[Premium-Rx] New radio selection
Bill Mason
cntaty at wcc.net
Sat Jan 31 11:58:52 EST 2009
Dear Michael:
Well put and spoken like a true Irishman! I certainly agree with your
analysis. I mainly use Collins, Racal and Harris receivers of various
nomenclatures though I have numerous other receivers.
When I first had visual contact with a WJ receiver of the series about which
you opine, I also felt it to appear flimsy, a fact proven upon lifting the
receiver expecting it to be heavier and almost losing control and dropping
it! After that and upon further inspection both internally and externally,
I have never coveted a WJ device.
I was employed by Collins (Dallas, Texas) in the '60s and having served on a
couple of their quality control committees (an adjunct to your normal
responsibility) I became aware of a design and construction philosophy that
no manufacturer or designer has surpassed before or since. I cannot view
other equipments without using that philosophy as a basis of comparison!
Enough of my chatter....Outstanding analysis and enjoyed the read.
Bill Mason
W5STP
-----Original Message-----
From: premium-rx-bounces at mailman.qth.net
[mailto:premium-rx-bounces at mailman.qth.net] On Behalf Of Michael O'Beirne
Sent: Saturday, January 31, 2009 8:27 AM
To: PREMIUM-RX
Subject: [Premium-Rx] New radio selection
----- Original Message -----
From: "Michael O'Beirne" <michaelob666 at ntlworld.com>
To: "Shane White" <shanewh at gmail.com>
Sent: Saturday, January 31, 2009 2:14 PM
Subject: Re: [Premium-Rx] New radio selection
> Dear Shane
>
> I read your email today chuckling and with a high element of sympathy.
> Put simply we both want the same things and we are both crying for the
> moon because no single receiver exists that I know of that encompasses all
> of your desiderata.
>
> I have never used a K3. The review in the RSGB's RadCom last year by
> Peter Hart (a highly respected engineer and reviewer) sang its praises.
> Other users have done the same. But, I query, what have been the
> comparable standards of comparison? If it's other ham gear, then that is
> frankly not a big deal. I have used some of industry's best and I reckon
> my ears and fingers know a good set or two. Once you have used commercial
> and military radios made by the likes of Racal, Redifon, Plessey, Skanti,
> Marconi, Dansk Radio, Collins, Siemens and Rohde & Schwarz, all made for
> the high end of the professional market, the likes of Icom, Kenwood and
> Yaesu pale significantly, though in fairness the very latest offerings
> from Icom have been a great improvement.
>
> Great claims are made for "digital" but you should never forget the tale
> of the "Emperor's new clothes".
>
> Digital Audio Broadcasting ("DAB") is supposed to be the bees' knees for
> hifi broadcasting and in UK will almost certainly replace Band 2 FM in a
> few years time. However, several commercial reviews have commented that
> the data stream is heavily compressed in order to cram umpteen dozen radio
> stations into the limited bandwith and that DAB is basically an MP3
> standard. That's great for trannie radios and MP3s but it does not stand
> critical comparison with good quality analogue FM. Everyone with sensible
> technical knowledge accepts that given current standards, the BBC would
> not have selected DAB today, but we are stuck with what is already a
> legacy digital system.
>
> Similar claims are made on HF for "digital". Certainly the technical
> specs of selectivity achieved by digitising the IF and AGC look
> impressive. But in my view the specs are merely the starting point. The
> real test is the impression of the sound in your ears. After all what
> earthy use has a radio unless to deliver quality audio to your ears?
>
> This said, most modern radios are not really designed for human operators.
> Most are under computer control and are listened to by computers owned by
> the security services for the usual unfortunate reasons or for data links
> for the commercial and military. Human operators are far too expensive to
> keep on the payroll!
>
> I do the usual critical technical tests but my ultimate test is to listen
> carefully on good quality Sony or Senheisser headphones to a station that
> I know well, typically the BBC on 198 kHz and on 15,400 MHz. Any trace of
> hum is a big minus issue. Any trace of microprocessor squeaks and bumps
> is an even bigger minus.
