RA1772. The RA1771 is identical except that it is decade tuned.See photo' at bottom of page.
Introduction.
All through the 1960's and the 1970's Racal built on the their past experience and increased and improved the products they manufactured.
I think its true to say that although the 12' series of receivers were of good quality , well built , compact and easily repairable for volume users (with the use of plug in modules), the RF performance was nowhere near that of the RA17.So.... It was time to produce a quality receiver using the "new" technology available at the time.
Enter the RA1772.
I will say now, before I go any further, that this has to be my favorite Racal receiver to use. It has excellent strong signal handling performance coupled with high frequency stability from cold.It is quite compact, being about three quarters of the height of the RA17, and slightly less in depth. It is a bit lighter too, weighing in at 45lbs.
It still has some features of the RA17 and 12' series sets.There are two headphone sockets on the front panel and there are still the two tuning controls. One small knob for the MHz setting and one larger knob for the Khz tuning.A "proper" analogue meter is fitted and, of course, all of the usual controls as befits a quality receiver.
It may be worth quoting the manual to give a general description.
The Ra1771 and Ra1772 are fully synthesized solid state communications receivers providing reception facilities for LSB/USB (A3A,A3H,A3J),AM(A3) and CW(A1), ISB(A3B),FSK(F1) and AFC facilities are provided by optional , internally fitted modules.
"The built in synthesizer is phase locked to the output of a frequency standard,which may be either internal or external, and covers the frequency range 15 Khz to 30 Mhz in switched 1 Mhz bands. In the RA1771, the Khz setting is selected by rotary decade switches, with digital indication in 10 Hz increments, while in the RA1772 the synthesizer is continuously tunable over each 1 Mhz band and an electronic readout indicates the Khz setting to 10 Hz. Except for the method of frequency selection both receivers are designed to the same specification."
The Front Panel.
From left to right we have......
The LS, mounted to the top, with a slide switch to select it On or Off. Below that is the RF Tune control with a wide Band position to switch it out of circuit. Then below that the first of the 'Phones sockets.Along from here we have the IF Gain control and above this the AGC switch.To the right of that the BFO knob and above this is the two position tuning rate switch.Center stage, as it were, is the tuning knob and below this two pre sets for setting the AM/USB and LSB line level outputs.To the right and below is the Power Switch and above this the Mode control. Next to the Mode switch is the Filter position switch. Then there is the Meter function switch and above this the Meter.To the right of the power switch is the AF Gain control and then, where fitted, the AFC switch with the Lock Light above.Finally there is the second Phone Socket.
Well I say finally,what I have not included is the lovely red Led Frequency Readout, and of course, not to forget the MHZ selection switch and display which is to the left of the main readout.
One nice feature of this set, is being able to tune continuously. On the RA17, RA1218, and tediously the RA1217, once you have got to the top of the 1 MHZ section you are listening to, you have to step up 1 MHZ and either tune down wards in frequency or spin the knob back and start again, ( this is not fun on the RA1217). The RA1772 is a dream in this respect. Once you have tuned above your 1 MHZ band, the MHZ indicator goes into "over spill" and lights up the next MHZ segment.The KHZ display then rounds over from 99999 to 00000. All you do now is switch up ( or down if you are tuning the other way) to the next MHZ band, and carry on from where you left off . Neat.
General Description.
I must point out that the set featured here is a "non standard" unit. By this I mean that it has options fitted which make it somewhat different from what I would call a "standard" set as seen in the sales brochure . This affects, mainly, the Mode and Bandwidth features.In other respects the design and function of this set are the same.All Racal receivers could be supplied in a number of configurations, but , looking in the book, it seems the RA1772 was supplied with more configurations than most.!
For some reason,Racal, who seem to have started with the 1770 series, and carried it on to the RA1792, have made the filter settings "fixed" for LSB/USB use. That is, where you could select the bandwidth settings at will on the earlier sets on the 1770 series these seem to be only available in the CW and AM modes .With SSB you are stuck with whatever filter bandwidths are fitted to the set. In the model described here the bandwidth can be changed on USB and USB/BFO setting but not AM, there is no CW position ,I assume you are supposed to use USB/BFO.To add to this the Bandwidths are....0.8-1.2 Khz,0.4-1.6Khz and 0.3-3.0 khz. Initially, I found these settings strange , but after discussion with a number of people it seems likely that this set may have been used with a telephony channel on LSB , with fixed 2.7 Khz filter, and frequency multiplexed teleprinter/telex channels on USB with selectable filters.
I will point out that this particular set has the ISB option fitted along with AFC.
The tuning rate can be set to Fast, which is about 50Khz per turn. Or slow which is about 2.5 Khz per turn. There is also a lock facility, which is needed ,as the spin tuning can be very , very "light" unless the drag is adjusted somewhat.Tuning itself is performed within the set, by rotary encoder.This, unlike that in the RA1792, is enclosed so that dirt and dust are kept out. If I have any criticism of this set it is that the tuning rate does seem to be a bit fast. Increasing the drag on the knob gives the impression of easing this, but, it is then slightly more difficult to quickly spin the knob to another part of the band. This is only a very minor criticism.
The rest of the switches/ controls are up to the nice "cluncky" Racal standard and the meter is pleasant to watch.On the subject of the meter it shows, depending on options fitted, Tune Carrier (for AFC), RF level,LSB line out,AM/USB line out,DriveLevel first mixer Lo level, +20,+12,+5,-7 volts level and where fitted FSK out put.
