G3XGC Z-match

[Richard Soennichsen]

Has anyone built this antenna tuner?  (Described on the elecraft website)  I
just got my ticket and am looking into equipment.  There are no detail on
its construction other than a schematic and pictures.  Questions that come
to mind include:
How are the transformers wound?
Sources for components such as the variable caps etc.

Thanks

Rich



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[Stuart Rohre]

Rich,
If you re read the text below the pictures, it pretty much details, along
with photos, how the coils are wound.   They are solenoid open wire coils,
and the coil forms are noted, as are the wire sizes and turns for each
winding.

Link coils such as in this Z match tuner, are typically made at the grounded
end of the coil, ie not the top side of the coil in the schematic, but the
side closest to ground symbol, or common at bottom of schematic.  They can
be wound end to end with the tuned coil, or even interleaved among the last
few turns, in some versions.

The caps are listed as salvaged from a particular old Yaesu model , but any
variable capacitor of similar range and spacing of plates can be
substituted.  The 1957 ARRL Handbook has this same Z match tuner built from
Air Dux or B&W coil stock.   I used for its capacitors, those salvaged from
a TU war surplus tuning unit, for the BC 611 transmitter.

You could use ham swap meet variable caps from E. F. Johnson, National,
Millen, Cardwell, or many other sources.   You can join the shafts of two
standard variables to make the split stator one needed.  Split stator is
really two capacitors driven from a common shaft.  Put them end to end, and
of course, you have to have the National or Johnson type cap that has a
shaft out the front and back.  There is a capacitor company that made the
caps for Heath Co. that still sells caps of suited types new.
Check Heath web pages for info on replacement caps for the HW8 QRP radio,
and the cap maker is listed.

Google Search "Z match Tuner" and you will find illustrations of similar Z
match designs which will give you alternate coil and capacitor ideas.  Many
types will work.  They just have to have the plate spacing and maximum
capacitance for the bands and power you run.

The Bill Orr Antenna Handbook, and the Capt. Lee's Verticals Antenna book
should also have tuner info.   The Radio Handbooks by Editors and Engineers
over the 60's and 70's typically had this kind of tuner described.  The B&W
Z match tuner of the 1950's was this type, and you could maybe find pictures
of it to follow in construction.

For QRP, there is the ZM1 and ZM2 kits from one of the kit firms.  They were
also Z match tuners for 10 watts or so.

Are there any swap meets for hams coming up in your part of the country?  If
so, I would look for any scrap tuner or capacitors there, you can sub out
those from any T tuner you can find.

-Stuart
K5KVH



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