My Love of Radio

[Dave]

I've always been interested in early radio, both amateur and broadcast. The graphic below isn't very early ... 1946 ... but I found it while searching on another topic and what intrigues me about it is that there appears to be only one Utica radio station listed, WIBX.

WGY 810 is still Schenectady. 880 is now WCBS, New York. 770 is now (I think) WABC. Was WJZ New York in 1946? Also, note WIBX at their old frequency of 1230.

By 1946 radio was fairly advanced and without all of the RFI noise in the air as there is today, reception from New York City may have been rather easy (on the U.S. AM broadcast band. Short wave would be different, of course.) However, I never remember my parents or grandparents tuning in any station but WIBX or WRUN in the late 1940's and early 1950's.

[keith]

It was easier to listen to long range AM broadcasts in the past. As a young teenager (1960) in North Dakota after sunset I could tune my portable radio to clear chanel stations, mostly WLS in Chicago and KOMA in Oklahoma City.

My portable radio was not like any I've seen since. It was the size and shape of a school lunch bnox. Power was a lantern battery or AC. Unlatching the lid and raising it into position exposed a square loop of antenna wire. I was unconvinced about the effectiveness of the antenna so I normally tapped into it with a pair of leads with aligator clips attached to the metal springs of my brother's upper bunk.

[Dave]

Clear Channel ain't what it used to be. On the chart, 770, 880 and 810 were/are clear channel, but the separation between clear channel stations on AM is now only 500 miles, I think, maybe less. Used to be you had either the east or west side of the Mississippi. Ran out of space, and that was before the band was expanded upward to 1700 KHz. I used to tune around at night with a German Navy radio and a good loop, just with an interest in propagation, but how many Michael Savages can a body take?

Bed springs are good. A friend in high school worked Hawaii on 20 meters (14 Mhz) with 50 watts RF out on his bedsprings. CW (Morse Code) of course. He and I were the scourge of Cornhill. He with his telephone pole antenna that was always falling over on his neighbor and me with my old Viking I transmitter that produced so many harmonics probably only half the power got out on the intended frequency.

Here's the Viking I. Mine had a cabinet.

[Dave]

Here is a list of medium wave (US AM Band) stations I was able to receive from where I lived near Woodstock until moving last fall. Some are small local stations like that in Catskill and Hudson, but most are clear channel stations


Mediumwave AM Stations

Khz. Call QTH Khz. Call QTH

560 WCKL Catskill
590 WROW Albany
610 WIP Philadelphia
650 WSM Nashville
660 WNBC New York
680 WRKO Boston
700 WLW Cincinatti
710 WOR New York
720 WGN Chicago
740 CHWO Toronto
750 WSB Atlanta
760 WJR Detroit
770 WABC New York
780
WABS Arlington, V
WBBM Chicago
800 CKLW Windsor
810 WGY Albany
840 WHAS Louisville
850 CKVL Montreal
860 da WSBS G Barrington
870 WWL New Orleans
880 WCBS New York
890 WLS Chicago
900 CHML Hamilton
920 WGHQ Kingston, NY
930 WBEN Buffalo
940 CINW Montreal
950 WHVW Hyde Park
980 WOFX Albany
990
CHTX Montreal
CBW Manitoba
1010 WINS New York
1020 KDKA Pittsburgh
1030 WBZ Boston
1040 WHO DesMoines
1060 KYW Philadelphia
1070 CBA Moncton, NB
1080 WTIC Hartford
1090 WBAL Baltimore
1100 WTAM Cleveland
1110 WBT Charlotte
1120 KMOX St. Louis
1130 WBBR New York
1140 WRVA Richmond
1170 WWVA Wheeling
1230 WHUC Hudson
1500 WTOP Washington
1520 WWKB Buffalo


And you can download from my site a list of North American clear channel medium wave stations (AM Broadcast band) as well as a description of frequency designations. The list should be fairly current since it's only a couple of years old. You'll see I misspoke above about 500 miles and that there are now two types of clear channel. That I had forgotten. It's here:

www.windsweptpress.com/TEMP/clrchnl.doc


Also, if I can find it, somewhere on line is routine into which you plug your location and it spits out every radio station in the U.S. in order of the transmitter's closeness to you. I found this useful, for example, when trying to ID a station.


