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Reviews Categories | Receivers: General Coverage | Racal RA1772 Help


Reviews Summary for Racal RA1772
Racal RA1772 Reviews: 7 Average rating: 4.9/5 MSRP: $Unknown
Description: Professional quality, 1970s vintage, solid state British communications receiver. Frequency coverage 15-30,000 KHz, AM/CW/SSB/ISB. American built version (RA6772) and Canadian built version (RA8772C)are similar.
Product is in production.
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GM1SXX Rating: 5/5 May 8, 2013 07:51 Send this review to a friend
Power Supply mod  Time owned: more than 12 months
The RA177X 'family' of receivers are excellent but in the years that I've owned mine, I've had to repair two power supply faults to date. This of course is to be expected with ageing equipment.
Due to it's compact design, the RA1772 power supply generates quite a bit of heat which leads to brittle wiring in the power supply area over time.

If your RA177X family receiver suddenly stops working, the PSU is the obvious place to start looking for problems. Check for missing insulation and short circuits on the wiring loom connected to the power supply PCB. I've even seen wires desolder themselves in the power supply area!

Remember that the receiver has a handy voltmeter with which to (quickly) check voltages, if your radio quits. You don't want to 'cook' anything so any voltage checks made should be very swiftly made.

For some reason, RACAL decided to place bridge rectifier D2 on the power supply PCB rather than on some metal surface that would conduct the heat elsewhere. In normal use, this rectifier runs really warm.
A far better solution, is to remove D2 to the card cage which is of course ventilated. This simple mod will dramatically lower the temperatures in the PSU area of the receiver, while only making the card cage slightly warmer. Use some heatsink compound applied to the bridge rectifier to aid heat transfer. The 'wet' electrolytics in the power supply will thank you for this mod by lasting longer than they otherwise would.

You can read about my power supply mod at..
http://hamradioal.wordpress.com/2012/01/08/the-racal-ra1772-psu-observations-from-scotland/

Because these receivers are now quite old, it makes sense to replace the large electrolytic capacitors on the power supply panel. These will all be well past their 'sell by' date. It's a simple job and worth the effort.

Moving the rectifier and replacing those tired old electrolytics will go a long way to getting years more service from a great receiver.

Regards,
AL GM1SXX



 
G8MOB Rating: 5/5 Jul 9, 2011 08:44 Send this review to a friend
A superb older synthesised professional HF receiver  Time owned: more than 12 months
This is one of my favourite HF receivers. There are many professional engineers and experienced amateur listeners who reckon it was one of the best receivers ever made by Racal.

I have owned mine for over 15 years. I swopped it for my first one and it had the "full works" servicing treatment by Pat, G3YFK. It looked almost brand new and came with all the original Racal manuals, two fatter than Yellow Pages. It's been living in a rack here and still looks pretty new.

The 1772 represented a major milestone in receiver development when it was first marketed in 1973/4. The seminal professional paper on this receiver was by one of the designers, Roger Winn, published in "Wireless World", October 1974, and is obligatory reading for any owner or anyone interested in receiver design.

The 1772 was the first HF receiver to do away with the need for any front-end selectivity (apart from a low pass filter to suppress the First IF and image). It was able to achieve this using the following features:

(1) A superb first mixer using four balanced switched FETs based on the slightly earlier Rafuse design. It is a tricky circuit to implement practically but Racal did it and were later imitated by Plessey in the PR2250 and by Redifon in the R500 receiver (both very expensive BTW) and probably many others. Similar mixers were used in the subsequent RA1792 and RA3700 series.

This design lifted the state-of-the-art IP3 mixer performance dramatically. Up till then top receivers would produce a IP3 product of 1 microvolt EMF for about a 3mV EMF input (and many like the 75A-4 were a lot worse). The RA1772 improved this to about 30mV EMF input. Racal showed that the maximum RF output of the average professional aerial into a 50 ohm match was less than 30mV and hence there was no need now for complicated and expensive pre-mixer selectivity to reduce the level of off-tune signals in order to accommodate the limitations of existing mixers.

Racal's IP3 spec for a 20kHz signal spacing is +27dBm compared with an average of +7dBm for earlier receivers (if that).

This improvement should not be underestimated because of the 3 for 1 effect of IP3. Thus an increase of 6dB in input level will produce an increase of 18dB in the intermodulation products. As the signal input level increases the receiver begins to "drown" in its own IP products and in consequence the lower level signal inputs disappear into the noise. It's the inverse of applying an attenuator. If you attenuate the input by 6dB, the IP3 product is attenuated by 18dB. Hence the use of aerial atenuators on receivers, but none was found to be necessary for the RA1772.

