It was dead from 4 to 8MHz. As it came with full service manuals, I decided to take a chance. The problem was a broken clamp connecting a gear wheel to a cam shaft in the front-end tuning rack.
This set has automatic preselector tracking. Permeability tuning slugs, in 6 octave ranges, are driven by the MHz and KHz knobs via a gearbox and differential.
Unfortunately, the broken clamp was buried deep inside the clockwork. I had to send the tuning rack to Rick Mish of Miltronix who has re-manufactured so many of these sets that he can fix them with his eyes closed. It's equivalent to 30 crystal controlled converters in front of a conventional MHz superhetrodyne receiver. The latter has a highly stable VFO, enabling absolute frequency setting precision of better than 1KHz. Although the set was lively enough when I acquired it, it went deaf within a few weeks of use.
I had it fully re-conditioned by Robin Filby in You can see his 'next service due' sticker in the middle of the front panel. Currently, my set has a minor fault. Occasionally, the 1MHz crystal oscillator fails to start. Eventually, it bursts into life if I leave it on for a minute or two. I must get around to changing the crystal one of these days! Still based on the Wadley-loop principle, these sets are transistorised versions of the RA The RA has a mechanically-driven digital frequency readout.
Of high-quality, modular construction, this set is beautiful to look at inside. Performance wise, it sounds great. I listen to it through my Hi-Fi as there is no internal speaker. I've only had one problem with this set: One of the capacitors in the mains input filter went short circuit blowing the mains fuse.
When other synthesizers could only be programmed with decade switches, the RA had a tuning knob offering a VFO-style search facility. It also had a bomb proof front-end.
The dynamic range is such that it doesn't need an attenuator and the preselector can be switched out of circuit most of the time. Some versions have an internal FSK demodulator. My set has AFC automatic frequency control which phase-locks the 2 nd conversion 34 MHz oscillator to the received carrier for synchronous AM reception.
Top left is the At the right you can see the 2N local oscillator drive transistors:. The synthesizer is a cascade of 3 multiplying loops and 2 summing loops, implemented in discrete 74 series TTL.
They don't make them like that any more! My second RA is quite different from the first one. This rig seems to be somewhat more conventional than the military version that I got the first time around.
No optional independent sideband, and no AFC included. This one has no markings to indicate that it was ever a military radio, so I have to assume it was originally sold on the civilian market. Go figure Internally there is more than enough space to add a second filter board, and the diode switching for filter selection is simple to implement in the existing receiver.
There are empty shielded compartments in the card cage that are meant for the RTTY converter, AFC, and ISB cards that can easily be pressed into use for a home fabricated second filter board. Racal was nice enough to include the necessary, tho unused, wiring for selecting SSB filters, all neatly tucked away in the wiring harness.
I have the filters, and design of a circuit board layout is under way to complete the project. It has already been tested in breadboard form, and it works quite nicely in testing. This second receiver, like the first one, has the high stability time base oscillator option for the synthesizer. I'm beginning to think that this "option" is pretty much the standard!
First off, the "new" Racal's panel mounted speaker has a warped cone, and sounds terrible. I use external speakers anyway, but the fact that the problem exists frustrates me.
I have been unable to find a Racal replacement, and there is seemingly no commonly available replacement that fits in the space and mounting provided. A minor point, but irritating. Second, I've had to dig a bit about the radio's electrical design.
Without the SSB filters, you find out something unfortunate in a hurry. It's more than stable enough for CW, but teletype converter audio filters aren't at all as adaptable as the human ear, and the best microprocessor based converter can't come close to matching the human brain's flexibility. The RA's wonderful stability and that 13 KHz IF filter seem to me to make it a natural for the step into the Brave New World of digital short wave broadcast reception. The Canadian and American made versions were apparently made in very small numbers, and are therefore quite scarce.
That's a shame. This is a great rig that could have become acclaimed as a classic over here. It's apparent that the 's career was cut short by the trend toward microprocessor based receivers that could be computer controlled.
This is the Last of the Mohicans when it comes to receivers that were actually designed with a human operator spinning the dials in mind. The ergonomics are excellent. The 4 rack unit high 7" panel is, in line with the trend toward more compact gear, smaller that the usual Everything is laid out in a logical and handy way. The radio is a real pleasure to use.
Operator fatigue is at a minimum by careful design. It's probably one of the last professional receiver designs to use a real bandswitch; there are 30 bands of 1 MHz each. The MHz display on the readout is a shadow disk attached to the bandswitch shaft.
