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Reviews Categories | Receivers: Commercial/Military/Marine adaptable to ham use | BC-348 WWII MW/SW Receiver Help


Reviews Summary for BC-348 WWII MW/SW Receiver
BC-348 WWII MW/SW Receiver Reviews: 6 Average rating: 4.3/5 MSRP: $348
Description: Businesslike wartime reciever used in planes and on the ground, recieves most
of the MW and SW bands in switchable ranges, has a BFO for CW work and an
xtal filter that's very nice for CW and even listening to AM SW broadcasts.
Product is not in production.
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KZ4B Rating: 5/5 Mar 15, 2016 21:12 Send this review to a friend
One of the very best pre-WW 2 Receivers ever!  Time owned: more than 12 months
About thirty years ago, I stumbled on a mint, un-modified BC-348R for only $85.00 because no one else at the little Greenville, S.C. Ham-fest was interested in buying it. As a Novice and early General Class Ham (circa 1959), I had struggled with a Hallicrafters S-53A and would have given my "eye-teeth" for a BC-348 (or similar receiver) if I could have found one at an affordable price.

With some difficulty I was able to locate an original B-17 shock-mount with "stock" power connector (from an aircraft "bone-yard" in an Arizona desert). This aircraft mount was essential to allow use of the "stock" power connector as it plugs into the BOTTOM of the receiver.

Wanting to keep the BC-348 receiver completely original to the degree possible--I home-brewed a 28 Volts Alternating Current (at nominal 8 Amps max.) to replace the original 28 VDC aircraft power supply. This allows powering the receiver's 28 Volt (indirectly-heated--so no ac hum) filaments at roughly 4 Amps without re-wiring for 6 or 12 VAC as is commonly done. In addition, roughly 4 Amps is available via a small (100+ VA) 28 VAC to 120 VAC "control power" transformer with silicon diode voltage doubler/filter for the receiver's B+/Plate Voltage. The 100 VA+ Control Power Transformer (wired backwards to step the voltage UP) is mounted along with rectifier/filter components on the "stripped down" original (28 VDC Input/Hi-Voltage DC Output) Dynamotor Base which plugs into the INTERIOR of receiver.

My BC-348R was marked at the Audio Output Jack "Wired for 600 Ohms". I therefore located an original "LS" Series Aircraft Loudspeaker (With built-in 600/3.2 Ohm (Impedance Transformer) and mil-spec. 600 Ohm Earphones. I have also located an LC Type Narrow 600 Ohm Input/Output Audio CW Filter that was supplied on many aircraft to supplement the BC-348's Crystal IF Filter.

A JAN (Joint Army/Navy) design policy required that all "tactical" super-heterodyne receivers have two (RF) radio frequency amplifier stages--not because the extra amplification/gain was needed--but because the extra RF Filtering was needed to prevent "Local Oscillator Leakage" which could allow Enemy Radio Direction Finders to detect the presence of potentially hostile radio receivers. While enemy detection is not a concern today, improved "Image Rejection" associated with two RF Amplifiers and somewhat analogous to modern "Multi-conversion" and narrow crystal/mechanical "Roofing Filter" designs is beneficial in today's operating environment.

Do Not Re-Cap these receivers unless a genuinely faulty component is found as the normally leaky foil/paper capacitors are individually packaged in metal oil-filed enclosures--so they tend to last indefinitely. The plastic-encased mica capacitors (as I have personally found) are less reliable--but I still wouldn't replace them unless found to be individually bad.

This 1936 vintage RCA-designed receiver is reliable, stable, compact, light weight, mechanically well-engineered, and absolutely state-of-the-art for it's time. The BC-348 Receiver coupled with the Collins-designed ATC/ART13 Transmitter as employed in the magnificent B-29 Bomber were so advanced that the USSR copied both for service in tactical and other aircraft well into the early 1980's! Don't take my word for it--the Russians knew a good thing when they copied the BC-348 virtually nut-for nut and bolt-for bolt. They even standardized on our vacuum tubes and other internal components to the degree that they are directly interchangeable with our (USA) communications gear. Nuff Said!
 
N8FVJ Rating: 4/5 Nov 2, 2014 06:34 Send this review to a friend
Fine AM Broadcast Receiver  Time owned: 3 to 6 months
The BC-348 was my first SWL receiver in 1965. I recently acquired another BC348R.

