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Johnny Novice's Guide to receivers - W3JN




 
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« on: June 04, 2005, 01:42:13 PM »

Johnny Novice’s 
Guide to Receivers
by John - W3JN

One of the most frequently-asked questions on the AM Forum is “What receiver should I buy?” Truthfully, such a question is as impossible to answer as “What car should I buy?” Of course both purchases depend largely on what you want and what you expect. Based on my experiences with almost every US-made receiver, I’ll try to help you navigate the potentially treacherous waters of this important purchase.

Everyone has their own prejudices on what constitutes a great receiver. What I appreciate in a radio may not be important to you and vice-versa. I don’t pretend to be 100% impartial here: I’ve had some bad experiences with some receivers that, for some reason, enjoy great renown in the amateur community; also, I’ll point out some receivers that for some reason are overlooked.

Several factors come to mind when choosing what type of receiver is right for you. Perhaps you are assembling a period “boatanchor” station, appreciate bygone technology, or just appreciate a “old buzzard” look radio. On the other hand, maybe you want the last word in performance and/or modern conveniences such as memories, passband tuning, and a digital frequency readout. Or you may want a particular property such as good audio response, frequency stability, or something that’s really easy to service.

Boatanchor-era receivers (those built from about 1935 through the mid 1960’s) can be extremely satisfying to own and use, or (if you make a poor choice) they can be a constant source of frustration and headache. Right up front I have to say that you should buy the best quality radio you can find and afford. The old adage “you can’t polish a turd” particularly applies to old receivers. They can be electrically and mechanically unstable, causing you to constantly retune the receiver or tiptoe gingerly around your op table lest a small vibration jump the frequency a hundred KC. And any radio that was inexpensive when it was new is going to show design choices that negatively impact on its utility as a receiver for use in the 21st century.

Early solid-state era receivers (say from the early 1960’s to the mid-1980’s) are generally a poor choice. There are some exceptions, but synthesizers and semiconductors have come a long way in 40 years, and most of these early solid-state radios aren’t worth the effort. Too, finding some replacement transistors is much more difficult that finding replacement tubes.

Modern Japanese receivers/transceivers are acceptable if you can live with the crummy audio fidelity, difficulty of service, and synthesizer noise. Generally, these rigs were/are intended for SSB service and are not particularly great for AM. Again, there are exceptions here. I won’t focus on these radios because I have limited experience (albeit universally negative) with them. Suffice it to say they’re all fairly similar, but it seems that Yaesus are much more popular in the AM community, and many hams like theirs very much – especially after the installation of some popular modifications found on this site and elsewhere.

Old military receivers can be a mixed blessing. Many of them are electromechanical monuments to the pinnacle of American engineering expertise. Others aren’t worth the considerable expenditure of energy necessary to drag them into the shack. Certainly, one of the most popular receivers in use in the AM community – the Collins-designed R-390 – would be my pick for best all-around receiver. But you can get mighty frustrated, after replacing all the capacitors in an ARC-5 and taking the time to build a power supply, to find that it’s really (REALLY) unsuitable for modern ham operation. However, they’re popular with military enthusiasts and most have their own charm (but think twice if you want to use one for serious operating).

Closely related are the so-called “professional” receivers. You’ll enjoy the cachet of using the best of the best – but remember, because no receiver is perfect, there are some downsides. Audio quality often is an afterthought (sometimes there isn’t even a speaker connection!), and strange ergonomics might tend to become tiresome. Some of these radios require special extender cards for their service – and many use custom integrated circuits that are virtually unobtainium.

You may want a particular receiver because it just looks cool, or it matches a particular transmitter you have, or it’s a “holy grail” radio like a 75A-4 or an SX-88. Certainly a valid goal, but be prepared to be disappointed! I certainly was with the 75A-4 I briefly owned. And while my SX-88 is a pretty nice radio, its utility as a receiver sure isn’t worth the $5,000+++ they bring on eBay.

Or, you may be enamored by radios from a certain manufacturer. Collins radios enjoy an almost cult-like following. I’d say that Collins receivers are generally a few notches above most other radios, but the price you’ll pay is commensurate with their popularity, and this price is seldom reflected by their actual utility as usable receivers. If you want to modify your receiver a bit (say, for better audio, a product detector, etc.) you probably don’t want to ruin your “investment” by modifying a rare/desirable radio, nor do you want to put up with the bleating of the “aficionados” who bow to the Art Collins altar. I found this out the hard way when I posted my experiences in repairing the PTO in a Collins 51J, and some interpreted my suggestions as likely to completely render the radio unusable. The armchair experts can believe what they want while I enjoy complete accuracy on my newly-repaired 51J PTO. Anyway, be prepared to be disappointed!

