[SOC] Matching G5RV
Hank Kohl K8DD
[email protected]
Mon, 18 Aug 2003 15:57:51 -0400
naw .... i was really SOC'ing it .....
condoms with a Brit pronounciation!
At 8/18/2003 02:58 PM -0400, you wrote:
ur thinking of
carborundum....
----- Original Message -----
From: {quot}Hank Kohl K8DD{quot} <[email protected]>
To: <[email protected]>; <[email protected]>;
{quot}Paul Bartlett{quot}
<[email protected]>
Sent: Monday, August 18, 2003 2:12 PM
Subject: Re: [SOC] Matching G5RV
>
> At 8/18/2003 05:51 PM +0100, Paul Bartlett wrote:
>
>
> Hi All,
>
>
> I have a conundrum to solve.
>
> Hmmm.... Trojan or Ramses?
>
>
>
>
> I have a K2, a full size G5RV
> (104') and an ex-miltary ATU (Redifon type
>
> A.C.U.9) kindly loaned to me by Paul MW3PWA.
>
>
> The ladder-line phasing section of the G5RV terminates in a
50R
> co-ax
>
> connector and is immediately followed by a 10 turn co-ax
'choke
> balun'
>
> (about 6{quot} in diameter). There's then a 30' run of co-ax to
the
> shack.
>
> Personally .... I don't see a need for the choke balun, but tis
my
> personal
>
> opinion ..... and opinions are like noses ..... everyone has one
....
> some smell
>
> ..... some don't.
>
>
>
>
> The ATU takes an RF input via a BNC
> connector which runs to the K2.
>
> Disassembling the ATU I see that the hot input passes to a bank
of
>
> switchable capacitors down to ground and thence to variable
series
> inductor
>
> (rather nicely made).
>
>
> There are three output terminals: Earth; the other end of the
inductor;
> and
>
> a third terminal connected to the second via a high-voltage cap
which
> value
>
> I can't determine.
>
> If I understand the description ....
>
>
> input
>
----------|--------|--------|--------UUUUUUUUUUUUU--------|--------
> output
>
>
> |
> |
> |
> |
>
>
> --- ---
> ---
> ---
>
>
> --- ---
> ---
> ---
>
>
> |
> |
> |
> |
>
>
> |
>
-------|--------|---------------------------------------------|---------
> earth ground
>
>
> |
>
> Ground
>
>
> Looks like a pi network .... The input caps are switchable in or out
....
> the output cap is switchable in or out
>
> Looks like a pi network .... If the only {quot}tuning
that
> can be done is the switchable input capacitors, I'd think it may
be
> usable. If one of the input caps and the output cap are
variable,
> I'd think it would be real usable.
>
>
>
>
>
> Questions:
>
>
> Is the ATU sensibly usable at all with my mix of antenna and feed?
If
> so,
>
> how?
>
> Here's what I would do ....
>
> Get a cup of tea.
>
> Hook the input up to the K2.
> Hook the output to the coax feeding the G5RV.
> Sit back, drink some tea, look at the set up and confirm that it
is
> correct.
>
> Listen on, let's say, 20M .... CW of course!
>
> Vary the inductor until you get maximum noise or signal.
>
> Switch the capacitors in and out until you get maximum noise.
>
> Vary the inductor some more for maximum noise or signal.
>
> Write down, while sipping on tea, which capacitors are switched in,
where
> the setting on the inductor is, and if the output capacitor is in
or
> out. And the S meter reading.
> At a watt or two, touch the tune button, or key the K2 with a
straight
> key and check the SWR.
>
> If it's not below 1.5 or so, vary the inductor to see if it goes up
or
> down .... adjust accordingly.
>
> Get another tea.
>
> Check if switching around with the input caps lowers the SWR.
>
>
> I think you see where this is going .....
>
>
>
>
> Do I need a further balun after the
> ATU to match the unbalanced feed?
>
> No .... but then I'm not a fan of baluns.
>
>
> Should I ground the ATU via it's
> EARTH terminal?
>
> Absolutely, unless it works better without a ground!
>
>
> 73 hank k8dd
> soc #69
>
>
> Any and all suggestions
> welcomed.
>
>
> Best,
>
>
> Paul M3CRQ :-)
>
>
>
>
> _______________________________________________
>
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>
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>
>
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>
> */ Hank Kohl
> K8DD [email protected]
> */ ARRL
> TS
>
http://www.qsl.net/k8dd
>
> */ MI-QRP - Vice Pres. QRP-ARCI
-
> Director
>
> */
>
> If God intended you to be on single sideband, he would have given
you
> only one nostril.
>
> - Steve, K2PTS (SK)
>
>
>
>
>
>
>
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*/ Hank Kohl
K8DD [email protected]
*/ ARRL
TS
http://www.qsl.net/k8dd
*/ MI-QRP - Vice Pres. QRP-ARCI -
Director
*/
If God intended you to be on single sideband, he would have given you
only one nostril.
- Steve, K2PTS (SK)
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