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Joe, LF,
thanks very much for this report, I am very pleased
that you (again!) managed to pull my signal out of the noise. People like you
make all the effort worthwhile.
Here's a follow-up on the antenna and
coil story. On Sunday, the first Decca litz prototype gave up after
only three minutes, with a sudden loud screetch and loss of resonance.
Careful inpection showed that it had arced in a gap between two segments,
where I had not laid the turns carefully in the correct
order, inadvertently overcrossing wires with a larger voltage difference.
My first thought was what Stefan's comment would be about me ruining
the precious litz! Anyway I unwound the coil completely and taped
the defect
Then I rewound it more neatly on a new bucket, this
time using only three layers and shorter segments to reduce the internal
voltages (3x5 turns instead of 4x9). The remaining long wire end was
used for a smaller variometer insert (1x40 turns) to coarse-tune the
inductance:
As I had hoped, the AC resistance on the the
network analyzer had dropped from 6.6 to 4.3 ohms (Q = 1000). The coil is
also thermally more open to air than the old one. Then I ventured into
the unavoidable nail-biting WSPR-15 soak test... no arcing and no heating this
time, the coil actually stayed completely cold. In the dark there
was no visible corona anywhere. But the noise level on the FM
broadcast band increases sharply when I transmit, indicating that
there must still be some partial discharges lurking somewhere in the
system.
To be able to transmit overnight, I
repositioned the temporary support mast from the rooftop window to the
balcony:
For the three Opera transmissions last night, I cranked up the
power to about 440 W, driving 4.6 A (22 kV) up to 9 m effective
height. This happens to be almost exactly one watt ERP.
Best 73,
Markus (DF6NM)
----- Original Message -----
Sent: Tuesday, April 02, 2013 3:16 PM
Subject: Re: LF: OP32 136K TA Opportunity tonight
Dear Group,
Despite very high mains noise
levels there were 2 Op32 receptions
of DF6NM at 0000 and 0449 at -37 and -35
dB respectively.
73
Joe VO1NA
On Mon, 1 Apr 2013, Graham
wrote:
> OP32 136K TA Opportunity tonight
> Joe
VO1NA will be monitoring 136.00 K tonight
for OP32
> Good luck all
>
>
73-Graham
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