Supposed comparison of Mobile HF Antennas in November QST
 

On Sun, 28 Oct 2007 14:52:13 -0700, Roy Lewallen
wrote:

John Ferrell wrote:
. . .
Modeling programs do not consider the radiation from the loading coils
but field measurements do.
. . .

Modeling programs do indeed include radiation from the loading coils,
provided that they're modeled as a wire helix rather than by use of the
lumped load object. EZNEC and NEC both have methods of automatically
creating a helix, making this process very easy. I believe most other
NEC based modeling programs also have this capability.

Roy Lewallen, W7EL
Ooops! I have not used that part of EZNEC yet so I accept I was wrong.
I will have to look a little deeper into why I was convinced that the
radiation from loading coils was not considered.

I still don't find a problem with publishing the article. If nothing
else it has generated discussion.

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

Supposed comparison of Mobile HF Antennas in November QST
 

Jimmie D wrote:

I once saw a demonstration that "BIG UGLY" cb antennas, these are
approximately 1/8 wl and have a huge loading coil, have more gain than a 1/4
wl radiator. This certaily appeared to be the case when both the antenna
being test and the field strength meter's antenna were both the "big ugly"
variety and relatively close together(50'). Could this "gain" be a result of
magnetic coupling between the coils or was some other trickery being
performed.

There's no doubt this was some sort of trickery. I'd bet any amount of
money that if properly measured, the loaded 1/8 wave antenna would be
shown to have less gain due to lower efficiency. Even moderately
accurate antenna gain measurements are much more difficult to make than
most people realize, and there are many ways to be fooled. I couldn't
begin to list the all ways you could set up a demonstration like that to
get whatever result you desired.

Roy Lewallen, W7EL

Supposed comparison of Mobile HF Antennas in November QST
 

Jimmie D wrote:
I once saw a demonstration that "BIG UGLY" cb antennas, these are
approximately 1/8 wl and have a huge loading coil, have more gain than a 1/4
wl radiator. This certaily appeared to be the case when both the antenna
being test and the field strength meter's antenna were both the "big ugly"
variety and relatively close together(50'). Could this "gain" be a result of
magnetic coupling between the coils or was some other trickery being
performed.

Most likely trickery but could conceivably be achieved
through phasing of co-linear radiators. The total radiated
power was no doubt less than the 1/4WL but the phasing
might have caused constructive interference in the remaining
RF waves in the direction of the detector. A loaded CB
antenna does not normally require a "huge loading coil"
so it may have been a phase-reversing coil of sorts as
described by Kraus.
--
73, Cecil http://www.w5dxp.com

Supposed comparison of Mobile HF Antennas in November QST
 

Very interesting, indeed. This probably accounts for the gradual shift (not
for the better) in QST technical articles over a number of years. There
seems to be more "publicity oriented" wording than precise technical content
compared to twenty or thirty years ago. I had assumed this was an
intentional effort to better address new hams, but I see it may have been
due to the editing process.

This editing problem is certainly not confined to QST. One of the few things
that sends my blood pressure to an astronomical level is for an editor to
make changes they do not understand. I depend on various font and
indentation settings for much of my material; now and then an editor will
decide to "standardize" these and I go completely off the wall.
Unfortunately, in many organizations the editors usually have the last shot
at material.

Bill - W2WO


"Roy Lewallen" wrote in message
...
QST editors can't be expected to be experts on all the topics they have to
deal with. Over the years, they've dealt with the problem in various ways.
One was to establish a pool of "Technical Advisors" -- volunteers who had
particular expertise in various areas. Some manuscripts being considered
for publication were sent to the appropriate TAs for comments and review.
This practice slowly died out, but I don't know why. I suspect it was
because the editors seldom had the time for this step in the process due
to erratic scheduling.