Early customers of the RA1772 complained to Racal that the set was insensitive compared with their existing radios. Racal told them to check with a signal generator and all was well. The reality was that most of the "signals" heard on earlier sets were in fact the sets' own IP3 products!

(2) The RA1772 has an excellent synthesiser fully tunable in 10Hz increments. I believe it was the first synthesiser to be fully tunable in a commercial receiver (though the WJ8888 may have predated it by a few months). It uses no fewer than 5 loops (three PLLs and 2 transfer loops). This is doing things the hard and expensive way but the result is low phase noise such that the receiver is fully spec'd down to 15kHz, and in my view it is still the best HF receiver down there without using an external or internal VLF up-converter.

When you listen on the 1772 you notice the relative quietness of the bands. Signals quickly enter and disappear as you tune. This is the mark of good mixers and a good synthesiser.

Other reviewers have commented on the superb mechanical build quality - it's built like a tank. I once met the designer of the very complicated cable loom that snakes its way all round the PCBs. He was nearly bald and blamed the 1772 for his loss of hair! As an example, there are about 50 cable connections to the PCB of the PSU alone, and each solder tag is only about 4mm away from its neighbour, which makes servicing tricky. In contrast the next generation of receivers, the 1792, has a vastly simpler PSU module using the (then) new three-terminal regulators and it only needs two standard D connectors - one for for AC power in and the other for DC out.

The recovered audio of the RA1772 is very good too. This is the product of:-

(1) The good mixers and synthesiser.

(2) The excellent IF intermodulation performance. The In-Band intermodulation spec is that two in-band signals of 30mV EMF will produce IP3 products of NMT -40dBm. This is better than many modern receivers and contributes to the cleaness of the sound particularly on CW and data.

(3) The good crystal filters which do not ring on CW unlike a few amateur ones I could mention.

(4) The low distortion AM and SSB demodulators and audio amp. I measured the total harmonic audio distortion at the phones output on a single CW input at about 0.75%. The AM detector is a constant current circuit rather than the normal simple diode and the SSB/CW demodulator is double balanced diode ring mixer.

The tuning feel is excellent, the shaft encoder being a huge diecast device incorporating a heavy flywheel and good quality ball bearings. A flick will spin the encoder for about 10 seconds with the shaft brake eased off.

The frequency stability of the set is good to superb depending on the option of the internal 5MHz standard. At the bottom end is the 9400 TCXO (made by ITT) which is utterly reliable. At the top end is the excellent Racal-Dana 9420 standard (fitted in my set) with a drift rate of around 6 parts in 10^10 per deg C - like not many Hz per year after a long warm up! For total purists, you can input an external frequency standard - eg from a R&S XSRM rubidium or GPS-disciplined OXO.

Some not so good things.

(1) The PSU runs hot and once in a while all power ceases. This is usually caused by dry joints in the +20V regulator circuit. This line drives the other supply rails like a daisy chain and a failure causes the others to close down. Thankfully the repairs are quite simple, aided because the back panel can be dropped quite easily giving good access to the whole of the PSU. A few dabs with a soldering iron is usually all that is needed (though the first time can be daunting thanks to all those 50 cable connections mentioned earlier).

A sensible antidote is to fit a small noiseless computer fan to the external heatsink.

(2) The BFO is free-running, it floats above chassis potential and drifts for the first hour. This is a total pain on CW and FSK and no one knows of an easy antidote. One solution is to fit a crystal on say 1.399MHz on an internal board (there is already provision for this) in lieu of the BFO. Thankfully the BFO is not used on SSB because the carrier injection on 1.400MHz is derived from the synthesiser.

To receive data signals with very high stability, a variant was developed whereby the USB filter position has three different filters offset into the USB thus enabling the normal CIO in the synthesiser to be used rather than the BFO. The prime driver for this appears to have been the RAF's extensive use of Piccolo (which originally demanded an absolute long term frequency drift of NMT a Hz or two). Accordingly, many 1772s originating from the RAF have these unusual features, but they can be still used on normal USB.

(3) Potential buyers are warned that these sets are now old and many were used 24/7 by the military and commercial boys for months on end in hot-running racks. The first thing to do is remove the top lid and look carefully inside for any "deep frying" of the cableform and PCBs. One RA1778 I saw (similar to the 1772) was a horrible mess. Unless you are a masochist and enjoy "knitting" new cableforms, look for another set.

