it is easy to make a radio that receives only one station. the station selector thumbwhell is nothing but a variable capacitor. just find the approriate capacitance needed to tune to the particular radio station being promoted (WABC) and install that particular capacitor in there (like 12 micro-farad's or whatever, instead of the wheel control).

you can have a radio manufactured cheaply without much redesign. just start with a willing manufacturer's standard model and have them substitute a less expensive static capacitor when they're soldering the boards.

why would anyone want this? well, only to promote their radio station. that's all i can think of. but for that, it's good. all it has is on/off/volume!

maybe the frequency (on in the case of AM, amplitude) changes slightly depending on your place in the geography, so maybe you'll need a fine-tuning variable capacitor, but it's a more beautiful piece without it.
-- gnormal, Feb 05 2001

The amazing one transistor (MPF102) VHF FM Receiver! http://braincambre500.freeservers.com
Without comprimizing for sensitivity, selectivity and audio output, this little jem is doing its' job fine! [braincambre500, May 11 2002, last modified Oct 17 2004]

Baked & deployed in Afghanistan http://www.wired.co...,2100,47447,00.html
The military is way ahead of you... apparently they did this in Vietnam, too. [gastronaut, Jul 11 2002, last modified Oct 17 2004]

cheap radio http://www.alibaba....724857.29.46.pf66qZ
small push button aut scan radio. They are so cheap you can buy them in bulk. [travbm, Oct 29 2015, last modified Oct 30 2015]

Frequency Calculator http://www.1728.org/resfreq.htm
This lets you pic inductance and capacitor for your one station radio [travbm, Oct 31 2015]

Amp http://myplace.fron...er1945/1QAFAmp.html
Poor mans audio amp. [travbm, Nov 02 2015]

LM386 amp http://www.rason.or...s/icamps/icamps.htm
Better than using an NE555 [travbm, Nov 02 2015]

µA741 http://www.mouser.c...05/ua741-556365.pdf
Was that it MB? [travbm, Nov 03 2015]

The frequency never varies (it's the same signal!), and AM radio is tuned by frequency, not amplitude (modulation is different from tuning).

But: Static capacitors aren't generally made with enough precision that you can rely on them to tune a particular radio station (which requires accuracy to better than one part in a thousand).

But: Modern radios (even cheap ones) typically use PLL synthesized receivers rather than the sort of inductive R/C resonant tuner you're describing. To make a fixed-frequency receiver, you use a fixed-frequency oscillator, which needs nothing more than a quartz crystal.

So, it should be totally possible.

Disclaimer: I am not an RF engineer. Analog signals scare me.
-- egnor, Feb 05 2001


I believe this was baked....for exactly the purpose you described, radio promotion. Unfortunately the competing radio station started giving away a set of pliers and instructions on how to change the station to their own. (In this case the radio was obviously not 'fixed', it just had the tuner knob 'hidden' somewhere.
-- blahginger, Feb 05 2001


I ad a vote for baked: I hada version of this years ago called a 'Target Tuner' which locked onto a single station. It was actually a very nice wooden box with a speaker that had an on/off button and nothing else. Unfortunately it was for a station that later disappeared.
-- RobGraham, Feb 05 2001


Baked for many years. The Nazis sold thousands of cheap radios with only one station...Guess what was broadcast? Not transistor, though...
-- StarChaser, Feb 05 2001


believing i had learned something from StarChaser during a conversation with a smark greek girl, she corrected me, saying that those nazis did not produce singlestation radios, but had some mobile outposts which detected those in the vicinity who listened to unauthorized stations.

i also heard that in the uk, where one needs a license for their tv, one can be busted by such a mobile unit (a van).
-- gnormal, Apr 14 2001


This may be quite baked but I'm still going to fish it. There's several problems.

