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Old April 8th 04, 10:54 AM
Steve Muir
 
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Default Homemade Antennae, help

I have recently bought a 2nd hand faihaven RD500, im really pleased with it,
having been an avid VHF/UHF listener before i wanted to get into HF/SW.
I currently have a telescopic aeriel plugged into the back, which im sure is
no use. Someone told me all you have to do is run a wire 33ft long around my
loft and plug it into the back of my reciever and ill pick up some great
stuff. Im particularly interested in Military but other stuff as well

Im not sure how true this is, can someone enlighten me, if so then can you
give me a breakdown of what ill need and any tips to installing it.

Any help will be very much appreciatted

Thanks in advance

Steve(Scottish)


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Old April 8th 04, 02:31 PM
'Doc
 
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Steve,
That 'someone' told you correctly for the most part. It
certainly
isn't the most exacting explanation for an antenna, but it will
get
you into the 'ball park'!
The length of an antenna has to be such that it provides
enough
signal to your receiver so that it (the desired signal) is
louder
than the noise. For most HF signals, 33 feet will be plenty.
Of
course, 'more' would be 'better' in some cases, but not always.
The
one thing that will do more to increase what you hear is
height. Get
the antenna as high as possible (sort of like you standing on
your
'tip toes' to see farther, right?). You also can only work with
what
you have, so if ceiling height is the most you have, then use
it.
The 'shape' of your antenna also can play an important part
in what
you hear. If the antenna is high enough above ground, it can
become
directional in nature. I wouldn't worry about that too much,
though,
just be aware of it. Stringing your antenna out as long and as
straight
as you can make it is much better than wadding it up into a ball
and
throwing it into a corner. There's also nothing that says that
you
can't change the 'shape' of the antenna, if you want to see what
would
happen.
The size of the wire used isn't going to make a lot of
difference,
as long as it is strong enough to support it's own weight. Make
it
ea$y on your $elf, co$t wi$e. The length isn't really that
critical
so you don't need to use a micrometer to measure the length of
your
antenna. A little more, or a little less isn't going to make a
big
difference. A foot or two is meaningless, twice the length is
"more
better", sort of.
Probably more important than anything else is how the wire is
connected
to your receiver. Use the proper connector, if possible. If it
isn't
possible, just make sure you don't short out the receiver's
antenna
terminals. Won't harm the receiver, you just won't hear much.
SWL'ing is fun, so have lots of it!
'Doc

PS - That's about as non-technical as you can make an
explanation of
a complex subject. There are 'exceptions' to everything I
said,
but what I said will certainly work for you. Knowing 'why'
it
'works' is interesting, but not really necessary to make it
'work'.
The 'having fun' is the important part...
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Old April 8th 04, 07:52 PM
Richard Clark
 
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Default

On Thu, 8 Apr 2004 10:54:29 +0100, "Steve Muir"
wrote:

I have recently bought a 2nd hand faihaven RD500, im really pleased with it,
having been an avid VHF/UHF listener before i wanted to get into HF/SW.
I currently have a telescopic aeriel plugged into the back, which im sure is
no use. Someone told me all you have to do is run a wire 33ft long around my
loft and plug it into the back of my reciever and ill pick up some great
stuff. Im particularly interested in Military but other stuff as well

Im not sure how true this is, can someone enlighten me, if so then can you
give me a breakdown of what ill need and any tips to installing it.

Any help will be very much appreciatted

Thanks in advance

Steve(Scottish)


Hi Steve,

Looks like a really nice rig. One comment to add to Doc's advice: add
a tuner between your antenna and the rig. The reason is that nearby
AM stations can overload and saturate your front end without you
knowing it and reduce the sensitivity considerably! This is not so
obvious with a whip antenna, but it becomes a big time problem with
longwire antennas if the front end is not tuned (a very expensive
feature, unless you go back several generations to tube models).

You can buy a cheap one that is already used by an amateur (or go for
the absolute cheapest model without meters that would do you no good
anyway). Or to cut cost even more, build your own (browse the net for
designs).

73's
Richard Clark, KB7QHC
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Old April 12th 04, 12:06 AM
John - G0WPA
 
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If you use a Magnetic Longwire Balun, ANY length of wire should present roughly
50 ohms to the receiver. The amount of extra signal will be considerable! I
used 33 feet of wire with a Roberts RC818 some years ago, which worked really
well, but when I added the MLB, there was a vast improvement. These MLBs have a
PL259(actually SO239) connection at one end and a wing nut for your longwire at
the other end. Hayden, W&S, and Maplin all supply them here in the UK for about
£20. A worthwhile investment for the terminally lazy! Otherwise, an ATU is
perhaps a better option, except that browsing a band will require constant
retuning of the ATU. Personally Id suggest an ATU over an MLB because there
will be attenuation of off freq signals that may otherwise cause you problems.
So theres your choice! If you want some help building an ATU or sourcing
parts, E-mail me, but take QRM off my e-mail addy, ...John.
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Old April 12th 04, 02:17 AM
Cecil Moore
 
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John - G0WPA wrote:
If you use a Magnetic Longwire Balun, ANY length of wire should present roughly
50 ohms to the receiver.


Where can I get one of those magic baluns? It doesn't happen to
have a 50 ohm resistor in it, does it?
--
73, Cecil, W5DXP



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Old April 12th 04, 03:16 AM
Mike Coslo
 
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Default

John - G0WPA wrote:

If you use a Magnetic Longwire Balun, ANY length of wire should present roughly
50 ohms to the receiver. The amount of extra signal will be considerable!


I wonder how the Magnetic longwire baluns work with the Isotron?

;^)


- Mike KB3EIA -

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Old April 12th 04, 04:44 AM
CW
 
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Default

It's not a balun and it doesn't magically autotune though they do help quite
a bit depending on circumstances.

"Cecil Moore" wrote in message
...

Where can I get one of those magic baluns? It doesn't happen to
have a 50 ohm resistor in it, does it?
--
73, Cecil, W5DXP



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----



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