Having never wound a balun before, pardon if this is an elementary
question, but...

I recently got a Murch 2000B antenna tuner off eBay. It's a commercial
version of the so-called ultimate transmatch. A T-network design.

For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

Thanks for any info.

Bob
k5qwg

Bob Miller wrote:
For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

It's probably a 4:1 voltage balun which does exhibit
a DC short. That's actually good for cutting down on
static electricity.
--
73, Cecil http://www.qsl.net/w5dxp


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Bob:

Totally normal, in fact, if you check secondary to primary--will also
show continuity--it is normal too...look at a schematic of a torrid
balun on the net, all windings have some sort of connection to all
others... in a "rf transformer" with seperate primary/secondary there
will be electrical isolation between windings...

Warmest regards,
John
"Bob Miller" wrote in message
...
Having never wound a balun before, pardon if this is an elementary
question, but...

I recently got a Murch 2000B antenna tuner off eBay. It's a commercial
version of the so-called ultimate transmatch. A T-network design.

For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

Thanks for any info.

Bob
k5qwg

In article ,
Bob Miller wrote:

For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

Very probably normal... or, at least, to be expected of many types
of balun and thus not diagnostic of a failure. You're probably
reading the DC resistance one or more of the windings, which would be
rather less than an ohm.

Based on what I see in Sevick's book on baluns and ununs, both the
Guanella 4:1 current balun and the various Ruthroff voltage balun
configurations would exhibit this behavior. A Guanella 1:1 with the
center of the load un-grounded would not, nor would a Reisert or W2DU
1:1 balun.

Now, for something completely different. If you want to revisit an
old controversy, and if you're not adverse to modifying a classic
piece of equipment, you might want to review the various debates about
the pros and cons of the Ultimate Transmatch vs. the SPC
configuration. See if you can locate a copy of the August 1981 QST,
and review the Technical Correspondence column on pages 42-43.

As I understand it, the SPC configuration can be shown to have some
significant technical advantages over the Ultimate Transmatch, in terms
of matching range and harmonic attenuation, when the same component
values are used in each. It is reportedly possible to re-wire an
Ultimate into an SPC configuration little or no cost, as both use a
split-stator capacitor (just in different places in the circuit).

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Sat, 04 Jun 2005 20:11:38 -0000, (Dave Platt)
wrote:

In article ,
Bob Miller wrote:

For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

Very probably normal... or, at least, to be expected of many types
of balun and thus not diagnostic of a failure. You're probably
reading the DC resistance one or more of the windings, which would be
rather less than an ohm.

Based on what I see in Sevick's book on baluns and ununs, both the
Guanella 4:1 current balun and the various Ruthroff voltage balun
configurations would exhibit this behavior.

I kinda suspected so, but wasn't sure.

A Guanella 1:1 with the
center of the load un-grounded would not, nor would a Reisert or W2DU
1:1 balun.

Now, for something completely different. If you want to revisit an
old controversy, and if you're not adverse to modifying a classic
piece of equipment, you might want to review the various debates about
the pros and cons of the Ultimate Transmatch vs. the SPC
configuration. See if you can locate a copy of the August 1981 QST,
and review the Technical Correspondence column on pages 42-43.

As I understand it, the SPC configuration can be shown to have some
significant technical advantages over the Ultimate Transmatch, in terms
of matching range and harmonic attenuation, when the same component
values are used in each. It is reportedly possible to re-wire an
Ultimate into an SPC configuration little or no cost, as both use a
split-stator capacitor (just in different places in the circuit).

Thanks, Dave, I have a 1985 arrl handbook that shows the differences
between the Ultimate Transmatch and the SPC circuit, and I also have
some modification instructions on the Murch unit itself, but I haven't
tried changing anything yet. Still playing with it, as it came.

Bob
k5qwg

On Sat, 04 Jun 2005 14:58:33 -0500, Cecil Moore
wrote:

Bob Miller wrote:
For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

It's probably a 4:1 voltage balun which does exhibit
a DC short. That's actually good for cutting down on
static electricity.

