Myths and Legends of Antennae
 

Myths and Legends of Antennae
 

(David Platt) wrote in news:hk20ib-
:

http://snulbug.mtview.ca.us/books/Ra...naEngineering/

Thanks, that might be a way in for me. My eyesight won't stand a lot these
days, so concise is good, which that one is.

Myths and Legends of Antennae
 

Lostgallifreyan wrote in
:

concise is good, which that one is.


I might be wrong about that. I really do need quick guides these days, my
days of long reading are long gone, it physically hurts now even when I can
do it at all.

Myths and Legends of Antennae
 

Lostgallifreyan wrote in
:

Lostgallifreyan wrote in
:

concise is good, which that one is.


I might be wrong about that. I really do need quick guides these days,
my days of long reading are long gone, it physically hurts now even when
I can do it at all.


Well, it's a neatly made copy, but a huge tome, and I think maybe I got very
lucky in hitting one paragraph by accident, paraphrsed so:
"A rhombic antenna is only efficient when matched with the propogation medium
for specific frequency". In opther words, a good plan for transmission
efficiently in some direction at some frequency, but well beyond my scope for
quick experimental listening efforts.

Myths and Legends of Antennae
 

Lostgallifreyan wrote:
wrote in :

A fair antenna is you have a bunch of telephone poles and a huge piece
of empty ground.


Ok, that rules me out right there. :) I can maybe manage a long wire laid out
temporarily, but for large scale that's about it for me.

Decades ago I was affiliated with an Army MARS station that had inherited
a WWII rhombic array of 4 antennas for 360 coverage that worked fairly
well from about 5 MHz and up.

The thing seemed to be a lightning magenet during thunderstorm season
and sections of the wire that had been vaporized required regular
replacement.

Eventually the Army decided it has better use for the nearly square
kilometer of land the thing took up and replaced it with a log-periodic.

The log-periodic was several dB better, both transmit and receive, in
part because there was no longer the 50% termination resistor loss.



--
Jim Pennino

Myths and Legends of Antennae
 

Myths and Legends of Antennae
 

Lostgallifreyan wrote:
wrote in :

The log-periodic was several dB better, both transmit and receive, in
part because there was no longer the 50% termination resistor loss.


Thanks, I'll look at those a bit next time I can see well enough to read
much. Even the name is new to me right now.. :)

What I'm wondering is shy so much current discussion of whombic antennas at
all. I try to follow the tech posts because short repeats of good info may be
my best shot at absorbing it efficiently, but I'm not sure how rhombics got
such repeated notice.

Someone is attempting to make some sort of point by comparing apples and
strawberries.

The rhombic was a big deal in it's day back when huge, empty areas were
readily available and better antennas had not yet been invented.


--
Jim Pennino

Myths and Legends of Antennae
 

Myths and Legends of Antennae
 

Lostgallifreyan wrote:
wrote in :

The rhombic was a big deal in it's day back when huge, empty areas were
readily available and better antennas had not yet been invented.


I like apples and strawberries, but I'll not go into it. :)

I had a very quick look at log-periodic antennas before I sleep. That looks
like a much more practical notion to me. I guess practical DIY might still be
limited to shorter wavelengths, but it looks like a neat, compact and solid
antenna design, ideally suited to anyone with some accurate tooling and a
need for directivity combined with a relatively broad bandwith reducing need
for adjustments. Would it be a contender against a tuned magnetic loop for a
beginner's experiment?

Like all things in life it is a trade off of various things.

The accuracy requirement, at HF anyway, is not that bad and there are
LOTS of plans for DIY log periodic antennas out there.

Upside: Basically frequency independant (over a range), all metal
construction, can directly match 50 Ohms, and gain can be increased
by increasing the number of elements and making it longer.

Downside: A high gain antenna can be quite large, require a lot of
expensive aluminum, be quite heavy and like any beam needs a tower
and a rotor.

Since it is truely frequency independant, for certain uses, like military
that could be operating on any frequency, it is an almost ideal solution.

For hams that are constrained to bands, something like a hex beam
might be a more economical solution.

Your call.


--
Jim Pennino

Myths and Legends of Antennae
 

On 10/26/2014 5:01 PM, gareth wrote:
"Brian Reay" wrote in message
...

He has less pleasant ploys which, hopefully, you will be spared.

Are you, perhaps, referring to the precedent that you set in 2005 to
threaten
the liberties and livelihoods of those who did no more than to openly
disagree with you
on Usenet by sending for them to be arrested by the ploddery?

Did it not occur to you that your victims could end up getting the sack from
their jobs when you did that?




You mean like you purposefully tried to get him sacked for things he did
not do - and got docked for it?

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================