>
> Any objectionable coloration is no good either. Most of that will be
> caused by phase distortion in crystal filters or mechanical filters. The
> true perfectionist will seek fully phase-compensated crystal filters.
> These can be very expensive. They were used mainly for receiving fast
> data on HF where phase distortion across the passband will completely muck
> up the relative timing of the data pulses and may well render the signal
> unprintable. I acquired a matched pair for my Marconi H2540 receiver for
> the princely sum of £10 at a flea market. The factory list price from
> Marconi was £350 for the USB filter and £1,200 for the LSB filter plus
> postage plus VAT in the mid 1980s. They improved the sound quality no
> end.
>
> Many amateur receivers and transceivers attempt to achieve better
> selectivity on SSB by using narrow SSB filters of 2.4 kHz bandwidth or
> even less. Under conditions of strong adjacent interference they are
> useful but the resulting boxy sound of the human voice (to me) more
> resembles a cat being castrated.
>
> If you are going to listen to music or the human voice using SSB mode
> (useful when there is lots of QRM) you need to use better professional
> filters with a bandwidth of at least 2.7 kHz. The SSB filters on my Racal
> RA1792 have a bandwidth of 2.9 kHz and sound very good.
>
> Great claims are made for using synchronous AM detectors. A few work
> really well but they are complicated and expensive. The simple designs
> are OK but often not much better than a traditional diode detector. I am
> told that the Sherwood "add on" detector unit is excellent. I use a
> fairly similar "one-off" professional design made by Surrey Electronics,
> but they had to stop selling under threat of patent infringement from
> another company called PhaseTrack. The latter marketed a superb HF
> receiver specifically designed for commercial rebroadcasting called the
> "F1-2". The IF selectivity was formed not by filters but by a complicated
> phasing system. The result was total lack of any phase distortion, a flat
> audio bandwidth from 50 Hz to about 4.5 kHz and a total harmonic
> distortion under 0.5% across the whole of that bandwidth. I have one and
> wow it is incredible. I have yet to meet any DSP that will match that.
> It will come in a few years but as far as I am aware not at present.
>
> Diode AM detectors are regarded as terribly old fashioned but that is
> mainly because some listeners don't know any better. The very best diode
> detector is on the ancient GEC BRT400E of the 1950s. The recovered audio
> quality is staggering. This is not just me. I quote a well known hifi
> reviewer and ham, the late Angus McKenzie G3OSS with whom I had many an
> exchange of views. These sets were used extensively for monitoring by the
> BBC, and BBC engineers demanded the highest professional standards. Alas
> the remaining ones are pretty bashed up and will need a great deal of
> renovation. They are also very big, hot and heavy.
>
> The venerated RCA AR88D still has an excellent reputation for AM quality
> with several selectable bandwidths and will hold its own up to 10 MHz but
> the selectivity is poor by modern standards, it weighs 100 lbs and will
> almost certainly need realignment. No one would really want to use one
> for SSB. The build quality however is superb and these radios originally
> cost a fortune.
>
> The valved Collins gear such as the R390 and 51J-4 are mechanically
> gorgeous and were even more expensive. You won't find better construction
> anywhere. They are heavy to tune (dozens of gears and moving slug racks
> inside) and the recovered audio is not so good. But they are fun to use
> if you like big panels, big meters and decent sized meters (as I do). An
> R390 plus the Sherwood synchro detector unit is said to be superb.
>
> In similar vein, the Racal RA17L is a nice old valved receiver but the
> audio is only OK, not outstanding, and they all need restoration after 40
> years +. However, their usefulness (and audio quality) increases mightily
> when married up with an external SSB adaptor such as the RA121 or RA298, a
> VLF converter such as the RA137 (listening down to 12kHz), a digital
> display adaptor (displays to 10Hz) and a bargraph tuning adaptor (displays
> to 10Hz). But you are then looking at a pile of gear 19 inches wide and
> about 22 inches high. Mind you it will impress all your visitors !!!
>
> Most (if not all) the valves are easily available, in contrast with
> numerous ICs. Repairs do not demand watchmaker skills except if you have
> to sort out the complex mechanics of the tuning drive of the R390.
