| GM1SXX |
Rating: 5/5 |
May 21, 2003 10:35 |
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| Racal RA1772 HF RX |
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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 (it 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
Footnote.
I have now owned the RA1772 for about three years and it still
beats any other receiver I've tried in that time. If I have any
complaints about this receiver, its simply that an additional 1Hz
tuning rate would have been nice to have. In all other respects, I
still rate it *very* highly.
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| W9LBB |
Rating: 5/5 |
Jun 16, 2002 20:01 |
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| The Last of the Mohicans... |
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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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