoted text
On 4/11/25 13:33, Jim Kortge, K8IQY via groups.io wrote: All,
Not to get into a dispute with Chuck and others, but my experience is that if you mount a toroid tight to the copper surface of PCB material, it will indeed change the inductance of the toroid, but more importantly, will cause small circulating currents to be created in the copper substrate under the toroid, leading to frequency instability, especially if said toroid is in a VFO or LO.? I always mount them between shouldered washers with a nylon screw to hold them down.? Early 2N2 style rigs confirmed the information above.
72/73,
Jim, K8IQY
On 4/11/2025 1:00 PM, davidgeorgerichards via groups.io wrote:
On Fri, Apr 11, 2025 at 12:09 AM, chuck adams wrote:
For Dave, AA7EE, and anyone else interested. I added about 3 mins
at the end of this
video showing that a toroid inductor in free space, vertically
mounted on a PCB or
horizontally mounted on a PCB has the same value.
That was instructive Chuck. I knew about the self-shielding properties of toroids, but didn't realize the fields around them are /that/ tightly restricted. On the PCB's I've seen that have horizontally mounted toroids, the ground plane on the other side is largely removed. I guess the designers are just playing it safe. In the past, I have spaced my horizontal VFO toroids above the copper substrate with an extra nylon washer, but it looks as if a single shoulder washer is enough. You are proving the value of measuring and verifying these things for ourselves instead of making assumptions.
Dave
AA7EE
--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
PA,CA,CO,WI,NE,ID,IL,NC
DXCC W,VE,JA,PY
|
Hi Chuck,
In reading your response to my post, it dawned on me that a simple
experiment might shed some light on the self shielding or magnetic
field containment of toroids.? Take a pair of wound toroids, drive
one with an oscillator of know amplitude with the two taped
together, and measure the passive toroid with an RF voltmeter to see
if there is any output.? My guess is that there will be, much lower
than the driven toroid, but some coupling.? I might gin that
experiment up tomorrow to see what happens.? Perfect experiment for
a S/A with tracking generator, and I have one of those!
72/73 and I tried 17-meters again today for you, but no go.? 17 in
really sad shape today, along with all of the other bands,
Jim, K8IQY
On 4/11/2025 6:34 PM, chuck adams via
groups.io wrote:
toggle quoted message
Show quoted text
Jim,
I do not consider it a dispute.? I was using an L/C meter to test
for effects.
Since the L/C meter evaluates at a much lower frequency, there is
room for
more experiments.? I would have to sit down and look at the skin
effect to
see the difference between 1oz, 2oz and 3oz coatings.? This is an
area
for lots of experimentation.
I've seen a lot of places where a nylon screw and nut with washer
were used
to mount a toroid.? I know it helps in a rough environment for
reducing
microphonics in a cheap way.? Some hams I've seen use a hot glue
gun to
lock down parts for the same reason.
This is the kind of area where you need a graduate student in a
lab
to spend a few hundred hours taking data from DC to daylight to
determine all the ins and outs.
As soon as I finish the current projects, I have a microvoltmeter
design to build and I can do some more testing.? From DC to 100MHz
in fact.
Thanks for the feedback and I stand corrected.
On 4/11/25 13:33, Jim Kortge, K8IQY via groups.io wrote:
All,
Not to get into a dispute with Chuck and others, but my
experience is that if you mount a toroid tight to the copper
surface of PCB material, it will indeed change the inductance of
the toroid, but more importantly, will cause small circulating
currents to be created in the copper substrate under the toroid,
leading to frequency instability, especially if said toroid is
in a VFO or LO.? I always mount them between shouldered washers
with a nylon screw to hold them down.? Early 2N2 style rigs
confirmed the information above.
72/73,
Jim, K8IQY
On 4/11/2025 1:00 PM, davidgeorgerichards via groups.io wrote:
On Fri, Apr 11, 2025 at 12:09 AM, chuck
adams wrote:
??? For Dave, AA7EE, and anyone else interested. I added about
3 mins
??? at the end of this
??? video showing that a toroid inductor in free space,
vertically
??? mounted on a PCB or
??? horizontally mounted on a PCB has the same value.
