If it hasn't been mentioned, the SAMS may probably be the ultimate
unit: http://www.eham.net/reviews/detail/6677 However, its cost is
probably equal to what many have invested in their entire shack. Still
not cheap, but more reasonable, is the AT-515:
http://www.hamware.de/hardware/tuner515/at515-e.htm Both were
represented at Dayton this year, and are clearly not Might Fine Junk.



--
Alan
WA4SCA

Both of these designs are of the Balanced L or Double L variety. Both
require a balun at the input to convert the 50 ohm unbalanced output
of the transmitter to the balanced tuner & feedline. You still haven't
gotten away from the main cause of inefficiency & power loss which is
the balun. [see http://www.somis.org/bbat.f1.jpg]

These double L tuners can be a PITA to build & use also. You need two
identical inductances at all times in the circuit. This requires
either some mechanical means of driving two identical roller inductors
simultaneously (so that the inductance in each leg always matches) or
two identical switched inductors with exactly the same tap points.

The link coupled design of the Matchbox takes the balun (and it's
potential for power loss) out of the circuit. They are also much
simpler designs, easier to homebrew & tune.

Terry
W8EJO





On Aug 1, 12:19 am, Alan WA4SCA wrote:
If it hasn't been mentioned, the SAMS may probably be the ultimate
unit: http://www.eham.net/reviews/detail/6677 However, its cost is
probably equal to what many have invested in their entire shack. Still
not cheap, but more reasonable, is the AT-515:http://www.hamware.de/hardware/tuner515/at515-e.htm Both were
represented at Dayton this year, and are clearly not Might Fine Junk.

--
Alan
WA4SCA

On Wed, 01 Aug 2007 11:44:12 -0000, Harry7 wrote:

Both of these designs are of the Balanced L or Double L variety. Both
require a balun at the input to convert the 50 ohm unbalanced output
of the transmitter to the balanced tuner & feedline. You still haven't
gotten away from the main cause of inefficiency & power loss which is
the balun. [see http://www.somis.org/bbat.f1.jpg]

These double L tuners can be a PITA to build & use also. You need two
identical inductances at all times in the circuit. This requires
either some mechanical means of driving two identical roller inductors
simultaneously (so that the inductance in each leg always matches) or
two identical switched inductors with exactly the same tap points.

The link coupled design of the Matchbox takes the balun (and it's
potential for power loss) out of the circuit. They are also much
simpler designs, easier to homebrew & tune.

Terry
W8EJO

I wonder if you have built a balanced L tuner? I made mine using only
hand tools and a drill press and had no problems. Also why do you say
they are a PITA to use? I adjust mine using only two knobs - the same
number of adustments I use on my Matchbox. Yes, I have both tuners.

Also, just how much of that terrible inefficiency and power loss does
that balun have? In the link you gave the balun consisted of nothing
more than a length of coax. There would be even less loss using a W2DU
type balun in that it requires a shorter length of coax.

Additionally, my balance tuner will give a 1:1 match on all the HF
bands (and anything in between) - something the Johnson Matchbox will
not do.

So are you talking from experience or just hear say?

Danny, K6MHE

Danny,

I've never built a balanced L tuner so I admit I'm speculating. The
link coupled designs I've built seemed much easier & simpler
mechanically & they will give 1:1 if the taps are in the right place.
Just takes some intial fiddling to find the right places but once
that's done you're good.

I'll agree the double L's seem to be just as easy to tune but the
building always deterred me.

Have you ever measured the balance of your double L at various
freqs. (current on each leg of the feedline)?

Terry
W8EJO



I wonder if you have built a balanced L tuner? I made mine using only
hand tools and a drill press and had no problems. Also why do you say
they are a PITA to use? I adjust mine using only two knobs - the same
number of adustments I use on my Matchbox. Yes, I have both tuners.

Also, just how much of that terrible inefficiency and power loss does
that balun have? In the link you gave the balun consisted of nothing
more than a length of coax. There would be even less loss using a W2DU
type balun in that it requires a shorter length of coax.

Additionally, my balance tuner will give a 1:1 match on all the HF
bands (and anything in between) - something the Johnson Matchbox will
not do.

So are you talking from experience or just hear say?

Danny, K6MHE- Hide quoted text -

- Show quoted text -

On Wed, 01 Aug 2007 14:46:35 -0000, Harry7 wrote:

Danny,

I've never built a balanced L tuner so I admit I'm speculating. The
link coupled designs I've built seemed much easier & simpler
mechanically & they will give 1:1 if the taps are in the right place.
Just takes some intial fiddling to find the right places but once
that's done you're good.

I'll agree the double L's seem to be just as easy to tune but the
building always deterred me.

Have you ever measured the balance of your double L at various
freqs. (current on each leg of the feedline)?