BTW, each band has 20 KHz of overshoot on each end which, rather amusingly, lights alternate bulbs behind the MHz shadow disk to keep the dial readout accurate when the overshoot is accessed! The design of the radio reminds me a lot of working on British sports cars and motorcycles; everything inside is familiar, but, as the English are wont to do, things are done a little bit differently than us Yanks are used to First off The rig's weight of 45 pounds is largely made up of a cast aluminum chassis, divided in to wells housing individual subassemblies.
The shielding is excellent, and construction is rigid. This is a double conversion reciever, with IF conversion frequencies of 34 MHz and 1. There are up to six crystal lattice filters in the IF; sometimes less, because some optional features like the AFC Automatic Frequency Control use slots for specialized filters.
I can't really state definitely what IF filters are normally installed. Racal produced this receiver to do a LOT of different jobs with the various option boards, and each configuration requires a different IF filter setup. The manual states that there are also optional 6. The S-meter includes some handy features, the likes of which I've never seen on any other receiver.
Besides serving as an S-meter and audio level meter for the line level outputs and independent sideband channels , it also serves as a tuning indicator if the internal RTTY demodulator option is installed, a tuning indicator for the AFC option backed up by an AFC LOCK LED , and it looks at the various power supply rail voltages! The front panel sports a small, but quite good sounding, front firing speaker! THAT'S something you don't see every day on a professional receiver It can be muted with a slide switch on the speaker grill if you're using an external 8 ohm speaker.
In addition, this rig is one of a very few around that has TWO headphone jacks on the front panel, located on the right and left lower corners. Plugging into the right one mutes the panel speaker. Frequency stability is excellent, once the crystal oven stabilized in 15 - 20 minutes more on that below.
The rig's stability after oven warmup is such that the receiver is excellent for digital mode DXing. Front end overload and intermod characteristics are outstanding! The design includes a once again, optional RF preselector which, frankly, I've never had the need to use! I was rather shocked by the manual specs on it; they specify that the radio will withstand an antenna input of 30 VOLTS of RF on a continuous basis without damage!!!
If input voltage gets any higher than that, they've included a gas arc gap in the design, and an antenna fuse MA cartridge! The audio stages seem pretty good to my ear; the audio quality clearly beats out my R71A tho that's not saying much!
Not bad at all in the way of distortion. As for design quirks A floater battery was offered as an option, but there's a catch to it. The small NiCad floater would only keep things going for 30 minutes in a power outage, and is cut off completely whenever the AC power switch is turned off, again resulting in a reset to zeros on next use.
The reason for this oddity is simple, really. Bad features? There's only one that irks me slightly. The synthesizer is rather noisy, as is typical of ALL '70's vintage synthesized radios.
It's considerably better than most on that score tho. It's really unfortunate that this radio isn't seen in the US more frequently. It has a LOT to offer, and the design is refreshingly different from it's American counterparts. This rig is one of my favorites.
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Those reviews will be removed. Do not offer rewards for positive eHam product reviews. With the terminals provided it's possible to set the primary voltage from a low of vac vac minus 10vac up to vac vac minus 0vac or vac - 10 to vac - 0. Terminal 23 - 6. The only schematic showing the terminal numbers as referenced to the actual windings of the transformer is in the RA manual.
Shown above is a portion of the schematic showing the terminal numbers. The terminal number to transformer winding connections are the same for both types of transformers. It would be expected that any date code will be a date somewhat earlier than the actual receiver built date. However, the Plessey filter cap has the date code of "MAY 59" - at least a month earlier. Probably the earliest this receiver would have been built would be in August of and that's just a guess.
Still, date codes can get you fairly close to a build date estimate. Some early RA receivers were equipped with a meter that has a "TRA" logo shown on the scale as the manufacturer. Turner meters have a red index line indicating the 10mw AF level into Z on the uA scale.
Ernest Turner meters are considered somewhat delicate by enthusiasts and defective ones were sometimes replaced with other types of meters. North American RAC versions added a three-position rotary "meter" switch and an S-meter function-scale in green was added to the meter.
Ernest Turner supplied this "S-meter" style of meter on early North American versions but the meter itself is still identified as Model W If the S-meter position is used it will show a relative indication of signal strength but the readings will depend on several factors including antenna type, the received frequency, the setting of the RF Attenuator or the tuning of the preselector. The adjustment pot behind the cinch-plug just below the meter is for the S-meter function only.
