开云体育

oooops. When I send them to the files section, I shall do so. Thanks
for the suggestion. I thought Apple could read .docx files. Are we back
to Apple vs. IBM? Humbug......

Dave

On Tue, Feb 2, 2021 at 6:15 PM Joe St. Clair AF5MH <saintc@...>
wrote:

I suggest that you convert the document to PDF format. The .docx format
seems to be problematic on non-Microsoft systems.

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

I suggest that you convert the document to PDF format. The .docx format seems to be problematic on non-Microsoft systems.

John:

1 SAVER- what is this, where do you get it, how do you use it?....reference
essential
NANOVNA SAVER is a SW application that runs on a PC or laptop. It was done
by the same folks who did the NANOs. It is free and downloadable at:


2. Stand-alone Procedure needed.
I can work on that if I receive other requests for that option. Once you
use SAVER, I believe you will want to use it as there are more options and
a large screen to work with.

3 Test fixture, which looks ok for HF, could have significant stray
coupling for use at v/uhf- a VHF CMC is the first project here. A plot of
the test fixture open cct coupling /loss up to the freq. limit of the vna
would be helpful. Converting everything to BNC is a GOOD idea.
I use BNCs for everything ≤ 100 watts. However, above 70-cm, I generally
use SMA connectors. The fixture I built is not appropriate for anything
much above 50 MHz. On occasion, I cal it up to 200 MHz, but that is a real
stretch and the data is not too reliable, requiring 'sanity checks' of
known standards. On an open after cal from 1 MHz through 30 MHz, it
measured into the megohms. If you really want to extend the frequency
coverage of the fixture, an entirely different design is required. I'd
suggest building a fixture using double-sided FR-4 board 0.625-inches or
160-cm thickness and cutting microstripline to/from SMA connectors at
either end of the line. The stripline width on that material for 50-ohms
Zo is roughly 0.125-inches or 0.318 cm. Leave an open gap in the center
of the line to connect (solder) your DUT (Device Under Test). Building a
reliable fixture can be done, but it is not trivial.

4 If you cite previous measurements, you should reference where they are,
or include them
I'll attach them to this post.

5 USA specific antenna wire types - not helpful to a world-wide audience,
again, reference desirable.
So far, the 'antenna' wire from DavisRF which I have sited is the most
successful for these CMCs. I wound one core with PVC insulation from Ace
Hardware. The insulation heated badly with any real power and I watched
the SWR climb on key-down at 400-watts. Not appropriate for this
application. Today I should have delivered a length of AWG #12 stranded
and Teflon insulated wire to further explore that option. The thickness of
the insulation indicates it should take as a minimum up to 20 kV so I
should not have the problem I had with arcing and coronal discharges with
the AWG #12 enameled conductor. A handy conversion chart between metric
cross section and AWG sizing can be accessed at:


I don't buy off on the 'king's foot' either. The US tried forcing
conversion to metric, but the house wives, civil engineers, . . . . . spit
it right back. Personally, I prefer metric, but I live in the world of the
'king's foot'.

6 I'm a little surprised that both wires at each end of the CMC are not
connected.
I knew I'd get this question. I've tried connecting both and the
difference is minor. Once you have things set up, try comparing single
winding vs. both in parallel. There is really very little difference which
does not justify further complication (I have 'shorting' banana plugs for
the purpose).

Dave - W?LEV

On Tue, Feb 2, 2021 at 12:17 PM John Button G8JMB via groups.io
<hornpipe112@...> wrote:

Hi Dave

Thanks for the procedure;Exactly what I want to do. It's generally clear
but as a 'new driver' of the VNA in my Santa sack, I have a couple of
comments / requests
1 SAVER- what is this, where do you get it, how do you use
it?....reference essential
2. Stand-alone Procedure needed.
3 Test fixture, which looks ok for HF, could have significant stray
coupling for use at v/uhf- a VHF CMC is the first project here. A plot of
the test fixture open cct coupling /loss up to the freq. limit of the vna
would be helpful. Converting everything to BNC is a GOOD idea.
4 If you cite previous measurements, you should reference where they are,
or include them
5 USA specific antenna wire types - not helpful to a world-wide audience,
again, reference desirable.
6 I'm a little surprised that both wires at each end of the CMC are not
connected.

73
Keep up the good work

John G8JMB

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

@brown.beard.2020:

A ferrite core may stop noise and interference leaking?into the cable, but not that picked by the antenna itself (which will likely be your biggest problem). For this you'll need an actual bandpass filter, which is not hard to do at 13.5 MHz if you have access to a soldering iron and some hand tools.
First you need a design, which I already did for you using one of the many available online tools:

You connect one side to the antenna and the other to the device. You can buy the components from online retailers such as Newark, Digi-Key or Mouser?for about $10. To build the filter you don't need a PCB; you can simply use a strip of copper or tin, and solder the components using the dead bug construction technique. You can even use an Altoids tin, which also gives you an enclosure. The lower continuous wire in the diagram represents the copper strip or tin box, which is your "ground plane".
Maybe not as simple as a ferrite core but definitely more effective.

