The AM Forum

I heard some AM guys just now on unaligned BC-348. I just plugged it in to align, and heard conversations. However, all signals were weak on my crap with 5 feet wire instead of antenna, but Mike KO6NM were heard loud and very clean. W7GMK I heard as well, and W6GS, but too weak on my crap. :D

PS: name of the topic had been corrected, it was 75 meters actually.

Fixed BFO now, and listening to SSB conversation on around 7.21 MHz (the dial scale of this beast is rough).

Actually 6F7 was good, the BFO switch was open inside (probably, because of a moisture). I installed 3 - position instead of it, so now it swihches BFO and AGC speed (AM slow - AM fast - BFO fast).

Tolly, вы не должны слушать к передачам ssb для слишком
длиной. Тип ssb радиоего водит к повреждению мозга. Используйте
BFO с предназначенная цель расшифровывать телеграфирование
незатухающей волны. Улучшайте для того чтобы курсировать интернет
смотря porn.
73, W2APE.

What could I do if no fellow AM'ers were on the band? You know, SSB reminds me лягушек на болоте. Как будто в лесу побывал! :D

Anyway, BC-348-R is completely restored, tuned, tested, so I may continue other projects.

After listening to frogs I finally have waited! :)
There were John K6JEK, Bill W6JUS and John W6MIT. Also, the most clear and strong signal had a guy with 1954'th transmitter, I don't remember his name. His callsign sounded for me like W9MZU, but I could not find him in the database.

Tolly - did you ever find the front dial cover for that old girl?

Yes John! Thank you!
Mike k7wtm helped me, thanks him a lot again!

Also, I took 915 KHz IF and put it to the AM band input of my Fisher hi-fi receiver. As the result, adjacent channel selectivity improved dramatically.
Mirrored channels (what's English term?) already filtered out well, because of 3 stages of RF selectivity, and relatively high IF frequency. I did not connect made from R-390A RF chassis preselector yet, I'll do that later. :)
However, as the result of such quick solution extra IF amplification amplifies loud noises between stations, when tune. :D

The term is "images", i.e. when you have a signal at 1000 KHz, your IF is 455 KHz, your local oscillator is at 1455 KHz, and the image is at 1910 KHz. (Fsig+2*Fif).

A popular conversion of the period was to use a Command Set LF receiver as the last IF/detector.  You can hook the AVC busses of the BC-348 and the Command Set together so you don't get the blasting in between station.s

73 John

Thanks!



Thanks John, it's temporary. I have in mind a device with couple of NE-612'th, and four 500 KHz EMF's with different bandwidth's. I'll put it in the same box with a power supply and S-meter. I don't want to modify the BC-348-R internally except one J-309 in the IF can to get IF output from. Also, I already replaced 2 position switch for BFO by 3-position one, and one mica cap that had been shorted I replaced by ceramic one. Otherwise it is original, as in 1943 when was built.
Also, I wanted to make a calibrator with digital reading, but as soon as I am going to get a license, I don't need it anymore, since an exciter may be used as a calibrator for fine tuning. I am currently looking on e-pay  for something from HP as you suggested.

Лягушки принадлежат в топи. Если люди хотят богом, котор для того
чтобы сделать шумом как лягушка после этого его изобрели бы зеленых
людей.
73,
Vlad, uh Dave W2APE.

Sorry Dave I could not understand you. :(

By the way, just now I listen how Mike KO6NM, David W6PSS and David W9AD from Illinois are trying to receive Brent W1IA but can't hear well. The best sound as usual have Mike KO6NM.

Great on listening in Tolly...Last night was fantastic. Worked from last nite - WA1KNX, KC9VF, W6PSS, W9AD, WA5QVS, N4WB, KA5RHK and many more. The band was almost dead quiet with Dino at S9.

Brent W1IA

Brent, I don't remember, who were in a truck? Someone in the team worked a mobile radio in a truck, if I understood well.

Tolly,

I heard that qso also, on my insomnia hq180 on the nightstand (cant believe the wife is putting up with it). Anyway, that was probably Marv, kc9vf, on his cell phone to internet to boatanchor setup. A very cool blend of new and old tech.

The signals were boomin in from all over here in Colorado.

Larry

Wow, it is really cool!
No need to carry heavy metal stuff, and possibility to use sophysticated antenna and transceiver remotely!

