gregz wrote:
Jerry Stuckle wrote:
On 1/7/2014 2:29 AM, gregz wrote:
Jeff Liebermann wrote:
On Mon, 06 Jan 2014 23:23:56 -0500, Jerry Stuckle
wrote:

On 1/6/2014 11:04 PM, Jeff Liebermann wrote:
On Tue, 7 Jan 2014 03:19:54 +0000 (UTC), gregz
wrote:

Jerry Stuckle wrote:
On 1/6/2014 1:28 AM, gregz wrote:
wrote:
"only 3 db", but that's twice the signal. I have mine stacked 12 feet,
but I believe Winegard says either 8 or 10 feet. Mine work swell. +:^] I
got mine just after they were discontinued in 2005/6. Had to email a
number of suppliers until I found the second one. I bet there are some
still in storage somewhere, email different places that sell Winegard,
you may still find one.
John K9RZZ

Twice the signal means twice the voltage, for me.
Greg

Twice the voltage is a 6 db gain. Twice the power is a 3db gain.

Exactly. If I got 1 microvolt, 2 microvolts will be twice the signal.
Greg

Sorta. If you got 1 microvolt, 2 microvolts will be twice the signal
voltage but only 1.414 times the signal power. That's why we have
units of measure to avoid such ambiguities. Just to be difficult,
working with antennas, the "signal" is the field strength measured in
dBuV/M. If you define what you're measuring and specify your units of
measure, you wouldn't be having such problems.

You've got it backwards, Jeff. Twice the voltage is 4 times the power.
1.414 times the voltage would be twice the power.

Very embarrassing. Temporary loss of IQ from working on my broken car
with a cold or flu this afternoon. It should be:
If you got 1 microvolt, 2 microvolts will be twice the signal
voltage but 4 times the signal power.

Thanks for the correction (grumble)... Maybe if I go to sleep early,
when I wake up tomorrow, this didn't happen.


I have not really been specifying units. I was just going over the
situation in my mind, and I straightened out in rf terms.

I got this going out terminology. IF, in audio, I got two speakers
transmitting equal energy, with two amps or channels, and I receive that
totally in phase, I got twice the signal or 6 dB power increase. I've
measured it. It's true. Same thing would happen with two antennas with two
transmitters. Two antennas, one transmitter, with one splitter would only
give 3 dB power increase at the receiver. I'm just thinking out loud. I had
to ease my mind. I think I'm ok now. Almost bedtime.

Greg


No, two in-phase speakers provide 3db increase, not 6db.

If you could double the signal and get 4x the power you could make
gazillions! Of course, you'd be creating energy out of nothing, but who
cares about the laws of physics?

The reason big speaker systems work in large places is efficiency gain
using multiple arrays, must be in phase. As I was saying, it's a known
fact, which I have measured. You can actually get near 10 dB gain using
several speakers. It's why horn loudspeakers have gain, better impedance
matching to air.

I once believed two in phase speakers provided 3 dB increase also. I then
read a speaker project by the now famous diAppolito configuration designer
in Speaker Builder magazine 80's ?. I can try to find a reference.

Greg

I found a reference by a well known author designer. The other tricky added
to the equation, is using one channel amplifier, and getting twice the
power with lowered Z. It still works for two separate amps. DiAppolito and
linkwitz, two biggies of speaker systems...

http://www.linkwitzlab.com/faq.htm#Q21

Greg