[Boatanchors] WTB - Antenna Tuner. . . . .

[JAMES BRANNIGAN]

I refer you to an April 2004 QST article by Paul N1II and follow up in 
October 2005 (technical Correspondance)

Jim


On Thu, Dec 10, 2009 at 1:47 PM, The Pollacks wrote:

> I defer to Bob's interesting analysis, and it's one that I was unaware 
> of.
> It may be of interest to the original poster if I comment on my 
> personal
> experiences of 40+ years of running balanced line with a variety of 
> tuners.
>
> I have used all of the following:  Homebrew link type tuner (butterfly 
> dual
> cap), Johnson Matchbox, Murch transmatch with home wound balun, Heath 
> 2040,
> various MFJ and TenTec tuners, and probably others.  Using low power ( 
> output), they all performed well with no RF in shack or TVI problems. 
> I
> don't disagree that the MFJ types with baluns have greater loss, but 
> don't
> know if they're significant at this power level.  Never experienced 
> SWR
> drift, even on AM.
>
> Where I did run into problems with RF in shack is when I acquired a 
> linear,
> in this case a 922L.  The RF problems were insurmountable with the 
> tuners I
> had, and I eventually replaced the balanced antenna, with its many
> advantages, with a G5RV, which works quite well.
>
> I don't know if I would have had more success with high power and a 
> link
> type tuner, but my home brew unit, long gone, would not have handled 
> that
> much power.  I do have some big caps, so maybe I'll get inspired to 
> build
> another one and try it!
>
> Since the poster indicated that cost was a consideration, and power 
> was
> moderate, I think one of the coax type tuners would work adequately,
> although not ideally, and worth trying considering the power and cost
> limitations.
>
> I am always impressed by the knowledge and generosity of those on this 
> list!
>
> Thanks
> Ron K2RP
>
> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net
> [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Rob Atkinson
> Sent: Thursday, December 10, 2009 4:27 AM
> To: Boat Anchors List
> Subject: Re: [Boatanchors] WTB - Antenna Tuner. . . . .
>
> the vast majority of those commercial tuners that claim to handle
> balanced line really don't, or rather don't do it properly or very
> well.  I have worked hams who have given up on balanced line, or have
> all kinds of RF problems only to find they are using some coax tuner
> with a balun somewhere between the tuner and the balanced line, either
> at the tuner or outside somewhere.
>
> To properly tune balanced line with no issues (common mode, RF in the
> shack etc. problems) you must tune the line with a link coupled
> balanced tuner that floats the balanced line above ground.  The
> Johnson matchboxes do this.  short of homebrewing (which is fine thing
> to do) nothing else out there on the market does this.   you can buy a
> twin coil balanced tuner from Palstar but it is not link coupled and
> will therefore pass common mode RF.  There is information on-line on
> how to homebrew a link coupled balanced tuner.   Don't fall into the
> trap of trying to get a coax tuner to do everything.  Even if it seem
> to work you'll have greater loss in the balun, and at higher power
> levels, heating during long transmissions.  This will be noticeable in
> vswr changing.
>
> 73
>
> Rob
> K5UJ
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html