Hello I hope I'm not intruding by asking for advice on a CB antenna but I
figured this would be the group to ask about such things for the straight
scoop. At any rate I'm considering a store bought beam with both vertical
and horizontal polarization and my choices are limited to these two below.
(not many being manufactured anymore)

The Maco has a 16 foot boom and an advertised gain of 12.5 db, while the JO
GUNN has an 8 foot boom and an advertised gain of 14.5 db. I know there is a
lot of smoke and mirrors involved with advertised gains and so my question
is...is it possible for the JO GUNN to perform as well as the Maco antenna?

The GUNN is of much stronger construction and a smaller windload so I'd
rather put it up, but the short boom makes me wonder if the gain and
rejection numbers are suspect.

Any help would be greatly appreciated, antenna choices, price tags and urls
below.

73
Stan

MACO-Shooting Star $279.95
http://www.mpaudio1.com/Macobeamantennas2.html

JO GUNN 3 + 3 STAR $382.00
http://tinyurl.com/6hzteu

Oh btw, I'll be tower mounting it about 40' from the ground and turning it
with a hamIV rotator.

Thanks again.

On Thu, 17 Jul 2008 18:37:40 -0400, "Stan Cooper"
wrote:

MACO-Shooting Star $279.95
http://www.mpaudio1.com/Macobeamantennas2.html

JO GUNN 3 + 3 STAR $382.00
http://tinyurl.com/6hzteu

Choose MACO for three reasons:
1. They understand the dB relationship to power gain;
b. their dB isn't relative to TRUE (whatever that means);
iii. it's cheaper.

On the negative side, neither seem to be acquainted with the dBi or
dBd basis of comparison (giving them the appearance of being yokels
selling out the trunk of their car). Imagine, having more "audio
gain" than rf gain from an antenna (do they inluded phased speakers?).

A claim of "2kw power handling capability!" is to suggest this is
part of the gain package? Don't exceed 2kw/28 input power?

Howabout "quad reflector to obtain the best combination of gain and
front-to-back ratio." Why not fully quad design to obtain the best
combination of ALL gains?

What's the difference between FRONT TO BACK RATIO and BACK REJECTION?

73's
Richard Clark, KB7QHC

Hi Richard

Isnt there a difference there? (I'll admit I dont think in these terms.
I use the actual pattern instead)

Isn't F/B a comparison of "forward" vs "backward" at the optimum/best
case "single angle" and Back Rejection (or some other name) the
comparison of all radiated power forward vs backwards?

Many parasitic designs end up with very good F/B but as soon as you go
off a few degrees a rearward lobe comes into play.

Cheers Bob VK2YQA

Richard Clark wrote:
What's the difference between FRONT TO BACK RATIO and BACK REJECTION?

On Thu, 17 Jul 2008 20:30:48 -0500, Bob Bob
wrote:

Hi Richard

Isnt there a difference there? (I'll admit I dont think in these terms.
I use the actual pattern instead)

Isn't F/B a comparison of "forward" vs "backward" at the optimum/best
case "single angle" and Back Rejection (or some other name) the
comparison of all radiated power forward vs backwards?

Many parasitic designs end up with very good F/B but as soon as you go
off a few degrees a rearward lobe comes into play.

Cheers Bob VK2YQA

Richard Clark wrote:
What's the difference between FRONT TO BACK RATIO and BACK REJECTION?

Hi Bob²,

If you examine the specifications for both, they reveal exactly the
same value. It follows they measure the same thing but use different
terms (one can only imagine they have ad writers who find their
inspiration for straining terms in claims for Gussian antennas).

There are very few antennas with a null located at 180° (Cardioid
comes to mind); and, as you infer, it quickly disappears off
boresight. Further, your suggestion of average forward compared to
average backward is, perhaps, a useful indicator. However, neither
supplier appears to interested in averages.

73's
Richard Clark, KB7QHC

"Stan Cooper" wrote in message
...
Hello I hope I'm not intruding by asking for advice on a CB antenna but I
figured this would be the group to ask about such things for the straight
scoop. At any rate I'm considering a store bought beam with both vertical
and horizontal polarization and my choices are limited to these two below.
(not many being manufactured anymore)

The Maco has a 16 foot boom and an advertised gain of 12.5 db, while the
JO GUNN has an 8 foot boom and an advertised gain of 14.5 db. I know there
is a lot of smoke and mirrors involved with advertised gains and so my
question is...is it possible for the JO GUNN to perform as well as the
Maco antenna?


well, there are a couple possibilities... first the Maco could be poorly
designed so it doesn't perform as well as the JO GUNN, or the Maco
advertisers could be more honest than the JO GUNN ones are... or the JO GUNN
is extremely well designed, or their advertisers aren't as honest as the
Maco ones are.

