> No, I was thinking of 7.5kW and upwards transmitters,
> where frequency changing wasn't that common ( once on a
> frequency, it would be there for hours, and each tx was
> likely to only need about 6 channels anyway), wideband
> antennas such as rhombics were used, and the max SWR at
> the tx was limited to 2:1 max.
> The HF marine bands are about as narrow as ham bands (in
> some cases much narrower), so the amount of retuning
> between band ends is in practice negligible. The exception
> is the MF band: in theory (and for Type Approval purposes
> in Europe), transmitters were required to operate over
> 1.605 to 3.8MHz, but in practice, after WW2, frequencies
> used were mainly limited to 2.009 at the bottom
> (International ship-ship) up to around 2.8 or 2.9 MHz. For
> Type Approval, the antenna load was 10 ohms in series with
> 250pF. In AM days, there were some Greek fishing boat
> frequencies above 3MHz, but not many - there was some (but
> very little real demand) requirement to cover up to 4.2MHz
And you looked at the tank values and know the systems
functioned as Pi-L's and not double L's?
What was the intermediate impedance at the loading
capacitor?
How do you know they did it for harmonic suppression and not
some other reason?
73 Tom
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