1) accuracy of a fixed tuner. 2) uniform frequency- not all stations can get the same frequency across the whole country (not in the UK anyway) 3) futurefroofing - what if the station moved frequency

4) The big one - Doesn't it say something really negative about the quality of your radio station that you have to stop people comparing it to other stations?
-- st3f, Apr 17 2001


gnormal: "tv detector vans" as they are called, do exist here in the UK, but only as an urban myth. What actually happens is that the licensing folks sift through lists of what houses do and don't have a tv license and then visit the houses that don't. They never, ever, believe you if you say you don't have a tv.

back on topic: if the BBC made a radio that only recieved Radio 1 (for John Peel & Andy Kershaw) and Radio 4 (for everything else), I'd be quite happy.
-- Jim, Apr 17 2001


I got one of these in the mail for Bloomberg Radio and it even had a head phone jack. There was a dial, but it only changed to frequency enough to get better reception on the one station.
-- Tysenworld, Feb 01 2002


When I said 'Nazis', I meant the National Socialist party circa 1938-1945. I can't remember what it was called in German, but it was translated to something like 'People's Radio'. They had no tuners and would only pick up the Nazi propaganda channels.
-- StarChaser, Feb 02 2002


Does anyone outside the public sector in England or Germany or anywhere else for that matter have the legal right to catalog observations of EM phenomena and loads thereupon? I would think it more effective to do the opposite. Allow anyone to observe, and encourage everyone to publish their findings, including raw data. You'd probably get a measurable amount of amplification over the van full of snoop or spook equipment or whatever.
-- LoriZ, Feb 03 2002


DeGroof:

Thankx for the 411 on radio technology. Are you in essence saying that every AM radio receiver is actually a transponder and a receiver wearing the same pair of pants? The receiver being precisely everything from the first IF stage forward, right? The transponder part being in essence everything except the receiver and the power supply, and is basically a multiplexer. I suppose on a thermionic radio (especially a pre-PC one) you could attach an output jack and an input jack and a DP3?T switch given a high school level of electricianry. This would facilitate connecting high performance IF amplifiers for both instruments..except the 455 MHz transmitting amplifier would be probably illegal and run like a 3000 volt plate voltage and 3000 watt plate power or something. Then the other twist of the hat is you make depultiplexers and other nice jack-rich toys just plugging things into other things. Or not?
-- LoriZ, Feb 03 2002


wowser
-- bristolz, May 11 2002


bristolz: wowser with knobs on - my head's spinning after just one read. I'm trying to pluck up courage for another go.
-- drew, May 11 2002


For a time, Bloomberg AM, the Stock reporting company owned by Mayor Bloomberg of NYC, was distributing free, promotional radios such as you suggest. You could only receive their station. I believe I still have mine...
-- indigo heretic, May 14 2002


That sounds like a very Bloomberg thing to do. Is the device also tamper-evident?
-- LoriZ, May 15 2002


This reminds me of the Busy Bee phonograph. The turntable had a lug on it that would lock in to only their records. Competitor's records would not spin correctly. The single station radio should be wind-up so you have to work hard to hear this crapostation. Sony CrapStation. What a name...
-- Amishman35, May 15 2002


[StarChaser]:The Nazis called these radios "Volksempfänger", but to the people, they were known as "Goebbels-Schnauze" (goebbels' mouth, where mouth is actually a bit to polite but I am Austrian and do not know a derogative form of this word)

I think this idea was used by the US when they showered Afghanistan with radios which could only receive their propaganda.
-- Saruman, Jul 07 2002


I have a clock that shows only one hour.
-- pashute, Jul 07 2002


Baked a few years agoin Australia as a single-use one channel radio for sprots events. Too many people were bringing loud radios in & they were audible to the cricketers & supposedly upsetting them. I dont think they do it now. my guess is it was FM, so that the range was limited. Today, you would do it with a pll tuner. The ones i saw were about 1/4'' thick, 1.5 by 2 inches.
-- pfperry, Jul 08 2002


