my thanks to all for the responses both direct and via the reflector to my
plaintive bleating.
Today being a glorious day hereabouts I said "thehellwithit, hang the
expense", and took m'lady out for lunch and a look at the Irish Sea so only
one experiment done That experiment confirms that WHATEVER configuration of
other earths is used, the system prefers to have the coil earthed back along
the screen of the coax and then by any tortuous route you care to use
through the shack to the mains and the station earth. Any attempt to go
direct to the special point so thoughtfully provided by a caring owner and
it goes into conniptions.
Wherefore the action described in the PS will be the one adopted!
However further attempts will be made to measure various resistances,
impedances etc by isolating the BK from ground completely and using it (fed
by a battery operated wide range oscillator) as the generator for 'on
frequency' measurements as suggested by Alan.
Use of elevated radials as mentioned by Mal and Alex is a non starter for
various reasons, which include washing lines; cupressus lylandii; the
assortment of apparatus used by visiting grand-children, and most
importantly marital QRM.
The antenna is shunt fed against ground at the 4-8ohms o/p impedance of the
BK. Attempts to get it to feed a toroidal 4:50ohm transformer without
getting its knickers in a twist have been fruitless. I am only prpared to
spend so much on fuses, so I harked back to a piece of wisdom gleaned from a
well known bar-room philosopher in early adulthood; - 'if at first you don't
succeed, try try try again and then - give up, because there is no sense in
being pigheaded about it' and found a matching point that worked. The fact
that the RF gets there by courtesy of about 25ft of RG213 with some
horrendous SWR is, I submit, an irrelevance at that kind of frequency.
The antenna current sensor toroid is located about a foot above the coil
round a short length of plastic conduit which carries the 'vertical' lead of
the antenna through the top of the 'dogbox' up the inside of a ceramic
insulator which is the antenna anchorage point. It is hard to see how this
could respond to anything other than antenna current, the vast majority of
which ultimately goes to comfort the worms.
The antenna itself is a 'bonsai' crib of the WWVL and WWVB antennas.
(http://www.boulder.nist.gov/timefreq) Four poles of 10m height at the four
corners of a 40ft(approx) rhombus carry a closed loop which has the diagonal
corners joined and also an additional 6 wires running in the spaces between
the longer diagonal and the perimeter of the loop.
From the centre point of the shorter diagonal and spaced 1ft each side,
three wires form the 'vertical' element.
About 200m of assorted bare, and insulated, stranded nominal 1sq.mm wire
used and the natural resonant frequency is 1.55MHz.
I model it as 730pF and 15 uH, and sucks to anyone who says substantially
different.
The 'R' of the system is the subject of ongoing negotiation.
Will now take time out for a while to actually use the sodding thing.
73 de,
Ian GI8AYZ/MI0AYZ
Alan; re. the meerschaum. If you substitute beer for baccy and modify your
input suction arrangements to swallow rather than inhale, then a one pint
bowl seems to me to be just about right!
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