On 14/10/2018 09:49, Spike wrote:
On 13/10/2018 20:43, Jeff Liebermann wrote:

I understand how antenna work and how to predict performance. I can
even do it without 4NEC2 or other antenna modeling program. For
example, the uglier the antenna, the better it works. Antennas that
are more expensive, bigger, and in violation of local building
ordinances, work the best. Experimental prototype antennas always
work while the production versions never seem to work as well. If
there are two ways to assemble an antenna, the wrong way will have
higher gain, lower VSWR, or both. High gain, small size, or wide
bandwidth; pick any two. Using these rules of thumb and others,
anyone can predict how well an antenna will perform by inspection and
without using computer models, Smith charts, or tedious calculations.

WHS

There has been much talk on UKRA in the recent past about the merits or
otherwise of various makes and models of VNAs. It's my view that the
point of having an Amateur licence is to be able to transmit signals
intended to be received by another station. One of the alleged virtues
of a VNA is to be able to set up one's aerial system. However, I
maintain that using cheap torch bulbs is an equally valid indicator of
the state of tune of one's station, and that a distant station cannot
tell the difference between a system set up with the aid of a VNA and
one set up with the aid of a torch bulb or two.



The PP seems unaware of retarded potentials, and has blustered his way
by responding to the question without actually any understanding of
the issues involved.

On Sun, 14 Oct 2018 08:49:51 +0000, Spike
wrote:

On 13/10/2018 20:43, Jeff Liebermann wrote:

I understand how antenna work and how to predict performance. I can
even do it without 4NEC2 or other antenna modeling program. For
example, the uglier the antenna, the better it works. Antennas that
are more expensive, bigger, and in violation of local building
ordinances, work the best. Experimental prototype antennas always
work while the production versions never seem to work as well. If
there are two ways to assemble an antenna, the wrong way will have
higher gain, lower VSWR, or both. High gain, small size, or wide
bandwidth; pick any two. Using these rules of thumb and others,
anyone can predict how well an antenna will perform by inspection and
without using computer models, Smith charts, or tedious calculations.

WHS

Thou shalt not abrev. What does WHS mean?

There has been much talk on UKRA in the recent past about the merits or
otherwise of various makes and models of VNAs. It's my view that the
point of having an Amateur licence is to be able to transmit signals
intended to be received by another station. One of the alleged virtues
of a VNA is to be able to set up one's aerial system. However, I
maintain that using cheap torch bulbs is an equally valid indicator of
the state of tune of one's station, and that a distant station cannot
tell the difference between a system set up with the aid of a VNA and
one set up with the aid of a torch bulb or two.

In a past life (1970's), I used to design marine radios and antennas.
At the time, my weapon of choice was the HP4815A vector impedance
meter:
https://www.google.com/search?q=hp4815a&tbm=isch
No fancy display, no pretty graphs, no Smith chart display. Just
accurate numbers for the HF bands. I used it for everything that
needed impedance matching, including antennas. If you're thinking of
buying one, make sure that it includes the probe kit. It's useless
without the probe kit.
http://electropuces.pagesperso-orange.fr/Photos/HP4193.jpg

One of my ace technicians had a different way of doing RF. During the
day, he would use the best test equipment that the company could
afford. After hours, he would work on his own radios. However,
instead of using proper test equipment, he would literally tune for
maximum into a light bulb. I was disgusted, tried to help, but
failed. He insisted that a light bulb was "good enough". It took me
a while to decode what was happening.

Anyone can produce a workable antenna using primitive techniques. By
workable, I mean minimally functional and generally usable. For at
time, I was building matching networks for using an aluminum step
ladder as a VHF directional antenna. It worked, but improvements
beyond minimally functional were difficult.

So, why bother with all the fancy test equipment (VNA) if a light bulb
will do as well? Because with the fancy test equipment will squeeze
the last few decibels of performance out the antenna while the light
bulb is unlikely to do the same. If minimally acceptable is your
standard of excellence, then please continue using a light bulb for
tuning antennas. However, if you want to get all the performance
possible, then you'll need some fancy test equipment.

What was happening with my tech was that he did not want to expend the
time learning how to properly operate, understand, and analyze the
output from the fancy test equipment. While I consider this close to
sacrilege in a production environment, to someone just trying to get
his radio or antenna on the air, it's sufficient. If I light bulb got
him close enough to a working system, and didn't require any time to
study, it was "good enough".

Some of the local hams are very much into DX, contesting, and EME. To
be successful, one has to have a very efficient radio system with
everything optimized to the best possible performance. Everything has
to be optimized for the best possible performance. One can't do that
with a light bulb.

Since your view of ham radio is "to be able to transmit signals
intended to be received by another station", you don't need a VNA to
do that. An antenna tuner and a random length of wire will suffice.
However, if you plan to do more than that, some test equipment might
be useful.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann
wrote:
(...)
However, if you plan to do more than that, some test equipment might
be useful.

Since you prefer a minimalist approach to test equipment, as an
alternative to your light bulb, may I suggest a return loss bridge:
https://www.google.com/search?q=return+loss+bridge&tbm=isch
Note that there are several basic designs and configurations but all
are fairly simple and easy to construct. Note that these are NOT the
same as directional couplers.