Tolly- nice to hear you got your BC348 working. it's a great old buzzard reciever. i literally grew up with one- a Wells Gardner BC-348Q that dad got from Harrison Radio in NYC about 1947, with AC power supply kit. it works to this day, NO MATTER WHAT. it's completely stock, and it's one radio i'm going to leave stock. by the way- the front end is good enough you don't need a preselector, and please- don't try to reinvent the wheel on the old thing. the classic "outboard slicer" consisting of a broadcast band ARC-5 for a second IF suggested by W3JN works just great. just ask former B-24 pilot Bill, W8VYZ. he's using that set up for 50 odd years- he say's "there ain't a sidebander in America that can touch me with that outboard slicer"... i have it teamed up ith a war ravaged ART-13 in my upstairs station, along with a BC-221 frequency meter (we don't need no stinkin' digital dial!). makes a nice WWII station. if i want a trip in "the wayback machine" i can strap on a set of HS53 headphones, grab a T17 carbon mic, and holler "bandits at 12 o'clock!" now get busy with that antenna and enjoy the sounds of REAL ham radio...

Thank you Chris for your warm words!
However, ARC-5 may be a good for second IF, but I don't have it. I have Fisher HI-Fi receiver, and I think it is good as well for such experiments, not worse than ARC-5. But I am not satisfied by such rough solution, so I am going to make my own second IF PCB with double balanced converter, synchro demodulator, and electro mechanical filters.
Speaking of preselector, what harm may be done by experimenting? Anyway, I already have a preselector made from Collins R-390A RF chassis, so I am going to try to connect it and see what happens.
Today I made a prorotype of a regulated solid state power supply for it.  It gives +12.6V DC for filament, +230V for plate, and -12 for bias. All voltages are increased slowly and smoothly when it is powered on. Also, the plate voltage starts increasing faster when receiver starts to consume  current from  plate source. It is nice, I like it. I'll post schematics later, I go to bed now. Tomorrow I am going to draw a PCB layout and itch it.

Tolly, no military surplus junk collection is complete without a BC-779. It has 2 RF stages and 3 IF stages. The front panel of this HF receiver was known to stop Luftwaffe machine gun rounds, and a shock from the power supply gave many a young JN ham his baptism under voltage.

BTW, I heard WA1HLR here in LA, he momentarily broke through the static about 0430Z in QSO with W6PSS on 3885 Mhz.

(http://www.aade.com/hampedia/military/bc779.jpg)

You'll note that the BC-779/BC1004/SP200/SP210/SP400 made my "second best" receiver for AM enthusiasts.  Truly a great radio.



Literally.  The Super Pro series is liberally strewn with opportunities to get knocked on your ass.  THe separate power supply means there are terminal strips on the PS unit and the radio, with 110VAC/-100V/300V/420V/6.3V.  Most of the time the metal covers for these strips are missing.  THe standby terminals also have about 400 volts on them (or so it seems!) and the cover for this is also almost always missing.

I was given a dead SP-400 when I was 12 or 13, and found the shorted bypass cap thoughtfully hidden in one of the IF cans.  One hot and humid day, I thought it appropriate to touch up the IF alignment after that (never mind I didn't have a sig gen).  Grabbing the front panel and gripping the metal shaft of a screwdriver for extra fine control, I nabbed the first IF and got thrown on my ass.  You see, the Super Pros have IF plate voltage right on the trimmer screws.  Got 300+ volts right across the heart, and thanks to my sweaty hands there was plenty of current flowing.  

I spent all day laying down and felt sick for a week afterwards.  If I had been older when this happened I probably woulda had my call in the Silent Keys column in QST.

I learned from this experience.  ALmost all accidents like this are preventable.  Keep one hand in your pocket.  Remove jewelry.  Don't work on equipment when you're tired, drunk, or pissed off.  Learn to walk away when things aren't going well.  Don't JS safety features like HV connectors, fuses, interlocks, HV bleeders, etc.  I don't wanna see ANY members of this board in Silent Keys because of an accident working on ham gear.

73 John

No Tolly...must have been someone else? Located in Derry, N.H.
To work the west coast is a treat with just a dipole.

Brent W1IA

John,
good advice. I was just on a plastic chair with my hand against an inlet heater blanket being pulsed at 270 VDC. We couldn't test untill the air flow was right.  I didn't lean on the copper plane either.

Truer words have never been spoken.

Generally, when working on a rig that has just crapped out, we are in a bad frame of mind anyway.

Remember those cheap Kung Fu movies where one guy gets hit and gets so POed he charges like a bull and gets hit again and gets even more POed?

It's like that with troubleshooting. Nothing like trying to fix something and you screw it up even more with a slipped tool, etc. The next scene is  the Kung Fu guy tearing you out a new Ash-hole with a high voltage probe...   :lol:    It's happened to me enuff to know to walk away.

Even if it means grabbing the cord and swinging the unit over your head and letting go.  Pete, W1VZR tells a story about an FT-101 with a shorted DC supply that met this fate a few years back.

T

Thanks Joe, Hammerland is in the list of my priorities, with Racal, RME, and Marconi receivers I want to try too.

