2m Receiver ROX-2T

Warning ! This receiver has no AGC, so has the potential to cause ear damage if not correctly used. If required, increase the the value of R15 to limit the audio output volume.

rox2t-v3view

This receiver uses an IC variant of the TDA1083 which is used in a well known ARDF design by OK2BWN.
The TDA1083  or TA7613AP is a one chip AM/FM radio, complete with audio amplifier. It has been around for a very long time so ICs should not be too difficult to obtain or salvage.

The ROX-2T uses a novel way of controlling the gain of the SA602 mixer (as found in the Elecraft K1 transceiver) but the SA612 must be directly feed by the stabilized supply voltage to the chip or a through a RFC, to minimize pulling of the VFO.

rox2t-v3-dia

Schematic

 

The resulting ARDF RX is just about as simple as a superhet can get with get two RF devices, and no surface mount components, (apart from the varicap diode.)

The ROX-2T is not suitable for (FM) foxhunting. If the fox stops talking, there will be no modulation to detect! so it is squarely aimed at Radio-O using MCW/AM transmissions.

CONSTRUCTION DETAILS

rox2tn-l1

 

The main winding L1 (3T+3T) must be wound in the same sense for each half i.e. NOT mirrored
Use a piece of 26swg wire 100mm long, folded in half. Tin the ends and centre fold. The easiest way to remove the enamel is to boil it off by holding the wire ends in a solder blob.

 

 

INTEGRATED ANTENNA

The 3 element is based on the WB2HOL yagi described elsewhere on this web site. On the version for the ROX2 there is no hairpin loop because there is no requirement to match to a 50ohm feeder. The antenna is directly connected to the front-end of the receiver. The driven element is longer than shown in the WB2HOL yagi.
rox2tn-3ele
The driven element connection to the ROX2 is the shown below.
rox2tn-driven

PDF DOWNLOADS & FURTHER INFORMATION.
FOR PCB dated 03:07

2 thoughts on “2m Receiver ROX-2T

  1. Bert van Lelieveld

    Dear reader,
    I like to know if there is a complete kit available for this 2 mtr receiver
    and off course the price including shipment to the Netherlands
    thanks in advance for your answer
    Best regards
    Bert van Lelieveld

    Reply

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