Balanced, swinging-link, dual-differential output tuners get rid of all the
problems. Build one. I did.
Go to the Cebik site.
If I can do it, anyone can.
73, Barrie, W7ALW
----- Original Message -----
From: "Jim candela" <[EMAIL PROTECTED]>
To: "Discussion of AM Radio" <amradio@mailman.qth.net>
Sent: Wednesday, April 19, 2006 7:33 PM
Subject: RE: RE: [AMRadio] Baluns for Zepp Antenna
Don,
You are of course correct about having a balanced tuner with split
stator
capacitor, center tapped inductor, swinging link, and series capacitor
with
the link, and other variations that have been around since radio's were
powered by steam. You leave out one important thing though that gets
picked
up by those who market tuners, and that is for every dollar spent on a
commercial amplifier, you need to spend half of that for a tuner suitable
for the job. There are tuners out there for more than a thousand bucks
that
still put the balun on the load side of the tuner. This does not have to
be,
and one solution dreamed up by folks wanting higher profit margins, is to
take a flawed design, and keep scaling it up until it works. This is kind
of
like building a 10KW tuner for a 1 KW job.
Maybe I am exaggerating a little, but not really that much. There are
tuners that put the balun on the input side of the tuner where when the
conjugate match is obtained, the balun only sees a resistive load at 50
ohms. These can use a conventional "universal transmatch" design with the
ground return floating (common to one side of balanced input, and one side
of the balanced output). I made a tuner like this, and used it for years.
It
worked great on 160-20 meters, but the compromise design starts to show
imbalance above 20 meters. I am pretty sure MFJ, and a few others do have
a
few tuners designed this way.
It is also refreshing to see MFJ marketing a line of tuners that are
somewhat similar to a Viking Matchbox.
I still think that those kilo-buck + tuners with a big balun on the output
are often used in ways that are not very efficient when the load is highly
reactive, and these will act exactly like Ron described below.
Regards,
Jim Candela
WD5JKO
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of [EMAIL PROTECTED]
Sent: Wednesday, April 19, 2006 11:54 AM
To: Discussion of AM Radio; amradio@mailman.qth.net
Subject: Re: RE: [AMRadio] Baluns for Zepp Antenna
Thanks Don
You make a good point everyone should consider. I have noticed a
teeker-totter effect with Toroids and un blanaced reactive feeders like
450
ohm ladder line. Get the SWR nulled out and in one minute it starts to
climb
again as a toroid saturates, null it out again and it happens again.
Your tuner suggestion is obviously the best but a few of us like to see if
we can noodle it out with home brew stuff.
Thanks again for your comments
Ron
From: "Donald Chester" <[EMAIL PROTECTED]>
Date: 2006/04/19 Wed PM 12:43:25 EDT
To: amradio@mailman.qth.net
Subject: RE: [AMRadio] Baluns for Zepp Antenna
From: <[EMAIL PROTECTED]>
Simple Coax Balun
www.southgatearc.org/techtips/coax_balun.htm
Toroid Balun
www.rason.org/Projects/balun/balun.htm
Romex and PVC under $3.00 Balun
www.bloomington.in.us/~wh2t/balun.html
All those baluns operate on the assumption that the balanced load is
primarily resistive. If the load is highly reactive, as is often the case
with open wire resonant feeders, the balun may not function properly,
especially the toroidal types at high power.
I still prefer an honest-to-god balanced tuner, with split stator
capacitor
and symmetrical balanced coil.
Don k4kyv
______________________________________________________________
AMRadio mailing list
Home: http://mailman.qth.net/mailman/listinfo/amradio
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:AMRadio@mailman.qth.net
AMfone Website: http://www.amfone.net
AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
Ron Weaver - W6OM
Web Site: www.qsl.net/w6om
______________________________________________________________
AMRadio mailing list
Home: http://mailman.qth.net/mailman/listinfo/amradio
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:AMRadio@mailman.qth.net
AMfone Website: http://www.amfone.net
AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.385 / Virus Database: 268.4.4/318 - Release Date: 4/18/2006
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.385 / Virus Database: 268.4.4/318 - Release Date: 4/18/2006
______________________________________________________________
AMRadio mailing list
Home: http://mailman.qth.net/mailman/listinfo/amradio
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:AMRadio@mailman.qth.net
AMfone Website: http://www.amfone.net
AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
