[Lowfer] Amplifiers for 136 kHz

Thu, 22 Aug 2002 08:05:11 -0400

Nevermind... Duh... I keep thinking of input power restriction as it is now with
Part 15 - not output power as proposed!..Duh...

Jay

WE0H wrote:

> Why would he loose a couple of DB by using a feedline on 136kc??? The amp
> and antenna will work just like any other amateur band amp and antenna.
> Match the output of the amp to the feedline and the antenna to the feedline
> and hokus pokus, the feedline, amp and antenna are happy. A guy could run a
> motor tuned circuit out at the antenna to peak the resonance of the antenna
> if they wanted it to be perfect across the 136kc band. The amp is just going
> to have a lowpass filter that is designed to present 50-ohm output impedance
> to the feedline across a certain bandwidth that the builder will select
> which of course will be the whole 136kc amateur band. I don't see where
> anything is going to be different than any of the other amateur bands with
> the equipment we run currently. Am I missing something??? This just seems so
> simple. On another note, the caps are in the mail for you Bill, thanks much.
>
> Mike>WE0H
> http://www.we0h.us/lf.html
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Jay Rusgrove
> Sent: Wednesday, August 21, 2002 9:54 PM
> To: [email protected]
> Subject: Re: [Lowfer] Amplifiers for 136 kHz
>
> Mike
>
> Hmmm...After all of the work Wild Bill has gone through optimizing
> conductors
> for loop antennas, do you think he would give up 2.0 dB on cw by going to a
> shack mounted linear amplifier? I can't say for sure but I'll bet he'd
> probably
> rather cut off a pinky finger...or two... than lose a couple dB!
>
> Jay
>
> WE0H wrote:
>
> > Just build the shack and loop amps linear and the feedline will be fine,
> but
> > then why not just build the shack amp as the final amp and not go outside.
> I
> > would think that the loop would be broad enough for a skinny 136kc band.
> >
> > Mike>WE0H
> > http://www.we0h.us/lf.html
> >
> > -----Original Message-----
> > From: [email protected] [mailto:[email protected]]On
> > Behalf Of Bill Ashlock
> > Sent: Wednesday, August 21, 2002 5:52 PM
> > To: [email protected]
> > Subject: Re: [Lowfer] Amplifiers for 136 kHz
> >
> > John A,
> >
> > > >One, a small high-efficiency switching amp located out in the
> > > > woods, just like I have now, but with TO-220 transistors (maybe
> > > > MJE15028/30?) mounted to a plate for heat sinking.
> > >
> > >Why handicap yourself by putting an amp out in the woods? Wouldn't >life
> be
> > >simpler to keep the active stuff inside?
> > >
> > 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?
> >
> > Don't see too much of a handicap with an untuned final in the woods (well,
> > not counting the loop tuning cap). Takes < 2 minutes each way to run out
> and
> > bring in the final box to the bench to make alterations and then return
> it.
> > I have a loop simulator coil and exciter simulator on the bench so there's
> > no surprises when I re-connect it back to the loop and shack cables.
> >
> > Bill
>
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