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I have both the first and second editions of J. D. Kraus's book, "*ANTENNAS*".
Either edition is likely the best book on antennas that isn't 'big time'
heavy in math, although a working knowledge of calculus should be under
your belt. Others are FAR heavier into math and not recommended for the
amateur. The second edition:

"*ANTENNAS*", by J. D. Kraus, publisher: McGraw Hill, ISBN:
0-07-0354 22-7

The first edition:

"*ANTENNAS*", by J. D. Kraus, publisher: McGraw Hill, ISBN:
None given

Either is an excellent and rigorous treatment of antennas and theory. I
highly recommend either edition to anyone who desires a starting reference
on the subject.

Another "reasonable" but brief reference I stumbled on while at HRO, Denver
follows a couple of years ago:

"*ANTENNAS AND TRANSMISSION LINES*", by: John A. Kuecken,
Publisher: MFJ, ISBN: None given

Dave - W?LEV

On Thu, Aug 20, 2020 at 4:27 PM Jerry Gaffke via groups.io <jgaffke=
[email protected]> wrote:

I assume the book you are referring to is "Antennas" by John D Kraus.
Jim mentioned it here: /g/nanovna-users/message/16645

FIrst edition printed in 1950, second edition (with Ronald Marhefka) in
1988.

I poked around on the web.
Lots of pdf downloads out there, they all look kind of dodgy.
For such a thick read, I'd probably want a paper copy anyway.

Amazon sells the 2001 third edition for $64.41, the fourth (2010) for
$847.00, and the fifth (2018) for $32.23.


Or maybe Amazons price for the third in paperback is $54.41, hardcover for
$139.65.



Here's a 5'th edition, $11.95 plus $13.03 to ship it from India:

"Territorial restriction maybe printed on the book. This is an Int'l
edition, ISBN and cover may differ from US edition ..."
Apparently the same one that Amazon sells for $32.23.

So kind of confusing.
I may just give Bezos his $32.23.
If somebody thinks there's a legit pdf out there, I'd probably sample that
first.
More than likely, I'll get sidetracked after a few pages anyway, trying to
figure out
Maxwell's equations again or some long forgotten math.

Jerry, KE7ER



On Thu, Aug 20, 2020 at 07:26 AM, Dallas wrote:

Thanks for the book link. I just downloaded it and read the first few

pages,

it will be a good read.

Dallas
N5fee

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

For those of you who would like to use the resistive pad to match 75 ohms to the 50 ohm nanovna, the series resistor is 25 x sqrt of 3 (about 43.3 ohms) and the shunt resistor on the 50 ohm side is 50 x sqrt 3 (about 86.6 ohms) . With that you can use 1% and 1/2% resistors and get as close as you want! Or you can distribute the resistance around the connectors to minimize inductance and capacitance.

Other than the name, "ANTENNA TUNER", why is the 'conventional knowledge'
so prevalent that the "ANTENNA TUNER" actually "tunes" the antenna. *IT
DOES N O T !!!!!* It functions ONLY AS A MATCHING NETWORK, nothing more,
nothing less!!!!!!

Please consult and digest the information presented at the following URL:



If you are one of the many that believe (for better or worse) that matching
networks (yes, the proper name for the function) are evil, consider the
following. At the collector or drain of the output stage of your modern
transceiver, the impedance presented to the 'load' is typically 0.5 to a
couple of ohms real and a bit of reactance. That plots to the extreme left
side of the Smith Chart which is the 'shorted' side of the chart. It may
be slightly above or below the horizontal line which represents only real
resistance with no reactance. Above or below that horizontal line
represents reactance of the impedance, only.

OK, that's a terrible mismatch to our communications standard of 50-ohms
(real, no reactance): a 50:1 SWR!! How do the designers of that PA get
from such a low impedance to 50 ohms, real??? Guess what?? A broadband
matching transformer is used between the collectors or drains and the
inputs to the various filters to keep FCC happy. That broadband matching
transformer can be viewed as a "matching network" that transforms a 50:1
SWR to a 1:1 SWR. Is that evil? No. Is there loss? Yes, and a bit more
that the typical "antenna tuner" introduces to the overall system. Is it
necessary? Yes, if we are to utilize a 50-ohm non-reactive 'load'. The
option is to drive a 1 to 2-ohm transmission line supported by a 1 to 2-ohm
load at the antenna.