Eventually, they adopted a solution which was easy on the editors and
their schedules: post the proposed articles to a restricted web site where
the TAs could review them and leave comments. This saved the time of
communicating with individual TAs, and made it unnecessary to wait for a
response -- if comments weren't there by the deadline, too bad. What I saw
as one problem with this approach was that comments and analyses were
regularly being made by TAs whose appointments had nothing at all to do
with the subject matter. As an example (not representing any actual
particular occurrence), a TA whose expertise was, say, legal matters or
publicity would review (for technical content) an article on phased
arrays. As far as I could tell, their reviews were weighted equally to
those from people who really understood the topic. In any case, the one or
few reviews from knowledgeable people were generally lost in the noise. I
don't know if this is the method still being used -- I resigned my TA
appointment several years ago when it became apparent that I was no longer
able to make any substantial contribution. I know of at least a couple of
very knowledgeable people who have done likewise. This is a shame, because
they're perfectly willing to provide free technical assistance, yet the
ARRL doesn't seem able to find a way to take advantage of it.

I'm not sure they've ever solved the problem of editors who don't
understand the material modifying it in such a way as to make it no longer
true. In all cases but one when this happened to me, I was able to correct
the problems before publication. In one case, however, I wasn't given
enough time to correct the numerous misinterpretations, invalid
"explanations", and other seriously wrong modifications made by the editor
and had to pull the article(*). Several extremely capable people I know,
however, have had serious errors introduced to their articles by the
editor *after their final review*, so they didn't even get to see the
errors until the article was published under their name. Most of these
people will never write for QST again as a result. This is one of the
reasons that QST has a smaller pool of knowledgeable and capable authors
to draw from.

So when you see a technically weak article in QST, the author might not be
entirely at fault.

(*) I want to make it clear that I'm very aware that my writing and
communicating skills aren't all that great, and I really appreciate having
an editor improve the style, clarity, and brevity of my writing, as well
as questioning any weak or inconsistent arguments I've made. [A good
editor would have cut half the words from the preceding sentence, and made
it a lot clearer at the same time.] So I welcome editing. What I do object
to is editing which changes the core meaning of the content and/or results
in its being technically incorrect.

Roy Lewallen, W7EL

Supposed comparison of Mobile HF Antennas in November QST
 

Supposed comparison of Mobile HF Antennas in November QST
 

"Michael Coslo" wrote in message I've been pleased so far.
I worked some CA QSO party from the middle of
PA on 20 meters with it, and all I could hear I could work (100 watts)

While you can not work a station if you can not hear it, that is no way to
compair an antenna. I have an off center fed antenna up 45 feet and a
tribander up 57 feet. I can hear more on the beam than I can on the OCF .
I can probably work all I can hear on either antenna. It is I just hear
beter on the beam on the bands it is cut for.

Supposed comparison of Mobile HF Antennas in November QST
 

On Oct 29, 11:51 am, Michael Coslo wrote:


It is narrow, but that's only been a big problem on 80.

I've seen some on 80 where the people would tune them
at driving speeds because the leaning back of the antenna
would detune far enough to be a problem. :/
They didn't have a wide enough bandwidth to really get
both positions with a good match. Good performing
antenna though.
How well mine does depends on the path, distance, etc..
On 40m, mine will beat my dipole which is at 35-40 ft
on paths over about 1000 miles or so late at night.
IE: Houston to Florida.
We tested that many times to make sure it was not
a fluke. I have no trouble on 80, but it also varies with
time of day, distance. It's probably at it's worst real early
in the evening to close NVIS range stations. But as it gets
later, it will usually get better and better once the band gets
stable and stretches out a bit. As usual, the longer the path,
the better it might do vs a med height dipole.
But I'm often pretty strong even to NVIS range stations.
Not uncommon to be over S 9.. Sometimes 10-20 over..
Course, all the guys on dipoles might be hitting them at
30-40 over.. :/ But no problem talking. And I've never run
an amp mobile.. Just 100w..
MK

Supposed comparison of Mobile HF Antennas in November QST
 

John Ferrell wrote:


Last year I purchased a radio especially to go mobile. I have yet to
find an acceptable mobile HF antenna to use on my Chrysler Minivan. I
am beginning to believe that there are no acceptable solutions to the
problem as I define it.

Then you need to change your definitions, John, -I mean that in a
friendly way. 8^)

Too often, too many time, we expect some sort of perfection. It isn't
going to happen. Mobile HF antennas are just not as efficient as a
"good" land based antenna. I'll leave the definition of good up to
everyone, suffice that the mobile antenna isn't as efficient as most.

That being said, you can have a lot of fun on HF mobile and can talk
around the world. Why let the needed compromises keep you from that?

