Crossed Field Antenna
Martin Spencer
I'm new to this ng so pls forgive what may well be a recurring
question (well, at least I checked the last 200 posts!).
Does the so called 'crossed field antenna' work?
I looked into this subject years ago and came to the conclusion
that the theory was mistaken and the 'antennas' did not work in
practice.
Now it is all in the news again. Apparently there are a large
number operational in Egypt. Allegedly, NOZEMA (Netherlands' PTT)
RAI (Italy's PTT) the US Navy are all 'believers'. A new one has
just gone on air in Kiel, Germany. The Isle of Man has granted a
500kW long wave licence based on CFA use. The UK Radio Authority
believe it may work!!!
After extensive websearching I can find NO authoritative
references.
Can anyone shed more light? (Please do not bother to recount
tales of far flung QSOs!). Has any controlled testing been done
with the device at ground level? If so, gain referred to a
suitable conventional antenna in the same location?
Cheers,
Martin.
Reg Edwards
Radio station owners, for a given service area, are at liberty to
spend their money either initially on gigantic full-size
antenna-plus-ground radial systems or, subsequently, on monstrous
electricity power supply bills.
The latter is a more economic option when the operationing life of the
venture is uncertain.
Whichever option is adopted, one thing for sure, listeners will be
subjected every day to 24 hours of pop, phone-ins, ads and lying,
brain-washing propaganda.
--
*************************************************
Reg, G4FGQ For free software go to:-
http://www.btinternet.com/~g4fgq.regp
*************************************************
AMDX
Does your statemant mean that you half agree with Martin?
>>"I...... came to the conclusion that the theory was mistaken"
You agree?
>> " the 'antennas' did not work in practice."
You disagree? A piece of wire will radiate!
Mike
Gray Frierson Haertig
Measurements by an independent consultant of the CFA in Alexandria
indicate that, as far as efficiency is concerned, the CFA performs no
better than one would expect of an antenna of its electrical size, and
far less well than its proponents would claim. Having said that, it
seems to perform better than many other implementations of electrically
very short antennas.
RAI is building its CFA as a flier, to investigate its performance, I am
told. Its construction should go a long way in answering a number of
the questions surrounding the CFA. Even if one is willing to forego the
inflated claims of efficiency, there is still considerable interest in
how matching and ground losses are minimized and how SWR bandwidth is
maintained. There are certainly instances where a proper antenna just
cannot be built where it needs to be. In those cases, an inefficient
short antenna is better than no antenna at all, and if you're stuck with
one, you might as well build the best possible short antenna.
The Isle of Man station is proposing the CFA primarily because they have
been remarkably unsuccessful in persuading the local authority to allow
them to construct a whonking big tower. In the face of adversity, hope
springs eternal. I am unsure as to whether the UK telecom authority (if
indeed they hold sway on the Isle of Man) mandates minimum antenna
efficiencies as does the FCC. At any road, if there are minimum
requirements, they may well be unwilling to engage in a pissing match as
to whether the CFA is a goer or not. Or, indeed, they just may be
curious as to whether it works or not and are quite happy to let a
private firm dump a few bejillion quid into the project to see.
Gray
Martin Spencer wrote:
>
> Hi all,
>
> I'm new to this ng so pls forgive what may well be a recurring
> question (well, at least I checked the last 200 posts!).
>
> Does the so called 'crossed field antenna' work?
>
> I looked into this subject years ago and came to the conclusion
> that the theory was mistaken and the 'antennas' did not work in
> practice.
>
> Now it is all in the news again. Apparently there are a large
> number operational in Egypt. Allegedly, NOZEMA (Netherlands' PTT)
> RAI (Italy's PTT) the US Navy are all 'believers'. A new one has
> just gone on air in Kiel, Germany. The Isle of Man has granted a
> 500kW long wave licence based on CFA use. The UK Radio Authority
> believe it may work!!!
>
> After extensive websearching I can find NO authoritative
> references.
>
> Can anyone shed more light? (Please do not bother to recount
> tales of far flung QSOs!). Has any controlled testing been done
> with the device at ground level? If so, gain referred to a
> suitable conventional antenna in the same location?
>
> Cheers,
>
> Martin.
--
Telecommunications Engineering
Gray Frierson Haertig & Assoc.
820 North River Street, Suite 100
Portland, Oregon 97227
503-282-2989
503-282-3181 FAX
g...@haertig.com
Roy Lewallen
> . . .