Below, a Sailor marine radio. Of Danish make, I had 3 different models over the years. (I love eBay!) Since at one time off shore navigation could be done by triangulating on shore AM radio stations, marine radios covered the AM Band as well as the lower marine frequencies. There's no reason why that couldn't be done today, but with GPS why bother. Anyway, because of their use, these radios were peaked for use in the 500 Khz to 1500 Khz range.

[Dave]

Remember when Lyle Bosely was on Channel 13 and he was just about to read the results from Vernon Downs and your TV went flooey and looked like it had acne? Damn that radio guy down the street with his wire antenna hanging from tree to tree. A neighbor of mine was so enraged at me in high school that he climbed a tree and cut my wire down. I was fifteen and told him I'd have the FBI at his door in the morning. He took a swing at me and missed and told me to get off his porch. What a spoil sport!

Here's a radio QSL card (confirmation of stations working each other) from way before my time in the lat 1920's. Dean Wallace, call letters 8DSM at the time, was probably running 35 watts out with "raw A.C." modulating his Morse signal. He was passing messages across the state that night and this confirms he received messages from 1HN and passed them on to another ham radio operator in Rochester. Old Dean probably had his little station in the attic of the house in the fifteen hundred block of Oneida Street in Utica and wore a coat up there on cold nights.

[Dave]

Here's a corner of my radio room collection containing short wave receivers and transmitters mostly from the fifties, with some from the late 40's and early 60's. They were all working and online to antennas and I used them often on the 3.5 Mhz band (80 meters) in the evenings.

All sold now along with the rest of the collection on the other walls when we moved south. I kind of miss them, but they didn't call them "boat anchors" for nothing!

[Dave]

Today, working with broadcast or shortwave radios is very difficult from a reception point of view. The myriad of dimmers, lcd screens, computers and computerized devices in a modern house hold produces a roar of radio frequency interference on any sensitive radio.
There are solutions to combat this problem, and one of them is the small aperture loop antenna. Mine is pictured below. In my new neighborhood it sits in the attic and does pretty well. In the photo below, I had it above my deck, as far away from near-field noise in my house.

A radio wave consists of two kinds of energy in equal parts, so to speak, an electrical wave and a magnetic wave. Small loops are mostly sensitive to only the magnetic part of the wave. And guess what? Radio Noise is electrical.

I have a spectrum scope on one radio that shows incoming signals across a band of frequencies, as well as their strength. Listening with a regular long wire antenna produces almost a bar of strong noise across the spectrum. When I flip the antenna switch to the small loop, the noise disappears and out of the muck comes each of the individual signals, as if by miracle.

[keith]

Dave, Is there any tech reference you can point me towards on the above? It's been decades since I did anything with Maxwell's equations so I'm not necessarily looking for something really calculus heavy. Just trying to get my head around what's happening.

Any radiated energy has to be E-M whether its noise or a signal. The only mechanisms I see for using an antenna for filtering signal from noise are frequency/wavelength, direction and polarization.

[Dave]

Keith, it's been a very long time since I last read up on the physics of transverse electro magnetic waves. Here's are a couple of places to start. Joe Carr, before he died, had a wonderful way of explaining antenna topics without recourse to calculus.
I'll look for more on the the web and then I'll look to see what my old Terman's says.

Here's a fairly straight forward treatment of small loops:

www.dxing.com/tnotes/tnote08.pdf


No calculus in this reference, either:

Newnes Radio and RF Engineering Pocket Book

books.google.com/books?id=3b-_InpSowcC&pg=PA73&lpg=PA73&dq=joe+carr+small+loops+and+rf+noise&source=bl&ots=NASj6u-APF&sig=LmswxDkoRS1V06fzRt-ab7LMcUk&hl=en&sa=X&ei=0rRFT9bqMIjcgQfV7c2mBA&ved=0CCMQ6AEwAA#v=onepage&q&f=false

[Dave]

This may be of greater help, and wouldn't you know it, it's from Wiki

"The small loop antenna is also known as a magnetic loop since it behaves electrically as a coil (inductor) with a small but non-negligible radiation resistance due to its finite size. It can be analyzed as coupling directly to the magnetic field (opposite to the principle of a Hertzian dipole which couples directly to the electric field) in the near field, which itself is coupled to an electromagnetic wave in the far field through the application of Maxwell's equations. Because of this fact it is somewhat immune to noise affecting the electric field ("static") generated in the near field. Since at low frequencies, such as the AM broadcast band, the near field region is physically quite large, this provides a considerable benefit in relation to static generating devices (such as sparking at the commutator of an electric motor) in the vicinity.[2] Contrary to myth, however, this immunity does not extend to noise sources outside of the near field: such noise is received as an electromagnetic (propagating) wave and would be received equally by any antenna sensitive to a radio transmitter at the location of that noise source."