If you are wanting to squeeze the last little bit of efficiency out of
your antenna, I would suggest a mid-loaded antenna with a capacity hat
on top somewhere (some say directly on top, but you'll have to put up
with a lot of wind loading) Use a loading coil that has as high a Q as
you can get, and bond everything you can in the van - doors, hood,
fenders, frame components, engine, radiator, exhaust system - and in
multiple places. You want as much ground plane as possible, even if at
best you don't get much.


Further, I have concluded that ALL MOBILE HF installations are poor
compared to a dipole five feet off the ground, some are just worse
than others.

I don't think that is an exact comparison, but the question is so what?
Get as good as you can afford/want to put in th elabor, and go have fun


The article simply sheds some light on the practical issues one
encounters with popular alternatives.

I think an auto tuner with whatever whip length one can tolerate is
the best one can do with a Chrysler Minivan.

Don't agree there. You could use a bug catcher or screwdriver and be
better than that.

Modeling programs do not consider the radiation from the loading coils
but field measurements do.

Tuner losses can be estimated from the software in the Arrl Antenna
Books.

If you can write a better article for QST, please do so. But please
remember, most of us don't choose the ethical we drive because of its
ability to carry a less bad radio antenna!

I'm driving a Suzuki Vitara -maybe the smallest SUV around. Yet I have
an antenna that allows me to have a lot of fun and yes it does get some
stares. If I put a football team pennant on it, everyone thinks I'm kewl.


AS for writing an article for QST, I don't think its a bad idea at all
to be critical of an article that could have been written better. That I
didn't write one does not mean that those who do have free reign to
write a poor one if they like.

- 73 de Mike KB3EIA -

Supposed comparison of Mobile HF Antennas in November QST
 

Ralph Mowery wrote:
"Michael Coslo" wrote in message I've been pleased so far.
I worked some CA QSO party from the middle of
PA on 20 meters with it, and all I could hear I could work (100 watts)

While you can not work a station if you can not hear it, that is no way to
compair an antenna. I have an off center fed antenna up 45 feet and a
tribander up 57 feet. I can hear more on the beam than I can on the OCF .
I can probably work all I can hear on either antenna. It is I just hear
beter on the beam on the bands it is cut for.

Its not meant to be a definitive test of the antenna, but I have used
some antennas where that was not the case, Hopefully this is not the
sort of group where one has to take their antenna to a range before they
are allowed to comment on it, good or bad.

I used it, and didn't have trouble making contacts. Others can determine
if it works or not according to their own guidelines.

- 73 de Mike KB3EIA -

Supposed comparison of Mobile HF Antennas in November QST
 

Hello Roy...

The definition of a committee is a dark alley down which you lead ideas
so that you can strangle them. My impression is that the QST editorial
process is riddled with committees, and they're quite effective (hi).

I've given up writing for them due to the many problems you recounted -
I don't say forever, but for the time being. I'm very tired of
objections that don't make any real sense, while seeing this kind of
article (which also makes no real sense) published as is.

QST used to be a respected technical journal. It's grown inbred,
inflexible, inaccurate and inconsistent. It no longer really serves the
amateur community - it seems to largely serve itself.

Maybe a (metaphorical) bomb will go off or someone will start a
revolution and it'll change. Not likely, but maybe.

Perhaps a group of (former) writers could prepare a joint "declaration
of limited support" to present directly to the ARRL brass (bypassing the
editors) to call for action/changes.

Nice to run into you here.

Best regards - Robert Victor VA2ERY




Roy Lewallen wrote:
QST editors can't be expected to be experts on all the topics they have
to deal with. Over the years, they've dealt with the problem in various
ways. One was to establish a pool of "Technical Advisors" -- volunteers
who had particular expertise in various areas. Some manuscripts being
considered for publication were sent to the appropriate TAs for comments
and review. This practice slowly died out, but I don't know why. I
suspect it was because the editors seldom had the time for this step in
the process due to erratic scheduling.

Eventually, they adopted a solution which was easy on the editors and
their schedules: post the proposed articles to a restricted web site
where the TAs could review them and leave comments. This saved the time
of communicating with individual TAs, and made it unnecessary to wait
for a response --

Roy Lewallen, W7EL