A nice enclosure for the RDF is Conrad # 523232, measuring 103x56x168mm, offering plenty of room for all parts.
But of course many types of housing will do. I made one out of one sided PCB sheet.
Note that a metal housing is preferrable, and if you want to send bearings to a computer you should keep the on-board USB connector very close to the right hand side of the housing,
so the USB is accessable through an opening in the side panel. I simply drilled a 20mm hole in the side for that purpose.
The calibration potentiometer
is an essential control; it will enable you to make the RDF point into the right direction careless of the orientation of your array. So, antenna 1 may be the one left, front, right, or rear, it doesn’t care.
The potentiometer has a range of 360 degrees so you will always be able to set things right. The calibration potentiometer can be mounted inside if you are going to use only one type of array.
In that case one single calibration session would do.
Or you can mount it recessed, so you can correct it from the outside using a screwdriver.
And the last option is to mount the potentiometer the classic way, with or without knob.
Putting a knob on will make calibration a bit more comfortable, but at the same time the chance of accidentally moving the knob will increase, corrupting your calibration.
I solved this by putting the knob in a cup, glued to the enclosure, as you can see on the following picture:
The volume potentiometer and the loudspeaker
are optional additions, depending on the type of receiver you are going to use.
The speaker in those cases where the radio’s speaker is turned off as soon as you plug in the audio cable. (earphone socket)
A small 16 ohm speaker will do in most cases.
A volume control can set a proper input volume for your RDF when you swap between different receivers.
The RDF interface board has a small blue trimmer that allows you to reduce input sensitivity.
(At the component side, visible after removing the display board)
So, for a single receiver setup you won’t need an extra potentiometer.
The antenna test mode switch
is optional. If you leave it out, the RDF will stay in normal operation mode with Averaging = 256.
The antenna mode however gives you a quick idea of the proper condition of all 4 antennas.
I used a 3- position (on-off-on)switch: Connect the center pin to ground, one pin to the Mode-switch contact on the PCB,
and the other pin soldered to the PCB contact with the “A” label. See the wiring diagram at the bottom.
This way the switch center position is normal RDF mode with Averaging = 256,
to the left is RDF mode with Averaging = 64 (faster response),
and to the right is antenna test mode.
The display shows the chosen settings.
The 12V dc input
is protected against reverse polarity.
You may use a 12V car battery or a 12V dc regulated mains adapter.
Don’t go beyond 14V dc to avoid damage to the RDF41.
Internally the RDF runs on 12V and 5V.
(Don’t use the on-board dc socket of the Arduino!)
The antenna control outputs
speak for themselves.
You need a cable and connector system of at least 5 conductors: 4 antenna control signals plus ground.
General current willl be around 10mA so thin signal cable (cat-5) will do fine for cable runs up to 25m.
4 wires for the antennas, and the rest of the wires for ground.
The antennas themselves have to turn/run clockwise looking down on them.
If you discover that you hooked them up the other way around you just have to swap antenna 1 and 3 (or 2 and 4) to get it right.
If you really manage to mix them up you will see eratic behavior of the RDF…
may be adjusted by a tiny trimmer at the back of the display.
Be very careful adjusting this tiny part…
The above picture shows how to connect the RDF41.
First remove the Arduino board, and you will see the PCB’s copper side as illustrated.
If you connect the pin labeled “A” to ground, the Long Time Averaging will be 4x faster than normal.
See the above text for a nice option with a 3- position switch.
The PCB on the left is a standard combiner for a doppler array, but with the possibility to add a ERA-6 preamp. Of course you can use it without preamp as well.