Thanks, Cecil, I noticed a more up-to-date MFJ tuner doesn't show
continuity across the balanced line terminals; just wanted to make
sure the Murch balun wasn't whacked out.

Bob
k5qwg

Bob:

If you don't mind me asking--how much did you pay for it, I have one in
the barn here I bought as lot with other gear from an estate sale--just
wondering...

John

"Bob Miller" wrote in message
...
On Sat, 04 Jun 2005 20:11:38 -0000, (Dave Platt)
wrote:

In article ,
Bob Miller wrote:

For balanced line, it has a "broadband toroidal transformer"
according
to the review in a 1980 QST. When I place a VOM multi-meter across
the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

Very probably normal... or, at least, to be expected of many types
of balun and thus not diagnostic of a failure. You're probably
reading the DC resistance one or more of the windings, which would be
rather less than an ohm.

Based on what I see in Sevick's book on baluns and ununs, both the
Guanella 4:1 current balun and the various Ruthroff voltage balun
configurations would exhibit this behavior.

I kinda suspected so, but wasn't sure.

A Guanella 1:1 with the
center of the load un-grounded would not, nor would a Reisert or W2DU
1:1 balun.

Now, for something completely different. If you want to revisit an
old controversy, and if you're not adverse to modifying a classic
piece of equipment, you might want to review the various debates about
the pros and cons of the Ultimate Transmatch vs. the SPC
configuration. See if you can locate a copy of the August 1981 QST,
and review the Technical Correspondence column on pages 42-43.

As I understand it, the SPC configuration can be shown to have some
significant technical advantages over the Ultimate Transmatch, in
terms
of matching range and harmonic attenuation, when the same component
values are used in each. It is reportedly possible to re-wire an
Ultimate into an SPC configuration little or no cost, as both use a
split-stator capacitor (just in different places in the circuit).

Thanks, Dave, I have a 1985 arrl handbook that shows the differences
between the Ultimate Transmatch and the SPC circuit, and I also have
some modification instructions on the Murch unit itself, but I haven't
tried changing anything yet. Still playing with it, as it came.

Bob
k5qwg

On Sat, 04 Jun 2005 14:58:33 -0500, Cecil Moore
wrote:

Bob Miller wrote:
For balanced line, it has a "broadband toroidal transformer" according
to the review in a 1980 QST. When I place a VOM multi-meter across the
two balanced line terminals, it shows continuity. Is that normal, or
is the balun cooked or shorted?

It's probably a 4:1 voltage balun which does exhibit
a DC short. That's actually good for cutting down on
static electricity.

Okay, Cecil, Dave, one more elementary question. My copy of the
instructions for the Murch 2000B says the following:

"Connect balanced line to connection marked Balance Line with Jumper
as indicated on back panel."

On the back panel, there's a painted line between the two balanced
line connections. Surely, they don't mean to run a jumper wire between
the two connections *while* a balanced line is attached?

It seems to tune fine without the jumper -- I'm afraid I'd blow
something up with the jumper.

Bob
k5qwg

On Sat, 4 Jun 2005 14:01:25 -0700, "John Smith"
wrote:

Bob:

If you don't mind me asking--how much did you pay for it, I have one in
the barn here I bought as lot with other gear from an estate sale--just
wondering...

John

The eBay bidding started at $100. There were 20 bids, and it finally
ended up at $171, plus $20 for shipping.

The case is a little scratched up, but the front panel and inside
components look good.

Bob
k5qwg

WOW, that makes me smile... I am going to dig it out!

Warmest regards,
John

"Bob Miller" wrote in message
...
On Sat, 4 Jun 2005 14:01:25 -0700, "John Smith"
wrote:

Bob:

If you don't mind me asking--how much did you pay for it, I have one
in
the barn here I bought as lot with other gear from an estate
sale--just
wondering...

John

The eBay bidding started at $100. There were 20 bids, and it finally
ended up at $171, plus $20 for shipping.

The case is a little scratched up, but the front panel and inside
components look good.

Bob
k5qwg