From PA0SE
Dave, G3YXM wrote:
Dick and all.
Very puzzling!
I worked Jim straight after you and found exactly the opposite..... 4dB
better on the "small" antenna. We tried the test twice and I continued to
listen, each time it was the same.
Directional?
Which side of the big mast was the little antenna I wonder?
73. Dave G3YXM.
Dave and All,
There is a simple explanation.
I was very busy doing the measurements, changing the receiver input from
aerial to signal generator and back, reading levels etc.
I therefore did not listen carefully to what Jim was sending (experienced
telegraphists can do a job and copy CW at the same time but I am far
removed from that category). So I assumed that the bigger signal came from
the bigger aerial. Rather foolish of course and I apologize for that.
So the S8 (-79dBm) signal I reported must have been from the small aerial
and the 4dB
weaker signal (-83dBm) from the Decca aerial.
That is 30dB less than the signal from G3WSC/P operating from Puckeridge on
April 16 at 1000 UTC. G3WSC/P at that time reported an aerial current of
9A.
In his e-mail of May 18, 15.54, Jim announced he was going to run an aerial
current of 0.34A into the Decca aerial. That is a difference of
20log(9/0.34) = 28.5dB; within 1.5dB of my measured values. That confirms I
got the two aerials mixed up.
Assuming that at the distance of 317km between our locations the inverse
distance law is still applicable my measured field strength of 8.6µV/m
yields a radiated power by the small aerial of 83mW, close to the 80mW Jim
was aiming at.
For the Decca aerial I find 33mW.
Up to now (0951 UTC I have heard no signal from Jim on 73kHz.
73, Dick, PA0SE
This was my earlier report:
To All from PA0SE
At 0955 today I worked Jim, M0BMU/P at the Puckeridge station.
On the Decca antenna his signal was exactly S8; corresponding to a field
strength of 8.6 microvolt/metre.
On the "amateur antenna" the signal was 4dB weaker.
I reported the signal exhibited a fast fluctuation in strength with a
frequency of a few hertz. But I later found out it was my signal generator
interfering with Jim's signal. even with the output turned down to zero.
It shows that even a HP606B is not perfectly screened!
73, Dick, PA0SE
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