Matching networks are necessary and an integral part of any RF design, be
it for high power or small-signal low noise amplification. We wouldn't be
able to utilize the 'wonders' of the RF world without matching networks.

Dave - W?LEV

On Thu, Aug 20, 2020 at 4:07 AM Miro, N9LR via groups.io <m_kisacanin=
[email protected]> wrote:

So, based on what Dave and Jerry are pointing out, I have two VALID
conclusions

1) Antenna tuners suck! They make t-line/antenna go gently on TX, but they
hide what's behind them. Strive to have (at least) antenna matched to
t-line, then antenna tuner (might) make more sense, or even better, match
TX to t-line to antenna and sell antenna tuner on ebay

2) I still have no idea what is the answer to my question :)
* short run of low loss t-line
* no match between TX, t-line, antenna impedances
* antenna tuner makes t-line/antenna appear to TX as TX's impedance (SWR
at that point is 1:1)

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

I assume the book you are referring to is "Antennas" by John D Kraus.
Jim mentioned it here: /g/nanovna-users/message/16645

FIrst edition printed in 1950, second edition (with Ronald Marhefka) in 1988.

I poked around on the web.
Lots of pdf downloads out there, they all look kind of dodgy.
For such a thick read, I'd probably want a paper copy anyway.

Amazon sells the 2001 third edition for $64.41, the fourth (2010) for $847.00, and the fifth (2018) for $32.23.


Or maybe Amazons price for the third in paperback is $54.41, hardcover for $139.65.


Here's a 5'th edition, $11.95 plus $13.03 to ship it from India:
"Territorial restriction maybe printed on the book. This is an Int'l edition, ISBN and cover may differ from US edition ..."
Apparently the same one that Amazon sells for $32.23.

So kind of confusing.
I may just give Bezos his $32.23.
If somebody thinks there's a legit pdf out there, I'd probably sample that first.
More than likely, I'll get sidetracked after a few pages anyway, trying to figure out
Maxwell's equations again or some long forgotten math.

Jerry, KE7ER

No, I mean to create a parallel LC-circuit: the inductor will be parallel to the series connection of the C32 and C33 (tapped to the ground in their middle but this does not matter). That LC-circuit will be differentially-fed through the R36 and R37 at its' both ends.
The inductor's resistance is quite low - even the largest of those coils are just tens of Ohms. The resonance will be rather sharp I hope.

The goal is to remove as much noise at the ADC's input as possible - to make software's job easier. At least DiSlord expects there could be some improvement regarding the S/N ratio and the noise floor.

Anton

Thanks for the book link. I just downloaded it and read the first few pages, it will be a good read.


Dallas
N5fee

On 8/20/20 6:05 AM, ZAO via groups.io wrote:

Hello!
Would you recommend an LC-circuit as an IF filter?
I'm looking into using one of [url=]these[/url] SMD inductors (~hundreds of μH) as a coil.
I'm going to inrease the C32, C33 (please refer to the rev3.4.2 schematics) and place an inductor between the R36C32 and R37C33. The new C32 and C33 values should give a 12kHz (the IF value) resonance with the inductor chosen. The same would be implemented in all the three mixers.

So you'd make a Rseries L series, C shunt, low pass configuration?

I think that won't have the effect you expect. Don't forget that those inductors have a fair amount of resistance, too. In any case, you don't necessarily want to tune it to resonance.

What you might want to do is model it in something like a filter program like Elsie (the student version is free and will easily model something like this)


Make sure you put some estimates of the source and load impedances in the model.

The real question, though, is why are you wanting to "improve" the filter. - most of the filtering is done in software - some milliseconds (5?) are collected and the IF is filtered there (which should give around a 200 Hz BW) - improving the filter performance would be best done by changing the firmware to collect more ADC samples, and/or, fiddling with the windowing function used.

Look in dsp.c, specifically dsp_process(). That routine implements what is basically a FIR filter for the 12kHz IF, using sincos_tbl as the taps.