The new to me BC-348R has a new custom CNC machined front panel, S meter and an AC power supply installed by the previous owner. The inside appears like new.

I replaced all paper and paper oil capacitors. Interesting that the original were still in good condition without excessive leakage.

The existing AC power supply had a SS bridge rectifier, 1HY choke and a dual section 50uF can type capacitor for a CLC filter. It also used a 500 ohm resistor on the output to drop voltage to 230 volts DC. The design produces low level hum due to poor filtering.

I replaced the 1N4007 rectifiers with low noise UF4007. The filter cap was replaced with a JJ dual 100uF can cap rated at 500 volts. The 500 ohm resistor was removed and the choke was replaced with a Hammond 30HY @ 40ma choke with a DCR of 595 ohms. The new power supply produces 235 volts @ .06mv ripple and the receiver is hum free.

Next was an alignment. Although not far off alignment, it is critical that an alignment is performed with the crystal filter in circuit. Once completed, the receiver only drops about 1 S unit with the crystal filter in line.

These BC-348 were built to use a 1-5 ohm antenna. The antenna trimmer capacitor in the BC-348R series is vague in operation (no sharp peak). I installed a 9 to 1 unun at the antenna input. Sensitivity went up and the variable antenna capacitor has a sharp tuning peak at about 50% value at all frequencies.

Further performance can be obtained replacing the 6K7s with 6S7 tubes. The dual RF front end will require a slight peaking of the trimmer capacitors to realize the slightly lower noise floor and hotter front-end with the 6S7 tubes. The IF section does not require any tweaking after changing from the 6K7 to 6S7.

Per another site, the BC-348R receiver was measured at a MDS of -137, 20kHz Blocking range at 106dB and a two tone Dynamic Range (20kHz) at 87dB. For a 'boat anchor' receiver designed in 1936, this is good performance. Definitely not a Collins R-390, but quite acceptable for SWL service.

 
VK2MS Rating: 5/5 Jun 23, 2014 16:18 Send this review to a friend
Possibly no set deserves more nostalgia or restoration and use  Time owned: more than 12 months
My first BC 348 was 50 years ago. The affection I feel for them is almost spiritual An extraordinarily beautiful receiver it is also evocative and a connection between the 1930's and 40's which people of generations after those of us who experienced the disposing of WW11 equipment cannot experience. We were of the era. That said I still own a BC348R and recently sold my "N". I prefer the style of the "R", it is much more reminiscent of its origins.I understand nevertheless the advantages of the Q/N/J. This Rx overshadows an even better performer, the BC 342/312 however my view of ham radio is not achieving some perfect situation (whatever the cost) but maintaining a tradition which has a large degree of the spiritual, the tactile, the experimental, the honour, the technical ability which for decades it required and encouraged to become a member of a very special fraternity.The more lazy minded and demanding of the 'right to become a ham' the more the rot set in.The VHF groups feeling technically modern and superior so often looked down on the HF operators, yet they also used nostalgia...954/955 tubes and WW11 components and the more adventurous converted the SCR522, loran radar, ARC sets, AN/APN and so on. Few used the incredible AN/APX6, another great bridge to tradition using cavity tuning and the opportunity to package information into short high power bursts, in other words offering opportunity to design and experiment rather than buy performance. What more does one need on HF...?...the 348 can resolve cw ssb and am.Digital radio/star/other binary (other than cq) for me is a total bore as is keyboard operation,software based computer building block manipulation of specifications and settings. They have merit, yes, but I can't see a connection to traditional ham radio, other than experimentation.

With the 348 you even have to make an effort in adjustments to receive as best one can.A $400.00 BC348 on a 450-$200 long wire or a dipole on posts irrespective of any limitations of any of it is for me far ahead in every sense of self worth than a $20,000 set on a $20,000-$50,000 antenna with a $5000 linear, a $1500 tuner and a $2000 armchair at a $2000 desk.

Yes commercial modern sets have advantages but they have disconnected and undermined Amateur radio as has the downplaying of cw and the introduction of the Foundation licence to pander to the people too lazy to earn a place in a once very proudly technical fraternity.

