As to components, Tentec has a selection of nice roller inductors, and
variable caps. They also have nice enclosures.
As to circuit configurations, the L network does a good job in most all
applications and Z's, plus will have ONLY one set of values that will
provide a correct match and requires only 1 variable C.
For a balanced tuner, a choke balun used on the input made of a short
section or RG-213 and 14 of the FB-77-1024 beads along with two roller
inductors with a common drive and one variable C, switchable across the
output or the input, depending on Z required to match, is all that is
necessary.
73
Bob, K4TAX
----- Original Message -----
From: "NJ0IP" <Rick@dj0ip.de>
To: <tentec@contesting.com>
Sent: Saturday, April 17, 2004 9:49 AM
Subject: RE: [TenTec] 450 Ohm feedline tuners
> Thanks Suart. I suppose the double PI NET would be a good solution too.
> What I'm not interested in is a double "T" and certainly no single "T"
> because they do no harmonic filtering, in fact no filtering at all.
That's
> the beauty of the Link Coupled tuner. It's like a preselector in the
front
> end. From reading the description of the MFJ's I've seen so far, they all
> sounded like the "T" with just a balun. Perhaps the manufacturers should
> all be more honest in describing their equipment so that we can make
> intelligent purchase decisions.
>
> It's been a couple of months since I spent a lot of time studying MFJ's
site
> so I'll go have another look. I thought someone here might have such an
> animal and be able to tell us exactly what's inside.
>
> I have the circuits for the Johnson and the Annecke. The big problem (at
> least over here) is finding components and even a cabinet.
>
> I have lots of people asking me (all the time) what matchbox to buy for
> feeding openwire and I honestly don't feel confortable recommending
anything
> on the market today except (maybe) the Palstar which has the ganged roller
> inductors. I'd like to use one myself or speak with someone who owns one
> before I recommend it.
>
> 73
> Rick
>
>
>
> -----Original Message-----
> From: tentec-bounces@contesting.com
> [mailto:tentec-bounces@contesting.com]On Behalf Of Stuart Rohre
> Sent: Friday, April 16, 2004 6:48 PM
> To: tentec@contesting.com
> Subject: Re: [TenTec] 450 Ohm feedline tuners
>
>
> I believe there is a NEW MFJ tuner with an extra control on its front
panel.
> It is, a ganged double PI NET, and therefore true balanced tuner; ie there
> is a PI net for each side of the line.
> I just saw it in last months ads in ham magazines, or even the April ads.
> Don't have a model number at this site. Might check descriptions on MFJ
web
> site.
>
> As to link coupled tuners, do a web search on google for "Z match Tuner"
> and you should get a circuit or several. On the Bama.edu web site where
> there are files of manuals to download, you can get the circuits for the
> famous Johnson Match Box balanced tuners. The Johnson had a kind of link
> but it was tapped off the coil on the output side.
> -Stuart Rohre
> K5KVH
>
>
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>
>
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