snip

10 or 12 db of forward gain means your recieved signal is about 10 to 16
times as strong as a dipole hanging in the air. If you interpret the
negative number as the amount the signal is down from the forward gain,
the numbers given (9 to 17db) would indicate reception off the back side
would be somewhere near a dipole in open space (1 db net) to -5db (about
1/3 of the signal of a dipole) pickup from the back. I have used aluminum
sheet (tested prior with aluminum foil) tied to the mesh to completely
block reception from the back (a near infinite front to back ratio) in an
extreme case where I had significant multipath reflections coming in from
the back. It really cleaned things up. In your case you may not need to
go to this rather severe step.

snip

Good luck!
--Rick AH7H

10 or 12db of forward gain goes NOT equal 10 "times" the received signal
strength.

"Bishoop" wrote in message
...
snip

10 or 12 db of forward gain means your recieved signal is about 10 to 16
times as strong as a dipole hanging in the air. If you interpret the
negative number as the amount the signal is down from the forward gain,
the numbers given (9 to 17db) would indicate reception off the back side
would be somewhere near a dipole in open space (1 db net) to -5db (about
1/3 of the signal of a dipole) pickup from the back. I have used
aluminum sheet (tested prior with aluminum foil) tied to the mesh to
completely block reception from the back (a near infinite front to back
ratio) in an extreme case where I had significant multipath reflections
coming in from the back. It really cleaned things up. In your case you
may not need to go to this rather severe step.

snip

Good luck!
--Rick AH7H

10 or 12db of forward gain goes NOT equal 10 "times" the received signal
strength.

Then what do you think it is equal to ?

In article t,
"Ralph Mowery" wrote:

"Bishoop" wrote in message
(snip)
10 or 12db of forward gain goes NOT equal 10 "times" the received signal
strength.

Then what do you think it is equal to ?


Well, 10dB of gain is a 10x increase in absolute signal, but 12dB of
gain would be about 16x the signal.

dB = 10 * log(S1/S2)
where S1 and S2 are the absolute strengths of two signals you're
finding the dB of difference between.

The regular absolute-value scale and logarithmic scale of dB "cross" at
the factor of 10; so 10dB = 10x, but that's the only place that's true
(at least, I think it is, off the top of my head).

-Kadin.

Bishoop wrote:
snip

10 or 12 db of forward gain means your recieved signal is about 10 to 16
times as strong as a dipole hanging in the air. If you interpret the
negative number as the amount the signal is down from the forward gain,
the numbers given (9 to 17db) would indicate reception off the back side
would be somewhere near a dipole in open space (1 db net) to -5db (about
1/3 of the signal of a dipole) pickup from the back. I have used aluminum
sheet (tested prior with aluminum foil) tied to the mesh to completely
block reception from the back (a near infinite front to back ratio) in an
extreme case where I had significant multipath reflections coming in from
the back. It really cleaned things up. In your case you may not need to
go to this rather severe step.


snip

Good luck!
--Rick AH7H


10 or 12db of forward gain goes NOT equal 10 "times" the received signal
strength.


OK, so it's semantics.
a 3 3db positive change is a doubling of "power", which I relate to
signal strength on reception, hence my use of the term above.
3db ix 2x power
6db is 4x power
9db is 8x power
10db is essentially 10x power.... (and a generally accepted
approximation).

Given the nebulous measurement methods used, stating that 10-12db of an
antenna gain is nearly the same isn't that far off, assuming the stated
10-12db is even remotely accurate to begin with....

--Rick AH7H