Description
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.
Manual: Fox Hunt Offset Attenuator V7 Manual
Click here for more information on fox hunting and the offset attenuator.
STL and FreeCad Files for alternate bracket mounts including 3/4″PVC (1″OD), Arrow, and ARRL antenna booms: FoxhuntV7-Holders.zip
There is a treasure trove of information with more tips, making fox boxes, and other events at http://www.homingin.com/
Example typical attenuation levels:
| Frequency | Attenuation | |
| Attenuator ON,No offset | 146.520MHz (Fox Frequency) | 8-18dB |
| -/+4MHz Offset | 142.520MHz or 150.520MHz | 30-60dB |
| 138.520MHz or 154.520MHz | 35-70dB | |
| -/+12MHz Offset | 134.520MHz or 158.520MHz | 60-80dB |
| Attenuator ON,No offset | 450.000MHz (Fox Frequency) | 6dB |
| -/+4MHz Offset | 446.000MHz / 454.000MHz | 35dB-70dB |
| -/+8MHz Offset | 442.000MHz / 458.000MHz | >-80dB |
| -/+12MHz Offset | 438.000MHZ / 462.000MHz | Not Measurable |
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