The 348 can't stand up to the specs of many modern sets but it performs extremely well remembering that these were purpose designed with just the war requirements being in mind. For me they also require a great deal more in terms of actually being an amateur radio operator as opposed to a modern lazy minded button pusher using KW because that's your 'best solution' in impressing others and dominating the segment.

Entire bands are taken up by American 'CQ Contests' effectively closing down entire bands ...nothing left in consideration of other hams. Nets are dominated by high power transmitters....awards unavoidably favour those with the most modern equipment, best beams and best locations. What's the point? Far better achievement would be a max 100W 348/ART 13 contest...a "Command Set" contest, a homebrew contest, a Collins contest, a TRC-77 contest, a nostalgic novice contest and so on, all limited to their original power limits and in any event max 100W and say using only dipoles or long wires antennas. Get away from the technology of "the best I can afford " for a while and become like boy again in spirit.How about home-brew "fox hunts"...get back to our roots.

The BC 348 is a reminder of a great era prior to the early 1960's when 'something changed". Back then the irritant was often high power. Today the Ham bands are used by anyone who cares to use them, Hams are castigated for telling them to move along and supervision and the prohibition on foul language, discussing politics, third party traffic and even regulary and often giving a call sign seem to have gone up in smoke. Just looking at a 348 is nostalgic to a better era.

Running a kw or two or more or even 400W...that was a part of the death throes of ham radio...the idea that might gives right and that power overcomes, with seemingly no idea of having fun, not even the fun of building a crystal set , then improving to a single tube regen...which gave me far more fun than any commercial radio I have used...the discovery and achievement of simple radio I built was exciting and still is that...yes we have to consider the need to limit transmissions from regen, itself a skill but in my view working the world on commercial sets with high power and outstanding modern technology including antennas isn't worth 'spit" compared with doing it on 5w with simple homebrew on cw.

The 348 more than the incredible Collins 390 series connects us to ham traditions and in my view the limitations one experiences in amateur radio and the personal effort, not the money, one puts into overcoming some of them, even one of them, succeed or fail is worthy beyond measure compared with buying performance.On that basis, quality, tradition, nostalgia, performance, tactility, even the smell,even that 'clunk' as one changes bands the BC348 represents equipment with a soul, perhaps gained by exposure to the theatre of death in WW11. Yes in a way they were 'commercial' but for military use using a limited number of valves (tubes)with discrete components which could be serviced at component level mostly with a multimeter if not a sense of smell and sight.Their style and circuitry had a connection with an era in which Hams contributed skills and lives and for some years when not away at war; their hobby in the use of these sets on which operations and others' lives depended.Their limitations are worthy of respect by us. I hope that more people will buy these sets, enjoy their occasional limitation, enjoy not having the best money or debt can buy enjoy overcoming what can be overcome by skill, persistence, self discipline and concentration, the care-of and
placement of antenna and use them often, reveling in an entry or re-entry into the essence of amateur radio thrills. I say njoy becoming a ham operator or even an SWL and leave behind at least for a while being a black box operator. More could be said, but need it be said?.. I give the BC 348 a resounding "5/5"!!..
 
K5UOS Rating: 5/5 Jun 1, 2012 13:57 Send this review to a friend
Great for a 70 year old receiver  Time owned: 0 to 3 months
I finished restoring to BC-348-Q models in May of 2012. Both we purchased on EBAY for approx. $100 each. The 2nd was going to be for parts but was repairable.

The first RX had a partial conversion that was never completed. The PS was poorly designed but there was no additional modifications. I purchased a suitable Hammond transformer and choke and built a +220VDC power supply using a 5Y3 rectifier. I found many sources of information on the net including some by Pete, AC7ZL.

I traced all the wiring expecting errors but all harnesses were stock and the only changes were associated with the PS connections. The terminal strip from the original RX was gone and I built a new one using a piece of fiberglass and solder lugs. I used the AVC/MVC switch for on-off. The original Jackson like PL-P103 plug had been partially dismantled to use two pins for AC plug. I removed the rest of the PL-P103 innards and mounted a 3 prong socket in the remaining frame. I also removed the large filter capacitor.

