Hi Stefan,
I have thought about LF & MF antenna coil switching but I am very wary about
the very high voltages on the LF coil due to my short vertical antenna. At
the moment I have 3 screw connectors to change over :-
1 - Main coil inductance
2 - Matching transformer input
3 - Matching transformer output
I have also thought about using 4mm banana plugs to make the change over
easier & quicker.
But not sure about using banana plugs, are they suitable ?
73,
Gary - G4WGT.
----- Original Message -----
From: "Stefan Schäfer" <[email protected]>
To: <[email protected]>
Sent: Sunday, January 13, 2013 3:20 PM
Subject: Re: LF: Re: MF variometer
Hi Albert and Gary,
Yes, here it is the same. The detuning due to wet soil is higher than on
LF. Also the relative rise of the resistive losses are higher than on LF.
It can make up to 3 dB here.
Now i think about a switch that allows to switch from LF to MF remotely.
The idea is that the LF coil remains connected to the antenna (i.e. is not
switched), only the MF coil would be switched in parallel. There will be
some reactive current through the LF coil when operating on MF but it can
be compensated and the losses will be low. I still did no calculations. At
least the MF voltages and currents are quite low compared to LF...
73, Stefan/DK7FC
Am 13.01.2013 11:28, schrieb Albert W:
Hello Stefan es Gary,
The same here depending on weather conditions and of course frequency
change, using a relative small variometer (DC-motor adjustable from the
shack) in series with the fixed L.
73, Albert PA0A
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