Note that the scales are slightly different between the Turner meter and the Stark meter. Stark meters were also used on the UK-built RA receivers.
The AF meter indication works only on the Z ohm 3mw line which has its own individual output transformer and is controlled by the Audio Level control located next to the AF Gain control on the front panel. If you have the Audio Level control set to minimum you will not see any indication on the meter.
The other unused audio outputs should also probably have similar load resistors installed. RF Level only shows received signal carrier levels in the AM mode. It has the same type of scale as the Stark Electronics Instruments HSR meter but the housing is somewhat different having a convex glass cover. The modular construction allows removing individual circuits from the chassis but almost all modules are a combination of hard-wiring interconnections to other modules or to component boards along with some coaxial cable-BNC interconnections.
Module removal will many times require partial receiver disassembly and always some wire unsoldering. With good documentation, the process isn't too difficult but be prepared - none of the modules just "plug-in. Some UK rebuilders actually even consider the British components to be "below average" in quality. Capacitors will probably require replacement since they are now at the half-century mark for age.
Resistors should be checked for value-drift. However, that's no guarantee that these components will have survived with no degradation over the past fifty years. Many of the component problems can be caused by a poor storage environment that has temperature cycling with huge excursions along with high humidity causing corrosion and moisture ingression.
Storage in sheds introduces the possibility of rodent infestation. If the receiver under inspection has signs of having been stored in these worst of conditions expect a multitude of problems to be encountered during the rebuild. There is an old adage about "Racal solder joints" that does seem to be a sort of common problem.
These are "cold solder joints" Brits call them "dry solder joints" that just need to have the solder "re-flowed" to correct. My RA had a cold solder joint in the 1. As with any "half century old" electronics gear, you will find problems - even on functional units. Besides electronic problems expect mechanical wear, cosmetic problems and corrosion to be encountered.
After all, most of these receivers were used by either the military or commercial users, so end-user abuse was fairly common. A source of instabilities and birdies can be poor contact on the shielding under the chassis. There are seven smaller shields that fit into place under the chassis. Six are providing complete shielding of the Wadley Loop circuitry and one shield is over the RF attenuator.
These must be present and must be making good contact with the chassis to prevent feedback and oscillations from occurring. Other instabilities can be caused by the components is the KC VFO where the underside is completely sealed with no way to dissipate heat build-up. The heat, especially in military operations, seems to have sometimes caused component drift.
Alignments need to follow the instructions in the manual as sometimes special equipment is needed. Check the instructions before "diving in.
Expect to have to receiver on its side for much of the alignment, however the IF bandwidth crystal filter adjustments are accessed on the side of the receiver, requiring the receiver to be "rightside-up. Paint Touch-up - Matching front panel paint color - I had some minor chips and scratches on the RAL that would look better if touched-up. I used Testor's Model Lacquer Paint.
It's the paint found in hobby stores in the very, very small glass jars. The gloss mixed with flat will dull down the gloss to match the panel better. Do your matching in as much natural light as possible.
I mix by eye to get the general tint and then get a close match by actually touching up an edge of the panel. Wipe off your mixes until you get it close. Remember, the paint will dry slightly darker so have your "wet" match just a slight shade lighter. Wait for the paint to dry to judge how close of a match you got. If it's good, then proceed with touching up the panel. This procedure is just for small nicks and chips, not to cover up major problem areas.
Cleaning Knobs with Collett Grips - If you plan on doing a soak cleaning of these types of knobs be sure to disassemble the collett grip from each knob.
There is a spacer in the smaller knobs that is made of garolite which is a fiber board type of material that might be damaged by soaking. The larger tuning knobs have a plastic spacer. The assembly consists of a brass collett, then a spacer and then the tightening nut. When the knobs are apart then the collett can be cleaned as they usually are somewhat oxidized even though they are brass.
Use a brass "tooth brush" to clean off the oxidation. After the knob body is clean and dry after its soak then reassemble the collett grip in each knob.
Best reception results will require a good, resonant frequency or "tuned" antenna system and very careful tuning of the RF antenna preselector. This circuit is very Hi-Q with the tuned "peak" being very sharp. When "band cruising," the preselector should be retuned every 50kc or so for best sensitivity. The signal gain with precise grid input tuning to the RF amplifier is impressive. The Hi-Q of the preselector plus the high first conversion frequency results in a very quiet noise floor but also excellent sensitivity.
