[ARDF] 80 meter antenna question

[Dale Hunt WB6BYU]

For a simple 80m transmitter, this circuit is my favorite:

http://www.qsl.net/g3pto/pippin.html

It doesn't need a circuit board or any special parts - I've made  
several of them from my junkbox.
No signal or current draw when the key is up, simple interface, good  
efficiency, etc.
It puts out about 1 watt (depends on the load impedance.)

In place of the output circuit shown, if you are using a base loaded  
antenna wire,  you can
just wrap a few turns of wire around the loading coil and use that as  
the output in place of
the RFC and the output filter.  Don't worry about the trimmer  
capacitor on the crystal - it
isn't necessary unless you are trying to net multiple crystals to  
exactly the same frequency.

I generally use a 2N3904 for the NPN and a 2N2905 TO39 for the PNP.   
Build it using
ugly construction on a scrap of PCB.  I haven't tried increasing the  
power, but have a
few other transistors that should work, including a D41E5 in a TO202  
package rated
at 8 watts dissipation with a fT of 175 MHz.  But one watt was what we  
used in 1999
and, while the course was rather short, seemed to be adequate.  I've  
heard it up to
10km away using an 8m wire and 3 6m radials.

My standard practice transmitter uses one of these with a Montreal  
Controller and
battery pack.  The antenna is a 12' wire and 3 8' radials, using a  
loading coil wound
on a T-68-2 toroid with a link output from the transmitter.  In place  
of the controller you
could build one of the circuits from Joe's book that uses a shift  
register to store the
callsign and just let it repeat over and over, or put a memory keyer  
chip in BEACON mode.
For practice all you care about is that it sends your ID often enough.

For quick testing I have a couple of low power signal sources,  
typically just a simple
crystal oscillator (using a transistor or logic IC) with a couple feet  
of wire for an antenna.
It is sufficient to test the receiver, but won't show you how well it  
will handle strong
signals.


	- Dale WB6BYU



On 09 Nov 2009, at 12:27, Mike (KA5CVH) Urich wrote:

> On Mon, Nov 9, 2009 at 6:59 AM, Mark Bayern <plcmark at gmail.com> wrote:
>
>> Michael was interested because he doesn't have an
>> 80meter system, and he likes to build stuff. I don't think Randy was
>> very excited about its performance.
>
> Mike adds
>
> Again why I also want to find a "relatively" inexpensive 80 meter
> transmitter so I can use it to practice / experiment with.
>
> -- 
> Mike Urich
> http://ka5cvh.com
> http://twitter.com/KA5CVH
>
> You know you're over the target when you start taking flack.
>
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>
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