John Magliacane wrote:
http://books.google.com/books?id=SNJhVlHGgC&pg=PP1&sig=qdNrli_UaJsiZB_gq3cRqvjy4DY#PPT961,M1
http://www.jampro.com/index.php?page=c-circularly-polarized-spiral-tv-antenna
Interesting, although it doesn't seem to be a compact antenna (each turn
of the helix is several w
If you want to deal with specifics rather than generalities let me suggest
you look at one of the computer programs by the late Reg G4FGQ and in
particular DIPOLE 3. You can play with various arrangements and get relative
values.
I often use this in conjunction with EZNEC for comparison. H
> John Magliacane wrote:
>
> > It's a traveling wave antenna where the helix is wound around a
> > supporting vertical mast that serves as a reflector.
David Woolley <[EMAIL PROTECTED]> wrote:
> None of the references I found (including university course
> notes), when researching this at the we
John Magliacane wrote:
It's a traveling wave antenna where the helix is wound around a
supporting vertical mast that serves as a reflector.
None of the references I found (including university course notes), when
researching this at the weekend, described anything other than a
dielectric cor
> John Magliacane wrote:
>
> >
> > I believe the Normal Mode Helix, as is used in HI-VHF television
> > broadcasting, is a travelling wave antenna, rather than a
> > resonant standing wave antenna, such as a dipole.
David Woolley wrote:
> You are thinking of axial mode helices. Normal mode hel
John Magliacane wrote:
When Skin Effect losses become an issue in RF conductors and
inductors, Litz wire is typically used. I see no reason why a
One has to ask why this isn't used in all the commercial "miracle" antennas.
I believe the Normal Mode Helix, as is used in HI-VHF television
br
bill KE5KWE wrote:
Let me bring this down to the practical world. My QTH is a 42.5 ft. Travel
Trailer which is insulated from the ground by 6 Rubber Tires and Air. It
Is it connected to the mains electricity supply? If it is, you will
probably need to consult someone familiar with your loca
Bill, let me first state that operating QRP makes a
good antenna much more a requirement than operating
QRO. Of course, the antenna does not need to handle
as much power, so some of the components can be
lighter weight. For someone to give you a really good
suggestion we need to know a few things
I made this system primarily for its mechanical properties. I will make
some measurements one fine day
David
G3UNA
- Original Message -
From: "Bob Cunnings" <[EMAIL PROTECTED]>
To:
Sent: Sunday, January 06, 2008 11:06 PM
Subject: Re: [Elecraft] dipole antenna e
The capacitance between individual strands in Litz wire limits it's
usefulness above 1 MHz or so. W8JI has an interesting discussion of
skin effect at:
http://www.w8ji.com/skindepth.htm
Bob NW8L
On Jan 6, 2008 3:54 PM, David Cutter <[EMAIL PROTECTED]> wrote:
> I've used several strands of enamel
I've used several strands of enamelled copper wire twisted together. I
usually twist 3 sets of 3 of quite thin wire, whatever is on hand; 0.2 to
0.45mm dia is easy to use; after twisting I give the group a good pull the
stretch and stiffen it a bit but it still remains very flexible indeed and
Ron D'Eau Claire wrote:
> We simply do not have conductors that will handle RF with
> anything like the efficiency they will handle DC or low frequency
> AC. That's because all the RF current 'crowds' onto the very
> surface of a conductor.
When Skin Effect losses become an issue in RF conductors
In a message dated 1/5/08 11:40:39 PM Eastern Standard Time, [EMAIL PROTECTED]
writes:
> We simply do not have conductors that will handle RF with anything like the
> efficiency they will handle DC or low frequency AC. That's because all the
> RF current 'crowds' onto the very surface of a condu
Hi,
I found another good link for the argument:
http://www.w5sf.com/article9.html
73,
IK4YNG Paolo
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Absolutely pattern is of significance, Alan, but unless you have a lot of
space, there's not much one can do about the pattern of HF antennas and most
wire antennas will be omni directional at heights most Hams can achieve on
typical lots.
Even a full-sized 1/2 wave horizontal antenna is essentia
Hi Bill,
I second in full what Ron told you. I would like to add my "two cents" of
personal experience...
Building an Elecraft K2 was a good choice. I have one too, together with
countless other radios; the difference is that the K2 stays, the other
radios have been sold. It is a very nice rig,
Interesting discussion. I have a question regarding this topic I hope the
more learned in the group cans help clarify. Although efficiency is important
is determining an antenna selection, is antenna lobe pattern just as
important? If the lobe pattern did not allow you to say work DX or to
ts of contacts even if you just use the basic mobile antenna
installation.