(4) Sometimes when switching between fast tune, slow tune and lock, the frequency changes. This is a symptom that the mark - space ratio output from the shaft encoder is not equal. The excellent maintenance manual explains how to reset it - not a difficult job.

(5) The IF filters are diode switched. Relay switching would have reduced filter leakage somewhat, but the leakage is not that bad.

(6) There are numerous variants of the RA1772 reflecting its many different applications. These include dual diversity reception, FSK, Piccolo, DFing, maritime and loads more. The variables are the many different IF filters (about 130 different filter sets) and the options for frequency standard, front end tuner, ISB, FSK and AFC. Some seem to be pretty rare - probably "specials" for GCHQ and the military - but be on your guard.

Thankfully Racal thought of this problem and the key is the ID plate on the rear panel. The coding on it should tell you what is in the set. Page 1-3 of the user manual sets out the decode from A to K, and covers (from left to right):
(i) the letter code from A onwards giving the IF filter set
(i) the frequency standard
(iii) RF tuner fitted or not
(iv) ISB filter I/D
(v) FSK facility fitted or not
(vi) AFC fitted or not.
However, there are very many IF filter sets not mentioned. The "usual" model seems to be "B/S3/R/0/0/0".

(7) There is no battery back up for the synthesiser. On mains power switch off the kilohertz reading defaults to zero and the synthesiser drops to the nearest whole MHz "hard wired" and set on the MHz switch. To get round this Racal introduced the MS540 12V battery module which screws to the rear panel. This has a nicad battery backup and charging circuit. The output is fed to an external terminal and keeps the relevant circuit alive when the power is off. The circuit is at Appendix 3 of the maintenance manual and it should not be too difficult to build a "Chinese" copy.

Overall, this is a fine radio and has a handsome front panel. It's so easy to tune but of course it has no memories, which to a modern kid might be a serious drawback.

Potential purchasers should try to read John Wilson's exhaustive technical review in the UK's "Short Wave Magazine" for January 2002, page 43. For example in an SSB bandwidth of 2.7kHz he measured the IP3 at 20kHz signal spacings at +33dBm and a 3rd Order dynamic range of 110dB. The IP2 wideband was +50dBm but increased with the preselector in to +82dBm. These are impressive numbers which explain why so many folk still regard this old set so highly.

Feel free to email any comments to me at michaelob666@ntlworld.com.
 
PA3FUN Rating: 5/5 Dec 14, 2009 01:17 Send this review to a friend
One of the best!  Time owned: more than 12 months
In my shack I have the Racal RA-1772 right beside the Harris RF-590 which is still regarded as one of the best surplus MF/HF-receivers on the market. I myself prefer to use the RA-1772. Exceptionally good radio in every aspect. Outstanding dynamic range and strong-signal handling capabilities. Only two minor issues: a/ the internal speaker sounds terrible b/ having no LSB-filter one has to use CW+BFO to tune in to LSB-signals. This works, the BFO is however very unstable during the first 15 - 30". Besides from these two points in every other aspect an awesome good radio. If you can lay your hands on one and have sufficient space on your desk - GET IT!
 
G3NCN Rating: 4/5 Jan 19, 2009 09:16 Send this review to a friend
RA1772 from the horses mouth  Time owned: more than 12 months
RA1772 was a ground breaker. We strove to make the signal handling performance the best achievable, the design cost effective, and the tuning revolutionary.
This receiver was the first fully synthesised table top receiver Racal had ever produced. By today's standards the synthesiser was crude, but it achieved outstanding stability compared to anything previously produced. The VFO version of the receiver was never produced since it was not cost competitive with synthesised versions, in view of the mechanical complexity of the tuning mechanism based on RA17 dial.
The signal path was certainly unequalled by successive Racal receivers, which went for cost effective mixer chips rather than the FET ring which the RA1770 series used. In fact I believe the signal path performance is only now being surpassed by current soft receivers. The filtering in the 1770 series left something to be desired, however. The diode switching was simple and cheap, but did not allow the ultimate filter selectivity to be realised. My one regret!
I was the engineer in charge of signal path and erganomics development, (operating controls and characteristics). I also shared the development of the fet ring mixer which formed the heart of the front end. I have owned a RA1778 for years.
 
W9LBB Rating: 5/5 May 22, 2003 22:35 Send this review to a friend
A Racal RA1772 Update  Time owned: more than 12 months
I wrote another review of the rig last year, and
it's now time for an update... mainly, because I
now have a SECOND one! If that isn't endorsement
of Racal's product, i don't know what is!