I checked all the resistors and capacitors and all were within tolerance. After converting the botched PS conversion I tested the PS and finding no issues installed the tubes. The receiver powered up and received well on all bands. I did a quick realignment of the IF using 915MHz. The receiver was out of alignment for 915MHz but I doubt it had been adjusted to the crystal band pass.
I also changed the low Z audio out to the high Z to match my LS-3 speaker. The alignment and the speaker matching was a marked improvement.

The PS - I used choke input and increased the filter cap to 60uF. I also included a 1000uF/63VDC cap with negative lead to the floating B- and positive lead to ground. The result is an almost hum free audio.

I learned that CW/SSB was not possible with the RX in the AVC setting. I use MVC setting which gives surprisingly good audio on SSB. The crystal filter and IF are not quite aligned which I will fix on an upcoming weekend. The IF and filter in the 2nd receiver are better aligned and there is a slightly better filter response in the 2nd rig.

I had issues with the anti-backlash gears and tuning which was cured with a slight shift in the large tuning capacitor. There is a QST article describing the 30 second fix. The tuning is now amazingly smooth.

The 2nd rig was not modified much more than the 1st. But some fool broke up the beautiful wire harness for some dumb reason. I had to install another power supply including a fuse and do some rewiring. I still have to go in replace some ugly cloth wire which, if you know the tech manual and the beautiful way the rig wiring is color coded, just does not match the original design. I did my resistance and capacitor check and was amazed that the components were also within tolerance. After replacing on tube the receiver operated almost perfect on all bands. I had to clean the BFO switch. Though I have the 2nd rig electrically checked and running really well, I have not checked the alignment yet but have been working on the cosmetics of the panels and cabinets.

I bought the rigs because my dad, W1KPS(SK) had several surplus military receivers back in the 50ís and 60ís. One was a BC-342 and at least one other a BC- 348. These are 100% fun to restore. Pete and many others have a lot of useful information for restoration of the BC-348 on the web. There are numerous QST and CQ articles or modification manuals to help. Off course the original receiver manuals are so awesomely detailed you will learn all about your receiver in short order.

If you are deciding to purchase BC-348 to restore and have a basic understanding of receivers I think you will be very happy. It is certainly not a SOTA receiver but the look, the feel and amazing quality of this 70 year old receiver will be lots of fun.

73, Don K5UOS
 
SWL377 Rating: 3/5 Aug 21, 2006 14:42 Send this review to a friend
Great history, OK performance  Time owned: more than 12 months
I like to imagine that my BC 348 flew in a B 17G over Germany in WW II, but I have no proof that it actually served in combat. Mine has a postwar civilian AC PS sited in an external speaker cabinet and an outboard audio amp to give loudspeaker volume. The original dynamotor was removed. I found dial accuracy to be outstanding on all bands. HF sensitivity is OK, not as good as my Hammarlund HQ 180 but good enough for normal listening. It is also a noisier rcvr than my Hammarlund. Stability my my BC 348 is good enough for decent SSB copy without frequent retuning even on 20 meters. I use the BFO for SSB demod and it works fine. I listen to HF USB marine comms in the 8 MHz band with the BC 348 and it does just fine once it has warmed up and stabilized. Sensitivity on LF is decent, I could hears some distant NDBs that are hard to hear in my area. On my set the XTAL FLTR acts only as a high low sensitivity switch and accomplishes nothing useful in narrowing bandwidth and maintaining decent sensitivity in the center of the filter response curve. Maybe it needs work but I cannot find any bad components in that section. I love having a rcvr with such a rich heritage, but I wouldn't depend on it for any serious DXing when I have my HQ 180 at hand. To be fair, it was designed much earlier and withstood a lot of abuse. My BC 348 hasn't had any mods other than the PS and 99% of the caps and resistors are orginal. I love the looks of the set, especially the Art Deco bezel over the main tuning dial. It is pretty amazing that it can deliver the goods over 60 years after it left the production line. I wish it covered BCB. If it did I'd put it in the living room. The BC 348 has looks good enough for a family room while the better performing surplus aircraft HF rcvrs (like my ARR 15)look like they belong in a ham shack or military airplane. BC 348s are still plentiful and not horribly expensive ($60-$150 at most swaps depending on cndx). I suggest buying one while they are still affordable. As a side note, I once saw a 100% solid state BC 348 owned by the late Command Set collector, Henry Engstrom. It looked VERY professional inside, with fiberglass PC boards etc. It didnt work and Henry had no documents on the conversion. I often wonder who has it now and if they restored it to operation.
 
