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Old December 19th 06, 09:32 PM posted to rec.radio.shortwave
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Default Getting ready to hook up a random and hav a question...

ooops,I haden't noticed you said the picture was taken in November,2001.
cuhulin

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Old December 20th 06, 12:13 AM posted to rec.radio.shortwave
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bpnjensen wrote:

dxAce wrote:

dxAce, Don't you have your antenna feeds connect to your wires a fair
distance from your house anyway? (I say this based on a cursory look at
the photos on your website...)


Yes, I'd say they're about 50-75 feet out back.


That's a good safe distance, I'd say.

Thus, in your circumstances, it may not be all that critical...in which
case I might not have stumbled across it either. If I could connect
farther from my house, I would - but in my case, it would put the
lead-in adjacent to one of two sets of electrical lines that partially
rim my yard. Living in the city can bite sometimes (to put it mildly).


Sorry, I still don't get it. The antenna is where the antenna is!

Now I could imagine that it would make a difference ( though slight ) if for example
I were to feed my 200' wire at the far end ( east end ) in which case it might just
receive just a bit better to the west depending upon the frequency.

By the way, my matching transformers are grounded at the feedpoint with about 9' of
ground wire ( horrors! ).


This may be the key right here. Getting the *groundpoint* well away
from the house keeps it out of the hornet's nest of RF that swarms
around most homes, and prevents it from becoming a significant conduit
(at least that's the theory). For most people, this will mean feeding
it at the far end of the antenna. In my own case, I have RF sources at
all points of my smallish yard, so it wouldn't make a lot of difference
where I feed and ground the thing. A windom-style antenna with a
central feed and ground point might help, but even then I'd only be
about 15-20 feet horizontally from any major RF source at best.

I don't think the groundwire length makes that much diff, as long as
it's well away from RFI.

http://www.iserv.net/~n8kdv/pics.htm

Antenna pic is looking west, at the end of the then 100' wire, now extended to 200'.
Pic was taken in Nov. 2001.


Nice setup - nothing too high, over open ground so it's easy to work
on. Even though it's sort of low (maybe ten feet?),


Supports are 9' high.

you get the
probable advantage of relatively quiet RF environment - well, I guess I
can dream!


Yes, relatively quiet... noise here is typically S2 or less. I work at it from time to
time though with our local BPW.

dxAce
Michigan
USA



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Old December 20th 06, 12:15 AM posted to rec.radio.shortwave
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Default Getting ready to hook up a random and hav a question...

wrote:
HFguy wrote:

wrote:


I have read that the best way, quiestest, to hook into a random wire is
at the far end, attach a balun, go thru a ground block attached to a
ground rod, bury the coax as it runs to the house, go thru another
ground block which is connected to another ground rod then into the
house.

I have 2 options here, one is the above (about 150 feet of coax), the
other is to hook into the random at the near end, thru a balun, feed
into the attic to a ground block that has about 40 feet of ground wire
attached coming from the ground rod, then to the receiver.

Which is the better? Is there enough difference to warrant the extra
expense of the 1st option, more coax, over the 2nd?


The first method is better because you can use a short ground wire
between the balun and the ground rod to make an effective RF ground. The
balun should be located close to the ground (earth) so the grounding
wire to the rod can be kept to a minimum length (no more than 2-feet).
The ground wire in the second method is much too long to be an effective
RF ground. It could act more like an antenna for picking up common mode
noise.



I am still having a problem getting my head around the short ground
connection to the rod.

What is the difference between say 40 ft. of ground wire to the ground
block versas the outer coax jacket going 40 ft after the ground block
that is 2 feet from the rod.

Would either not act as an antenna for picking up common mode noise?

Brian


When the coax (shield) is grounded near the balun which is located close
to the ground rod at the bottom of the random wire's vertical section of
wire, a common mode signal picked up on the coax shield going to the
house, can not feed back into the center conductor of the coax through
the antenna connection at the balun. When the coax ground is *only* on
the other end of the coax, the shield can pick up noise and feed it into
the center conductor at the antenna end where it becomes a differential
mode signal that the radio can receive.

http://www.hard-core-dx.com/nordicdx...eed/feed1.html
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