What ever happened to the good old (and simple) 2:1 unun which can be set up
to give BIP, TO, or BO. with 4x SPST (QST, Feb 1994, p43) or 3x SPDT
relays? In a contest I like to leave the lower on the Carib and use the
upper for the rest of the world except on the rare occasion that the "stack"
noticeably outperforms the top alone.In fact I would seriously consider not
even putting a rotator on the lower. I would keep the unun though so I could
cover two directions when just looking for Q's in a contest.
In my case the "stack" consists of a 7-60 Mhz LP at 100 ft and a TH-6DXX at
45 feet. Granted, it's not the best combination, but if you keep track of
the varied "phase center" in the LP it's not bad.
Gene / W2LU
----- Original Message -----
From: "David J. Sourdis - HK1A" <hk1kxa@hotmail.com>
To: <towertalk@contesting.com>
Sent: Monday, November 22, 2010 11:56 AM
Subject: Re: [TowerTalk] STACKED 40 METER BEAMS MATCH
>
> Not as elegant nor as good like the ones exposed before but this is a poor
> man's, or emergency, stack match.
> Needed:
>
> Two antenna selector switches with two antenna ports
> One antenna switch with three antenna ports.
> One antenna tuner with bypass switch or a 2:1 unun or a fixed matching
> network that brings the 25 ohms to 50 ohms or 37 to 75 ohms if needed or a
> Q-line transformer
> Equal lenght lines come from the antennas and each line arrives to the
> input (common) ports of each the two-antenna port selectors.
> Then connect from, say, antenna port #1 of each of the two-anntenna
> switches, coax jumpers of equal lenghts that will go to each of the sides
> a "T" connector. The third or common port of the "T" junction connects
> with the middle position of the three-antenna selector switch. (Could be
> logical to connect to position number one, so when BOP is wanted, all
> selectors go to #1 position and the matcher in line, but it may be worth
> to check the simmetry and the paths of the selectors for phasing's sake.
> Better keep simmetry and color-code the positions)
> The remaining two ports of the three-antenna selector connect with equal
> lenghts of coax to the antenna ports #2 of each of the two-antenna
> selector. I.E.: Position A of the three port switch goes to the selector
> of the upper antenna. Pos C goes to the lower antenna selector and B in
> the middle is left for "Both"
> The input of the three-antenna selector goes to an antenna tuner with
> bypass capability. OR: Instead of the matcher, a 2:1 unun or a fixed
> network matching device or a quarter wave transformer line of the proper
> impedance (SQUARE ROOT OF 25 times 50) can be inserted between the common
> of the "T" junction and the port B of the three position switch. NOTE: You
> can insert the matcher here too, specially if it is one of the
> always-on-line-tune.
> For BIP : Select the middle position (B) of the three-port switch and
> select port #1 on each of the two-port switches. The matcher must be
> in-line to take care of the 25 to 50 ohm transition.
> Upper: The three-port switch selects the position that goes to the port #2
> of the two-port selector linked to the upper antenna. And, of course,
> select port #2 on that switch! Select the bypass in the matcher if used.
> Lower: Same as upper with the corresponding two port selector and the
> corresponding port at the three-port switch. Select the bypass in the
> matcher if used.When selecting a single antenna, the other two-port switch
> can be left in any position.
> WARNING!!!!!: It is very easy to get the wrong switching and pour all your
> power in to a dead end! That is a no-no, specially if your amp has no
> protection for that mishap. Better if done with coax relays or in line
> relays with foolproof selection, but to do this I would rather get or
> clone a stack match.This is an emergency solution. Positions can be color
> coded, one color mark near the right selectors position's for each of the
> antenna combinations, . Not the best choice for a long term usage of after
> 40 hours of contesting on a Sunday's afternoon. But it can do the trick
> while in a hurry.
> Some antenna tuners are easy to modify to form part of a better version of
> this bad idea :o)
> BTW: There was an interesting article about phasing with quarterwave lines
> combinations, I think it was written by K1EA for The DX Magazine around
> 1990. If anybody here knows the issue number I would appreciate to know. I
> have looked for this article in my colection with no success.
> 73
>
> David
> HK1A
> EC5KXA
> ex-HK1KXA
>
>
>
>
>
>
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