"Bruce" wrote in message
...
...

Now, if the receiver IS well shielded enough, if you can insert a
switchable attenuator in the coax, you can reduce the signal strength
significantly...and, FM receivers get very non-linear below about 20dB
quieting, they quiet faster than the actual input. In otherwords, you
could get 3-4 dB quieting change for 1dB of singal change. What this will
do is make you antenna pattern SEEM narrower.... -Bruce

Two things here.

The "offset attenuator" gets you the equivalent to a shielded receiver
without the shielding and very simple construction.

There are designs on the web for "quieting meters" and I have even seen one
design where the receiver s-meter signal was summed with the quieting signal
resulting in one very large dynamic range signal strength indicator.
73, Steve, K,9.D;C'I

"Jim" wrote in message
...
True, I haven't thought of everything, but I have done this:

... My
transmitter antennas are horizontal trailing insulated wire.

I think talk about polarization is relatively meaningless with this.



I have a
fairly long cable so am able to hold it at arm's length from my body. It
does have a very good null and I use both front and null in my RDFing.

With a good rear nul, your presence in the rear should give minimal
effect.


My radio might not be the best as far as sheilding.....it is plastic
cased.
So I made a fiderglass holster for it with aluminum screen embedded in the
fiberglass resin all the way around...kind of like a Faraday cage. I
don't
really know how this helps. It is not grounded,

Ground is sort of meaningless at this point. Look up the "Offset
Attenuator".

73, Steve, K,9.D;C'I

"Bob Bob" wrote in message
...
Hi again Jim

I'd suspect you need an attenuator of maybe 60dB in 6dB steps! I cant
see the 10dB variable one as being useful. Of course at 50dB or more
coax leakage might be an issue!


When you see the numbers for the Offset attenuator you won't believe them,
though true.



Okay on the screening. Well as I mentioned the test is to plug a 50 ohm
load in the antenna socket and see if it responds at a distance of say
5ft. If it doesnt then dont worry about screening. If it does it depends
on how much and then whether things like coax leakage have to be
factored in.

Good test.

73, Steve, K,9.D;C'I

Sorry I'm too tired to look up a better example, but
http://members.aol.com/BmgEngInc/Adcock.html
is still pretty good. It's essentially about like the
"phased verticals" the other fellow mentioned, in that
they both result in a "cardioid" pattern, i.e. a sharp
*notch* in the pattern, broadside to the array in this
case.

Thanks, Sluggo, but this is partly an oops!

The BMG pages are a very good resource (as are many RDF sites).

OOPS! The Adcock is just like a loop -- two nulls off both broadside faces.
The version that looks similar (previously mentioned) where you have two
vertical dipoles spaced 1/4 wave and a 3/4 wave connecting cross-feed line
gives the cardioid -- one null.

"Sluggo" wrote in message
news:h3dmk1p0od57ig3q5qpm1qgq5gkdtdq3lm


73, Steve, K,9.D;C'I

On Wed, 12 Oct 2005 15:37:17 -0500, "Steve Nosko"
wrote:


OOPS! The Adcock is just like a loop -- two nulls off both broadside faces.
The version that looks similar (previously mentioned) where you have two
vertical dipoles spaced 1/4 wave and a 3/4 wave connecting cross-feed line
gives the cardioid -- one null.

"Sluggo" wrote in message
news:h3dmk1p0od57ig3q5qpm1qgq5gkdtdq3lm


73, Steve, K,9.D;C'I

Thanks for the correction; I'm only in my 40's but I've been
hamming a long time, and the years are starting to blur...
Now that I think back on my "real world" experience, the boom
on what I thought was an Adcock could well have been a
wavelength at 2M, tho, as I said, it's kinda fuzzy now... so
it may be that the elements were NOT fed at the center.
Oh well, either way, a good notch is going to beat the
best yagi.

Man, those must be some tasty turtles, to go to all this
trouble to track 'em down...

73, tnx agn..

Sluggo

On Wed, 12 Oct 2005 15:11:29 -0500, "Steve Nosko"
wrote:


wrote in message
.. .
On Tue, 11 Oct 2005 01:03:34 -0400, "Jim" wrote:

...
You already got two good suggestions from others. Here's a third.
Build a MOXON square, less gain than yagi but if built right the MOXON
has a very distinct readward null, you exploit the null. Another
small advantage is it's smaller than a 2 element yagi for the same
band.

Allison
Look up the "Tape Measure Yagi" It is designed to have a null off the back,
but you'll have to adjust the center freq.
73, Steve, K,9.D.C'I

I've built both. The Tape measure yagi is not nearly as good off the
back and a bit larger. Moxon well done is an easy 35+ db null off
the back and sharper.



Allison

"Sluggo" wrote in message
...
...

Thanks for the correction; I'm only in my 40's but I've been
hamming a long time, and the years are starting to blur......
Sluggo


Damn young whipper snappers... (;-)

73, Steve, K,9.D;C'I