> After extensive websearching I can find NO authoritative
> references.
> . . .
This should be a clue.
Roy Lewallen, W7EL
Martin Spencer
>
> Martin, ANY bloody thing will WORK !
Yeah I know that. But for broadcasting, you need efficiency
comparable to a quarter wave vertical, or as you point out you are
going to waste a helluva lot of money on electricity. The CFA
camp claim greater efficiency than a monopole.
> Radio station owners, for a given service area, are at liberty to
> spend their money either initially on gigantic full-size
> antenna-plus-ground radial systems or, subsequently, on monstrous
> electricity power supply bills.
>
> The latter is a more economic option when the operationing life of the
> venture is uncertain.
>
> Whichever option is adopted, one thing for sure, listeners will be
> subjected every day to 24 hours of pop, phone-ins, ads and lying,
> brain-washing propaganda.
Unfortunately, how true. But broadcasting does not have to be so
vile and boorish.
Cheers,
Martin.
Mark Keith
The CFA
> camp claim greater efficiency than a monopole.
I haven't even seen their info on the CFA antennas, but I look at that
one statement right there, and hummmmmmmmmmmmmmmmmm. A smaller than 1/4
wave antenna outdo a full size 1/4 antenna? Assumming equal ground
radials,...Ok dokie...I've got some ocean front in Kingman AZ too. MK
--
http://web.wt.net/~nm5k
Martin Spencer
>
> I haven't even seen their info on the CFA antennas, but I look at that
> one statement right there, and hummmmmmmmmmmmmmmmmm. A smaller than 1/4
> wave antenna outdo a full size 1/4 antenna? Assumming equal ground
> radials,...Ok dokie...I've got some ocean front in Kingman AZ too. MK
They say a conic section on top of the 'E' plate (yes I do feel a
little odd saying this stuff) squashes the VRP and achieves higher
FS at the horizon than a quarter wave. All quite possible if the
basic premise is correct...
Cheers,
Martin.
Martin Spencer
Very, very interesting.
Can you point me at that consultant in Alexandria? Or has he
published? I would dearly like to see those figures.
Interesting about RAI too. I suspected as much.
The UK radio authority do not hold sway in the isle of Man. I
suspect they are as befuddled as everyone else.
As you say, an efficient short aerial could still be useful even
if it works on conventional principles. Has anyone modelled a CFA
in miniNEC?
Using stubby conductors to broaden the bandwidth is an old trick,
and the 'E' plate would certainly rate as a stubby conductor!
Cheers,
Martin.
====================
> > After extensive websearching I can find NO authoritative
> > references.
> >
Reg Edwards
about to be licensed I merely stated the obvious that the same service
area can be covered by using either a full-size half wave vertical
with relatively little power, as when using a very small inefficient
antenna with a megawatt.
Its all a matter of economics. The station owners have never heard of
radiation resistance - only construction, maintenance and running
costs. I'm confident they have made the correct choice to satisfy
THEIR requirements.
Reg.
====================================
AMDX <AM...@worldnet.att.net> wrote in message
news:01befac2$888a0a60$52874d0c@default...
> Reg,
> Does your statemant mean that you half agree with Martin?
>
> >>"I...... came to the conclusion that the theory was mistaken"
>
> You agree?
>
> >> " the 'antennas' did not work in practice."
>
Tom W8JI
<g...@haertig.com> wrote:
>
>Measurements by an independent consultant of the CFA in Alexandria
>indicate that, as far as efficiency is concerned, the CFA performs no
>better than one would expect of an antenna of its electrical size, and
>far less well than its proponents would claim. Having said that, it
>seems to perform better than many other implementations of electrically
>very short antennas.
...and worse than others.
The CFA is not new, it was around in the late 70's and early 80's a
died an abrupt death when no one could see one work, and a few people
bought them and the worked like any other antenna the same size.
Now, thanks to a new wave of publicity, it is back until the new wave
of fresh suckers drys up.
It does have one very useful effect for some people, it causes money
to change hands. What does it cost this time for information on how to
build this antenna?
73 Tom
Roy Lewallen
> . . .
> if it works on conventional principles. Has anyone modelled a CFA
> in miniNEC?
> Using stubby conductors to broaden the bandwidth is an old trick,
> and the 'E' plate would certainly rate as a stubby conductor!
Jack Belrose, VE2CV has modeled the CFA very carefully with NEC-4, and
has been unable to see anything like the claimed performance. He's
posted comments about this from time to time on the NEC-List.