The Attenuator can be used to reduce intermittently strong signals while still keeping the preselector tuned. The tuning "feel" is very light and the filmstrip dial is easy to read providing accuracy "to the kilocycle" if the CAL oscillator is used.
IF Bandwidth selections will usually be 3kc or 6kc for normal listening. SWBC stations sound fine on 6kc and if they are particularly strong and transmitting something interesting the 13kc bandwidth provides excellent reproduction. The 13kc can be used on AM BC in the kc to kc part of the band. Performance below kc is okay for about kc or so, then it begins to degrade. The bandwidths of 1. For reducing adjacent frequency SSB signals while in the AM mode, "off frequency tuning" is the easiest and most effective defense.
The dial readout is accurate "to the kilocycle. Despite this, the performance differences are hardly noticeable. The Mark II is an excellent receiver, even if it is the earlier version. The same concept of using triple conversion with a Wadley Loop became the basis for these new receivers.
Mechanical digital readout and a tuned preselector, along with a very small, light-weight package were the main features of the RA and the RA These receivers were comprised of several plug-in modules fitted to a main frame chassis.
As with earlier receivers, many Racal accessories were available for these receivers and there are many inputs and outputs on the rear panel to accommodate all of the optional equipment. The receiver operated on vac to a power supply module that then supplied the vdc to operate the circuits. At only three and a half inches in height, several receivers could be operated within a very small rack space. The RA and RA were produced up into the late-seventies. Note that there is another RAE dual receiver and panadaptor setup behind the foremost operator.
This US Army photo is from their website, army. All three receivers were jammed into a shelving unit at the rear of an extremely "packed" storage unit that had more slot machine parts and junk test equipment than radios.
One RAE receiver was almost a complete unit, lacking only the top cover and the shield over the RF input section. Getting one RAE Working - On the test bench, I checked over the mostly complete RAE and, other than being filled with sand and tree leaves, it looked like it was in pretty good shape.
A careful power-up had the receiver working, The RF meter was pinned to the negative but worked in the Audio mode these problems ended up being corrected with adjustments that were on the IF module and the meter driver board.
The audio was taken off of the Phone jack Z and used to operate an eight inch Z loudspeaker. Audio was impressive. The mechanical digital readout on the working receiver was in really rough condition but the two "parts sets" had excellent digital readouts.
It requires moderate disassembly of the receiver's front-end along with maintaining a mechanical alignment during the readout swap. Before starting, tune the receiver to and slowly tune further negative in MC and KC until the mechanical stops are contacted.
In my case, the MC stopped at and the KC stopped at When removing the readouts, the MC readout is one unit and the KC is another unit. They are removed individually. Then dismount the meter, the meter switch, both dial lamp mounts, the fine tuning pot, the VFO switch and the harness clamp. Access to and removal of the MC readout is now very easy.
The RA version "E" was optimized for use with a panadaptor. I used binder head screws. These should be FH undercut screws. The KC readout is mounted with four screws, two screws are easy to access but the other two require a low profile, offset blade screwdriver to remove. Once these two difficult to remove screws are out then the KC readout can be removed. Installation of the good condition readout set was essentially the reverse of the removal procedure. The mechanical alignment of the various gears has to be checked during reassembly because it is possible to have the mesh too tight resulting in difficult tuning.
When the mechanics are correct the tuning is very light. If accurate mechanical settings were maintained during reassembly then the receiver should power-up and receive signals at the proper frequency readout , Two problems remained, Then there was the missing top cover.
I made the top cover out of. Luckily, there's no venting of any type - just a flat piece of metal. Once the aluminum piece was cut the mounting holes were measured, marked and drilled. NaOH will produce a matte finish on the aluminum surface. Just spray on, let it set for a few minutes and then rinse with cold water.
Don't rub, let it air dry or use a heat gun to dry. The finish will be flat or matte aluminum which is like the original. There's no need to coat the finish with any sort of "clear coat spray. Also, remote standby is on the same connector. I will have to make individual pin connections using push-on terminals.
Photo left shows the top of the RAE with the top cover removed. The left-most module is the RF module. The long narrow modules are VFO and Mixer filters. The long module to the right is the IF module. To its left upper are two Mixer modules. Though it's difficult to see, the chassis is a complete aluminum tub with welded corners and an almost complete bottom. There's a small access cover on the bottom side of the chassis. Most modules plug into sockets though most do have other wiring also.
The front of the receiver has most of the components mounted to the chassis and the front panel then mounts to the front of the chassis. The meter mounts using its bezel through the front panel and secured at the backside of the front of the chassis which complicates front panel dismounting. The "B" indicates that this version was built in England for use in North America and is equipped with USA-type tubes, hardware and connectors.
