FOXREX-144 Foxoring Receiver
Similar to the well know 80m receiver Foxrex-3500 the VHF foxoring receiver FoxRex-144 offers a great solutuon for VHF fox hunting. The receiver is built into a solid aluminium profile, which at the same time functions as the boom for three antenna elements. So the antenna is a three element Yagi antenna with good directionality, suitable for direction finding on 2m (144 MHz). The element construction follows an idea of WB2HOL and are made from flexbile steel tapes, in fact they are recycled tape measures. This makes the antenna nearly undestructible and extremely lightweight.
The central antenna boom houses the receiver, an LC display, the rechargeable battery and all controls. A coaxial DC connector is used for charging the battery with a 12 V supply. This is very useful, because you can recharge the battery while driving in your car to the foxoring competition. A 3.5mm headphone plug serves as an On/Off switch, i. e. operation is only possible with a headphone (32 Ω).
All operating controls of the FoxRex-144 are arranged in a well thought out layout: easy to reach and not to interfere with operation while on the chase to the transmitter site. An LC display with a size if 2x8 characters shows frequency, timer, the current transmitter and many other details. A slide switch selects the mode: normal operation, attenuator operation, menu programming. A rotary encoder with push button serves as main control for the menu settings. On the side a separate volume control is located. A small microprocessor controls the receiver functions, i. e. frequency, timer, alarms and so on. It supports various foxoring modes, as they are used in official international competions around the amateur radio world.
The receiver itself is a superhet design with 107 MHz IF and a quartz filter. A quartz controlled PLL is used for sufficiently precsie frequency control, the frequency range is from 143.9 to 148.1 MHz. The sensitivity is 0.1 µV, absolutely sufficient for the ranges used at regular foxoring events. An adjsutable attenuator helps in close range detection of the transmitter. The signal strength is show as a bar graph in the LC display and also presented as an acoustic signal in the headphone. The processor can be calibrated in respect to the transmitter output power, with this calibration a rough distance estimation is made. Depending on the selected competion mode (European style, chinese style etc.) up to 11 frequencies for different foxes can be stored. The built in battery supports the receiver for about 30 hours, an automatic power down mode prevents accidental deep discharge. The weight of the Foxrex-144 is only 530 g.
Included in the shipment is one miniature foxoring transmitter ARDF-144-xx. This is one of the five models (MOE, MOI, MOS, MOH, MO5), randomly selected.