On Sun, 23 Apr 2006 09:43:00 -0400, Buck wrote:

On Sun, 23 Apr 2006 06:17:35 -0700, Wes Stewart
wrote:

On Sun, 23 Apr 2006 08:08:46 -0400, Buck wrote:

[snip]

In other words, a 6 element beam of some given element spacing has a
(number from the air) gain of 6db. A twelve element version with
twice the boom length will be in the ballpark of 12 db gain.

You want to rethink this? I've always figured 2.5 - 2.6 dB increase
for each doubling of the boom length (or array size) for practical
purposes.

That's pretty close. I don't know the exact numbers and my numbers
are just ballpark. yours may very well be more accurate. I haven't
tried modeling for accuracy, just what I remember reading about
antennas. If you build a 2 lambda antenna and a 4 lambda antenna, they
the 4 will have about the same gain as a pair of 2 lambda antennas
phased, which is about, but not necessarily exactly double the gain of
one antenna.

give or take 1/2 db, what is that to signal strength anyway?

Quite a bit on an EME path.


BTW, going from 6 dB to 12 dB isn't a two times increase.

Owen Duffy wrote:


Ian, I have plotted the data in VE7BQH's table, along with a
polynomial (1) curve fit and also the function given by K0TAR for
comparison.

The plot is at http://www.vk1od.net/lost/VE7BQHYagiGain.htm .

It would be dangerous to assume the fit function applies much below
the limits plotted.

Owen
--

Owen,

I will try and dig out the original spreadsheet I used. It will be
problematic to use, since it's not compatible with anything Microsoft,
and there's nothing alse anymore.

tom
K0TAR

On Sun, 23 Apr 2006 06:17:35 -0700, Wes Stewart
wrote:

On Sun, 23 Apr 2006 08:08:46 -0400, Buck wrote:

[snip]

In other words, a 6 element beam of some given element spacing has a
(number from the air) gain of 6db. A twelve element version with
twice the boom length will be in the ballpark of 12 db gain.

You want to rethink this? I've always figured 2.5 - 2.6 dB increase
for each doubling of the boom length (or array size) for practical
purposes.

Wes, that is pretty consistent with the fit to the VE7BQH collation
which gives me 2.64dB for doubling of the boom length (for a long yagi
( 2 - 8 wavelengths) with sufficient elements). Alternatively, 1dB
increase for each 30% increase in boom length.

Owen
--

On Sun, 23 Apr 2006 08:31:10 -0700, Wes Stewart
wrote:

On Sun, 23 Apr 2006 09:43:00 -0400, Buck wrote:

On Sun, 23 Apr 2006 06:17:35 -0700, Wes Stewart
wrote:

On Sun, 23 Apr 2006 08:08:46 -0400, Buck wrote:

[snip]

In other words, a 6 element beam of some given element spacing has a
(number from the air) gain of 6db. A twelve element version with
twice the boom length will be in the ballpark of 12 db gain.

You want to rethink this? I've always figured 2.5 - 2.6 dB increase
for each doubling of the boom length (or array size) for practical
purposes.

That's pretty close. I don't know the exact numbers and my numbers
are just ballpark. yours may very well be more accurate. I haven't
tried modeling for accuracy, just what I remember reading about
antennas. If you build a 2 lambda antenna and a 4 lambda antenna, they
the 4 will have about the same gain as a pair of 2 lambda antennas
phased, which is about, but not necessarily exactly double the gain of
one antenna.

give or take 1/2 db, what is that to signal strength anyway?

Quite a bit on an EME path.


BTW, going from 6 dB to 12 dB isn't a two times increase.


you are right. A 6 element antenna to a twelve element antenna or
double boom size is about 3 db gain, double power. Sorry.
--
73 for now
Buck
N4PGW