In the default edy555 version from hugen, the sincos_tbl is uniform in amplitude. So that's effectively creating a filter that has -13dB sidelobes (rectangular window). I think you might be able to get better filtering by changing that table to put a window function on it - perhaps slightly broadening the mainlobe, but pushing the sidelobes of the response spectrum down. That would reduce the "out of band" noise into the detection.

There's some fiddling that might needed to trade off numerical precision vs spectral performance, but with a tool like Octave or numpy, I think you could find a new set of values in a few days of work.

Please comment.
Regards,
Anton

Jim,

Then Miro's question remains: What happens to power reflected back from the antenna feedpoint
if there is no antenna tuner? Without a tuner, it is not all getting sent back out to the antenna.
Conservation of energy says the transmitter has to put it somewhere.

I can't think of anything the transmitter could do with this energy other than turn it into heat.
Either by design with your isolator and load, or just heating up whatever's handy.

I don't know for sure exactly where it goes in a typical amplifier.
Hence my weasel words: "What happens then depends on the transmitter design."

Jerry, KE7ER

On 8/19/20 10:09 PM, Jerry Gaffke via groups.io wrote:

Antenna tuners cause any energy reflected from the antenna to turn around
and head back out to the antenna again.
So if the antenna is reflecting 1/4 of the energy back to the antenna tuner,
after 2.5 round trips through the coax all but 1/(4*4*4) = 1/64'th of the energy
has been radiated out the antenna.
If the coax and antenna tuner have no losses, eventually all the power is radiated.
Without the antenna tuner, that reflected power comes back to the transmitter.
What happens then depends on the transmitter design.
At least some of it will likely be getting dissipated as heat in the transmitter.

Only if the transmitter has some sort of isolator (in a logical sense) to push the reflected power to a load, and that's pretty rare in a HF transmitter.



What really happens is that the transmitter is operating less efficiently with a load other than its optimum. And that depends a lot on whether it's something like a tube amplifier with a tuned tank, or a broadband solid state design.

Jerry, KE7ER
On Wed, Aug 19, 2020 at 09:06 PM, Miro, N9LR wrote:

If TX sends 100w out, how much "enters" antenna? If answer is "less then 100W, where is the rest? (assumption is no loss or very low loss t-line!!!)

I use a small zippered cases for my VNA that was made for a small PC projector. I has a carrying handle, rings to attach a shoulder strap (that I don’t use) and plenty of room for a clear box with all my adapters, cables etc.

I have 8 or 10 of similar small cases I use one for my RJ45 crimp tool and connectors, one for my TV coax stripper and tool, one for my signal tracer etc. I put a small tag on the handle of each one saying what’s in the bag. They are very handy to keep things together. I buy them at thrift stores for $2-3 each. There are tons of laptop bags, smaller bags from projectors, CD player bags etc.

Case Logic makes some really nice cases for lots of things, search that name on Amazon.

Dallas
N5fee

On 8/19/20 9:06 PM, Miro, N9LR via groups.io wrote:

So, based on what Dave and Jerry are pointing out, I have two VALID conclusions
1) Antenna tuners suck! They make t-line/antenna go gently on TX, but they hide what's behind them. Strive to have (at least) antenna matched to t-line, then antenna tuner (might) make more sense, or even better, match TX to t-line to antenna and sell antenna tuner on ebay

Not necessarily - for small mismatches, the tuner, even at the end of a transmission line with 10% loss (1/2 dB) makes it so you don't have to go out and keep readjusting an antenna that's narrow band, or it means you can use the same antenna on different parts of the band. The incremental loss from using an antenna resonant with 100kHz bandwidth at 7MHz at 7.3 MHz is going to be pretty small.

2) I still have no idea what is the answer to my question :)
* short run of low loss t-line
* no match between TX, t-line, antenna impedances
* antenna tuner makes t-line/antenna appear to TX as TX's impedance (SWR at that point is 1:1)

Hello!

Would you recommend an LC-circuit as an IF filter?
I'm looking into using one of [url=]these[/url] SMD inductors (~hundreds of μH) as a coil.
I'm going to inrease the C32, C33 (please refer to the rev3.4.2 schematics) and place an inductor between the R36C32 and R37C33. The new C32 and C33 values should give a 12kHz (the IF value) resonance with the inductor chosen. The same would be implemented in all the three mixers.

Please comment.