en.wikipedia.org/wiki/Loop_antenna


The difference in the small loop (non resonant) antenna's response to the electrical versus the magnetic wave components evidently has to do with radiation resistance, the way I read it. Note Wiki says the small loop (L= < .15 lambda) works best the lower the frequency because that implies a more distant near-field (edge of the near field, was it half lambda times pi?) From a typical noise point of view my experience was that the 3 to 21 MHz frequencies I used for ham work can almost be lumped together as far as the noise elimination, which was pretty good (receiving.) The 25 to 1700 KHz. areas of interest to me were even better, of course.

Tuning a small loop is normally crucial, but that's also a problem if you want to get the loop outside away from the emi generated in your house (but don't forget the noise from neighbors.) Most of the emi fell off rapidly by 20 feet of distance, except light dimmers, which according to documentation I read from a manufacturer (Lutron) were able to use the house wiring as an antenna. I fouind (with a portable radio) that I had to place the small loop at a distance of over 50 feet to not hear the dimmers.

You can eliminate the need to tune a small loop and therefore place it anywhere by using small amps and coupling them in a very broadbanded manner, but the resulting gain suffers. Wellbrook, the small company in Wales who built my small loop, solved the gain problem by using very, very low noise FET's. and cranking up the gain.

And yes, small loops are just as sensitive to far field noise, such as atmospheric noise as a dipole. But it's the stuff around the house in the near-field, all the lcd's and other computerized devices that cause a lot of the noise.

I couldn't find anything any better in my Terman's and in my Radiotron Designers Handbook.

[keith]

I'll have to do some reading. I'm not afraid of the math but when it gets to vector calculus I'm really rusty.

By the way did you see that yesterday Google was celebrating Hertz' 155th birthday.

[Dave]

No I missed that about Hertz. By the way, while you're researching, keep in mind the current around a small loop is constant, not nodal (no standing waves), compared to a dipole or large loop. And I'm wondering if that might have something to do with its ability to discriminate between the electrical and the magnetic part of the wave.

[Dave]

Also, I wonder if its similar to transmission lines where common mode noise can produce in-phase signal voltages on parallel conductors, but be cancelled out when a current balun introduced into the circuit reverses the phase of one leg. then the out of phase signal on opposite legs cancel each other out.

[Dave]

My apologies to readers for us getting a bit technical. I had wanted to share my love of radio. As a kid I'd be up in my attic on Brinckerhoff Ave at night with a shortwave radio I built from a kit and an old less sensitive parlour radio that received shortwave stations. To listen to a signal from across the Atlantic even in the mid 1950's was still a thrill for an adolescent. And when I learned Morse Code and could listen to hams, I though that was just the most fun a kid could have, before puberty anyway. Speaking of sex, puberty definitely put a dent in my radio time, but I struggled on with both endeavors.

Here's a transmitter I wanted when I was a kid. It was old even then, having been made in the 1940's after he war, but like many other radio hobbyists, I thought this radio was so cool!

The Harvey Wells Model TBS50A CW (code) and phone transmitter could transmit on every amateur radio frequency then available, including 2 meters (144 Mhz.) I've owned two models of the TBS50 over the years, but I didn't buy my first one until I was in my fifties. On eBay, of course.

A fifty watt transmitter, the components were so old in both of the transmitters I had that I never got more than about 15 watts out. That was enough for occasional contacts up and down the east coast when conditions were good. When they weren't, I ran the little trooper through a 100 watt amp.

[keith]

Feb 23, 2012 22:06:24 GMT -5 Dave said:

Also, I wonder if its similar to transmission lines where common mode noise can produce in-phase signal voltages on parallel conductors, but be cancelled out when a current balun introduced into the circuit reverses the phase of one leg. then the out of phase signal on opposite legs cancel each other out.

In the design of magnetic heads, some coils are wound with bifilar wire (magnet wire with two conductors, normally different colors, laid parallel to each other & bonded together before being spooled). They are then wired like a center tapped transformer. Record heads normally have a centertap because it's much easier to design a push-pull driver than a single ended one.

An alternative configuration is two single wound coils wired together. Bifilar coils have an advantage in common mode rejection ratio so better signal to noise.