If you’re like me (and probably few of you are), you get bored by a receiver that works perfectly (or at least as well as it’s ever going to) the minute you bring it home. Receiver restoration can be deeply satisfying as well as hugely frustrating. Some radios are so difficult to fix you wonder how they assembled them in the first place. Others are models of good RF and mechanical engineering. Face it, the radio is going to crap out at some time (if it wasn’t already DOA when you bought it at the hamfest!), so I recommend that you give some thought to serviceability. ALL of the boatanchor-era receivers can be fixed with simple hand tools, a volt-ohm meter, and a cheapo signal generator. More modern receivers will need oscilloscopes, special de-soldering tools, sweep generators, etc., for their alignment and repair. Strangely, I find more modern receivers to be LESS reliable than boatanchors filled with tubes and 60-year old resistors and capacitors.

Let’s try and narrow your choices down a bit. Do you want a ham-band only receiver, or one that provides general coverage? Too often, ham-band only receivers took the ARRL advice on restricting audio response to heart. If you want to fully enjoy the East Coast Sound from stations like W2INR, K1KBW, K1JJ, W3NP, WA1HLR, et. al., don’t bother with one of these unless you want to perform some simple modifications and feed the detector audio to an external hi-fi amplifier. The advantages of a ham-band only receiver include better frequency readout (although few, with the exception of Collins radios, will provide better than a 5 KHz accuracy), better bandspread, and battle-mode controls like notch filters, sharp bandpass filters, and passband tuning to eliminate QRM. If you can put up with the inherent shortcomings of a ham-band only receiver, the National NC-300/303 and Hallicrafters SX-101 series are all outstanding choices and highly recommended (although they don’t make my top 10).

General coverage receivers, on the other hand, are nice when you want to tune in WWV or listen to Fidel Castro’s lunatic ravings on Radio Havana. If you can only buy ONE receiver I strongly recommend that it be a general coverage model. Some offer outstanding fidelity from a push-pull pair of tubes, and you don’t necessarily need to give up frequency readout or battle-mode readiness if you choose wisely. However, many boatanchor receivers are less stable (both physically and mechanically) than their ham-band counterparts and tuning accurately depends on setting both bandset and bandspread dials accurately.

There are definitely some receivers you should avoid if you’re on the hunt for a primary station receiver. I would say that any radio with less than 10 tubes, any solid-state radio made before 1985 (with the exception of the HRO-500 and Drake SPR-4 or R-7) should be avoided. Even then, there are some real turkeys out there: the Icom R-71A (bad ergonomics, crummy audio, noisy synthesizer), the Heathkit Mohawk (numerous design faults), military BC-348 (won’t drive a speaker, too wide selectivity, lots of work necessary for acceptable results), Collins 51S-1 (way overpriced and one of the worst front-ends out there), Kenwood R-1000 (bad front end, noisy synthesizer). Don’t even consider S-38s, Hammarlund HQ-100/105/110, National NC-57s, Hallicrafters SX-99s, etc., especially when there are much better choices out there.

So, here are my Top Ten choices for consideration for some of the best (and ten worst!) receivers out there for AM work. I’ve owned all of these (some I’ve owned ten or more examples over the years) but they reflect my biases. I’m not interested in hearing “why don’t you recommend the XXX – I love mine!” – that’s OK FINE by me that you like yours but I’m the one making the recommendations here! Feel free, though, to send me a PM if you want to discuss a particular receiver you have an eye on, or if you want further amplification of any of the points discussed in this brief article.

Ten Best Receivers for AM Use

1. Drake SPR-4 or R-4A/B/C

Upsides: Great stability, overall excellent performance, easy to fix, and good readout. Capable of decent (not great) audio.

Downsides: need crystals for each band covered, additional bandwidth filters expensive.

2. Hallicrafters SX-100

Upsides: General coverage, selectable sideband, nice notch filter, small size, cute looks, easy to fix, common as dirt.

Downsides: relatively poor stability, tinny stock audio, very wide range of trading prices (I’ve paid as little as $25 but have seen them go on eBay for >$1000!)

3. Collins 51J-4

Upsides: General coverage, good frequency readout, superb quality, outstanding stability, great overall performance, personifies what a boatanchor ought to look like.

Downsides: no product detector, bandwidth filters limited to 1.4/3/6 KHz and, if missing, very difficult to find and expensive; very poor stock audio, needs 12 VDC to trip the standby relay if you’re using it with a transmitter, expensive.

4. Tie. Hammarlund SP-600 and Hallicrafters SX-117

 - SX117

Upsides: A sleeper. Ham-band only, very good all-around performance, small and light. Essentially an SX-115 (a hugely expensive receiver that matches the HT-32).

Downsides: relatively uncommon, slightly funky looks, relatively poor stock audio quality.

 - SP-600

Upsides: General coverage with extremely smooth tuning, buzzardly looks, and very good RF performance.

Downsides: difficult to repair, no product detector, frequency readout difficult to determine exactly where you’re tuned.