Terry
W8EJO

Terry,

I have not measured the current balanced on my feed line as the
antenna system is not perfectly balance. Although my antenna is as
geometrically balance as I can construct it, the environment where it
is installed is not symmetrical . (Yard clutter, ground conditions
and etc) That is a whole different topic but is explained very well
he http://k6mhe.com/sub/BalancedFeedLine.pdf

I have measured the balance of my antenna system by measuring the
impedance for each leg. On twenty meters, for example, I am seeing
about a 10% unbalance. http://k6mhe.com/sub/Balance_Z_L1_L2.gif

Additionally, checking feed line balance by measuring current using
RF amp meters of each leg of open line will not accurate due the fact
that RF amp meters do not give any phase information. Roy corrected me
on that some time ago.



73,
Danny, K6MHE

Danny Richardson wrote:
. . .
Additionally, checking feed line balance by measuring current using
RF amp meters of each leg of open line will not accurate due the fact
that RF amp meters do not give any phase information. Roy corrected me
on that some time ago.

The thing to do is run both conductors through a single ferrite core
(type 43 is fine) -- you can squeeze them together or use a short piece
of two close spaced two conductor wire. Wind a secondary of 10 turns,
and terminate the secondary with about 50-100 ohms. Measure the
secondary voltage with an RF voltmeter (diode, capacitor, and DVM) or
scope. This directly measures the common mode current. Then compare that
to the reading you get with only one of the conductors going through the
core.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Danny Richardson wrote:

. . .
Additionally, checking feed line balance by measuring current using
RF amp meters of each leg of open line will not accurate due the fact
that RF amp meters do not give any phase information. Roy corrected me
on that some time ago.


The thing to do is run both conductors through a single ferrite core
(type 43 is fine) -- you can squeeze them together or use a short piece
of two close spaced two conductor wire. Wind a secondary of 10 turns,
and terminate the secondary with about 50-100 ohms. Measure the
secondary voltage with an RF voltmeter (diode, capacitor, and DVM) or
scope. This directly measures the common mode current. Then compare that
to the reading you get with only one of the conductors going through the
core.

Roy Lewallen, W7EL


Hi.
Well after many years (over 50) as a Ham I still reckon the Z match
tuner the best.
In its original form it was designed for 10/80 metres but there is no
reason why you couldn't scale the parts for 160.
It will match from 50 Ohms coax to anything from 20 Ohms to 1500 Ohms
balanced and tune out quite a bit of reactance too. And all this with
only 2 controls.
I have used one with a G5RV 102' doublet for many years and have got WAC
and DXCC with never more than 120 watts.
Other tuners I have tried require hard to get variable inductors and
even then can do some fairly nasty things to your Final if well out of
whack. With the Z match you can calibrate the dials for a particular
antenna and reliably get a reasonable SWR straight off.
The old RSGB amateur radio book has a circuit and it has been published
elsewhere from time to time. I'm sure a Google search will find it OK.
&3's Cliff Wright ZL1BDA ex G3NIA.

Harry7 wrote:
Both of these designs are of the Balanced L or Double L variety. Both
require a balun at the input to convert the 50 ohm unbalanced output
of the transmitter to the balanced tuner & feedline. You still haven't
gotten away from the main cause of inefficiency & power loss which is
the balun. [see http://www.somis.org/bbat.f1.jpg]

The best way I have found to tune a balanced antenna
and feedline system, especially at high power, is at:

http://www.w5dxp.com/notuner.htm

The balun always sees a purely resistive differential
impedance between ~35 ohms and ~75 ohms. A 1:1 balun
with a choking action of 1000 ohms will virtually
eliminate conducted common-mode currents. Symmetrical
placement of the feedline to the antenna reduces
inducted common-mode currents. The needle on the MFJ
current meter barely moves on the most sensitive scale.
Under these circumstances, a w2du balun is not lossy.
--
73, Cecil http://www.w5dxp.com

I have gone to homebrewing link coupled balanced tuners... Currently
have three for 80 meters and 1 for 160 meters and starting 3 more 160
tuners... All massively overbuilt for ham power levels... Motorized
tuning with remote controls and coax from the tuner to the shack...

I gave up on commercial tuners... None are actually balanced... All
are compromises for maintaining their profit margin as opposed to
optimized for power transfer...

denny / k8do

In article . com,
Harry7 wrote:

The link coupled design of the Matchbox takes the balun (and it's
potential for power loss) out of the circuit. They are also much
simpler designs, easier to homebrew & tune.

The Z-match is another link-coupled design useful for driving balanced
feedlines. Compared to the Matchbox, its matching range may be
somewhat wider, especially if both low-Z and high-Z output links are
provided. I'm not sure how its losses compare to the Matchbox...
they'll probably vary depending on whether the Z-match uses an
air-core or toroidal-iron-core link.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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