Where the AFC option is fitted this can be selected to either Full Carrier or Pilot Carrier.
The rear panel is, to say the least, Interesting..!
I will only include the main features.To the right is the 50 ohm ant input, pretty standard with a BNC fitting. What is a nice touch is the facility to change the fuse in the protection circuit, to the front end, by means of a fuse holder above the ant input on the rear panel. If you have ever needed to do this on a 1218 you will appreciate how handy this can be.Below the Ant input is the LO in/out socket.To the left of this are the terminals for audio out, line out,FSK in/out, diversity AGC etc, etc. .There is a 12V/STD connection .When the power is shut off from the front panel the supply to the Standard and the VFO is cut.There is no "Stand By" mode.Connecting 12v dc keeps these items powered up ( on this set anyway ). Handy if you have, like this set, the 9420 Frequency Standard fitted, as , theoretically the set will not be that stable until it reaches operating temperature. Although in practice I have not noticed any problems.
In the center of the rear panel are the power transistors etc, mounted on a heatsink, for the PSU. To the left of this we have BNC connectors for Main IF out,ISB IF out, I MHZ In/Out and 34 Mhz In/Out. Slide switches to select 34 Mhz Int/Ext,1 Mhz Int/Ext, LO Int/Ext. The AC power connector and of course the AC line voltage connector. All in all a well packed rear panel.
Internal Views.
Inside the set we have the RF unit to the left in a screened enclosure.To the middle are the main IF boards and to the right of that the large mains transformer.In front of this the frequency standard and then mounted to the front panel the display board, shaft encoder and the logic board. The underside of the set has the Mixer boards 34 Mhz board etc.
To the left is a view of the top of the radio showing the mains transformer, frequency standard (grey module) and the various boards for IF/AF,IF Filters, AFC, etc.
To the right is a view of the underside of the set.
Rear Panel.
Maintaining the set is relatively straight forward, but,it is a bit more of a complex design than the earlier models and a bit of knowledge of digital circuits would be handy.The IF boards lift out of their "enclosures" and can be mounted on nylon lugs, where they stand vertically, so that access can be made for fault finding, alignment etc. It is a shame, however ,that these modules are wired in rather than plugged in like later sets (or earlier if you consider the 12 series modular approach ).This would have made repair or replacement that much easier.One point to note is that there are a lot of Tantalum Capacitors fitted in this set and most of them will be, by now , due for replacement.Another thing to note is that the internal wiring tends to get a bit "brittle". This can result in broken wires , especially around the rectifiers mounted on the rear chassis. This is no different to any set over 15 years old ,and is not the end of the world.
To the left is a view of the filter board, in the middle is a view of the rear of the front panel, showing the enclosure that houses the tuning encoder.
To the right a view of the ISB board mounted vertically for "servicing".
Brief Technical Spec.
It is difficult to give specifications as, mentioned earlier, this set can be found in a number of configurations. Generally this is how they go.
| Frequency Coverage | 15 Khz to 30 Mhz |
| Modes | CW,AM,LSB,USB (ISB,FSK) |
| Tuning Accuracy | +- 5Hz |
| Frequency Stability | +- 6: 10*10 Short Term (9420 only) |
| Antenna Input. | 50 to 75 ohm nominal.Will stand 30V emf of RF continuously .Fuse & spark gap protected for higher voltages |
| Sensitivity | CW,SSB.500Khz-30Mhz S/n is15db with 1uv emf |
| Bandwidth | SSB 3.0 Khz, alternatively 6.0 Khz.Additionally 0.3,1,3,6,8,13 Khz may be fitted. |
I have made some measurements to determine the sensitivity of my set and they are as follows.
| At 1 Mhz | 1.18 uv PD for 15 db s/n AM |
| 1.34 uv PD for 15 db s/n SSB | |
| At 14 Mhz | 1.27 uv PD for 15 db s/n AM |
| 1.50 uv PD for 15 db s/n SSB | |
| At 29 Mhz | 1.30 uv PD for 15 db s/n AM |
| 1.60 uv PD for 15 db s/n SSB |
I also checked the RF meter.
| Meter Reading.db. | RF Input.dbm |
| 100 | -0 |
| 80 | -19.5 |
| 60 | -53 |
| 40 | -72.4 |
| 20 | -98.1 |
| 0 | -101.8 |
RA1771
The RA1771 is identical to the RA1772 with the exception that tuning is by means of 5 decade switches for the Khz section.Conclusions
For my money this set is the most desirable Racal for serious use. I love using all of my Racal collection but if I feel the need to listen to something and not have to worry about it being on frequency hours later this is the set I use.It can match the RA17 for strong signal handling ( I never have to use the "RF Tune"), it seems more sensitive above 25 MHz and the audio quality is very good. I have switched on my 1772 in the morning and left it monitoring Navtex on 518 khz, it is still spot on tune in the evening, for that matter it was still on tune 3 days later,not missing a single transmission. The best of my RA17's cannot do this, although they are fine for SSB use. It may not have the Memories or scanning of the 1792 or the other nice features of that set, but for my money the RA1772 stands a long way above the RA1792. If you only ever get the chance to buy one Racal receiver then make it this one.
Model Variations.
It is impossible to list all of the variations for the RA1772 , and the others from this series. I have details of over 140 different I.F Filter configurations alone. When you add to this the other options such as AFC,ISB,FSK etc you can see that there are a lot of combinations.
There is usually an "Option Number" on the rear of the set. This will give the full configuration of the unit , or, at least, the configuration when it left the Racal Factory.
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