On Tue, 2 Feb 2021 at 18:37, Dragan Milivojevi? <d.milivojevic@...>
wrote:

It's a SimSmith graph, I have attached the circuit and the S file that was
used:

[image: image.png]





On Tue, 2 Feb 2021 at 18:25, David Eckhardt <davearea51a@...> wrote:

Dragan:

I have not seen a way to plot the second chart. Please let me know and
I'll take a look at my chokes in that respect. The dotted lavender line in
the second plot looks like series resonance somewhere near 7.5 MHz.

Dave - W?LEV

JOHN,
I have the same issue with metric-only BOMs from Europe. Cross-referencing 0.4mm wire to what we have here in US AWG.
Gary
W9TD

On 2/2/21 5:04 AM, brown.beard.2020@... wrote:

Hi All

Sorry if this is not the right place to ask. Feel free to point me to a more suitable place for my questions.

I have an antenna connected to a 13.56MHz RF signal and would like to add a ferrite core to the cable from the antenna to the device to filter out any noise coming from the environment.
How do i determine the appropriate specs for the ferrite core?

That's the ISM frequencies just below the amateur radio 20 meter band, so anything that works for 14 MHz (20m) will probably work just fine for 13.56 MHz.

In general, 31 mix is a good choice for HF - it's suitably lossy at those frequencies.? You might check out K9YC's choke cookbooks and other writeups..



You're presumably at low power for something like a badge reader, so you probably aren't as interested in low loss transmitter designs.




*RFI, Ferrites, and Common Mode Chokes For Hams <>**Most recent update April 2019.*This tutorial is directed specifically to RFI in ham radio applications. It includes an extended discussion of the use of common mode chokes in antenna systems and for suppression of RFI. A chapter on audio and computer interconnections in ham stations shows how to make bulletproof connections between a computer sound card and ham rigs for SSB, RTTY, PSK31, and SO2R contesting without expensive interface boxes, using nothing more than simple cables with the right connectors on each end. There's also a chapter on grounding and bonding.


This is a new applications note summarizing my work on *Chokes and Transformers For Receiving Antennas. <>**NEW!*October 2018

Try the ham-antennas group.

DaveD

Hi All

Sorry if this is not the right place to ask. Feel free to point me to a more suitable place for my questions.

I have an antenna connected to a 13.56MHz RF signal and would like to add a ferrite core to the cable from the antenna to the device to filter out any noise coming from the environment.
How do i determine the appropriate specs for the ferrite core?

Thanks

They are all true. :-)

Zack W9SZ

On Sun, Jan 31, 2021 at 9:48 PM Cierra <dubosec@...> wrote:

This might be a dumb question, but where are the answers listed?

<>
Virus-free.
www.avast.com
<>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

As I wrote in my original post, bookfinder.com is currently the best resource for locating used books.

I have found that the information about the condition of used books offered by booksellers through Amazon can be sketchy. But, then, there are all kinds of shenanigans practiced by new booksellers has become rampant over the past fifteen or do years. Caveat Emptor, in other words.

DaveD

On Mon, Feb 1, 2021 at 11:21 AM, Dave Daniel wrote:

RSGB “Antennas for all Locations”

This book by Les Moxon, G6XN, is a great one for those of us without a strong college mathematics education. It's available used, from Amazon and other booksellers. I'm very glad to have a copy.
--
Doug, K8RFT

Hi Dave

Thanks for the procedure;Exactly what I want to do. It's generally clear but as a 'new driver' of the VNA in my Santa sack, I have a couple of comments / requests
1 SAVER- what is this, where do you get it, how do you use it?....reference essential
2. Stand-alone Procedure needed.
3 Test fixture, which looks ok for HF, could have significant stray coupling for use at v/uhf- a VHF CMC is the first project here. A plot of the test fixture open cct coupling /loss up to the freq. limit of the vna would be helpful. Converting everything to BNC is a GOOD idea.
4 If you cite previous measurements, you should reference where they are, or include them
5 USA specific antenna wire types - not helpful to a world-wide audience, again, reference desirable.
6 I'm a little surprised that both wires at each end of the CMC are not connected.

73
Keep up the good work

John G8JMB

Hello,

I found the last V2 firmware releases are stored on:



It looks the 20201122 release fixes the issue with markes move that sometime freezes the device.

Regards,
Simone

I promised this, so here it is. See the attachment for a procedure to
measure the CM attenuation through CMCs and other 4-terminal devices (as in
s-parameters). Comments and improvements are welcome before I post it to
the files section.

Dave - W?LEV

We are talking about power transfer here. "Taking power away from the transmitter" IMHO, is a misnomer that leads to confusion.
The Maximum power transfer theorem states that the AC voltage source will deliver maximum power to the variable complex load only when the load impedance is equal to the complex conjugate of source impedance.

