[FoxHunt] Attenuator

[Anthony Levand]

If one has a standard type of in line attenuator, it could be adapted to make an
active stepped attenuator. This would be easy to do.

Tony
AA9CC

Clay Melhorn wrote:

> Jeffrey Madore wrote:
>
> > Has anyone tried putting steps in an active attenuator, then using the pot
> > for fine adjustment between the steps?
> > Just a thought.
> > Jeff  K1LE
>
> Hello Jeff and all,
> To answer your question, yes I did and it's the best thing since sliced
> cheese!!!
>     I built a FAR oscillator circuit board recommended by Dick Arnett WB4SUV out
> at Dayton 2000. (Great guy!)
> Next I made a box out of double sided pc board with four sections. One section
> large enough for the oscillator and associated active circuitry and three
> smaller sections for the passive sections 20dB, 20dB, 10dB.
>     The active attenuator is "switched in-line" like the passive sections except
> it is a 3-pole, double throw switch
> in that one of the poles is used to turn the power to the oscillator "on" from a
> AA battery holder when the active section is switched in-line.
>     All wall seams are soldered together.
> The back is screwed down. (I used screw terminal lugs from a 15 amp toggle
> switch and soldered them to the back side corners, held them in place with
> pliers and soldered.)
> The holes for passing wire through were pre drilled.
> The key to making this work VERY well is to make those holes "just big enough"
> for the wire to pass through.
> NO MORE THAN IS NEEDED, "Make it a snug fit."
> Use light gauge wire, say 22 gauge stranded or smaller.
> Don't let there be "any" space between the hole wall and wire insulation.
>
>     I use my Active / Passive attenuator with an Alinco DR-610 dual bander (with
> dual vfo.)
> One vfo gets set to the actual receive frequency,
> The other vfo gets set to the difference (mixed) frequency.
> I use the passive "only" at first when the fox signal is weak.
> As I get relatively close I switch in the active attenuator and dial the signal
> down in huntable range,
> then I use the passive attenuator sections once again.
>     All I can tell you is that it works "VERY WELL"!!!
> I've built three so far.
> The first did not work very well.
> Upon experimentation with the very same oscillator board and passive components
> in a "new box" with those snug fit holes I was telling you about I got
> "FANTASTIC" results.
>
>     My daughter Crystal W9IOU helped me out with the tests on my new toy.
> This is my 16 year old that's been hunting with me since she was 12.
> Actually she was 6 weeks old at her first hunt but she doesn't recall, Hi!
> Crystal was in our motor home transmitting on 2 meters with 50 watts into a 1/4
> wave spike antenna (at a campground.)
> I was able to be 10 feet away from the antenna, switch in the active attenuator
> and literally turn my 2 element quad away either direction and watch the signal
> drop off to "nothing"!!! zero! nada!
> Built these little jems in the summer of 2000.
>
>     I've even experimented with the quad and an Alinco DJ-41 2 meter hand held
> (One of the baby 300mW ht's)
> We call them our hamfest handies...
> Since it only has a telescoping antenna I leave the antenna collapsed at it's
> side and run a short piece of coax connected to the output of the attenuator and
> at the other end the center conductor is soldered to an alligator clip.
> The Alligator clip gets attached to the tip of the collapsed antenna and taped
> down as not to damage the antenna in the heat of the hunt...  Even with the
> small LCD S-meter display of this baby hand held I get pretty much the same
> results.
>
> I'm inspired by this writing to take photos of my Active / Passive attenuator
> and post them on the KARS web site...
> I'll let the group know when I get them posted.
>
> 73' and happy hunting!!!
> Clay Melhorn  N9IO
> KARS Web Master
> Fox Hunt coordinator
> http://www.w9az.com
>
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