Roy Lewallen, W7EL
Roy Lewallen
efficiency than a monopole. Their claim is a higher field strength. They
couldn't get the claimed field strength increase (up to 6 dB greater, as
I recall) even with an efficiency of well over 100%. They claim that the
field strength increase is due to greater concentration of the field at
low angles as a result of a small conical metal shield-like structure on
the top of the antenna.
To me, this sounds even more ridiculous than a claim of higher
efficiency.
Roy Lewallen, W7EL
Mark Keith wrote:
>
> Martin Spencer wrote:
> The CFA
> > camp claim greater efficiency than a monopole.
>
> I haven't even seen their info on the CFA antennas, but I look at that
> one statement right there, and hummmmmmmmmmmmmmmmmm. A smaller than 1/4
> wave antenna outdo a full size 1/4 antenna? Assumming equal ground
> radials,...Ok dokie...I've got some ocean front in Kingman AZ too. MK
> --
> http://web.wt.net/~nm5k
Tom W8JI
wrote:
>My reading of the CFA literature is that they're not claiming greater
>efficiency than a monopole. Their claim is a higher field strength. They
>couldn't get the claimed field strength increase (up to 6 dB greater, as
>I recall) even with an efficiency of well over 100%. They claim that the
>field strength increase is due to greater concentration of the field at
>low angles as a result of a small conical metal shield-like structure on
>the top of the antenna.
>
>To me, this sounds even more ridiculous than a claim of higher
>efficiency.
It must be true that magic comes in threes.
Do you suppose if I put a pie-pan above my low band mobile antenna, it
will lower the wave angle?
I sense a market unfolding to replace the double loading coils and
ski-pole rings sold to CBers.
Imagine, 6 dB gain with the addition of a pie pan.
73 Tom
Jake Brodsky
wrote:
>Now, thanks to a new wave of publicity, it is back until the new wave
>of fresh suckers drys up.
Hey Tom, it ain't all that bad: It separates the kids from the
adults. If we eliminated this nonsense, those who would have fallen
for it would fall for something else.
What they've done is actually a public service in a backhanded sort of
way. Anyone so technically inept that he or she actually purchases
this thing is doomed to a weak signal. That ought to keep their other
mistakes and misdeeds from bothering the rest of us.
I have to consider the bright side of things once in a while or I'd
drive myself crazy...
Jake Brodsky, AB3A mailto:fru...@erols.com
"Beware of the massive impossible!"
W6RCecilA
> Do you suppose if I put a pie-pan above my low band mobile antenna, it
> will lower the wave angle?
Make it a 12 ft. diameter aluminum pie pan and I will believe it.
--
73, Cecil, W6RCA http://www.bigfoot.com/~w6rca
Richard Harrison
Imagine, 6 dB gain with the addition of a pie pan.
Before dismissimg the idea completely, I`d consider Cecil`s mobile
antenna.
Best regards, Richard Harrison, KB5WZI
Roy Lewallen
> . . .
> Do you suppose if I put a pie-pan above my low band mobile antenna, it
> will lower the wave angle?
>
> ski-pole rings sold to CBers.
>
Depends. If you have a good marketing department to make the
measurements, anything is possible.
Roy Lewallen, W7EL
Tom W8JI
wrote:
>Hey Tom, it ain't all that bad: It separates the kids from the
>adults. If we eliminated this nonsense, those who would have fallen
>for it would fall for something else.
You made a good point Jake.
I think I'll start telling everyone stateside I'm using a CFA, and
encourage them to build one for the pileups....
That has the potential to give me an outstanding signal with no work
on my end.
By the way.... the CBer down the road has pie pans on his coax, and a
big jug filled with salt water and pocket change in his basement with
wires running into it.
The pie pans deflect lightning from following the cable, and the big
jug gives him a saltwater ground. (Dolly Parton never gets struck by
lightning, that must be proof of something.)
You may think the part about the CBer is a joke, but I am absolutely
serious. Prior to the pie pans and jug, he said his tower got hit two
times.
73 Tom
Martin Spencer
>
> You made a good point Jake.
>
> I think I'll start telling everyone stateside I'm using a CFA, and
> encourage them to build one for the pileups....
>
> That has the potential to give me an outstanding signal with no work
> on my end.
HA HA! Now THAT is FUNNY!
Martin Spencer
you can buy a 50MW transmitter!
Cheers,
Martin.
===========