My second RA1772 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. However, it has a
whopping SEVEN selectivity positions (all crystal
lattice filters) giving 100 Hz, 400 Hz, 1.3 KHz,

3.0 Khz, 6.0 KHz, 8.0 KHz, and 13.0 KHz bandpass
positions.

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.

It was clearly set up at the factory to give the
CW operator every IF tool he could possibly want,
but oddly it did NOT have the LSB and USB filters
for SSB operation. Go figure...

Looking over the manuals it appears that the main
problem with installing SSB filters (other than
FINDING the appropriate 1.4 MHz IF filters, that
is...) is mechanical rather than electrical; the
filter board in this radio is maxed out.

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!

After well over a year's day to day experience
with the RA1772, I'm STILL very happy with the
radio, but a few minor things have popped up.

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. To tune in SSB with a rig
set up WITH the proper filters, the BFO signal
used is derived from the synth, and therefore is
rock stable.

WITHOUT the filters, you're forced to use the
variable BFO, which is NOT locked to the synth
(just a free running oscillator). That BFO is
VERY unstable as compared to the synth, and a
LONG warmup period (1 hour plus) is required to
make it settle down enough for serious RTTY or
data use. 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.

Others have noted the tunable BFO as the RA1772's
Achilles heel, but it has to be counted as a very
minor design flaw in an otherwise EXCELLENT
reciever design. In any case, after an hour the
BFO settles down nicely for ANY use.

After completion of the aforementioned SSB filter
project, the next step for my pair of Racals is
to explore the possibilities of using another of
the empty card cage slots to house a homebrewed
DRM interface board, adding computer in / out
connections to the rear for that purpose, and
putting a toggle switch into the unused & plugged
AFC switch hole on the front panel to choose DRM
digital audio in addition to normal analog. The
RA1772'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.


73's,

Tom, W9LBB

 
GM1SXX Rating: 5/5 May 21, 2003 10:35 Send this review to a friend
Racal RA1772 HF RX  Time owned: 0 to 3 months
The Racal RA1772 is my second Racal receiver. The first was a Racal RA117 bought many years ago, and still in use.

As boatanchors go, the RA1772 is a relative lightweight at around 45 pounds.

Because the radio was designed to do many different jobs. military, maritime, point to point HF links etc, there are a multitude of optional items that may or may not be fitted. Some include ISB, Diversity reception, various filter options and a choice of crystal references... standard or high stability.

Mine is a very standard set and fitted with the high-stability crystal reference.

At only 7 inches high, it is quite a lot smaller than the valved RA117 radio.
Tuning is by means of a rotary switch, to select the 1Mhz band segments and a rotary tuning knob for the Khz tuning. In short, it has a similar design philosophy to the Racal RA117.

The tuning display is by means of LED indicators that are very soothing on the eyes.
In conjunction with the silky smooth tuning dial (drives an encoder disk and has internally adjustable friction), this radio is a delight to use.

The RF performance is superb and it is fitted with a switchable tuned preselector.
In normal use the tuned preselector is not needed but it can be of use in crowded band conditions.

All the controls are laid out in a very ergonomic manner and are clearly labelled and obviously designed for use by a human operator. Although this radio uses a VCO, I found its performance to be very similar to the RA117 but with improved sensitivity.
With a 50R load across the antenna terminals, only a very few low-level spurious signals could be detected across the entire tuning range. I could not hear any synthesizer noise at all.


The receiver is a dual conversion superhet and great care has been taken to maximise the performance of this radio. It tunes from 50Khz to 30Mhz in 30 1Mhz bands with a 200Khz 'overlap' at the band edges. Unlike the RA117, you dont have to 'rewind' the Mhz dial every time you want to flip up or down across a 1Mhz 'boundary'. You just click up or down the MHz switch and continue on your way.

One thing you quickly notice about these premium radios is the silence when tuning between stations. The HF bands are not as noisy as some people think. With many radios, some of that noise comes from within. Not so with the RA1772. It is an absolute joy to use and only on longwave where there really *is* a lot of background noise does it sound like lesser radios.

To its credit though, it happily goes down to 50Khz with good sensitivity. I can copy many LF beacons and time standards at good strength.

The mechanical construction of this radio is similar to the RA117. A cast aluminium chassis is used with deep 'bays' on the topside to hold the various receiver modules and optional extra PCBs. The PCB's are hardwired to the wiring loom rather than using connectors. In my opinion, this is a plus point for reliability. The boards can be rotated out of their bays for servicing.