A 2mc bandpass filter was added to the RAB input circuit which isn't in the earlier versions. The RAB uses a six-tube circuit. The use of the converter allows the RA tuning range to be extended down to 10kc, giving the combination a total frequency coverage of 10kc up to 30mc continuous.
The RF input is routed through a low pass filter system and the 1mc Xtal Oscillator is routed through a harmonic generator and a band pass filter. Both signals combine in the Mixer stage.
From there the remaining RA circuitry functions can be utilized. The RAB provides a tuning range of 10kc up to kc. Wideband and Wideband with a kc low pass filter can be selected which bypasses the preselector.
Using the preselector allows precise tuning of the incoming RF signal before its routed to the RF amplifier grid. The attenuator allows signal reduction if extremely strong adjacent frequency signals are present, such as on the AM BC band. The ANT. TUNING control tunes the RF signal input within each selected range and the approximate resonant frequency is readout on the illuminated slide rule dial.
The drum dial rotates with each range selected and displays "band in use. The LF antenna input is via a SO connector. The converter has shielding to the various modules but full shielding of the chassis was not provided. Racal indicated that a special cabinet could be provided to house both a RA and a RAB 14" x 19" opening.
Of the six tubes, four had to be replaced. I ended up replacing both dial lamps because one was open. I replaced both lamps with 40 lamps, threaded base v mA. This required loosening the set screws on the fiber tuning condenser drive gear, setting the condenser to full mesh and then adjusting the readout to slightly below the low end of the scale.
This really isn't "calibrating" or alignment, it just mechanically has the dial readout agree with the mechanical position of the tuning condenser. I also changed the AC input voltage primary on the power transformer from vac to vac since our line voltage here runs around vac. A few sheet metal dents and bends required minor body work. Minor cleaning, mostly dust.
The dial drum was sluggish in changing position with band switching. A small drop of 10W machine oil on the bearing got the dial drum rotating properly. Using the Kilocycle tuning and observing the red scale on the RA dial select a frequency, e. As you near kc, the background noise in the RA will increase and will peak somewhere near kc as read on the RAB dial.
The converter's preselector circuit has a very high Q and the tuning is very sharp. The frequency is read directly on the red scale of the RA and the approximate antenna peaking frequency is read on the RAB dial. When searching for very weak signals, switch off the AVC and control the front end gain manually. This will prevent the noise level from controlling the AVC and reducing the front end gain. Manual control also is necessary during very noisy conditions.
FN kc - Ft. Collins, CO MA kc - Midland, TX FQ kc - Foremost, MN 3. Reception Log for Nov. Other stations heard in this session are listed in the other logs.
AL kc - Trina, WA Total NDBs logged with wire antenna - 61 Antenna for these four sessions was the ' "T" which is an 80 meter Inv Vee fed with 99' of ladder line with the ladder line wires tied together and connected to the center conductor of the Antenna Input of the RAB.
So far, the performance of the loop has allowed receiving NDBs east out to Quebec and west to Hawaii. More details shown in the reception logs below.
The loop was indoors second floor and pointed NE most of the time. Conditions were great. The numbers, e. AA kc - Fargo, ND The first four reception logs shown above list the NDB stations received with a wire antenna which usually presents a fairly high noise level. However, the very Hi-Q of the preselector in the RAB helps to reduce noise as does the double conversion scheme.
The last four logs are results using a Pixel Technologies Shielded-Magnetic Loop antenna located indoors 2nd floor. These last four logs show that there is an definite advantage to using a loop antenna on MW, even in a quite, rural area.
However, the signal to noise ratio is improved using the loop and this usually provides the ability to copy weaker signals, that is, those signals that are "right in" or "just slightly above" the now lower noise level.
None of the listening sessions were longer than 30 minutes and the total number of NDB stations tuned in was NDBs, six of which were newly heard stations. The manual specs the sensitivity for the combo at 1uv for A1 and 3uv for A2 which is certainly believable, although noise levels in the MW, LF and VLF regions usually don't allow reception of signals at that level of sensitivity.
Noise levels are lowest at night during the winter hours. That is one consideration when looking at these logs, More reception reports in the updates below. Since the received noise is low, very weak NDBs are easy to copy. The tuning dial is amazingly accurate, one of the best, usually holding 1kc accuracy taking into account the BFO offset.
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