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write your own review of the Racal 6217.
Apr 13, 2004 17:41
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Dual diversity permits 95% reliability under severe path fade
Time owned: 6 to 12 months
First let me correct a few errors in the 6217A
1. The 1217 has 1 microvolt sensitivity not .1
2. tune info is given in the manual for both
hi-gain ants and lower gain. Overload problems
with a hi-gain is eliminated by proper rcvr
This review considers the Racal MA168B dual diversity switch when used with a pair of
Racal 6217A rcvrs.
Dual diversity by definition requires the use
of 2 identical rcvrs in a master slave configuration with the master rcvr controlling
the VFO of the slave and providing a means of
either combining the audio, agc, or IF output
of the rcvrs...in the case of the 6217 the IF
is used...the output of the diversity switch is
LINE (data device) or audio...headphone or
amplified spkr. 2 antennas are used utilizing
either space (ants seperate by 1 wavelength at
the lowest freq in service) or polarization i.e.
a vert and horiz ant. Both methods have advantages
and disadvantages. In this review each will be
considered. Components of the received signal
will display both vert and horiz polarization
and the two methods can be combined in complex
receiving situtations. with so called quad diversity and multi ant configurations but these
systems are far from the consideration of this
The MA168B is a solid state dual channel switch
with a 40db attenuation of the path not in use
at any given moment in time.. The switching time
between master/slave is less than 10 micro secs..
Path selection, depending on IF input signal
is determined when either input is varied by 6db
with a 10mv input and 30mv will cause a switch
at 3db ... the MA168B requires and IF output
from each rcvr of 100khz and this is an option
vs the std 455khz IF out. 168B provides resolution
of CW, MCW, SSB, RATT, AM, and most data modes.
Switch can be used with the RA17, RA117 and
6217 series except the 6217A-7(1W)S which contains
no means of switching the 2ND VFO from internal
to external i.e. allowing the master to control
the KHZ VFO in the slave.
2 non resonate dipoles spaced about 135' apart and
at some angle to each other are very effective in
eliminating path fade. The 168B has 2 small
gas filled bulbs that indicate the rcvr in use
and its easy to see the switch when fade causes
a drop in sig strength. Space diversity with 2
dipoles assumes that there is a significent
horizontally polarized component.
A vert ant spaced appox 1 wavelenth from the
horiz dipole (at lowest freq in svc) provides
somewhat better performance under certain condx.
Typically the vert is fed to the slave and horiz
to master and in my case a means is provided
switch ants between the 2 rcvrs (an/srr-4 ant
switch mfg by Bird)
The 168B manual states that 2 ants with equal or
nearly equal noise characterstics should be used
obviously theres somewhat of a difference between
a vert and horz ant under normal operating condx
but the switch will only default to the A (master)
rcvr if both signals drop below the ambient
noise at the same time which does not happen
very often Therefore noise is less a consideration
than rcvrs of equal or nearly equal specs (rcvrs
within the same family) both sets of IF amps should be aligned flat and sensitivity should be
as equal as possible. AGC characteristics are
a consideration as well.
The 6217 likes 75ohm Z at the ant input and
consideration should be given to the use of
ants with this Z at the feed point. Hook up
between master/slave is also 75ohm
Resolution of different modes is switchable and
in the case of A1 or A2, data the switch assumes BFO control with a plus or minus 8.5khz range
the same as the individual 6217 rcvr.
The switch is 1 RU or 1.75" tall and 19"
rack and about 17" deep...the 6217 is 3.5" tall
19" rack mount and 17" deep making for a compact
system only 8.75" tall. The system is fairly
easy to set and adjust and the only adjustment
is the MHZ VFO switch on the slave has to be
switched to follow the master...the master KHZ
VFO controls the KHZ VFO in the slave. The system
is a bit akward as far as band cruising is
concerned but use of a spot rcvr will reduce
tune-up to moments. The reduction or elimination
of fade is obvious with 95% ckt reliability
possible under even severe conditions. As pointed
out the 168B will default to the "A" rcvr only
if both rcvrs go below the noise floor at the
same time and there is no detection of rise
within the time constraints of either channel.
The MA168 is considered by most as the finest
dual diversity switch ever produced. The switch
is seamless (important in data modes) and internal
distortion is hardly a consideration unlike
audio or agc driven devices.
The next generation used in the Racal 1772 is
an audio system and an optional module.
If you detect any errors in either review pls
email...likewise any question do same
This review is the MA168B, the MA168 is nearly
identical except no gas bulb is used to indicate
the rcvr in use...a manual switch is provided.
Apr 11, 2004 05:30
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A lengthy production speaks volumns for this rcvr
Time owned: more than 12 months
Believe it would be best to review this rcvr in the context of the design purpose and the Racal US production period (1965 to 1976). This was/is not
by anymeans an amateur rcvr. It was purpose built and sold only to the US govt as an intercept/surveillance rcvr at which it excelled.