You can purchase them on eBay:
https://www.ebay.com/sch/i.html?_nkw=return+loss+bridge

There are tutorials on YouTube:
https://www.youtube.com/results?search_query=return+loss+bridge

I have three of these made by Texscan:
https://www.qsl.net/n9zia/wireless/rtrn_loss-pics.html
https://www.qsl.net/n9zia/rlb/texscan.png

and a few that I've built for microwave frequencies:
http://pe2er.nl/wifiswr/

and one for HF:
http://www.dicks-website.eu/return%20loss%20bridge_part1/part1.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part2.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part3.html
http://www.dicks-website.eu/return%20loss%20bridge_part2/part4.html
http://www.dicks-website.eu/return%20loss%20bridge_part5/part5.html

A return loss bridge is similar to a VNA except that it does not
produce numbers for the real (resistive) and imaginary (reactive)
components of the antenna impedance. It just produces the return loss
compared to a reference termination resistor, which can then be
translated into the VSWR.

To use it, you need a minimum of an RF signal generator and a
voltmeter or oscilloscope. I prefer to sweep the frequency range of
interest, so I use an RF sweep generator, and display the result on an
oscilloscope. With this arrangement, you can tune your antenna
without requiring a light bulb.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 15/10/2018 01:20, Jeff Liebermann wrote:
On Sun, 14 Oct 2018 11:12:14 -0700, Jeff Liebermann
wrote:

Since you prefer a minimalist approach to test equipment, as an
alternative to your light bulb, may I suggest a return loss bridge:
https://www.google.com/search?q=return+loss+bridge&tbm=isch
Note that there are several basic designs and configurations but all
are fairly simple and easy to construct. Note that these are NOT the
same as directional couplers.

To use it, you need a minimum of an RF signal generator and a
voltmeter or oscilloscope. I prefer to sweep the frequency range of
interest, so I use an RF sweep generator, and display the result on an
oscilloscope. With this arrangement, you can tune your antenna
without requiring a light bulb.

So, let me get this right. By employing a return-loss bridge, an RF
signal generator, and either a voltmeter or an oscilloscope, you can get
results that a distant station can't distinguish from those obtained by
using a torch bulb?

Given your ability to estimate the performance of an antenna by looking
at it rather than employ modelling methods, I would have though you
would be sympathetic to the merits of the torch bulb approach.


--
Spike

"Nearly all men can stand adversity,
but if you want to test a man's character,
give him an internet group to manage"

In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?


4NEC2 and EZNEC are just a fancy front and back ends for NEC2 (and
NEC4) Engines.

Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard...tail/ADA956129.
xhtml.

"Part I of the document includes the equations on which the code is
based and a discussion of the approximations and numerical methods used
in the numerical solution. Some comparisons to demonstrate the range of
accuracy of approximations are also included. Details of the coding and
a User's Guide are provided as parts 11 and 111, respectively."

It's pretty straight forward stuff for someone good (1st year uni) at
maths*. The rest of us just have to take their word for it. The code is
written in good old FORTRAN, so I can at least follow the code.


*It's USAnian maths. Which is a different dialect to British maths.

Brian

--
Brian Howie

On 14/10/2018 20:30, brian wrote:
In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?


4NEC2 and EZNEC areÂ* just a fancy front and back ends for NEC2 (and
NEC4) Engines.

Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard...tail/ADA956129.
xhtml.


Thanks for the heads up, Brian, but a quick glance suggests that some
revision might be necessary of my 3rd year uni textbook, "Fields and
Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer.

ISTR it to be an excellent book explaining complicated things in words
of one syllable, but 46 years down the line, I might have a more
romantic memory of it in reality :-)

In message , Gareth's Downstairs Computer
writes
On 14/10/2018 20:30, brian wrote:
In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?

4NEC2 and EZNEC are* just a fancy front and back ends for NEC2 (and
NEC4) Engines.
Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129.
xhtml.


Thanks for the heads up, Brian, but a quick glance suggests that some
revision might be necessary of my 3rd year uni textbook, "Fields and
Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer.

ISTR it to be an excellent book explaining complicated things in words
of one syllable, but 46 years down the line, I might have a more
romantic memory of it in reality :-)



I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From
the inscription in the fly leaf, it looks like I used it in 3rd year
too. Mine has one of the equations printed upside down, which threw me a
bit.

Brian



--
Brian Howie

On 15/10/2018 04:49, brian wrote:
In message , Gareth's Downstairs Computer
writes
On 14/10/2018 20:30, brian wrote:
In message , Gareth's Downstairs Computer
writes
Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?

Â*4NEC2 and EZNEC areÂ* just a fancy front and back ends for NEC2 (and
NEC4) Engines.
Â*Program description is here :-

https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/ADA956129.

xhtml.


Thanks for the heads up, Brian, but a quick glance suggests that some
revision might be necessary of my 3rd year uni textbook, "Fields and
Waves in Communications Electronics" by Ramo, Whinnery and Van Duzer.

ISTR it to be an excellent book explaining complicated things in words
of one syllable, but 46 years down the line, I might have a more
romantic memory of it in realityÂ* :-)



I've got mine here. We used to call it Ramo Whinnery and Bamboozle. From
the inscription in the fly leaf, it looks like I used it in 3rd year
too. Mine has one of the equations printed upside down, which threw me a
bit.

Simon Ramo is an undoubted expert in that "field", but probably deals
only in that area. Much more difficult for we polymaths who must have a
working knowledge of so many more subjects, eg, the low level
programming of computers.

Brian Morrison wrote:
On Sat, 13 Oct 2018 09:33:55 +0100
Gareth's Downstairs Computer
wrote:

Whereas such antenna predictors seem to feature in amateur usage,
does anyone, anywhere, in the world of amateur radio have an
understanding of the underlying principles involved in
predicting the performance of antennae, or have we all,
regrettably, become indistinguishable from
consumerist CBers or beginner licensees?


I currently have a build of openEMS going on my Fedora system, once it's
built and installed I shall have a play and see what I can glean from
it.

Yes, I understand the underlying principles of antennas,

Burt thought he did, too.

--
STC / M0TEY /
http://twitter.com/ukradioamateur