Okay, I have the ability to loft 1/4 wave of wire on
160m (just in time for next weekend). I'm planning on
elevated radials. I'm using a base from an MFJ-1792
vertical (40-80m vertical) for tethering and feeding
the 135' vertical wire (easier than doing my own
SO-239 jazz).
However, the MFJ1792 base has a nice coil from center
to ground on the base, measuring ~92 ohms at 3.5 Mhz,
and ~252 ohms at 7 Mhz. At 1.8 Mhz, ~45 ohms. I
*think* mfj intended this to do two things
1) Bleed any static off the vertical
2) Provide a better match to the usual 50 ohm
impedance that most rigs like
Of coures, the MFJ 1792 manual calls this a "loading
coil", and doesn't mention anything more.
I intend to add a much larger coil in series with the
stock one, with a switch (might want to try it on 40
sometime) to short it in and out. My intent is to use
the additional coil to provide low DC resistance for
static avoidance, yet provide a high resistance at
1.8
Mhz. The coil I wound on my 2" form (PVC, the grey
kind) I calculate to be around 72uH, or around 800
ohms at 1.8 Mhz -- is this enough? Or, should I just
use some 100K resistors?
-Brian N9ADG
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