[FoxHunt] Attenuator

[Ernie Howard]

I've found that 99% of the time I hunt mobile with a passive resistor step
attenuator. I use a high quality unit and use double shielded coax. This
runs to my Icom-706. Using the 706 I can select a preamp for the weak ones,
and the internal 20 db when real close. But when I used a different radio,
I could still get 85+ db attenuation when sitting on the transmitter.

On foot hunting, the offset attenuator is the only way to get close.
I've calibrated my active attenuator on a service monitor/generator. I am
using the Joe Leggio attenuator that can be found at:
http://home.att.net/~jleggio/projects/rdf/a_atten.htm
Using the signal generator function, I would step up the signal in 10 db 
steps and mark a line at each step. That way I know just how close that I 
am. I also know how much attenuation there is at zero. 

I've also made some additions. 

One is to place a momentary switch across the antenna terminals to allow
quick bypassing of the diode and cap. I can quickly switch from the offset
freq to the direct freq and pick up those very low QRP transmitters that
they like to use around here. 

The other was to mount a double throw, double pole switch with a simple
20 db resistor attenuator. We hunt in very high RF areas in Cincinnati
and having that 20 db of passive attenuation at the flip of a switch
really comes in handy at times.

So, if you end up building your own active attenuator, consider adding these
extras to help out.

73 Ernie W8EH

See my fox hunt page: http://home.cinci.rr.com/w8eh/fox.html


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Ernie Howard, Jr    W8EH    Middletown, Ohio
E-mail: w8eh@arrl.net
How's the weather at W8EH? - http://wx.findu.com/w8eh
Web Page: http://home.cinci.rr.com/w8eh
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