RA.1218 H.F. COMMUNICATIONS RECEIVER RA.1218 front

This is the follow-up of the RA.1217 receiver. There are two things that you notice immediately when the RA.1217 and the RA.1218 are put next to each other. First, the RA.1218 is 1.75 inches (4.6 cm) higher than the RA.1217, and of course the prominent nixie frequency read-out! But there are more differences between these two receivers.

On previous RACAL receivers the band selection (if available) was always a number of steps, and further peaking of the input circuits was done with a 270 degrees rotating control, RF TUNE. If you switched bands, for example from 3700 kHz to 7050 kHz, you must put the band selection knob in the next position and rotate the control until you heard some noise.
RA.1218 receiver RF range After that, you could go ahead and tune in on a signal. If the band selection or the RF TUNE control are not in the correct position chances are good that you do not hear anything. The RA.1218 has a feature that I liked: the band selection knob has a Wide Band position, and has that WB position at both ends. So you do not need to click through all the other positions, just turn the knob to WB that is most close to the desired band.
RA.1218 if selection

An other option in these new transistorised receivers was the availability of several IF bandwidth filters. The front panel control reflected the installed filters by a small plate that was installed under the knob, as you can see on the picture.
RA.1218 tag plate

The DRG. number reflects the filters that were factory-installed.

The standard filters installed are 8 kHz, 3 kHz and 200 Hz. Optional available are 13 kHz, 6 kHz, 1.2 kHz and 500 Hz.

Connections at the rear side
RA.1218 connections

On the rear side of the RA.1218 are 5 fuses and some BNC sockets.

The BNC sockets on the rear side are 75 Ohms types.
This means that when you plug 50 Ohms BNC connectors in these sockets you will ruin them! The center pin of a 50 Ohms BNC connector is thicker than the center pin of the 75 Ohms BNC connector, hence damage to the center receptacle in the 75 Ohms socket will happen.

At the left side (as seen in the picture) are 3 BNC sockets (but the bottom one is not there!). I am not sure if this is connector plate is an original RACAL modification, or a kludge ... From top to bottom there are the following connections.

1.6 Mc/s IF OUT
100 kc/s IF OUT
1.7 Mc/s IN/OUT (only the hole)

Further there is a connections strip for power supply and AGC voltages and a detector tap.
The other BNC sockets are the following.

1.7 MHz
Accepts 1.7 MHz input to 100 kHz IF converter. The 1.7 MHz crystal must be removed.
This connection is used by the ISB Adapter, RA.298C or RA.298D.
1 MC IN and OUT
The input accepts an external 1 MHz refernce signal. The internal 1 MHz crystal must be removed.
The output signal is needed by the LF Adapter RA.337. The LF Adapter has a harmonic generator driven by the 1 MHz signal from the receiver and filters the 3rd harmonic which is used in the mixer stage to generate the inverted spectrum output IF signal (2.997 - 2.02 MHz) from the 10 - 980 kHz reception signal.
2nd VFO IN and OUT
The input accepts a 3.6 to 4.6 MHz signal from an external synthesizer.
The output provides 2nd VFO control for a slave receiver (diversity reception setup).
LF
Input connection of the RF signal from the LF Adapter RA.337
PAN
Output connection of the 2 .. 3 MHz IF spectrum from the 2nd mixer stage to the Panoramic Adapter RA.366

Note that if an external reference oscillator is used, the appropriate switch (top left) must be set to the position EXT.