It would have come up sooner than later by someone!
My induction is that I don’t have the capacity to take this any more and time to go ohm.
Then there was a story about a diner who was getting fed up with one badly prepared course after another, finally stood up and yelled “What’s butter worth to a shabby chef!”. (non-EE’s probably won’t get this)
Warning: There’s mho where that came from…
My head is shaking like a monstable multivibrator
I tried to just filter this out, but my response fell flat.
If this is part of some kind of plot, it doesn’t bode well…
You must have looked up ‘Saskatchewan’ on the Classic Trains forum recently… [:-^]
way off topic but the vibrations of car radios before solid state electronics were the cycles of those times. Took up to a minute to amp up the speaker(s) for their rms vibrations.
Overmod wonder how many understand how effective radative power (ERP) comes about, is calculated, and works ? Its all about the antenna!
I’m afraid you’re going to have to explain this to me. Part of what made Motorola possible was building tubes that would ‘take’ vibrations without enhanced failure, the heaters often being the thing susceptible to breakage; the greater part wasn’t vibration at all but the realization that the air tuning capacitor, the thing that restricted miniaturization of radio receivers up to that point, could be miniaturized with the right dielectric between smaller plates. In order to produce sound you had to warm the tubes up to where they would conduct push-pull, but at that point you could reproduce complex waveforms (the things that make speakers ‘speak’ with music or voice instead of just tones) perfectly well. RMS is a measure of average power, which isn’t really a concern for peak waveform fidelity (without clipping).
And when he says that, he MEANS it – not only in terms of getting the RF energy effectively ‘coupled’ into the air, but in the right pattern and directionality. Most people don’t think too carefully about how FM can possibly work … electromagnetic propagation goes into space weakening with the square of distance, right? So why does the 50-microvolt contour go proportional to distance? Hmmm – antenna magic!
The output of the Wilkinson we bought to replace the infamous Collins was nominal 10kW. Our ERP was 17kW, neatly beamed where humans’ receivers would pick it up. We could test the emission pattern with an old fluorescent light tube wielded lightsaber fashion; it would light up neatly where the RF pattern hit the tube…
How soon we forget! Back in the old days people didn’t worry so much about whether the car radio worked as much as they did whether the heater worked! Especially up north, trust me!
I remember a TV car ad from the '60s ( I don’t remember which make) where one of the selling points of the vehicle was “…and a heater that WORKS!”
Ah, the good ol’ days!
I thought Blue Streak was talking about the vibrators in the radios in the cars with 6-volt batteries. I remember seeing a driver banging his fist on the dashboard apparently trying to un-stick the vibrator.
And Flintlock, speaking of heaters, I still think of the heater in my '54 Pontiac as the most comfortable design. It was under the front seat and spread hot air onto the floor, warming the feet of front and rear passengers. Later designs blow hot air on your shins.
Does anyone remember the original topic of this thread?
That was before my time; in fact I don’t even remember seeing three-cap batteries anywhere as a child. I inherited a car with a generator, and almost bought a straight-eight Buick in college - that’s about it… except to wonder how anyone started anything in winter on 6 volts.
The Panelescent doohickeys were vibrators too, to get battery voltage up to high tension, like a version of the trembler coils in a Model T ignition. Only much, much cruder and cheaper. (Of course the electroluminescent panels did not require any sort of clean waveform – I forget how they cured the EM interference on the radio. There was a fairly long article in some classic-car magazine about all the ways those things went bad, and how to fix them or replace them (the replacement being the ‘done thing’ before the value of many of those cars in ‘concours’ condition went through the roof…)
I remember often seeing virbrators being sold along with tubes at the tube checker kiosks. Modern solid state equivalent is a switching power supply with synchronous rectification, though these are normally used to STEP DOWN the voltage, e.g. 48V to 3.3V.
(RF power minus feedline and matching loss) times antenna gain. “Gain” can be a bit ambiguous, whether it is in respect to isotropic, quarter wave monopole or half wave dipole.
.
Like he said: “it’s all in the antenna!”
Fascinating stuff in the field in the past few years, some of the techniques being things that still look like science fiction after you’re shown how they work. And that’s just the stuff in the literature…
I’ve said it before, I’ll say it again, I’ll never get tired of the magic of radio.
I can recall hearing the motor/generators in the radios in patrol cars winding up to produce the high voltage necessary to transmit.
Which brings us back to railroads (albeit subways). I have a friend who retired from the NYC subway system as power supervisor. Among the equipment he maintained were the huge motor generators used to convert AC to 600VDC.
As for antennas - how about this one for 2 meters (147 MHz):
It’s called a slot cube… You’ll have to click on it…
I’ve played with slot antennas in the past. One of the coolest demonstrations is taking a sheet of copper or aluminum with a half-wave long slot cut in it (easier to do at 1.2GHz than 2M). Place the sheet with the slot between two half wave dipoles, one transmitting and the other receiving. Maximum power transfer occurs when the slot is perpendicular to the dipoles.
IIRC, the old mobile two way radios used dynamotors for voltage step up. A dynamotor is a special M-G set with a single armature with commutators at each end and the high and low voltage windings occupying the same slots in the armature (think DC-DC version of the synchronous converters used for 600V electrifications). The advantages were that the overall device was smaller than an M-G set, more efficient and less sparking at the commutator. The disadavantage is that you had a fixed step-up or step-down ratio.
Dynamtors were commonly used on 600V/1200V interurbans to provide 600V power for lighting and control when running off of 1200VDC. The DL&W 3,000VDC suburban cars used a dynamotor to step 3,000VDC to 1,500VDC for the air compressor.
Found it – American Engineer and Railroad Journal (became Railway Mechanical Engineer) for September 1907:
"The choice of frequency was practically fixed by the manufacturing companies within limits of fifteen and twenty-five cycles, and the comparative merits of those two rates only were considered.
"The lower frequency afforded a material reduction in weight, size and cost of motors, a reduction in conductor losses and induction disturbances, together with an increase in the power factor of the motors. Per contra, its adoption would have materially impaired the commercial value of the system as a whole, in restricting or preventing its extension for many other uses incidental to railway operation. The standard power and railway frequency in general use is twenty-five cycles, and as the New Haven Company already owned a number of power houses generating current at this frequency for standard trolley operation, and, in addition, had equipped many of its shops with twenty-five cycle motors, the adoption of fifteen cycles would have required the abandonment of a large amount of standard apparatus, or the interposition of costly and inefficient means of translation. The lighting of stations and other buildings was quite an important factor, as 25 cycles is the lowest frequency at which the carbon filament lamps in general use can be satisfactorily operated. It was also considered desirable to provide for operation in parallel with the 25 cycle generators already adopted by the New York Central Company…
"It was at first proposed to increase the economical radius of transmission to the utmost by generating current at the highest initial voltage for which generators could be safely designed (about 22,000 volts) and to provide substations at suitable intervals, equipped with static transformers, for supplying current at 3,000-6,000 volts to secondary contact circuits…
"It became evident, however, that a great gain in
Nice work!
I did not think about damage to the carbon filaments.
A solution to HOAs that’s been seen in the ham radio press is to do that with a satellite antenna. While HOAs may restrict amateur radio antennas, they seem to be OK with the small satellite dishes. Apparently they work well for two meters. Don’t know if they’ve been tried for 70cm.
Few people will notice the slot, or the coax that’s connected… Even if they did notice the slot, a little non-metallic putty and a fresh coat of paint render that moot.
Back to electrification…