The 6217 series...6217A-3, 6217E, 6217-7(1W)S,
6217A(1W)S were all human intervention rcvrs in
that they were manually tuned, the 6217D and 6225
were either remote controlled or slave rcvrs. 6217D rcvrs were widely used in HF DF applications as were other series by the FCC
typically with the RA6337 or 6367 panoramic display unit. The 6217E with the RA6397 was used
by the ASA and others...the 6397 is the ant. filter unit sometimes called a preselector. There
were other options, notably synthesizers and the
MA168 dual diversity switch (which i will review
at a later date) ISB adapter, LF adapter and a few others which would fill out the very wide application possibilities of this rcvr.
The rcvr involves a learning curve...potential
intercept oprs were sent to a school at Vent
Hill Farms, VA an ASA/CIA facility for 2 weeks
to grow accustomed to the full potential of the
series....Vint Hill was closed in 1995.
The rcvr is sensitive (<.5 at 15db or about
<.25 at 10db) and has 5 stock filters .2, 1, 3,
6, 13khz). The tunable preselector is unremarkable except it is very sensitive to tune,
quite effective in tuning out noise and adjacent
channel interference. The rf ATTEN is also
useful for eliminating overload if the rf (preselector) tune doesnt eliminate the problem. AGC is well designed and smooth except on CW
where it pumps which is typical of other Racal
rcvrs...but you're not supposed to use the agc
on CW anyhow. Modular construction throughout
with cast aluminum base on several of the modules. The gear train of the MHZ and KHZ
VFOs is positive and presents a very solid feel,
the machine work is first class including a split bronze anti-backlash gear on the KHZ VFO. The
mechanics are supurbly built. This was a well
thought out design, extremely stable (Wadley
loop) all solid state with the highest possible
components available at the time used. It runs
off -16volts throughout and like many high end
rcvrs then and now there were no facilities for feeding a speaker except in the -7(1w)s AND
(1W)S series which included a 1watt audio amp.
otherwise the 1mw and 10mw on the back of the
rcvr were used to feed headphones or line equipment NOT a spkr...these outputs are 600ohm.
The series has a module which includes the 1st
mixer 40mhz band pass filter and this particular module is particularly difficult to align...the
manual eludes to this. Otherwise alignment and repair are fairly straight forward tho a thorough understanding and a good knowledge of the rcvr
operation is required. In the field
modular swap was the order of the day. Depot centers had test stands and typically repaired
the modules HOWEVER local repair of printed
ckt boards is possible using good pcb repair
Sadly many 6217 rcvrs are out there that are
sub standard in performance leading to big
misunderstanding of the capabilities of the rcvr.
Many have problems in the IF module which
includes the agc pcb and/or the detector board..or
the 40mhz BPF or 37mhz filter need alignment...
the 2nd and 3rd mixer as well. A 6217 that meets
factory specs is one of the finest rcvrs of the
period in the demanding field of intercept and
surveillance. It was the next generation and
very similiar in design to the RA117 (not 17)
and was followed by the US 6772 and UK 1772
which outshine it in some respects. The 6217 is
only similiar to the UK 1217...modules are not
interchangable because the plug gender is reversed
and also some subtle ckt differences....the 1217
is rated at .1 sensitivity...and was produced in
the UK concurrently with the 6217.
A manual is essential with this rcvr and its
use and understanding will greatly aid in
getting the full potential out of the rcvr...theres even a section explaining how to
tune with either a resonate or non-resonate ant which
they refer to as hi-gain ant. Its a very high
gain (hot front end) not broad at all if you
understand how to use the preselector switch and
rf tune and atten switch.Theres 2 Wide Band
position which obviously presents the whole
spectrum to the front end and its use is explained
in the 1 inch thick manual. The general use is
limited to certain tune requirements.
Its one of my all time favorites and I've heard
some pretty high end rcvrs in my life. The BROAD
term "working" is misleading in the operation of
a rcvr. Working to what standard? Factory spec is
the standard of review and by that very standard
the Racal 6217 is a supurb general coverage
Mar 25, 2004 22:26
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Interesting but nobody's favorite
Time owned: more than 12 months
The Racal RA 6217 and its British made counterpart, the RA 1217, seem to have been Racal's first transistorized products following the famous RA-17 tube set. As such, they suffer from all the problems you would expect of early bipolar transistor technology. The 6217 uses the Wadley loop just as the RA-17, and is thus superbly stable. The Achilles' heel of the 6217 is the front end, it's broad as a barn door. There is an input attenuator and an input preselector built in, but later models also added the external RA 6397 remote-controlled antenna preselector. The standard 6217 has a wimpy 10 mw of audio, so you may want to get out the soldering iron and hook up a surplus computer speaker which has a built-in audio amp. The AGC in the 6217 is awful, but to be fair, I haven't tried an alignment and full overhaul yet. The FM feature is interesting but not particularly useful. There were many accessories for the 6217 such as frequency standard options (used by the FCC to check off-the-air signals,) remote control setups, and so forth. The 6217, in my opinion, sells for far too much money on eBay and elsewhere, probably to people who have never tried one and who dream of what will never be. A good price for a working 6217 would be in the $ 150 to $ 250 range. Be careful of some versions of the 6217, which have no local tuning control and were just slave IF strips for such applications as the CIA and NSA. There are also useless models which have only part of the local tuning control installed, so that you can only tune a small segment of the band (same original users as above.)
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