Antenna current accidental observation
n4xy at ATT.NET
Mon Oct 30 19:09:19 EST 2000
Hello All... earlier this evening I took a notion to replace my usual
SWR/Wattmeter (a SignalCrafter Model 30 dual meter unit that calculates both
SWR and power out) with a really neat looking Waters Model 369A
Reflectometer. The Waters unit uses a vertical dual-needle meter-really
slick-displaying watts out and watts reflected. Well... it seemed like a
good idea at the time. But once all the cables were sorted out, etc. and
connected, it physically just didn't look very good, and my 45W (output)
Ranger II wasn't exactly impressing it either. We won't even mention what
its 5W reading would have been.
So... disconnect the cables, and put the Signalcrafters back.
All this wasn't too difficult-with the caveat that the Signalcrafters uses
'regular' UHF (SO-239) connectors, and the Waters uses BNCs. Uh-hunh.
OK... all cables reconnected, etc. etc. and so I key the Ranger II. Uh-oh.
Loaded differently. Bottom line: no matter what I did: 30W out maximum.
Cable check... everything looked fine. Touchy-feely check next. Ah-hah!!!
The PL-259 cable connecting to the Ranger II (e.g. RF output) was plugged
in, and LOOKED connected, but truly had 1 or no turns.
So the RF (center) lead was plugged in just fine. Its ground connection was
another story. The Ranger II's excellent Pi-Net loading worked as hard as it
could, and did load... after all, it was slightly touching... but the amount
of current was surely limited by the circuitous route and reduced contact
area ground had to use. Complete the connection, and voila! Back to 45W
I don't know about you, but I found it fascinating to see theory illustrated
so very well.
P.S. The Waters is back on the shelf.
73 Ed Tanton N4XY <n4xy at arrl.net>
LM: ARRL QCWA AMSAT & INDEXA;
SEDXC NCDXA QRP-ARCI NoGaQRP
OK-QRP QRP-L #758 K2 (FT) #00057
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