Alex
Us loop users here have been seeing the ground loss contributing about 0.3 ohm
(plus or minus .1 ohm depending on soil type and moisture content). In my case,
using an RG-11 loop conductor, the Rac of the loop is about .28 ohm for a total
resistance of about .58 ohm. If I were to change to a lossless conductor I
would
expect to only pick up about 4.6 dB.
Using my RG-11 as a reference, and .3 ohm ground loss, the performance of other
conductors should be as follows:
#12 -3.94 dB
#8 -2.35 dB
RG-11 (.325") 0
1/2" Cu tubing (.630") +1.23 dB
7/8" Heliax (~.925") +1.68 dB
Of course, lower ground loss (which I'm not blessed with) would make a somewhat
bigger difference.
Bill Ashlock's measurements have shown that the loop needs to be at least 5 - 6
feet off the ground. He's currently running a 1/2" copper tubing loop. If you're
interested, I'm sure he can forward volumes of data on these loops to you!
Jay Rusgrove, W1VD
"Alexander S. Yurkov" wrote:
Hi, Mike and Group.
On Thu, 14 Nov 2002, WE0H wrote:
> Hi Alex,
> We use vertical loops here. The trees don't affect them much. I can walk up
> to my loop and watch the RF current meter and not see any change until I get
> closer than 1 foot from the loop and then it drops a little. They work nice
> with all my trees in my yard.
It seems to me the problem loop vs vertical requre to solve very worth
problem pointed as folows. Certanly if one increase diameter of wire (may
be long flat band?) effectivity of a loop should be increased also. But if
wire diameter is very (!!!) large then enviroment (ground also) losses
became significal. If the coper resistance is less then enviroment loss
resistance it is no reason to increase wire diameter more. So enviroment
loss give a physical limit of loop effectivity. But what is this physical
limit? How much one should increase wire diameter? Enviroment loss is
not large but what it's value? It is very worth...
It seems distance of loop from the ground and loop dimensions should
affect very much to ground loss of a loop and then to required wire
diameter. Quantative study of this mater should be very usefull.
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
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