Wireless analog audio

"Jan Panteltje"

** Fuck off - wog imbecile.

mkr5000

needed) wireless system that is high performance and good

channel.

Naw, just switch out the antenna to a leaky feeder (slotted coax) along the long side of the patio. No worries about multipath then, the wavelength of the carrier is ~3 meters.

?-)

On a sunny day (Fri, 4 Nov 2011 10:01:16 +1100) it happened "Phil Allison" wrote in :

Si, Phyllis, if you do all that in that madhouse, it is understandable that you pick up some of the jargon there. But why not buy a book on electronics, or better even a soldering iron and build your first crystal radio? Then you can hear just a few stations if any on the medium waves, and post here interesting things about your experiment, other then blurbs of your conversation with your madhouse inmates.

Exactly what is wrong with "10kHz wide 'channels' on the AM band"? The fact is that AM stations (US) are on a 10kHz pitch. They're not often called "channels", but that's just word usage. Apparently modulation up to 10.2kHz is allowed making for a 20.4kHz "channel width" (there's that bad word again).

Even the loon you're talking to admitted as much when he came up with the (wrong) number of frequencies supported.

You were insane?

wireless system that is high performance and good range?

Well, sure: just fire up a laptop with WiFi, and any of the music-player apps (like iTunes) will glom good audio from a bunch of sources. Including your own library of recordings.

True, and in some countries spacing is also 9 KHz.

wireless system that is high performance and good range?

channel.

Try Googling stereo encoders or fm exciters or something like that. There are several types of those for FM band 88-108MHz available. No video and they are boxes, not chips.

Nothing. To be honest, what I know of AM radio is probably on par of what AlwaysWrong knows. IOW almost nothing. In my original post in this thread I was only responding to Phil's ridiculous statement of "Local AM transmitters are 100kHz apart in most places."

Which, at least in areas with a reasonable population density, just isn't true.

The he claimed I said a number of things that I didn't say. Things went downhill from there as most discussions do with him.

No, just the stupid part.

c, Radio

Interesting there is a station on 910Khz, since that is the second harmonic of the IF frequency (455 KHz). I had an AM radio with the IF misaligned to 435KHz, and I could never get a local station on 870KHz without a lot of whistles and interference. Readjusting the IF to

455KHz fixed the problem. Seems any station on 910KHz would present a IF harmonic problem. But I just have a cheap radio.

-Bill

It did. WPFB, in Middletown Ohio sounded lke shit if you were very far from the transmitter. Why do you think Delco used 262.5 KHz IF in their early AM car radios?

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You can't have a sense of humor, if you have no sense.

This must have been some kind of plastic construction, i.e. the local station signal entering the IF chain after the first IF transformer, but prior to the last IF tube/transistors. In the old days, radios had tunable front ends, thus, entry through the antenna is unlikely.

The choice of IF is quite complicated issue,

A low as possible IF would be preferably, since the IF bandwidth would be smaller at lower IF frequencies, thus the IF transformer could be loaded more heavily to get the same loaded-Q bandwidth, i.e. saving one tube/transistor and IF transformer.

For early transistor designs, the very limited transistor fT meant that you could get 6 dB more gain at half the IF, potentially saving one (expensive) transistor stage.

On the other hand, using too low IF, would make the image frequency problem (RF+2xIF) much worse, requiring good front end selectivity. Since a typical superheterodyne receiver would have one section of the variable capacitor for the RF tuning and the other section for the local oscillator, there is a limit, how much image rejection could be achieved.

In the Americas with no LW band, the IF selection is quite easy, anything below 500 kHz will do, limited by the image sensitivity only.

In Europe with the LW band, the IF selection is more critical. You either have to put it somewhere between the LW and MW bands or below the LW band. Putting the IF below the LF band (below 150 kHz) would put a huge demand of the front end design (two variable capacitor/variable inductors sections) to avoid the image frequency problem. Thus the only logical place for the IF would be between

400-500 kHz,

Since Delco was a subsidiary of GM, they would not bother with some customer complaints at some few rare locations with whistles, unless it would hurt the _car_ sales for GM cars :-).

Thus I very much doubt that the selection of such low IF would have anything to do with 2xIF whistles.

Sigh. Car radios had steel cases and were tuned with variable inductors. The problem was caused by the mixer circuit. The IF was 455 KHz. The RF was 910 KHz and the LO was at 1365 KHz. Since the mixer is non linear, you ended up with birdies. The cheaper car radios weren't much better than a $6 '60s Japanese pocket transistor radio. People who were into AM BCB DXing loved the old Delco car radios. People in Central Florida used to use them to listen to WLW in Cincinnati at night.

Some people stagger tune AM radios to improve the received bandwidth. AM broadcast was never HI-FI, but some people used a TRF tuner and fed an audio amp, when the station didn't have another that would cause interference.

They used 262.5 KHz in tube car radios long before their first all transistor car radios. They were six transistor and had enough gain to drive you out of the vehicle.

The Delco PTO front ends had three tuned coils inside a cast aluminum frame. RF, Mixer and LO.

They could have followed the design of the ARN-6 Direction Finder made for W.W. I aircraft. The IF frequency was different for each band to prevent mixer byproducts.

Sigh. Early Delco radios were battery powered tube radios for homes.

Good luck with that doubt. I was a Broadcast engineer, and as a teenager I worked on hundreds of AM radios. The radios with 262.5 KHz IFs were clean across the band. The other common IFs were 450 or 455 kHz and they all had birdies at 900 or 910 KHz.

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You can't have a sense of humor, if you have no sense.

Crap, you could listen to WLW on your teeth, with dental floss as an antenna.

I'm a LOT further away than you are from WLW and power line nise from those crap LED traffic lights wipe out a good part of the AM band these days. They were easier to pick up when they ran 500 KW, though.

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You can't have a sense of humor, if you have no sense.

I thought that was the period you were talking about. Yes, the AM band is lousy these days. At night, we used to get WLW and WLS booming through all over the Eastern two thirds of the country. No more.

Brings back fond memories - scrounging wire, getting it into trees, learning about a "ground rod" (what the heck is that??!) snaking wire in the window, getting radios (Delco was king!) and tooobz! from the junk yards and after dark listening. :-) And batteries! And XERF! And a BC 348 for "short wave". What the heck was short wave??

It was a time of wonder and awe. :-)

Ed

Selectivity, what else?

Jim

Here's some pictures of the Russian Woodpecker antenna that used lots of wire. I could hear it in So. California.

"It's height is 150 meters and about a kilometer width. In a bright sunny day you can see this grid from anywhere in the forest of the Zone."

-Bill

I built a radio from a kit I got for my 8th birthday. I was hooked on electronics that night when I discovered WSM, in Nashville. I was glad it had headphones, so I could listen to it without my parents hearing it and telling me to turn it off. :)

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You can't have a sense of humor, if you have no sense.