Terman's Radio Engineers Handbook (1943) shows the following as "Required Field Strength" for acceptable AM broadcast station reception in areas of their primary coverage.
Terman's Radio Engineers Handbook (1943) shows the following as "Required Field Strength" for acceptable AM broadcast station reception in areas of their primary coverage.
Note: mV/m means millivolts per meter
City business or factory areas.... 10-50 mV/m
City residential areas...... 2-10 mV/m
Towns (2,500-10,000 population)..... 2 mV/m
Towns (under 2,500 population)..... 0.5mV/m
Rural -- all areas during winter, northern areas in winter.... 0.1-0.5 mV/m
Rural -- southern areas during summer..... 0.25-1.0 mV/m
Of course the electrical noise level in the home was much less in 1943 than it is now (SCR light dimmers etc).
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Rich,
Thanks for the information. I believe that the most important point that you mentioned is the preponderance of man (or woman) made noise in today's home environment.
Back when I was "Lost in the 50's" I had copies of White's Radio Log (published in some electronics magazine) and I was quite the AM DXer with my old junkyard Buick tube car radio (25 cents if I removed it myself which I did) which I converted to base use. I very cleverly replaced the vibrator with two pieces of #12 wire and ran it on 6 VAC. Despite the 0Z4 rectifier this radio was a "hot" receiver (still have it and it still works!). At the time I lived in a small rural farming town in West Central Ohio and even using a 3 foot whip antenna I could receive stations from hundreds of miles out. On a GE clock radio using the "all American five*" I would regularly listen to WLS from Chicago and WJR (you have heard of them haven't you?) from Detroit.
But things have changed. Today it is virtually impossible to listen to AM radio, even local stations, in my home due to the QRM (man made noise) coming from almost anything that screws in or plugs into the AC lines here. I suspect that even our friends in rural areas have the same situation.
Thanks to all reading this for letting me ramble a bit but it all comes down to signal to noise ratio at the receiver when it pertains to AM reception and satisfactory listening. Sadly, the AM band is over populated and the QRM and other distractions deprives youngsters, as I once was, from enjoying the adventure of tuning in the DX (distant) stations. Despite my school activities and my after school job I had time to play with radio. Then I discovered girls....
Neil
*The door prize goes to anyone who can tell me what the All American Five is. Hint: 35W4, 50C5,.... The door prize is my continuing respect and admiration.
You almost threw me off with giving those teasers 🙂
Others' guesses?
Experimental broadcasting for a better tomorrow!
SCWIS,
Sorry, no door prize for you since the answer was not enumerated...but let's not spoil the fun. You still have my unending respect and admiration. (I made the rule, I can cheat). BTW, I am sure Ermi and probably WEAK know so they are disqualified, but not on the admiration and respect aspect.
Neil
I suppose I won't qualify for the door prize, but as I remember the rest of the lineup Neil started, it consisted of a 12BE6 "converter," a 12BA6 IF amplifier, and a 12AV6 or maybe 12AT6 detector/1st audio stage.
However my AM reception experience here in west-central Illinois is not quite as dismal as suggested, with respect to locally-generated electrical noise.
I can receive the daytime groundwave signals of Chicago Class A stations WSCR, WGN, WBBM and WLS here on a cheap, solid-state clock radio in my home, some 250 miles away from their transmit sites
The pop count of my city is about 45,000, with maybe 5,000 more in the metro area.
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Rich,
If I recall the 12AT6 had two diodes in the package but I don't recall that it was part of the AM5. You already have my respect and admiration so you don't need the prize but now I am going to have to do some homework because I realize that I probably don't qualify for the prize.
No intent to hijack your thread was intended, I did however want to point out the problems of interference in the modern world. It is terrible here.
Neil
I guess that we were all boy geniuses in the 50s, and there was nothing like the AA5 to enhance our reputations. With so many models built the same way, repairing an AM radio was a snap. There was nothing that astonishes the uninitiated as much as being able to repair a radio or a TV. It was really a parlor trick, because we hadn't had time to gain any real knowledge yet. Today, I can hardly repair anything.
For TVs, there was the Tube Replacement Guide, and, for really advanced work, there was the Ryder publication, "How to Troubleshoot a TV Receiver."
I might add that the 12AV6 had two diodes, but only one of them was used as the detector. The other diode was wired with a short across it. This was the only wasteful aspect of this product, which was designed for good performance at minimum cost. The 6.3 V pilot light, in contrast, was connected between heater pins 3 and 6 (the filament center tap) of the rectifier tube, eliminating even the need for a resistor for this component.
The price was about $20, or so, which is about $200 in today's dollars.
White's Radio Log was published in "Radio-TV Experimenter," a sister publication of Science and Mechanics Magazine.