[Lowfer] Amplifiers for 136 kHz

[John Andrews]

With the likelihood of the FCC authorizing a ham allocation at 136 kHz, I've
been thinking about ways to generate more power. Let's assume that they
stick with the 100 watt P.E.P. output figure in the NPRM.

It seems to me that the most flexible amplifier arrangement would be linear,
either class B or AB. You'll pay more for electricity than you would for a
class C or "switching" amplifier, but you gain the ability to preserve
waveform shaping or use multi-tone modulation systems.

In my case, I have a phasing-type SSB exciter which can easily be used with
sound card generated formats such as WOLF, Jason, PSK31 and so forth. Others
have build filter setups with sharp LC filters following a balanced mixer.
Such arrangements are a lot more flexible than the classic Lowfer
approaches.

That being said, most of the current formats don't require a linear
amplifier, though PSK31 and especially its slower variants appear to be
touchy about the rise and fall times of the signal.

It just seems to me that the linear approach would be worth the effort.
Anyone have any thoughts?

John Andrews