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Old 9th Jul 2018, 7:11 pm   #1
John KC0G
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Default The Racalator and the Racalok

I would like to know more about the Racalok which was part of the Racal RA.1220 receiver, and possibly a successor to the Racalator.

The Racalator was a frequency stabilization system for the Racal communications receivers. From what i can determine it first appeared as a stand alone unit, ie the MA.210, for the stabilizing the khz oscillator in the RA17 series of receivers.. See:
http://www.pdp-11.nl/racal/ma210/startpage.html
The MA.210 included a digital frequency display.

Sometime around 1966, Racal introduced the transistorised version of the RA.17 receivers, ie the RA.217 and its rack-mounted version the RA.1217. The RA.217 was mentioned in the Communications Receiver survey in the April 1966 issue of Wireless World. The RA.1217 was followed by the RA.1218, which had a digital frequency display.

Then came the RA.1219 which had a digital frequency display and the Racalator frequency stabilization system built in. Information on the Racalator is scarce, but does exist. In my files I have copies of:
i) K. R Thrower, The Racalator - an Alternative to Frequency Synthesis, IEE Conerence on Frequency Generation and Control for Radio Systems, IEE conference publication no. 31, May 1967, pp 122-128
ii) Keith Thrower, The Racalator, Systems and Communications, June 1967, pp 18-20. This was short-lived publication which seems only to have been published from Sept. 1965 to August 1967
Pat Hawker referred to the Racaltor in his Technical Topics columns a number of times, eg, April 1972 (p. 236), July 1973 (p. 473) and July 2004 (p. 59). There may be more. The latter mentions were part of discussions relating to the "Huff & Puff" stabilisation sysytem originally developed by Dick Rollema, PA0SE. Pat also did a write-up on the Racalator for Electronics Weekly. To date I have not traced it.

The June 1970 issue of Wireless World contained a fabulous article titled "Communications Receivers" by Pat Hawker. It also included a Communications Receiver survey (pp 305-310). The Racal listings included the RA.17, RA.117, RA.1217, RA.1218, RA.1220, RA.329B (military version of the RA.217), and the RA.6217 (US built version of the RA.1217). The RA.1219 is not listed, and had presumably been replaced by the RA.1220. The survey describes the RA.1220 as a RA.1218 "with additionally the "Racalock" frequency stabilizer with one part in 10^7 per day stability"

There is also a full page ad. for the RA.1220 on page a65 of the same issue of Wireless World. In fact it and page a66 are between pages 308 and 309 (At that time Wireless World used separate page numbers for advertisements). The ad does not add much to the above, merely stating "Racalok stability of 1 in 10^7"

So how does the Racalok differ from the Racalator - improved stability, more features, etc? Keith's vintage Racal enthusiasts web site merely notes that RA.1219 used the Racaltor and that the RA.1220 used the Racalok. Fred Osterman in the 4th ed. of "Shortwave Receivers past and present" notes that the RA.1220 is similar to the RA.1219 "but adds circuitry for locking to external master osc."

And so if any of you can shed light on the Racalok i would like to hear it

Thanks and 73

John
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Old 9th Jul 2018, 7:56 pm   #2
G6Tanuki
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Default Re: The Racalator and the Racalok

As the keeper of a RA217D/MA323 I'm interested in knowing what these terms mean in regard of my radio.

I'm pondering they're just marketing-terms for the "Wadley Loop".
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Old 9th Jul 2018, 8:16 pm   #3
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Default Re: The Racalator and the Racalok

Not sure.

Nested Wadley systems (They're not actually loops - nothing circulates.) can be assembled in a decadic structure and would form a decimal frequency synthesiser with basic scales on one tuning capacitor knob per decade of resolution the system was built for. Racal would have found this easy.

Alternatively, it's easy to add a huff-n-puff stabiliser running from the rolling of the last digit of a counter. Pat Hawker covered this pretty heavily. A definite possibility as an internal stabiliser for an RX already with a counter.

Other stabilisers can phase detect the beat of a VFO with harmonics of a low frequency reference, and lock the VFO so it tunes in steps equal to the harmonic spacing.

Then there are pre-tuned PLL methods. Plenty to go at, but which ones got which name in the Racal pantheon?

The RA1772 was a full multi-loop PLL synth with digital dividers and control.