Ron AC7AC
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of bill KE5KWE
Sent: Sunday, January 06, 2008 7:53 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] dipole antenna effi
Bill,
My Lady and I are serious half-time RV'ers and I've had
very good results with my K2 into a modified High Sierra
screwdriver on a 5th-wheel Holiday Rambler.
I'll send you photos. It's also pictured on K0BG's mobile
site.
73! Ken Kopp - K0PP
[EMAIL PROTECTED]
or
[EMAIL PROTECTED]
__
Let me bring this down to the practical world. My QTH is a 42.5 ft. Travel
Trailer which is insulated from the ground by 6 Rubber Tires and Air. It
has Metal, I presume Aluminum, siding and a Rubber over Wood Roof which is
approx. 10 ft. off the ground. My K2 is almost built and I will be
opera
John Magliacane wrote:
When it comes to antenna efficiency, it is important to understand
that when RF energy is applied to any antenna, three things will
invariably happen:
For antennas in practical locations, at least one other thing will happen:
d) The antenna will convert part of the AC po
John wrote:
b) The antenna will convert a portion of the applied AC voltage and current
into heat energy as a result of resistive losses in the antenna structure.
Unless steel or nichrome wire is used, or electrically poor connections
exist in the antenna structure, losses due to (b) will be low.
This thread started with a person trying to find an
antenna that would work reasonably well that does not
take up much space. While in theory, you are correct
the practical aspects of making a very small antenna
for low frequencies lead to impossible parameters.
The radiation resistance of a dipo
David,
Actually, if you follow some of the other related articles Lloyd
wrote, the effect of this design seems to approximate a full wave dipole
with a device about 2% of a wave length. That is, a 40 meter antenna
about 3 feel long. He also purports a kind of "folded" antenna for 80
meters at
When it comes to antenna efficiency, it is important to understand
that when RF energy is applied to any antenna, three things will
invariably happen:
a) The antenna will convert a portion of the applied AC voltage
and current into electromagnetic energy and radiate it into space.
b) The antenna
- Original Message -
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>;
Sent: Saturday, January 05, 2008 7:28 AM
Subject: Re: [Elecraft] dipole antenna efficiency
In a message dated 1/4/08 4:34:29 PM Eastern Standard Time,
[EMAIL PROTECTED]
writes:
I've nev
Absolutely. Even when you look at Joe's site, www.k1jek.com there is
enough info in what you see to make the antenna. Rotor cable, ladder
line, a balun and coax. I personally do not think what he asks for the
on the website is overly much. He makes the products himself, and
stands behind them.
Ha, ha! Check the date on the article.
VK5BR has a parallel tuned circuit (two plates for the capacitor and coil
for the inductance) with the "feed" tapped across a couple of turns of the
coil.
One could use any parallel coil/capacitor combination with adequate voltage
and current ratings to do
David,
Actually, if you follow some of the other related articles Lloyd
wrote, the effect of this design seems to approximate a full wave dipole
with a device about 2% of a wave length. That is, a 40 meter antenna
about 3 feel long. He also purports a kind of "folded" antenna for 80
meters
Ooops. I must apologise for my mistake: I've read the article in more
detail and Lloyd is not feeding a small antenna, he is using the "feeder" as
the antenna by deliberately unbalancing it with a terminal unit to obtain
maximum current at the far end of the feeder. Presumably this would then
In a message dated 1/4/08 4:31:49 PM Eastern Standard Time, [EMAIL PROTECTED]
writes:
> The most expensive thing is ground to install
> them where antenna restrictions don't bring down the
> wrath of the taste police.
AMEN!!
(I have been trying for
>
> over 50 years to convince the world tha
In a message dated 1/4/08 4:34:29 PM Eastern Standard Time, [EMAIL PROTECTED]
writes:
> I've never understood the popularity of the G5RV. It's
> achieved a sort of "cult" following.
It's an ingenious compromise antenna for several bands, that's all.
Actually, just a ~102 foot dipole with a mat
Here is an interesting antenna made by Lloyd Butler VK5BR. It uses open
wire feeder to a VERY small antenna.
http://users.tpg.com.au/users/ldbutler/ReverseFeedTopLoading.htm
David
G3UNA
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bloody 'ell,,, that was slightly more than I barganned for. oh well,
every little bit helps, and ultimately confuses.
shaun.
On 4/01/2008 11:58 PM, the old scribe known as Dale Putnam was able to
impart this pearl of wisdom:
What is needed is a good effecient, multiband antenna with a general
Folks,
Not to dispute the info that Ron has provided, but to add a bit to it ---
Let me throw in my $.02 worth in this. Any antenna will radiate if you
can feed power to it, and it will radiate all the power that is fed to
it, but there is loss to consider too. If the radiator and the
transm
WILLIS COOKE wrote:
>I have a 1973 and a 1977 Handbook and I don't see it in either. What
>matching method did they use?
