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.