Regards,
Anton

@Dr. David Kirkby:
Just like Dragan Milivojevic, I am also curious to hear what the flaws are in Larry Benko's videos. I actually find his videos very interesting and helpful. But I also understand that he is, unlike you, probably nowhere near an expert on the subject. So could you please elaborate?

Best regards,
Klaas

On Tue, Aug 18, 2020 at 08:07 PM, Dragan Milivojevic wrote:

Every video on the topic or all of them?
What is wrong with it? As I see it he is just trying to make
his homemade set behave similar to the HP one.
Could you point to a better article/video about
the topic (making your own cal standards).

On Tue, 18 Aug 2020 at 06:59, Dr. David Kirkby, Kirkby Microwave Ltd <
drkirkby@...> wrote:

On Tue, 18 Aug 2020 at 03:06, Dragan Milivojevic <d.milivojevic@...>
wrote:

For flush open etc you might find this interesting:

It is technically flawed in several ways as are several other videos from

the same author. *Every* video I have seen from him are wrong, although
this is is not as bad as others.

<snip>> >

2) He has a totally flawed video on reference planes. His misunderstanding
of that can be seen in this video too, but it more subtle.

I find YouTube to be awash with people creating videos about things they
know
a little about. He is one such example.

Dave.
--
Dr. David Kirkby,
Kirkby Microwave Ltd,

Folks,
You can translate/convert PDF documents online at:

I translated the document to English and attached it.

Enjoy!

Larry

Here is an application report on the NanoVNA-H and SPICE simulation. The report is in German. Enjoy!

If you want some encouragement read Kurt N. Sterba’s articles from the Olde World Radio journal. It’s free now. That’s $0.00



His thoughts are Olde but he quotes the major antenna engineers of the day. Antenna physics hasn’t changed any.

The bottom line: the antenna tuner does tune the antenna and all the power eventually gets out the antenna. What losses there are won’t make a difference to the ham on the other end. Use a tuner, be happy. Your finals, tubes or solid state, will thank you and you can sleep at night.

David J. Wilcox K8WPE’s iPad

Antenna tuners cause any energy reflected from the antenna to turn around
and head back out to the antenna again.
So if the antenna is reflecting 1/4 of the energy back to the antenna tuner,
after 2.5 round trips through the coax all but 1/(4*4*4) = 1/64'th of the energy
has been radiated out the antenna.
If the coax and antenna tuner have no losses, eventually all the power is radiated.

Without the antenna tuner, that reflected power comes back to the transmitter.
What happens then depends on the transmitter design.
At least some of it will likely be getting dissipated as heat in the transmitter.

Jerry, KE7ER

Jerry wrote: "...No, you can't just add transmission line length and get any purely resistive load looking into the transmission line that you might wish."

I agree, having complex impedance involved makes this all even more complex :)

Two examples I used are extreme special cases that do not apply to any other (either to antenna with complex impedance or to "random" t-line lengths), but the two questions are still the same:

1) is the "transformation factor of a random t-line length "symmetrical"?
if the t-line "adjust" Z2 to Z1, then the same t-line adjusts Z1 to Z2 (apparently it's not the case, with rare exceptions like lambda/12 t-line with strictly resistive loads)
2) what happens with reflective power in scenario explained above (total mismatch + antenna tuner + lossless line)

...I hit "reply" too soon...

... given:
* short run of low loss t-line
* no match between TX, t-line, antenna impedances
* antenna tuner makes t-line/antenna appear to TX as TX's impedance (SWR at that point is 1:1)

If TX sends 100w out, how much "enters" antenna? If answer is "less then 100W, where is the rest? (assumption is no loss or very low loss t-line!!!)

So, based on what Dave and Jerry are pointing out, I have two VALID conclusions

1) Antenna tuners suck! They make t-line/antenna go gently on TX, but they hide what's behind them. Strive to have (at least) antenna matched to t-line, then antenna tuner (might) make more sense, or even better, match TX to t-line to antenna and sell antenna tuner on ebay

2) I still have no idea what is the answer to my question :)
* short run of low loss t-line
* no match between TX, t-line, antenna impedances
* antenna tuner makes t-line/antenna appear to TX as TX's impedance (SWR at that point is 1:1)