Sorry my error, I should have said the 13th (1974) edition of the ARRL
*Antenna* Handbook - page 219.
They used an airwound transformer at the centre of the driven elemen
David wrote:
I'm also fairly sure that the amount of wire to wind on the helix is
significantly different from the amount that would be used in a straight
line. My gut feeling is that it should be less, but I haven't
researched that, either,
-
I have experimented with cont
WILLIS COOKE wrote:
Shaun, it will decrease the efficiency drastically. A
two meter long 80 meter dipole will be about 10% as
efficient as one 40 meters long at the same height.
That's only conditionally true, although the conditions are probably
going to apply in this case. An antenna that
.
Ron AC7AC
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of David Wilburn
Sent: Friday, January 04, 2008 3:05 PM
To: David Yarnes
Cc: Dohn; elecraft@mailman.qth.net
Subject: Re: [Elecraft] dipole antenna efficiency
I understand many G5RV's are gett
On Fri, 4 Jan 2008, David Wilburn wrote:
I understand many G5RV's are getting replaced with these antennas. I
have the Grampy version, that is 100' long on each side, for a total of
300' of wire on each side, all in a 100' on each side package. Have had
good luck with it. Their shortest is a
efficient as a
> good wire antenna, but they are quite small, and the results can often
> surprise you. Besides, they are fun to build!
>
> Dave W7AQK
>
>
>
> - Original Message -
> From: "Dohn" <[EMAIL PROTECTED]>
> To: "'Shau
Shaun Oliver <[EMAIL PROTECTED]> wrote:
I was thinking of using 18 mm electrical conduit. with 2 mm spacings for
each turn of the wire.
-
The diameter is a bit on the small side for the low bands, but NM Helix
antennas working
Dave's observations are "right on" and good reading.
I've never understood the popularity of the G5RV. It's
achieved a sort of "cult" following. The original design
was for a 20M -ONLY- antenna, and somehow has
morphed into a do everything hoax.
I do antenna talks at conventions and hamfests,
There are many forms of shortened antennas that work
to varying degrees. Antenna selection and
installation is a very complicated situation and the
ARRL Antenna Handbook, as large as it is only has a
fair sampling of all the information that is
available. Any antenna that completed the desired
co
David, the beam was descibed in the 13th (1974) edition of the ARRL
handbook, perhaps in an earlier edition also, it performed well..
73,
Geoff
GM4ESD
David Cutter <[EMAIL PROTECTED]> wrote:
I seem to remember a 40m beam made this way in one of the old ARRL books.
David
G3UNA
While Cookie
We're back to wanting our RF "superconductor" again .
First, to add a note to the original question, it's useful to think of the
RF field as flowing OVER the outside of the conductor, so a helix (coil) or
any form of zig-zag arrangement of wires simply look like fat conductors to
the RF field. In
surprise you. Besides, they are fun to build!
Dave W7AQK
- Original Message -
From: "Dohn" <[EMAIL PROTECTED]>
To: "'Shaun Oliver'" <[EMAIL PROTECTED]>;
Sent: Friday, January 04, 2008 2:50 AM
Subject: RE: [Elecraft] dipole antenna efficiency
Sh
I seem to remember a 40m beam made this way in one of the old ARRL books.
David
G3UNA
While Cookie's comments are true, there is a useful type of short antenna
known as a Normal Mode Helix, which if built, tuned and matched correctly
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Shaun Oliver <[EMAIL PROTECTED]>
if I were to make a dipole, would coiling it round a piece of plastic
piping decrease the efficiency of the thing? I intend on making one for 40
meters, one for 80 meters, and one for 10 meters. I've worked out that1
meter of piping will suffice for each leg o
On Behalf Of Shaun Oliver
Sent: Thursday, January 03, 2008 9:20 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] dipole antenna efficiency
Hi all,
if I were to make a dipole, would coiling it round a piece of plastic
piping decrease the efficiency of the thing? I intend on making one for
40 m
Shaun, it will decrease the efficiency drastically. A
two meter long 80 meter dipole will be about 10% as
efficient as one 40 meters long at the same height.
Most texts quote dbi information for a full sized
dipole 100 feet high. If you put your antenna near
the ground it may not be much more th
Hi all,
if I were to make a dipole, would coiling it round a piece of plastic
piping decrease the efficiency of the thing? I intend on making one for
40 meters, one for 80 meters, and one for 10 meters. I've worked out
that1 meter of piping will suffice for each leg of each antenna.
thanks in
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