The underside is home to several more PCB's, this time, mounted flat onto cutouts in the chassis. The digital circuitry (tuning circuitry mainly) is therefore segregated from the RF and IF boards on the topside.

Two tuning rates are available, 100Hz and 10Hz steps. A tuning lock is also present.

The radio I have is fitted with a high-stability frequency reference. This seems to be pretty common with these radios. The reference is ovened and runs at 5Mhz. This is further divided to provide a 1Mhz reference and also provides the reference for the 34Mhz oscillator. Stability is truly exceptional.

The meter is worthy of reference. I have never seen a meter do so many jobs. Apart from the usual stuff, it can monitor the various power supply lines used in the receiver.. +20, +5, +12 and -7volt lines.

As with most things RACAL, the rear panel is covered in various connectors, switches and fuses.
Almost anything you might want to be able to make a connection to is there on the back panel.

From the time I ordered it, until I received it, I had to wait seven weeks for my 'new' radio. Being an impatient sort, this didn't please me too much but the wait was well worth it. I got a radio that had been serviced with several parts having been replaced including the speaker and meter and was in virtually new condition along with the user manual. It had been wrapped in several layers of bubble wrap and placed in a
huge box full of styrofoam 'worms' so it arrived in excellent condition.

These radios vary greatly in price on the secondhand market. Mine came from Telford Electronics in Shropshire, England. I've seen RA1772's advertised at four times what I paid for mine. Silly I know, but these radios are not available in large numbers. I have no connection with Telford Electronics except as a happy customer.

For ease of use, performance, stability and sheer build quality, this is the best HF radio I've ever come across.

Grab one while you still can. You will not be disappointed. I give this radio a 5 out of 5.

Allan Copland GM1SXX
 
W9LBB Rating: 5/5 Jun 16, 2002 20:01 Send this review to a friend
The Last of the Mohicans...  Time owned: 0 to 3 months
The English built Racal RA1772 isn't a well known receiver in the US. 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. I understand it's quite popular among British hams & SWLs.

The radio was clearly designed for maritime and military use, and with the various optional packages it's EXTREMELY flexible.

It's apparent that the 1772'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 10.5" high rack panel that was almost a standard for communications receivers. 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.


The frequency readout is LED digital, and the dial moves it in front panel selectable steps of 10 and 100 Hz (the American & Canadian versions reportedly include 1 Hz tuning steps). 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 radio's rugged and almost bulletproof. 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 1.4 MHz. 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. In my particular radio there's LSB & USB sideband filters (2.7 KHz), an AM filter (8 KHz), an RTTY filter (1.4 KHz), a CW filter (400 Hz), and a so-called "carrier" filter for the AFC option (100 Hz).

The LSB & USB filters do double duty, setting the bandpass of the ISB (Independent Side Band) channels. The manual states that there are also optional 6.8 KHz filters available for that purpose should you have the need to read wide bandpass multiplex signals (!!!).

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!

You're REALLY getting your money's worth out of that little meter movement!


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.


Performancewise... it's a pure joy to use.

Quite good sensitivity & noise figure; it rivals my Racal RA6790/GM, and that's one of the best LF / HF front ends I've ever encountered.

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. BTW, I was pleasantly surprised to find a mechanical vernier drive on the BFO control which has been a VERY big help in 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!

It's VERY clear that this radio was designed for use in a high RF level environment. 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 (500 MA cartridge)!

Quite low distortion SSB audio recovery, and the AGC seems to be timed well for that service.

AM sounds quite good through that 8 KHz IF filter. The receiver is VERY good for AM DXing, and is quickly becoming one of my favorites for LF / VLF work too.

The audio stages seem pretty good to my ear; the audio quality clearly beats out my R71A (tho that's not saying much!), and rivals my modified Hammarlund SP-600LF. Not bad at all in the way of distortion.

As for design quirks... the radio design doesn't include a memory floater battery for the digital display and synthesizer's data latches! In the event of a momentary AC power blip, the synth & display reset to all zeros.

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. All versions of the radio (near as I can tell) use an ovenized time base oscillator (various accuracy / stability options available), and the floater battery ALSO powers the heaters in it!

I've dealt with this partially by hooking a 12 VDC gel cell to the +12/STD terminal on the rear panel, keeping the oven heated at all times, and built a small floater charger for the battery.


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.


73's,

Tom, W9LBB

 


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