OR, they could just be comparing to completely different references, thats
the basic problem with antenna gains, they usually don't tell you what they
are compared to if the JO GUNN was compared to an isotropic radiator where
the Maco was compared to a dipole that buys them a couple db right there.

confused yet? there's even more...

Maybe the JO GUNN is measured over real ground at the best height and
elevation angle they could find... and the Maco was measured in free space.
Measuring an antenna over real ground and finding the max gain lobe could
give the JO GUNN a whole bunch more gain than the free space Maco... enough
to make up for half the boom length and a worse design put together.

So there you have it... my suggestion, put up a ground plane to talk to your
local buddies and get a ham license so you can legally and openly talk
around the world.

Stan Cooper wrote:
Hello I hope I'm not intruding by asking for advice on a CB antenna but I
figured this would be the group to ask about such things for the straight
scoop. At any rate I'm considering a store bought beam with both vertical
and horizontal polarization and my choices are limited to these two below.
(not many being manufactured anymore)

The Maco has a 16 foot boom and an advertised gain of 12.5 db, while the JO
GUNN has an 8 foot boom and an advertised gain of 14.5 db. I know there is a
lot of smoke and mirrors involved with advertised gains and so my question
is...is it possible for the JO GUNN to perform as well as the Maco antenna?

The GUNN is of much stronger construction and a smaller windload so I'd
rather put it up, but the short boom makes me wonder if the gain and
rejection numbers are suspect.

Any help would be greatly appreciated, antenna choices, price tags and urls
below.

73
Stan

MACO-Shooting Star $279.95
http://www.mpaudio1.com/Macobeamantennas2.html

JO GUNN 3 + 3 STAR $382.00
http://tinyurl.com/6hzteu

Oh btw, I'll be tower mounting it about 40' from the ground and turning it
with a hamIV rotator.

Thanks again.



Stan;

I don't know if you have considered it but I would like to suggest that
you look into ham radio. It is a more adventurous hobby,one that offers
greater opportunity to exercise your operating skills. By and large the
licensed ham radio operators offer a courteous, friendly and extremely
helpful environment. I have to assume that since you are here looking
for assistance you already have a feeling for all this.
Getting a ham license has never been easier. There are only three
classes of license now, Technician, General and Extra. The code test has
been eliminated so that shouldn't be a problem. The tests are multiple
choice and have a minimum passing level of 80%. That works out to be 28
correct answers for tech and general out of 35, the extra test has 15
more questions and so requires 40 correct answers. All questions are
published and if you go to http://www.qrz.com you can take sample tests.
Take enough samples and you should be able to pass the exam. Go to
http://www.arrl.org for locations and times for exams. There is a cost
for the exam but it isn't much.

Now as to your question. There isn't much to recommend either antenna.
They are based on designs used in the ham radio field. You might look
for these antennas and compare the numbers there. A source of ham radio
equipment is www.aesham.com. This is one of the premier ham radio houses.

Good luck
Dave WD9BDZ

David G. Nagel wrote:

I don't know if you have considered it but I would like to suggest that
you look into ham radio. It is a more adventurous hobby,one that offers
greater opportunity to exercise your operating skills. By and large the
licensed ham radio operators offer a courteous, friendly and extremely
helpful environment. I have to assume that since you are here looking
for assistance you already have a feeling for all this.
Getting a ham license has never been easier. There are only three
classes of license now, Technician, General and Extra. The code test has
been eliminated so that shouldn't be a problem.

Since he did not say where he is, your answer may be wrong. While I
agree with it in principal, not everyone has it so easy. Here in Israel
there still is a code requirement, testing is twice a year, and ANY
permanent antenna requires a permit which no one seems to know how to
get. Technicaly any operation over 20 watts EIRP requires radiation
level certification.

But then CB is just as bad. Except for a few off-roaders who have not gone
to 446 mHz it's even deader than ham radio.

Geoff.


--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

Geoffrey S. Mendelson wrote:
David G. Nagel wrote:

I don't know if you have considered it but I would like to suggest that
you look into ham radio. It is a more adventurous hobby,one that offers
greater opportunity to exercise your operating skills. By and large the
licensed ham radio operators offer a courteous, friendly and extremely
helpful environment. I have to assume that since you are here looking
for assistance you already have a feeling for all this.
Getting a ham license has never been easier. There are only three
classes of license now, Technician, General and Extra. The code test has
been eliminated so that shouldn't be a problem.

Since he did not say where he is, your answer may be wrong. While I
agree with it in principal, not everyone has it so easy. Here in Israel
there still is a code requirement, testing is twice a year, and ANY
permanent antenna requires a permit which no one seems to know how to
get. Technicaly any operation over 20 watts EIRP requires radiation
level certification.

But then CB is just as bad. Except for a few off-roaders who have not gone
to 446 mHz it's even deader than ham radio.

Geoff.