I have gotten zapped a few times by the standby terminals [trying to change out to another recvr while 'hot']. This rig is full of old paper caps that go short, too. Some shorts will give you really HV on the chassis and you'll never know it's there, until that day you accidentally put yourself between chassis and ground. The BC-779 is like a nasty, dangerous, fully-armed war vet with a grudge. Tolly, forget those pretentious Racals and snooty Marconis. It's important to own one truly "bad ass" receiver.

Are you going to donate it, Joe? ;)

Ha ha, no way, dude.  :grin:  But one shouldn't be hard to come by. All you gotta do is hang around hamfests and internet forums for a while. Eventually someone will unload one, thinking they are getting the better of the deal, but YOU will be the wiser.

BTW, one way to avoid the mute relay terminal zap might be to do like Bill N6PY suggests on the SX-28 (similar relay voltage).

He modifies the receiver to open the RF and IF cathode ground circuit at the RF gain pot to allow the tube cathodes to float up to around 50 volts and cut off these receiver stages - so the relay terminals will have no more than 50 volts on them when the receiver is muted during transmit.  This method of muting by opening the ground return on the RF, IF, and audio output tubes is less exciting - but much safer.

Here it is, as promiced.


Upon request of Jay, N3WWL the picture had been removed. You may see it going to the link, http://www.wavebourn.com/forum/viewtopic.php?p=2143#2143

B+ voltage depends on a bias voltage. Bias voltage increases while the capacitor C3 is charged by a load. When tubes are cold they draw small current. When they start conducting, they charge C3 faster. While bias voltage increases it increases B+ voltage until stabilizes. Both voltages depend on D3 zener, B+ depends also on R7 position.

D1, D2, R2, R4 - "fool proof" protection.

Attention: 315V source musn not be grounded! Why 315? Because I used industrial transformer, they are cheap on e-pay (120/240V)

THis would also be a good circuit to rid the R-390 (non-A) and R-391 of those miserable 6082 regulator triodes.  The grid on those, however, is already regulated, IIRC.  I replaced both 6082s with one TV horizontal transistor.

Also great to regulate screen voltage on that leenyar!

Thanks for sharing the circuit, Tolly.

Gary - I nominate this circuit go in the Archives!

73 John

Sure, why not?

But significant condition is, B+ current must be bigger than a bias current, othervise positive FB by B+ current will not work. Or you'll need to add a bleeding resistor to the output of B+ regulator to make it starting when switched on, but in such case it will not wait for tubes to warm up so patiently.

Actually, minimum input voltage may be no less than 12V + output voltage plus peak-to-peak pulsations on the filter cap plus about five volts to drop on a resistor that biases FET. Output voltage may be changed by varying feedback resistors R5-R6-R7. They may be cauculated by condition: voltage on the base of the transistor should be about 0.4 volt.
However, I myself don't believe in the "Cathode stripping on cold tubes", I just developed such a device to satisfy guys who actually do. :D

Enjoy it!

Here is a filament voltage regulator. Speed of growth of output voltage depends on the C2 capacitor. It helps fo warm up cathodes slowly so filaments will live much longer. Thanks to Shottky diodes in rectifier and FET loss of voltage on open diodes and transistors is less than if to use ordinary diodes and bipolar transistor, so 12.6V AC from a filament transformer may be easily converted into the slowly increased 12.6V DC for less hum and longer tube life.

Upon request of Jay, N3WWL the picture had been removed (it is too big to post to the forum). You may see it going to the link,

http://www.wavebourn.com/forum/viewtopic.php?p=2143#2143

Larry told, "that was probably Marv, kc9vf, on his cell phone ".

Wow!  :impact:
BC-348 has high enough voltage on heterodyne trimmers! I just lost my screwdriver under the table...  :badgrin:

But as the result, all circuits had been perfectly aligned, and I hear much better Frank W7ND from Seattle talking to Bill N6PY, right over my head, 800 and 360 miles wvay to opposite directions.  :D

Don't say I didn't warn you!  :lol:  :lol:

BTW I've *never* been able to align band 1 (the LF band) in a BC-348 to my satisfaction.  Most of the time the trimmers do nothing at all.

73 John

No, you warned about Hammarlund's IF cans  :oops:



Looks like mine is in better condition. They act sharp enough. ;)

Tolly - cheez... I thought I was warning about IF cans in general. :oops:

You're lucky with the BC-348... most of the ones I've had were ham-specialed to death, although I did have one that was 100% stock including the dynamotor.  *That* one wouldn't align at the upper end of any band.  IIRC it was something bad in the local oscillator... 'twas about 15 years ago so I'm kinda hazy on it.

73 John

Guys, who know where to order to print cheap but good PCB's?
I would make kits for power supplies...