AC7ZL Rating: 4/5 Jul 31, 2006 12:40 Send this review to a friend
Fun to play with  Time owned: 3 to 6 months
A while back I was fortunate to stumble across a BC-348-Q at a hamfest. I am partial to vintage electronics and boatanchors, and the BC-348-Q has a certain aesthetic charm to it---maybe it's the "military" look, the illuminated, shuttered dial face, or the tuner crank that requires nearly 100 turns from lock to lock! Whatever the reason, I purchased the radio and took it home.

I'm no old timer, but from what I gather, the BC-348 series of radios enjoyed some popularity as convert-to-ham-use surplus following WWII. For this reason, finding an unmodified BC-348 is somewhat difficult. The radio was originally designed to be powered from a 28 volt DC supply. An internal dynamotor produced the 220 volts for the radio's plates. For these reasons, at the very lease, most BC-348's have been rewired for a 6 volt filament string, and often contain homebrew power supplies mounted in the dynamotor bay.

My own radio contained wiring errors, a bad tube, several weak tubes, and a full set of dried out capacitors. I also found several fractured carbon resistors which lead me to repopulate the entire chassis with new caps and resistors. My radio came with neither a dynamotor nor power supply, so I built and installed my own supply.

Repairing equipment like this is made much easier with proper documentation. Schematics are available at the BAMA site, but the best scans I found were available at www.jamminpower.com/main/bc348.jsp .Note that there are several siblings in the BC-348 family, denoted by a letter extension. In my case, the radio is a BC-348-Q, originally built under contract by Wells Gardner. The revision letter is important, because there can be significant wiring differences from one radio to the next.

The radio offers 6 bands of coverage, from 200 khz to about 18 mhz. The AM broadcast band, unfortunately, is omitted. This probably has to do with the fact that the set uses a 915khz IF. The dial features a shutter mechanism that selectively occludes the tuning dial during band changes, such that only the frequencies associated with the selected band are visible. Mechanically, tuning is very precise. A worm gear drives a zero-backlash gear-train with such reduction that the dial crank has to be turned nearly a hundred times to get from one end of the tuning scale to the other. In addition, the set features an adjustable BFO and crystal filter for CW work.

While the set has great character and I do not for a second regret any effort that went into restoring it to operation, its use as an everyday ham receiver is questionable. Sensitivity seems good. Selectivity is not all that great (though I've been told that this may be due to leaky caps in the IF cans.) Even if it was better, the resolution of the dial markings are such that, at best, you will never know more than your approximate frequency.

Tracking on my set leaves much to be desired. The low band tracks fairly well, but the other bands do not. Without going into excessive detail, alignment adjustments are fairly limited, which leads me to postulate that some of the caps inside of the rf compartments may have drifted. Digging that far into the radio is doable, but something of a mechanical nightmare, and something that I will likely avoid for now.

Some writers have complained about the amount of volume that the radio's audio amp (6K6) will produce. In fact, one of the common radio modifications found is the insertion of additional amplifier stages. This criticism is not entirely fair, in my opinion. A headset of proper impedance will produce more than enough volume for ear damage. If you want to drive a speaker, make sure to use a matching transformer, and if that's not good enough, add a stage of outboard amplification.

The crystal filter, by the way, has significant attentuation when it's switched in. One trick that I discovered to improve the radio's performance was to measure the actual resonant frequency of the filter crystal, then align the IF cans in the set to the measured frequency. For example, my crystal resonated at 914 khz, so I aligned the IF path to 914 khz. The radio works fine and the filter works much better.

For day-to-day useability, selectivity, dial resolution, and features I'd rate this set a 3. On the other hand, a fellow ham noted that the BC-348 was not designed for stellar performance. Rather, it was designed to "...work ok while you were being shot at." It certainly does. Moreover, for charm, charisma, and historical appeal, the radio scores a 5. It is easy to troubleshoot and repair, and it is my expectation that this 60-year-old radio will still be functional in another 60 years. Therefore my composite score is a 4.
Pete, AC7ZL
www.hpfriedrichs.com
 


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