ZM-1 & ZM-2 Questions


From: Coote, Jay (
Date: Sun Jun 25 2000 - 16:13:54 EDT

I am thinking about building a Z Match from scratch (or the kit) based
on ZM-1 and ZM-2 schematics and test data someone was kind enough to
send me....but had some questions:

1. Are there values which can be changed for 160 meter coverage,
without losing
        15-12-10 meters?

2. What is the best type of capacitor to use for the fixed value
(switchable) caps...

3. I wonder if an air-core inductor with the same values as the
T-130-2 core as seen in the ZM-1 or ZM-2 would help with efficiency?
(Using AL - uH formula for the toroid allows
        you to take the number of windings in the project and figure the
value in uH for your own air-core coil)

4. How does one measure balance in a resistive load on the output-
use a center tap load to ground and E2 on each end to ground
using a scope and RF probe?

5. How does one measure efficiency in "odd" resistive loads (100,
300, 800 ohms..etc)-
        Check E2 across the load using a scope and RF probe?

>From what I've read, it looks like the Z-match would be a good low-loss
antenna tuner for field, travel and stealth QRP. I'd appreciate any
comments and discussion.
Jay, W6CJ

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