Fox Hunt Offset Attenuator

(1 customer review)


When your closing in on the fox you may find the signals to be strong enough you can no longer find a peak or null with your antenna. Sometimes the signal is so strong that the RF will leak straight into the radio, connections and other equipment making the antenna useless. The solution is to use an offset attenuator. The circuit consists of a small RF generator, in this case 4MHz, which will mix with the incoming fox signal (such as 146.52MHz) and produce new signals at plus and minus the fox signal (142.52Mhz and 150.52Mhz). A potentiometer on the board changes the injection level of the RF generator which in turn attenuates the incoming mixed signal to your radio to a level where tracking can continue.

This is a bare bones unit.  You need to supply for own connectors and enclosure.

 Click here for more information on fox hunting and the offset attenuator.

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Add a tape measure beam and you have a great club kit build project!

Looking for an offset attenuator that includes connectors and enclosure?

Check out the FoxHunt Offset Attenuator V7

Manuals can be downloaded at:

Several plans for a 3D printable box is available on the Fox hunting page.

There is a treasure trove of information with more tips, making fox boxes, and other events at

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Kit, Assembled

1 review for Fox Hunt Offset Attenuator

  1. bearskinrugmaker (verified owner)

    GOOD Kit compilation! Excellent planning for parts completeness! VERY nicely laid out PC Board. Works VERY well, as far as signal purity (lack of spurious emissions) on a Spectrum Analyzer, using the recommended 9V “transistor radio” battery. Dynamic range on mine after I completed the assembly of the kit (in only 45 minutes, start to finish!) : Low setting = -61 dbm WITHOUT any other input signal into the Attenuator ( into a 50 ohm Motorola Communication Service Analyzer), Max Output Setting = -20 dbm w/o any other signal input. Only recommendations I would make to IMPROVE the usefulness of the little Attenuator/Mixer system would be to make the “Gain” potentiometer a Linear Taper rather than an Audio Taper pot. As is, with Audio Taper, 70 % of the dynamic range of output level settings occurs within the first 45 degrees of potentiometer knob rotation from the lowest output levl setting. Also, a One (1) MHz Crystal would probably be more practical than the 4 MHz crystal (to keep the mixer product frequencies within the 2 Meter HAM Band, for those radios that don’t like going very far out of the band, due to their narrow bandwidth internal bandpass filtering). The 1 MHz Offset would provide more available mixer output product frequencies that are still WITHIN the 144 – 148 MHz range. Still a GREAT little gadget, AS IS ! Thank you KC9ON for a great, low-priced, and easy to assemble, & well-packaged kit!! Keep up the good work! Hope to see more kits from you! Dave, E.T.A. Certified Electronic Technician, USAF Retired Electronics Maintenance/Repair Technician/Instructor, & Motorola Certified Radio Repair Technician.

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