The 3700 Series
A huge leap forward

As with my experience with the RA1792s, I set about finding out just what I had filled my car with. To start with, there appeared to be ten chassis assemblies, three RA3701 Front Panels, four RA3712 front panels, two MA3700 Controller Front Panels and one MA3751 Transmitter Drive Unit Front Panel. Some of the chassis were populated or part-populated with modules whilst a couple of big blue plastic crates were filled with the remaining modules.

The chassis are essentially generic. The PSU and back-plane are common across the series. The only difference between types appears to be in how the slots are labelled. There is one exception to this however: There are two types of  5MHz frequency standard employed. The 3701 is fitted with a type 9442 and the 3712 is fitted with a type 9420.

So, I began to sort through the modules … marrying them to the appropriate chassis, being careful to check the drawing numbers since the Processor modules differ in terms of Firmware and although the Front-End modules all looked identical, there is a difference between the 3701 and 3712 … more on that later.

Since the chassis actually carries the overall type and serial numbers, that was my starting point. Out of the ten chassis, four were labelled RA3701, four were labelled RA3712, one was labelled MA3700 Controller and the last one labelled MA3751.

I already have an RA3701, so I already knew a bit about it. I wasn’t too excited about the Controller units since as their name suggests, these are for controlling receivers remotely. The RA3712 Dual HF Receiver sounded interesting and the prospect of an MA3751 TX Drive-Unit was indeed tantalizing.

However I was more than a few modules short. I did not have enough of the right modules to populate all the chassis and the Controllers and TX Drive-Unit were non-starters … both lacking significant modules … which was a shame.

At the end of the day … and after some repairs, I ended up with three working RA3701s and three working RA3712s and a spare Front Panel.

June 2017 …

Back in February of this year (2017) I started writing a ‘piece’ on the various valve-based Sideband adapters that Racal manufactured. Well, that  is still ‘work-in-progress’ but somewhat delayed due to a car load of 3700-series modules and chassis which came my way. The owner asked if I were up to re-building about eight RA3701s … to which I said “Sure!”. However, when I picked up the ‘loot’, they turned out not to be solely 3701 but a selection of 3700-series kit in various stages of disassembly.