While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Thanks for any insight,
Frank
KE5MJZ

On 03 May 2007 20:43:19 GMT, Spam Collector
wrote:

While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Hi Frank,

Your question encompasses a lot of territory (beyond the literal 300 x
500 feet).

You could get every question answered and still not be informed. An
other approach would be to download EZNEC and (even with the
limitation of 20 segments) model this and just see what happens.
Within its limitations this modeler will reveal many insights AND
allow you to vary things to suit those outcomes.

73's
Richard Clark, KB7QHC

On 3 May, 13:43, Spam Collector wrote:
While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Thanks for any insight,
Frank
KE5MJZ

Frank, all of your antennas will work for receiving in one way or
another, the real problem is matching your radio to the antenna
whether it is for receive or transmitting the latter being the most
important. Cofiguration of the antenna determines the matching ability
as well as the directivety. The bottom line is where do you wish to
communicate to and then design accordingly which means determining
first the frequency, then the direction and then attaining a suitable
match between the radio and the antenna. If you are only concerned
with receiving then most of those requirements fall by the wayside in
terms of operational importance. The main excitement that antennas
bring is when you introduce skywave type of deflections of radio
paths, even the simplest of antenna arrangements provides unexpected
surprises that tittilates your imagination such you become more
adventurous about your desires and where you are aware that your
transmitter could easily fail if you did not take protective measures
which requires good matching between the antenna and your radio.
Regards
Art

On 3 May, 13:43, Spam Collector wrote:
While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Thanks for any insight,
Frank
KE5MJZ

Frank, I did not adress your comment with respect to antennas of
narrow bandwidth. For receiving you have relatively unlimited
bandwidth because the antenna match is for extremely small power
transfer, the signal may become weaker but no damage is going to
occur. For transmitting it is a whole new ball game since the matching
syystem will have to transfer power in the order of a few watts or
even a kilowatt which is O.K. for a light bulb which is enclosed but
you really don't want the wires inside your transmitter to glow!
This is where matching the connection becomes important because tho
you can match the radio connection easily the antenna makes it harder
as you stray from the initial matching frequency such that wire
connections could easily glow and fail. Unfortunately it is very
difficult to design a antenna that will remain a close match to your
radio, this is just a fact of life. Usually you have to design an
antenna for a narrow band of frequencies which means more than one. In
your case where you have long wires it is possible to insert a black
box
that will provide a useable match across a large band of frequencies
but the other side of the coin is that antenna directivety is lost
since directivity is directly related to frequency.
As with all things there is no free lunch but it will sure provide a
lot of fun when playing with antennas and talking to the World.
Art
Art

You will get many, many lobes in various directions. If one happens to
be pointing in a direction you want to communicate to, you'll find that
the antenna "works". If it doesn't, you'll find that it "doesn't work".

Roy Lewallen, W7EL

Spam Collector wrote:
While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Thanks for any insight,
Frank
KE5MJZ

On 03 May 2007 20:43:19 GMT, Spam Collector
wrote:

While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

I use a ~550 foot horizontal loop fed with 450 ohm window line. A
balanced double L tuner is used as a matching device on HF. Homebrew
balanced tuners permit the loop to be used on 6 and 2M. On 6M the loop
performs well for an omnidirectional antenna. My primary 6M antennas
are Sterba curtains. The loop works FB on 2M FM but it is not suitable
for weak signal work.

73 de n4jvp
Fritz

"Spam Collector" wrote in message
...
While reading about antennas, I've been unable to find
answers to what I thought would be basic questions.
Most of what I've read seems to concentrate on narrow-
bandwith antennas, and even at that seems to concentrate
on what happens when lengths become shorter and ignores
the effects of longer lengths (for definitions of 'longer'
meaning 'much longer, as in many wavelengths longer).
The question is how various low-band antenna types
will perform at higher bands. For example, if I were
to run a wire around my property (about 300 x 500 feet),
giving me about 1600' of antenna length, I could run it
as a folded random wire (fed from one end), a loop (fed
from a corner or the middle of one side), or as a dipole
(if fed like the loop but cut on the oposite side).
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Thanks for any insight,
Frank
KE5MJZ



When I was a kid I did pretty much what you are suggesting with a receiving
antenna hooked up to a hallicrafter s40 b. At first I thought this was a
really great antenna becuase it picked up a lot of staions I had never heard
before. Unfortunately it didnt pick up the stations I wanted to hear so I
went back to using a 15ft piece of wire thumb tacked to my bedroom wall.

Jimmie

On 03 May 2007 20:43:19 GMT, Spam Collector
wrote:

While reading about antennas, I've been unable to find
Random antennas yield random results.
John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

Spam Collector wrote in
:

....
What are the performance differences between the
three configurations, and is there a upper frequency
limit for practical use of them? For example, would it
work on say 2m or 70cm, where the antenna would be
hundreds of wavelengths long?

Frank, as you will have noted from others' responses, the answer to this
is not simple.

Longer or larger antennas are not necessarily better. You would benefit
from examining the changes in pattern and feedpoint impedance of a loop
as it grows from 1/10 of a wavelength to 10 wavelengths per side, and
compare a very large loop with a rhombic.

You can only evaluate different antennas in your own context if you list
the relevant factors and rank their importance, factors like size,
height, frequency agility, transmission lines, matching arrangements,
automated operation etc.

Efficient and effective multi-band antennas don't happen by accident,
they are a significant challenge, and an efficient and effective 160m to
70cm is an extreme challenge. On the other hand, you will see proof that
"loading up the fencewire works", but it goes to the meaning of 'works',
which is less specific than 'effective and efficient'.

Owen

On 2007-05-04, Owen Duffy wrote:

Efficient and effective multi-band antennas don't happen by accident,
they are a significant challenge, and an efficient and effective 160m to
70cm is an extreme challenge. On the other hand, you will see proof that
"loading up the fencewire works", but it goes to the meaning of 'works',
which is less specific than 'effective and efficient'.

Thanks to all for the insightful replies. Evidently the reason
I couldn't find much information on 'oversized' antennas is that
they aren't very effective. Then again, if you never experiment
with unconventional ideas you'll never discover anything new, so
I may just try it and see what happens. If all else fails I can
always make several smaller narrowband antennas out of the wire.

Thanks again,
Frank
KE5MJZ