RA218 - seeking info

[evets1967]

Hi, I have recenty had the good fortune to come by a RA117 and an RA218. After a little head scratching and replacing of components etc. the RA117 is now working quite well. I would like to try and get the RA218 working but have absolutey no infomation about the unit and am not even sure how to connect the unit to the RA117(do I have to remove the 1.7Xtal?). Could anyone provide me with a manual or at least a schematic and a little advice how to proceed. The unit looks complete.
Thanks in advance.

[Radio Wrangler]

The RA117 is definitely the nicest of the RA17 family. It has several differences:

Cascode RF amplifier
An extra mixer and 1.6MHz IF
More audio output power 1W compared to 100mW

I used one for several years as my main receiver, but I never came across an RA218 to go with it.

You can use it with just the 100kHz IF output from one of the rear panel BNCs fd to the RA218 and it will demodulate SSB for you. But the fine tuning control won't work. This is how it is used with an RA17. The kilocycles tuning knob is a bit quick, but can be positioned finely enough.

The fine tune system in the RA218 is a 1.7MHz source which is fed to the RA117 for use in place of its internal (fixed frequency) crystal oscillator. It's quite independent of the SSB demod circuits other than the power supply.

THe 1.7MHz signal from the RA218 should be connected to connector SK303A, labelled 1.7MC/s. the 1.7MHz crystal should be unplugged and the oscillator valve then operates as a buffer amplifier. I'm trying to remember if there was a stowage place to put the removed crystal so that it stayed with its receiver.

The RA17 and RA117 both used a tuneable IF of 2 to 3 MHz following the Wadley converter. The RA17 had a few tuned stages at 2 to 3 MHz before mixing straight down to 100kHz. The tuning capacitor tracked the 2-3MHz stages with the 'kc/s' VFO.

For the RA117, Racal were targetting the North American marker (so they changed some valve types and connector types and upped the audio poler with a 6AQ5) But they also wanted to sell a fine resolution frequency synthesiser accessory to replace the 'kc/s' VFO. This wouldn't work with an RA17 unless someone still kept moving the 'kc/s' knob to tune the 2-3MHz IF.
So, for the RA117, they added a conversion stage and an IF. A bandpass filter covered the full 2-3MHz range for that IF and the 'kc/s' VFO tuning range was shifted to convert 2-3MHz into a new fixed IF on 1.6MHz. The new converter and a 1.7MHz crystal oscillator mixed the 1,6MHz (fixed-tuned and fairly narrow) IF down to the original 100kHz IF.

Two things to be aware of when running one of these receivers:

1) The front end is not as immune to overload and intermodulation as most modern transistorised receivers and is significantly more prone than the latest radios. You have to drive the preselector filter and the attenuator fairly carefully for the best results.

2) The IF structure is fairly wide right up to the narrowest bit right at the end (The RA218 in this case) so your wanted signal is accompanied through many stages by a collection of other signals surrounding it. They only get stripped away right at the end, when it's too late to stop them driving earlier stages into non-linearity and intermodulation, so again, you have to be clever with the attenuator.

Anyway, they are gorgeous receivers. I bought one in the early 1980s which had been stored from new, unused in preservative packing. It shone! The aluminium castings looked like new.

David

[Radio Wrangler]

I forgot two things...

The RA17 meter has an S-meter position, the RA17 one only measures detector level and line audio level.

There's a screwdriver slot switch on the front panel to switch off the internal 'kc/s' VFO and select an external one (eg that synthesiser unit)

David

[ms660]

Originally Posted by evets1967

Hi, I have recenty had the good fortune to come by a RA117 and an RA218. After a little head scratching and replacing of components etc. the RA117 is now working quite well. I would like to try and get the RA218 working but have absolutey no infomation about the unit and am not even sure how to connect the unit to the RA117(do I have to remove the 1.7Xtal?). Could anyone provide me with a manual or at least a schematic and a little advice how to proceed. The unit looks complete.
Thanks in advance.

The RA117 manual say's remove the 1.7Mhz xtal if feeding the 1.7Mhz input from an external source (The RA218)

The 100Khz input socket on the R218 connects to the 100Khz output of the RA117.

If that's any use.

Can't do the whole RA218 manual, too big. I don't do Emails either.

Might be able to do the RA218 schematic in the next day or so if no one else comes up with one.

Any questions the answers to which you feel might be in the manual then post them on here and I'll try to answer as best I can.

Lawrence.

[ms660]

RA218 schematic, 1st part.

Lawrence.

EDIT: Not come out to brilliant but readable, open in new tag and then Ctrl+ to expand.

[ms660]

Two sets of PDF schematic attempts, hope they're of use.

Lawrence.

[ms660]

LP & HP filter innards.

Lawrence.

[ms660]

Complete installation instructions (3 pages) Includes valve pin data and typical valve voltages.

Lawrence.

[ms660]

Operating instructions (Complete...2 pages)

Couldn't get the manual to lay flat on the scanner....So:

Second page of this lot: 1st sub heading actually reads...SSB Reception...in the manual.

2nd sub heading actually reads DSB Reception in the manual.

Sorry all this lot is in dribs and drabs

Will try and do the alignment pages in a bit.

Lawrence.

[ms660]

First five pages of Alignment Instructions, more to come.

Lawrence.

[ms660]

Remainder of the Alignment Instructions pages, total posted for alignment = 10 pages, numbered 3-1 through to 3-10.

A few layout pages next including filter testing layout, then that's about it except for parts list and circuit description.

Enough to keep you going hopefully.

Lawrence.

[ms660]

Test layout for filters.

USB/LSB Audio filters etc.

Block diagram.


Component layouts to follow.

Lawrence.

[ms660]

Component layouts...3 pages in total in manual.

That's yer lot.

Lawrence.

[evets1967]

WOW! thanks for the quick response and all the information, I really appreciate this.
I must agree the audio is far better on the RA117 when compared to the RA17. The 1W o/p makes a big difference especially listening on broadcast bands.
I have quite a bit of reading to do now! Will post if I get it working or... more likely need to draw on your combined experience to crack it.

The RA117 was deaf when I received it and it works quite well now but its not as lively as my RA17 so I still have some work to do. The one part I have not touched on the RA117 is the 40M BPF and I dont have the kit to do so. Is there anyone in the North Wales (or sensible travelling distance) area who could assist, for a fee of course?

I have not checked it yet and will do what I can with a sig gen to ascertain its accuracy but - given every other area has needed some alignment I suspect it is probably not optimised.

Thanks again,

Steve

[evets1967]

Hi Guys,

After rectifying a few simple faults I can report the RA218 is working
It seems too resolve USB on 20M better than LSB currenty and the audio is poor but at least I have a good basis to move forward.

Does anyone know a guy called Rob Filby? I met someone a couple of days ago who informed me he can set up, align/restore Racal kit. Unfortunately all he could remember was he lived in Derbyshire but had no contact details.

Thanks for all the help again.

Steve

[G4XWDJim]

You have a PM,

Jim