5. National HRO/HRO-5/HRO-7

Upsides: General coverage, can be switched to ham-band only. Excellent stability, even 70 years after the first one was made. Extremely reliable and one of the easiest to service receivers ever. External power supply keeps hum and heat out of the radio, compact, extremely buzzardly looks.

Downsides: plug-in coil drawers for each band (they came with four sets covering 2-30 MHz, other bands available but expensive), need to move screws on the coilset when changing from general coverage to bandspread, no direct frequency readout (you interpolate the dial readout onto a chart printed on the coil drawer), needs external power supply, no product detector.

6. National NC-183 or NC-183D

Upsides: Push-pull audio gives much better than average audio (lacks deep bass and highs for my taste, though), general coverage, good front end, “D” version is charcoal gray with double conversion, very easy to repair, cool looks.

Downsides: “Where am I?” frequency readout, not the greatest stability, no product detector.

7. Hallicrafters SX-28

Upsides: General coverage, THE best looking boatanchor ever, superb audio, decent noise blanker (yes, even in 1941!), decent RF performance even up to 10 meters, bazillions made so they’re real common (SX-32 is very similar).

Downsides: very difficult to repair (especially in the front end compartment!), no product detector, used relatively poor quality components when new so they generally need a complete rebuild.

8. National HRO-50/HRO-60

Upsides: Similar general-coverage receivers except the HRO-60 offers double conversion on upper bands, uses coil drawers like the HRO described above). Direct frequency readout, easy to flip from general coverage to bandspread (you need to pull the coil drawer), push-pull audio much better than average, extremely reliable (except see caveat) and easy to repair.

Downsides: bypass capacitor on secondary of power transformer prone to shorting which destroys the transformer, no product detector (although it’s an easy mod), plug-in coils somewhat a pain.

9. Hammarlund SP-400 Super Pro (SP-100/200/210, BC-779, BC-1004)

Upsides: General coverage (some variants skip the AM broadcast band but to go 40 MHz), outstanding audio from a push-pull pair of 6F6s, buzzardly looks, very good RF performance for its age, continuously adjustable selectivity from 3-16 kHz PLUS a crystal filter, very reliable and relatively easy to fix.
Downsides: no product detector, separate power supply weighs a ton (but is bulletproof!)

10. Collins-design (military) R-390A

Upsides: THE best receiver ever. Superb quality and performance, selectable mechanical filters, although very complex it’s easy to repair thanks to the removable modules, lots of signal chain outputs, good mechanical digital frequency readout, very common, replacement parts easily available.

Downsides: ugly, no product detector, poor stock audio (but no mod necessary to connect to an external audio amplifier), a few reliability trouble spots (but these are easily overcome). Note that the R-390 (non-A) is a COMPLETELY different radio – it has no mechanical filters, uses uncommon 6082 voltage-regulator triodes, and is considerably more rare than the A model.

Ten Worst Receivers for AM Use

1. Heathkit Mohawk

A passel of design mistakes make this very attractive receiver almost worthless for ham use. Heathkit took advantage of every opportunity to add distortion they could. Electric Radio had a 3-part article several years ago that outlined the steps necessary to correct these deficiencies. If you have the patience and expertise to do the mods, this radio has definite potential.

2. Hallicrafters S-38 and S-120

5-tube radio little better than an All-American 5 clock radio. Cute to put on the shelf but worthless for ham use. There are many other receivers in this class including many Heathkits, Nationals, etc.

3. Hammarlund HQ-170/180

My personal prejudices at work here; many guys love theirs. Incredibly distorted audio with a real JS audio feedback network. Ugly. The BFO and notch filter coils prone to breakage. Chassis prone to corrosion. It is a pretty decent battle-mode receiver with selectable sideband and an effective notch filter.

4. Collins 75A-4

The most over-rated receiver ever. A pretty decent radio for SSB, the audio is restricted and distorted. Front end design not commensurate with Collins reputation for high performance. The huge number of modifications out there are testimony to the weaknesses of the stock radio. Extraordinarily expensive for what you get.

5. Collins 51S-1

Another over-rated receiver. Matches the Collins “S” line. Again, this radio is pretty decent for SSB if you don’t connect it to an effective antenna. Otherwise you’ll find Deutche Welle and Radio Havana all over the place. Very poor front-end performance.

6. Icom R-71A

Noisy synthesizer, not very reliable and difficult to fix.

7. Hammarlund HQ-100/105/110

Poor performance coupled with awful audio. Small and cute; decent backup receivers, but don’t buy one for the primary station receiver.

8. Hallicrafters S-85, SX-99, SX-110, S-105

All pretty much the same radio in different cabinets and slightly different features. Not truly awful but frustrating to chase a signal around due to the drift.

9. Hallicrafters S-20R

“Champion of the Sky”.Sounds better listening on an outside speaker – like a PA horn.

10. Realistic DX-300/DX-302

Synthesized receivers that seemingly have potential, but lack any sensitivity whatsoever. Noisy and prone to overload. Their only saving grace is they’re cheap.
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