From: "Howard"
Subject: ? for the group
Date: Thursday, December 02, 2004 8:26 PM

On Thu, 2 Dec 2004 14:08:25 -0600, "Dave" wrote:


"Michael Lawson" wrote in message
. ..

"Dave" wrote in message
...

"Dale Parfitt" wrote in message
news:25Krd.8148$1z5.1438@trnddc06...

"



Thanks for the quick response, Mike!

65 feet of coax between the radio (DX-402/ATS-505) and the
antenna
(200 feet
of 300 ohm twin-lead hidden along the ridge on the roof of the
house.) And
I don't think I would call it "severely" degraded, only
slightly so.
Only a
little less than the old "temporary" antenna (60 feet of four
strand
copper
wire thrown over the house.) Also, the new antenna is oriented
primarily E/W
while the "temporary" antenna was oriented primarily N/S, if
that
matters.

The orientation does matter if you're not using a vertical,
but the first thing that popped into my mind was overloading
the ATS-505 with 200 feet of antenna wire. The longest
I've ever run into my old DX-440/ATS-803A was about
40-50 feet, and while I never overloaded it, I've never
tried anything close to 200 feet into it.


But yeah, the E/W orientation will work well for stations
that are north or south of you (like tropical band stuff),
but not so good for hearing things east or west of you
(like from Europe or Africa or -depending on where
you're at- relays like Sackville).

Unless the antenna is a approx. 1/2 wavelength up or higher ( at
tropical
band= 150' or so) the end nulls fill in making even horizontal
antennas
near
omni.

Guess my question is, how are you connecting the twin lead- if
simply
connecting it to the balun, you have little more than a 300 Ohm
transmission
line, not an antenna.
In fact, if the baluns were perfectly balanced, and the twin lead
clear of
metallic objects ( which would unbalance it) you would
theoretically get
zero signal.
Dale W4OP



Hey Dale, thanks for jumping in.

Well, get the calculator out. The two freqs of interest to me are
9335 KHz
and 11710 KHz, so I am going to work with something between those
two
numbers (10 MHz). If I am correct, 10 Mhz has a wavelength of 30
meters,
which works out to about 98 feet. And I am working with 200 feet.
(Maybe I
should call this a long-wire antenna?) Question for you: what is an
end
null?

And yes, I simply connected the 300-ohm to the baluns to the coax,
to
another balun, and then a third that plugs into my external antenna
socket.
And I a definetly getting a signal. Whatcha think?

Are you using the 300 ohm balanced as a twin lead folded
dipole or as an equivalent of a longwire?? If you're using it
as a longwire and have hooked up a 300/75 balun to it,
Dale's right and it's effectively a long transmission line.

I'm with Ace on this, I don't understand the 2nd and 3rd baluns.

--Mike L.

I am using it as a longwire. What is a "transmission line" and how does
it
differ from a recieving antenna?

The second and third baluns are to allow me to plug it into my external
antenna connector. The first (attached to he coax) makes it possible to
carry the received signal to the second (with the mini-plug on it.) I am
using this with a small portable radio.

Dave


Dave,
Two too many baluns and the 300 ohm cable is not being used to it's
best advantage. Suggest the following:
1) use the 30 ohm cable to make a folded dipole, at each end connect
the two wire, then in the middle of the length cut the bottom wire and
strip some insulation from each lead.
2) Connect the balun to the two leads of the folded dipole.
3) Connect the 75 ohm coax to the balun, hook the shield to ground and
route into the house.
4) Get an "F" to 1/8 phone plug adapter, Radio Shack carries them.
Attach the 75 ohm cable to the adapter & plug into your radio.
5) Turn radio on and expect better performance than you now have.

You may wish to consider that a dipole is a resonant antenna and a 200
foot dipole is going to be resonant at a little over 2 MHz. Though to
be realistic, you should be more concerned about signal overload than
resonance. A consideration is to whack about 50 feet from each end of
the cable to give a 100 ft folded dipole.

I suspect you are using a stock 300/75 ohm balun as used for TV
antennas: these do not function as well at HF as they do at higher
frequencies and that could well be stealing some signal from you.
Suggest you read the following article
http://www.anarc.org/naswa/badx/ante...e_antenna.html which
describes how to wind a balun using stock 300/75 ohm transformer - the
wind ratio of 30/10 is for a 9:1 balun so you could use a ratio of
10/5 which would give a 4:1 balun.

Good Luck!
Howard

Thank you, Howard. Will check this out. Was afraid to use a folded dipole
because I understood it to be so directional. No?

Will check out that article. Thanks for the link. And yes, I am using
standard 300/75 ohm television baluns, which I figured would steal some
signal, but decided to try it first and see what I got. 50 or 60 feet of
four strand copper wire gave me so much signal I had plenty to waste. Not
with this rig though. Will definetely check out winding some more efficient
baluns.

Oh, and I didn't know anyone made a F connector to 1/8" mini-plug adapter.
Will look for that. Would indeed be much better.

Thanks again,

Dave