OK Bob, I agree that your suggested dual-inductor box will match the
ballanced line, but what about the "filter" part? The Link-coupled (like
the Johnson and the Annecke) and the Z-match are true bandpass filters and
aid the receiver's front-end. How does your suggested matchbox perform
here? I suppose as a ham I should know the answer to that question but I
must admit I don't.
To construction, where do you find components to gang-tune the roller
inductors?
I've built several tuners in my career, but most people want to buy them.
My enquiry here is not for my personal use but for those many who are always
asking me where to get a good symmetrical tuner like my BIG Annecke. The
answer "build it yourself" sounds nice, but at the end of the day, most
people either can not or don't want to build it.
Now some of the American companies are advertising "Ballanced Tuners". My
question is, are they any good. So far nobody has even been able to tell me
what type of circuit the things run. I can speculate, but I will never make
a recomendation to anyone based on speculation.
Personally, I think that if I were going to build another parallel tuner,
before I use ganged roller inductors, I'd build the single-coil Z-Match
described by Lloyd Butler, VK5BR, on his web page (
http://www4.tpgi.com.au/users/ldbutler/SingleCoilZMatch.htm ). It seems
easier to find parts for, cheaper, and it is indeed a bandpass filter.
It just seems odd that nobody ever thought of copying the old Johnson Viking
Matchbox, or better yet, the Annecke. With 9 shortwave bands, the need for
an all-band solution is greater today than it was in the 60's.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Robert & Linda McGraw
K4TAX
Sent: Saturday, April 17, 2004 6:04 AM
To: tentec@contesting.com
Subject: Re: [TenTec] 450 Ohm feedline tuners
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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