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Re: Sun noise measurement of 2.4G



Most combiners are specified by the loss of one port. Each port of a 4 way
combiner would have 6dB of loss if it was ideal (10*log .25). A 7.5 dB loss
combiner has an extra 1.5 dB above the 6 dB split loss. Assuming this is the
case, you can subtract 1.5 dB from the gain of one antenna and add 6 dB
combining gain for 4 antennas. So if the antenna has 15.5 dB gain and you
put 4 of then in an array you would get 20 dB gain instead of the 21.5 dB
you would have gotten if you had a good spplitter.
On an interesting note, it is possible to get more and not less gain than
the theoretical maximum when phasing antennas. If the radiation pattern is
improved in phasing to null unwanted lobes the gain will increase.

Pieter
N4IP


ok, but where's the gain?

you only see 1.5 dB of the 7.5 dB shown as loss because you still have the
6dB of improvement by adding 4 antennas. The four antennas and combiner give
you an additional 4.5 dB of gain.



----- Original Message -----
From: "Jens H. Jensen" <topcat@hardware.dk>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, April 09, 2001 4:50 PM
Subject: Re: [amsat-bb] Sun noise measurement of 2.4G


> At 23:44 28-03-2001, you wrote:
> >Like others, I plan to be on the rig Sunday to see what gives with the
> >signal now. By the way, I am using a 4:1 combiner (about 7.5 dB loss) to
> >combine 4 antennas for the VR-5000. Even so, I still have PLENTY of
signal
> >to work with.
>
> Maybe this is an unneeded comment, but....
>
> Stacking two antennas is supposed to give a maximum of 3dB
> Stacking four antennas is supposed to give a maximum of 6dB, theoretic max
> which is never achieved.
> But the combiner, you say, has 7.5dB loss.
>
> Where's the gain......?
>
> 73 de OZ1LRG
>
> ----
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