Two suggestions for
This page gives you two ideas for installing the ARDFrx2-v16 PCB in a screening housing, and completing the construction. But of course you can do that according you own insight.
R5 and R21 are Vishay precision potentiometers 50k, type 249 : Conrad 424196. Not cheap, but they are small, accurate, sturdy, and 15 turns knobs with scale and lock fit onto them.
On the TUNE potentiometer R5 is a 23mm 15 turns knob
with lock installed : Conrad 183464.
On the GAIN potentiometer R21 is a 1-turn version installed : Conrad 184078.
Fp1 and Fp2 are 9,5 x 9,5mm ferrite pipes
: Wurth 710-74270033 (www.distrelec.com). Absolutely necessary for accurate
bearings by the antenna.
Through Fp1 three or two turns 2.5mm coax is wound.
Through Fp2 three or two turns twisted thin wire or thin twin lead is wound.
S1 is a micro miniature tumbler switch 1x on/on : Conrad 700568
HpH is a 3,5mm jack plug bus : Conrad 718574.
1. Using a piece of square 45mm aluminum pipe.
Download this PDF and print it on A4 in size 100%.
Printing the above DF gives a 1:1 idea for using a 181mm long 45x2 mm square aluminum tube, closed by two plastic end caps, which are fastened in the ALU tube by means of two small self tapping screws..
If printed in original size, you can extract accurate locations and distances for drilling all holes.
By choosing external parts, remember the small free space of 18mm above the PCB.
The crystal Xt has to be positioned horizontally, in order to let enough free space for the battery. It wires have to be bend to 90 degr, and the crystal should be connected to mass, to prevent radiation and instability.
To be able to adjust the frequency range after closing the housing, you could drill a 3.2mm hole exactly above the core of L2, and close it by a M4 screw.
The PCB is fitted with two 10mm long distance bushes. This makes shifting the PCB, with connected wires, easier into the tube.
See to it that connecting wires cannot come near the PCB surface around L1 and L2, to prevent oscillator instability when shaking.
From the right hand end cap seen,
the 9V battery could be placed in the top-right or top-left. The 3 mm x 20 mm
screws M3-1 to M3-5 act as a battery compartment. They should be tapped, screwed
and glued into the ALU pipe. A piece of soft plastic foam in the end cap presses
the battery rattle-free into its location.
This construction is easy to complete, space saving and problem-free while participating ARDF in rough terrain.
2. Using a Hammond 1590P1 die cast aluminum box as housing.
Download this PNG
Advantages of this box are a bigger width an a top lid. The installation and adjustment of the receiver PCB are therefore simpler. Also can wiring be shorter and more stable.
For each locking Mentor knob an extra 2mm hole has to be drilled.
At the headphone connection must a ferrite choke be installed with a few windings thin wire wound through it.
The antenna is connected to an SMA or BNC connecter in the side of the box. Mantle currents on the outside of the coac cable cannot travel to the inside of the box, and a RF choke is here not needed. A short piece of coax is soldered into the PCB antenna connection.
The 9V battery fits between the switch, headphone connector, and a box side. It will be clamped to the bottom by cluing a piece of soft plastic foam to the inside the lid.
The box could be screwed onto the antenna boom by two screws in the bottom of the box..