That was instructive Chuck. I knew about the self-shielding
properties of toroids, but didn't realize the fields around
them are /that/ tightly restricted. On the PCB's I've seen
that have horizontally mounted toroids, the ground plane on
the other side is largely removed. I guess the designers are
just playing it safe. In the past, I have spaced my horizontal
VFO toroids above the copper substrate with an extra nylon
washer, but it looks as if a single shoulder washer is enough.
You are proving the value of measuring and verifying these
things for ourselves instead of making assumptions.
Dave
AA7EE
|
Jim, I know from something I read decades ago that turning two toroids 90deg to each other greatly reduces any interaction.? Makes since from a E&M standpoint. I would think that you have to be careful with this experiment. Imagine that the windings interlock so that they are adjacent.? Capacitance between the windings would look like magnetic field interaction.? I'd place a very thin sheet of plastic (say a milk carton slab) between them to prevent physical overlap of windings.? First impression in the brain I get.? I assume that you might do a N number of turns where N is as large as you can get. Then try it with a smaller number of turns and the field is not self enclosed. The experiments I see on the web using the nanoVNA are amazing.? We certainly couldn't do this a long time ago and maybe even a short time ago.? I got one to play with crystals, but that is always for tomorrow..... I'll be looking for you and anyone else on 17.? The receiver is right in front of me all the time I'm building something and cataloging parts. Two days ago was the first day that I couldn't get anyone and the A-index was at 23 and K-index at 4.? I closed the band last night with LA and a ZL.? The RBN looked like a spider web.? He must have been running more than 5W.? :-)? And this was an hour after the band had closed in the US.? It pays to stay up late sometimes.? The ZL must have $50K worth of aluminum in the air..... Just got NY. ciao dude, On 4/11/25 16:09, Jim Kortge, K8IQY via groups.io wrote: Hi Chuck,
In reading your response to my post, it dawned on me that a simple experiment might shed some light on the self shielding or magnetic field containment of toroids.? Take a pair of wound toroids, drive one with an oscillator of know amplitude with the two taped together, and measure the passive toroid with an RF voltmeter to see if there is any output.? My guess is that there will be, much lower than the driven toroid, but some coupling.? I might gin that experiment up tomorrow to see what happens.? Perfect experiment for a S/A with tracking generator, and I have one of those!
72/73 and I tried 17-meters again today for you, but no go.? 17 in really sad shape today, along with all of the other bands,
Jim, K8IQY
...snip snip... -- chuck adams, aa7fo QRP WAS 17m started Apr 2, 2025 WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN PA,CA,CO,WI,NE,ID,IL,NC,NY DXCC W,VE,JA,PY
|
Hi,
I have a number of Kits and Parts dual BPF boards which show extra suckout at the opposing band on the filter response, so it is possible that the toroids are coupling at a low level.? However I could reduce (but not eliminate) the unwanted response somewhat by putting up a PCB 'wall' between the filters. Alternatively it could be the responses are coupling via the common earthplane. On of RF BPF filters that PA3AKE designed he had splits in the groundplane to reduce ground coupling effects, even on one filter board.?
?
|
My solution is based on testing of toroids is that they do have
external fields.
?
In a 10M radio I needed small bandpass filter but the toroids
did interact if too close.? MY solution (since they were t37 size)
was old HC6U crystal cans, unsolder the top and save it.? Wrap
the wound toroid in card stock strip so there would not be
metal contact to the windings.? Mount the cans to copper clad
board?open end up by soldering.? Leads out the top allow for tuning
and coupling connections.??
?
The added capacitance would make them move down in frequency
but since they were externally tuned that was easy to adjust.? Filter
performance with cans shielding them was excellent.? The
result was very compact as well.
?
?
Allison
?
|
Jim Kortge, K8IQY