John is right. The transductors at SAQ can be seen in this photo in
google street view:
https://www.google.se/maps/@57.1139306,12.4045874,3a,75y,221.02h,87.43t/data=!3m7!1e1!3m5!1sA9thq95lEHf5u-4IrG4StQ!2e0!3e2!7i13312!8i6656
The transductors are the big "rolls" at the top and were called
"magnetic amplifers" in SAQ documentation from the mid 20's.
73 de Johan SM6LKM
John Rabson wrote:
I believe something like that is used at SAQ (Grimeton Radio) on 17.2 kHz as a
saturable reactor for keying the transmission.
John F5VLF
On 18 Apr 2017, at 18:18, DK7FC <[email protected]> wrote:
Hi all,
I'm just thinking about transductors and find them them quite fascinating
again. I read a bit Wikipedia and thought about the use as a steerable
transformer.
Imagine you have a hard switching class D PA, H bridge or so. The output is a
constant voltage source and it is no problem to connect no load, as long as a
proper type of low pass filter is used.
Then imagine a simple 1:1 ferrite transformer, 50 Ohm to 50 Ohm. The
transformer has a 3rd winding for a DC current (to compensate the AC component
transformed from the RF windings, 2 cores must be used, which are in parallel
for the RF and anti-serial for DC).
Then i can saturate the transformer with the DC so the µr falls down to 1.
With this arrangement i could build a linear PA out of a switch mode PA, even a
fast one, which avoids key-clicks, at least in QRSS-3 (you remember the mode)
or OP32 or even EbNaut on LF?
Sounds like an interesting experiment at least. The question is how warm the
transformer would become when the RF output current is permanently reduced to
50%.
Has someone ever tried that on LF/MF?
73, Stefan
[email protected]
Researching history of RABSON, BLACKSHAW, GAUNTLETT, VERLANDER and ROBSONNE
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