>
> WJ sets are of superb construction and look handsome but many are getting
> on in years. Some parts may be difficult to source.
>
> My ultimate advice is to get either the newer Racal RA1772 (of the
> mid-late 1970s (but only if in good condition) or the much newer RA3701.
> You are assured of excellent built quality, a bomb-proof front end, decent
> IF filters, 8kHz AM filter, superb velvety tuning feel with light finger
> tip control and are generally nice to use. They have no unobtainable ICs
> or other parts. The 1772 uses a low distortion AM detector based on a
> constant current circuit. The 3701 uses a synchro AM detector. Both have
> IF outputs for external adaptors. The frequency display in both is to
> 10Hz and stability can be measured in fractions of a Hz per week. Neither
> has IF shift or a notch filter. Few professional receivers until the
> latest bunch of DSP rigs have these since such functions can be
> implemented at little or no extra cost within the mathematics of the DSP.
>
> Two other sought-after radios with excellent audio are the Plessey PR2250
> and 2280. However, there are few around and many of the Plessey-made ICs
> inside them have not been manufactured for many years.
>
> I was not impressed with the 340. The tuning is awful compared with the
> Racals and in the UK their cost is huge. Others swear by them. You need
> to try one out and see if you can live with the tuning. The knobs and
> displays are good.
>
> The current "must have" is the WJ 8711A. I tried out the original version
> at an exhibition when they first came out and was horrified at how
> mechanically flimsy it was, the cheapness of the knobs and meter and the
> number of spurious noises I could hear. This view was echoed in a
> detailed technical review in SWM where many unkind (but accurate) words
> were voiced. The new A version is said to be a lot better but is just as
> flimsy. I prefer more mechanically robust rigs. I commend the words of
> Julius Caesar (if you remember your Shakespeare): "Let me have men about
> me that are fat............Yond Cassius has a lean and hungry look".
>
> Your needs may also be met by the Rohde & Schwarz EK085 but big, big
> money, rare even on eBay, and repair bills ........... more big money!
>
> I hope this helps.
>
> Regards
> Michael O'Beirne
> G8MOB
>
>
>
>
>
> ----- Original Message -----
> From: "Shane White" <shanewh at gmail.com>
> To: <premium-rx at mailman.qth.net>
> Sent: Saturday, January 31, 2009 2:26 AM
> Subject: [Premium-Rx] New radio selection
>
>
>> Hi Group,
>>
>> I'm after advice for the selection of an HF radio receiver (or
>> transceiver) please. I currently own an Elecraft K3 but the audio is
>> terrible, especially on AM. Despite discussing this matter with the
>> manufacturer, it seems modifications to improve this aspect of this
>> radio are some way off, if at all. The problem seems to me to be
>> caused by the AGC (which can be disabled) resulting in over emphasis
>> in voice of received Bs, Ks, Ts etc. In addition, the audio generally
>> sounds "odd" for want of a better description and nowhere near as
>> pleasant to listen to as my Kenwood R2000.
>>
>> Now I'm selling the K3 and am undecided about what to buy next. Here
>> are my requirements -
>> 1. 500KHz to 30MHz coverage at least
>> 2. Capable of an AM audio bandwidth of at least 5KHz (ie 10KHz IF
>> bandwidth)
>> 3. SSB, AM
>> 4. Tuning resolution of less than or equal to 10Hz
>> 5. Preferably have an internal PSU capable of 240V/50Hz operation
>> 6. Preferably capable of S-AM reception
>> 7. Preferably include IF shift, width and notch
>>
>> I've thought of the following options -
>> 1. An Icom IC-7700. I haven't heard one in person, nor can I since I'm
>> in South Australia where shops (all two) don't stock radios.
>> 2. The soon to be released Icom IC-7600
>> 3. The Ten Tec RX340
>> 4. An older radio such as the WJ-8718A
>> 5. A Collins tube radio
>>
>> Being in Australia I'm concerned about buying an older radio because
>> parts may be difficult to source. I'd probably also need to buy a CRO.
>>
>> I'd appreciate any thoughts on this matter thanks.
>>
>> Shane.
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>
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