Geoff;

Your are right in one sense, however the antenna's in question are, I
believe, USA products so it is fairly save to assume that the writer is
a USA resident.

From your comments I assume (that word again) that you are a resident
of Israel. Given the situation there I can see why the government would
try to make it hard for someone to install and operate a radio station.
I look forward to the day when everyone in the Mideast can live together
in peace and harmony.

Until that time thank you for your comments.

Dave WD9BDZ

David G. Nagel wrote:
Your are right in one sense, however the antenna's in question are, I
believe, USA products so it is fairly save to assume that the writer is
a USA resident.

I thought so, but sometimes the people asking are not. They only have
access to U.S. manufacturer's products and catalogs via web sites,
with no local dealers.


From your comments I assume (that word again) that you are a resident
of Israel. Given the situation there I can see why the government would
try to make it hard for someone to install and operate a radio station.

Well, actually it's not. The antenna restriction is because the
"cellphone towers will kill you" people have forced laws through to prevent
anyone setting up a radio transmitter in their neighborhood.

The morse code requirment is because the people who run the Israel equivalent
of the ARRL pushed the Minstry of Communications to keep it. It keeps out
new hams from foreign countries. I have no idea how they handle visiting
operators now.


I look forward to the day when everyone in the Mideast can live together
in peace and harmony.

Thanks,

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

The Maco has a 16 foot boom and an advertised gain of 12.5 db, while the JO
GUNN has an 8 foot boom and an advertised gain of 14.5 db. I know there is a
lot of smoke and mirrors involved with advertised gains and so my question
is...is it possible for the JO GUNN to perform as well as the Maco antenna?

I would be sceptical. The fact that both manufacturers are quoting
gain in dB, without saying what it's in reference to (dBi for
isotropic, dBd for dipole) is a bit of a warning sign. Assume it's
dBi - the numbers come out bigger, and that's attractive in ads.

I'd be sceptical of the numbers offered for both of these antennas,
but I'd be quite a bit more sceptical concerning the JO GUNN.

It's probably useful to compare the design, and the numbers, with
what's known and published about various reference Yagi designs and
the results that can be achieved. I looked at some of the
documentation that Cebik (SK) published on his excellent web site.

The Maco is advertised as a "6-element" antenna, but the drawing
doesn't show a full set of six elements on either vertical or
horizontal polarization. I can't tell whether they omitted showing
some elements to leave the drawing less cluttered, or whether it's
supposed to be a "three elements vertical plus three elements
horizontal, equals six elements" design. It looks to me as if it's
essentially a Quagi antenna - a quad element in back (reflector?) plus
one or more set of linear elements in a Yagi-style arrangement.

At 11.5 feet, it's about a third of a wavelength long... and for any
antenna of this general type, the boom length is likely to be the
parameter which dominates the maximum gain figure you can achieve.

Cebik's figures indicate that well-designed quarter-wavelength-boom
Yagis typically deliver somewher around 8 dBi of gain, and one-half-
wavelength-boom Yagis are up somewhere around 10 dBi. Front-to-back
figures in the 25 - 35 dB range seem to be achievable. There's
usually a tradeoff in the optimization process... for any given boom
length, optimizing for maximum gain will usually cost you F/B ratio,
and vice versa.

I'd guess that it's *possible* that the Maco actually achieves 12.5
dBi of gain (at least on paper) at some frequency with its
one-third-lambda boom length, but that's more than I'd expect.

This assumes that the Maco has separate feeds for horizontal and
vertical polarization, and that it feeds only one at a time (e.g. via
a switch) and that there are no losses involved. If it's actually
feeding power to both polarizations at once (either linear or
circular), subtract 3 dB from the effective gain to a
linearly-polarized vertical or horizontal antenna at the other end.

The JO GUNN... well, I'm not sure just what sort of antenna it thinks
it is, other than "tries to be snazzy looking". It seems to be a
three-element short-beam antenna (at 8 feet it's less than 1/4
wavelength long), and yet it's claiming a 14.5 dB gain. This is
around 6 dB more gain than Cebik indicates is delivered by Yagis in
this boom-length class. The F/B ratio, "side rejection" and "back
rejection" are all extremely high (40 dB)... such high numbers suggest
that these are the best-looking numbers, taken from the deepest
rejection lobes of a mathematical model of the antenna in free space.

The GUNN is of much stronger construction and a smaller windload so I'd
rather put it up, but the short boom makes me wonder if the gain and
rejection numbers are suspect.

Well, before I trusted these numbers at all, I'd want to get a NEC2 or
similar model of the antenna from the manufacturer, and run the model
myself.

My guess is that the Maco folks *might* give you a model deck if you
ask nicely, and that the JO GUNN folks with either refuse or say "What
are you talking about?" or claim that their antenna incorporates
principles that cannot be accurately modeled.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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