[Lowfer] Amplifiers for 136 kHz

[Bill Ashlock]

John A

>>Haven't figured out a way to drive a 100ft coax with a square wave 
>> >>having an impedance near 0 ohms, unless I use a tuned circuit between 
>> >>the final and the coax to convert the output Z to 50 or 70 ohms. But 
>> >>that makes it two circuits to tune rather than one each time I want 
>> >>to change frequency. Any ideas?

>You see, I ducked that here.

That's where I'M at too!! The complementary output is a neat, low cost, very 
efficient, way to drive a Lowfer antenna, particularly a loop, but I see no 
efficient way to drive a coax without some tuned impedance matching 
components. I use a 47 ohm in series with the output of the complementary 
output stage in the exciter (as you do) and that works great - but of course 
power is wasted. This whole question is only academic for driving an antenna 
because the final is supposed to be located at the base of the antenna (ala: 
"Length of the antenna including transmission line not to exceed 50ft"). But 
this could all change in a heart beat!

>Of course, you'll be feeding a little more DC power out there, as well.

Yes, no more power-feed in the 8-wire cable I'm using. I guess the days of 
'no fear in touching anything in the circuit', could be over, too.

>But it does provide good exercise to keep walking out there!

Doesn't happen THAT often - at least, these days :)

Bill

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