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G8MNY > TECH 24.01.05 20:39l 48 Lines 1468 Bytes #999 (0) @ WW
BID : 30049_GB7CIP
Read: GUEST OE7FMI
Subj: Coupler for 2 Tx into 1 ant?
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Sent: 050124/1857Z @:GB7CIP.#32.GBR.EU #:30049 [Caterham] $:30049_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
Hi & thanks for reading. I am looking for a design for coupling 2 low power VHF
Tx (1W band1 for 2 SAB mono links) close in frequency into 1 aerial. There are
no Rx involved at the Tx sites so absolute nulling is not required, but the
problem is that each Tx must not see any significant power from the other Tx as
PA mixing will occur giving normal mix products.
I computer modelled the normal low loss RF TV combiner & I was disgusted at the
results.
SOURCE 1 ÄÄÂÄÄÄÄ¿ 1:1
75ê ³ |)
300ê |)ÄÄÄ COMBINED 75ê
³ |) LOAD
SOURCE 2 ÄÄÁÄÄÄÄÙ
75ê
Although this nulled OK as signals from SOURCE 1 were cancelled at SOURCE 2 the
impedance seen by source 1 was 150ê & the O/P was 6dB down on the SOURCE 1 port
level, although this would be less in practice as the level will jump up with
less load.
So I have come up with a theoretical 2 ferrite transformer design, that may be
practical. And with suitable trimmer Cs I expect I can get a good mix product
null on a spectrum analyser.
Cross over
TX1 ÄÄÄÂÄÄÄÄ¿ ÚÄÄÄÄÂÄÄÄÄ TX2
50ê ³ X ³ 50ê
³ ÚÄÄÙ ÀÄÄ¿ ³
)|( )|(
1:1 )|( )|( 1:1
)|(_______)|(
³ ³ ³
³ 50ê ³
³ AERIAL ³
ÄÄÄÁÄÄÄÄÄÁÄÄÄÄÄÁÄÄÄ
There are coax designs that may be better, I wait for replies on designs.
Why Don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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