The purpose of the "tuner" is to make the above happen, therefore facilitating maximum power transfer.
When the Z is right, the SWR is 1 and there is no power loss - it is all going out the antenna.

Of course, nothing is perfect. However, I worked on the Apollo tracking ships back in the day, and we had 3 helical HF antennas with a very large remotely variable HV capacitor at their base. We were able to tune them at power (5KW) to a VSWR of 0. Pretty amazing. The only problem with that was the Teflon insulation couldn't handle the voltage and every time we changed the insulator the Q went up and the voltage followed and it broke down again. What was more amazing is that they made it back and were found immediately.

On 2/1/21 8:21 AM, Dave Daniel wrote:

There are many textbooks out there. Some are:

Any revision of John Kraus’ “Antennas” text (classic and probably the best choice when starting out)

2nd ed is available on scribd in various formats and is sufficiently new for most amateur purposes.

Kraus is my "go-to" book in general when I need a good explanation, and some theory.

My general take is that Kraus approaches antennas from a "start with antenna, and explain why it works", while Balanis is a bit more like "start with first principles and, hey, you can make an antenna".? Both are good.

Another useful text book is Orfanidis's Electromagnetic Waves and Antennas, which is online. It's kind of written from the optics perspective, and is fairly math heavy. However, he has a whole bunch of matlab code available to do useful stuff like calculate impedances, mutual coupling, design Yagis,e tc. Whether you run Matlab (or Octave), or you use that as a guide to rewriting in some other language, it's really useful.

Another Kraus.

The big, old, "The A.R.R.L. Antenna Book" has a foreword by John

Kraus. If John Kraus thought that a treatment of antennas was
alright...then it was alright!

The book here is from 1988 and the copyright is from that year.? The

I.S.B.N is ?? 0-87259-206-5 ?? , ? ? Library of Congress ?? 55-8966?? .

Now, please note, when scouting flea markets or looking on the web,

this is the "big, old" antenna book not one of the more recent "little,
new" antenna books. This Kraus approved volume is the size and heft of
the A.R.R.L. Handbooks in the days of yore.

Never mind that it is old: Maxwell's ideas haven't been changed!

John

at radio station VE7AOV

+++++



On 2021-02-01 9:59 a.m., David Eckhardt wrote:

Surprisingly enough, MFJ has an excellent resource. I picked up a copy at
HRO a couple of years ago, well before the COVID thing. It's a bit terse
in treatments, but its pretty good:

*ANTENNAS AND TRANSMISSION LINES* by John A. Kuecken, Published: MFJ,
First edition, 2nd printing ......... no ISBN number

While one can hardly treat the subject without a little calculus, he has
kept it to a minimum. However, a solid and working knowledge of algebra
and trigonometry is required.



Beyond that, an excellent starting reference for the educated ham is the
old standby:

ANTENNAS, by John D. Kraus, Second Edition, published by McGraw Hill,
ISBN: 0-07-035422-7

Calculus is required for this reference.


It may be wise to place these references in the files section for future



Beyond those, the references posted by Dave Daniels are excellent, but you
better know your calculus. The subject can NOT be treated properly without
that tool.


Dave - W?LEV

On Mon, Feb 1, 2021 at 3:27 PM Cierra <dubosec@...> wrote:

Other than the ARRL Antenna Book, are there good resources to investigate
to learn more about these topics?

--

Surprisingly enough, MFJ has an excellent resource. I picked up a copy at
HRO a couple of years ago, well before the COVID thing. It's a bit terse
in treatments, but its pretty good:

*ANTENNAS AND TRANSMISSION LINES* by John A. Kuecken, Published: MFJ,
First edition, 2nd printing ......... no ISBN number

While one can hardly treat the subject without a little calculus, he has
kept it to a minimum. However, a solid and working knowledge of algebra
and trigonometry is required.



Beyond that, an excellent starting reference for the educated ham is the
old standby:

ANTENNAS, by John D. Kraus, Second Edition, published by McGraw Hill,
ISBN: 0-07-035422-7

Calculus is required for this reference.


It may be wise to place these references in the files section for future



Beyond those, the references posted by Dave Daniels are excellent, but you
better know your calculus. The subject can NOT be treated properly without
that tool.


Dave - W?LEV

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

The transmatch is only a lowly matching network. I use parallel conductor
transmission line. It really doesn't care about voltage and/or current.
It consists mostly of parallel conductors 40 feet across the back of the
garage of #6 solid copper wire spaced nominally 1-inch apart. I fail to
see how a transmatch can 'consume' or dissipate significant power. Most
hams think it is evil in that respect. I don't buy it. If it consumes
power, then where is the heat? My L-network generates very little heat,
barely enough to detect at full power, 2-minutes solid carrier. It deals
with some challenging impedances - I'll attach a measurement of my
antenna/feeder I made using an isolated VNA. Judge for yourself. No
heat........no lost power........ Have a look at the attachment.

Dave - W?LEV

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