[Elecraft] Strange: KXAT1: SWR goes up, but so does forward power?? +Baluns

[Martin Gillen]

Hi,

I recently built a W1CG low power balun (Guanella 4:1 two-core design).

I'm pretty new to amateur radio and my on-air results were pretty
confusing to me
so I was hoping someone could help me understand what is or may be going on
here:

For these tests I was using an inverted vee dipole, each leg 32ft
(64ft total length),
fed in the center with 32ft radio shack 300 ohm twinlead, held aloft
by a 20ft fiberglass
fishing pole, with the ends held 6ft off the ground by fiberglass
driveway markers.

Rig was a KX1 with KXAT1 ATU.  Forward power and SWR readings taken from
the KXAT1 (ie. no external metering).

I started by connecting the twinlead directly to the KX1 using a binding post to
BNC adapter.  I was able to tune the radio on 40m, 30m and 20m to under 1.5:1
SWR, often 1.0:1.  Power out read as:

1.5W on 40m
3W on 30m
2W on 20m

I then replaced the binding post to BNC adapter with the 4:1 balun.  Now the SWR
increased on all 3 bands:

1.8:1 on 40m.
3.2:1 on 30m.
4.2:1 on 20m.

On 20m and 30m there was a noticeable attenuation of signals but 40m
sounded fine.

So... so far it looks like the antenna simply didn't need the
impedance transformation,
and has degraded all 3 bands.

I gave up on 20m and 30m with the balun due to the high SWR.

However the odd thing I noticed was that the forward power reported by the KXAT1
on 40m had increased to 3W!

So... I established contact with a station and asked him how my signal
sounded with
and without the balun.

Here is the summary:

Without Balun:

KXAT1 SWR 1.0:1
KXAT1 Forward Power 1.5W
Signal report: 579

With Balun:

KXAT1 SWR 1.8:1
KXAT1 Forward Power 3W
Signal report: 599+

I switched the balun in and out a few times to accound for fading.

So I am left confused.  Why did the SWR go up if the forward power
also went up?

My working theory is that the antenna fairly well matched already on all 3 bands
but unbalanced.  Adding the 4:1 balun had two effects:  (1) Impedance
transformation
(2) Balance the transmission line (& dipole).  The impedance
transformation wasn't
actually required and actually placed the impedance outside the KXAT1 matching
range on 20m/30m, and degraded the SWR on 40m, but the balancing of the
transmission line meant more energy radiates from the dipole elements and not
from the transmission line.

So the data seems to be telling me that this antenna could really use
a 1:1 balun.

What am I missing??

:)

73
Martin.