David
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Old 9th Jul 2018, 8:22 pm   #4
John KC0G
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Default Re: The Racalator and the Racalok

Quote:
Originally Posted by G6Tanuki View Post
As the keeper of a RA217D/MA323 I'm interested in knowing what these terms mean in regard of my radio.

I'm pondering they're just marketing-terms for the "Wadley Loop".
The Racalator is more than just a marketing term. In the Racal "Wadley Loop" receivers, and all of the ones I mentioned are of that ilk, the MHz selection oscillator has drift cancelling, and the stability is determined by a crystal oscillator. The kHz tuning is done via a free-running VFO with a 1MHz span. The Racalator is a frequency stabilzing system for that VFO. It works by doing an absolute count of the frequency when the system is engaged, and then controlling the VFO to that frequency. It acts as a frequency-locked loop with a narrow (+/- 2kHz) tuning range.

HTH and 73

John
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Old 10th Jul 2018, 1:35 pm   #5
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Default Re: The Racalator and the Racalok

Hi All,
I was working in Redifon during the late 60's/early70's and remember discussions about the Racalator - Racal being a key competitor in the communications receiver market. There was talk of the company buying a Racalator to find out how it worked but I don't think this actually happened. The general opinion seemed to be that it was a "band-aid" to fix the poor VFO stability of aging RA17's and the like as the RA217 and its successors didn't sell well as their performance was pretty poor compared to other receivers in the market. My boss, the late G3FRB, was convinced that the Racalator was nothing more than a tarted up Huff-and-Puff VFO stabiliser and wondered if Racal were paying royalties to PA0SE!
I wasn't aware of the Racalok system - just a name change, perhaps, to more accurately convey the purpose of the device?
Somebody somewhere must have one - or a handbook - and can enlighten us all.
cheers
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Old 10th Jul 2018, 3:22 pm   #6
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Default Re: The Racalator and the Racalok

It was probably a stop-gap before the RA1772 was released.

The RA17 and RA117 are a bit lacking in some aspects of performance (soft front ends) and the change to transistors made it significantly worse (RA217/RA1217). But the RA1772 was definitely a big step in the right direction in several respects, not just stability.

David
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Old 11th Jul 2018, 2:57 pm   #7
John KC0G
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Default Re: The Racalator and the Racalok

Thank you for the many interesting points in the replies.

Looking again at the advert for the RA.1220, under "Frequency setting" it lists three modes:
i) free tune
ii) 100 Hz steps
iii) +/- 100 Hz Interpolation
The +/ 100 Hz interpolation is a digital incremental tuning feature which is available only when the VFO is locked. This is in addition to the presumably analogue fine tuning control. Looking at online pictures of the RA.1219 it seems that it also had the same features. As such it looks like a poor (or in this case probably not so poor) man's synthesizer. And as RadioWrangler (David) states, it was probably a stop-gap. before the RA1772.

I have found two patent applications relating to the Racalator:
i) GB1168438, Frequency Control Circuit Arrangements, priority date 1966/12/31
ii) GB1168439, Digital Control of Pulse Widths, priority date 1966/12/31. This was divided out of GB1168438.

The two papers from 1967 seem to relate to the MA.210 stand-alone unit. The frequency display and frequency locking elements were almost entirely separate. The latter used a 9-bit binary counter. I do not see how this would have worked for tuning the RA.1219 and RA. 1220 in 100 Hz steps. I wonder if there was a change in the counter system.

Picking up G8BBZ's comments, I think that Racalator predates PA0SE's deign which seems to have appeared in 1973. Also the Racalator provided a lock to a specific frequency, not just the nearest harmonic of the tuning incement as in the Huff-Puff. The RA.1220 looks like at most a minor change to the RA.1219, with a more desriptive name. And yes, I think that I probably need manuals for both radios to work out the changes.

73 John
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Old 14th Jul 2018, 4:10 pm   #8
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Default Re: The Racalator and the Racalok

Hi All,
I re-visited the documentation on Huff Puff VFO stabilisation out of interest, and discovered that the originator was Klaas Spaargaaren PA0KSB rather than Dick Rollema PA0SB. The original PA0KSB article was published in 1973, so yes, several years later than the Racal work it would seem.
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