Saruman, a translation might be 'GoebbelsGob"! When radio (or wireless as it was) the first sets licenced in Australia were sealed to pick up only one station. Kind of like a single channel cable TV situation.
-- pfperry, Jul 08 2002


Check Out www.radiostationpromo.com they have them for order there!
-- sharkhead, Jul 10 2002


I like the name Saruman. Almost as much as Gandalf. Or Frodo...
-- Amishman35, Jul 11 2002


B A K E D AND S I G H T E D -- i told a friend about this idea. he showed me the single station radio he got from bloomberg. i held it.
-- gnormal, Aug 11 2002


Saruman, I believe the literal English translation of Schnauze is "snout", as in the snout of a dog. In Spanish "ocico", the French I believe use "bec", literally "beak" but having the derogatory connotation of snout in the andropomorphic context, similar to the Dutch "bek". Of course "Goebbels-Gob" is the perfect translation of the original phrase in German, an elegant idiomatic solution. Good one, pfperry.
-- panamaxer, Aug 12 2002


I've been thinking about this for a while I want an inexpensive single station radio that receives and decodes a scrambled signal. I want to broadcast radio to a discrete group of persons, any ideas?
-- senatorjam, Aug 30 2002


I had one of these a few years ago, for radio 1. Cannot remember what it was given away with. Had a tuning cap with a smaller range than normal for fine tuning.
-- si_pronto, Aug 30 2002


wait, it was for north sound one. was given away at a music festival.
-- si_pronto, Aug 30 2002


[st3f], drift would be kept at a minimum if it was crystal controlled for a specific frequency.

Also, futureproofing isn't really much of a problem, its just a cheap promotion to draw in more listeners. If the station changed frequencies, and they decided they really liked the station, they would most likely use their conventional radio to listen to it.
-- BinaryCookies, Aug 30 2002


.. so that would be a.m. and p.m. times.. or a two-timing clock! I couln't resist...

I built a Radio Shack crystal radio when I was about 10, and for some reason it only picked up one station throughout its entire frequency sweep (luckily it was the popular station of the time).
-- Cedar Park, Jan 08 2003


He's not a troll, he's a golem!
-- snarfyguy, Jan 10 2003


Baked. Cheltenham Festival uses them (and has done for several years). Little in-ear radios that just receive Festival Radio (transmitted locally for the duration of the Fest)
-- ivanhoe, Oct 08 2003


Hey, if anyone has one of the Bloomberg radios hanginf around give me a call at 863-409-9054--I would love to see one of those units up close!
-- sharkhead, Sep 19 2007


As far as manufacturing goes, it's probably cheaper to buy a big batch of one variable part than it is to buy a whole bunch of different values of a similar part and try to keep track of each batch. I'm also pretty sure that FM circuits vary in frequency based on minute differences in manufacturing--it'd be hard to build an FM radio to a certain frequency.

I just saw an earphones-only FM scanning radio (no thumbwheel), which might be entirely solid state, for $5.

Little AM radios don't need batteries, hardly. Old headphone AM radios used to work off the power of the station's signal.
-- baconbrain, Sep 19 2007


Baked or not, except for talk radio, radio stations are in big trouble. At least in America. They need some kind of clever idea to compete with iPods and the internet.

This is a really clever idea.
-- doctorremulac3, Sep 22 2007


Er, now what you need is actually iheadphones that suddenly outpredict your software radio station of youtube music video playlist with a AI suggestion of something better than what the other computer is suggesting

then your iheadphones are the DJ of preference even if you are listening to your prefence of onlineness.
-- beanangel, Oct 30 2015


Baked in North Korea
-- MaxwellBuchanan, Oct 31 2015


It may be possible to use an inductor and capacitor and a single germanium diode to run some ear buds should you add an antenna and a large enough audio transformer if may even run a small 2 inch speaker with a ground connection. With out the need for even a single transistor unless you just want to put in a battery amp. Which a single ne555 or other 8 pin chip can handle for one watt.
-- travbm, Nov 01 2015


µA741 was the secret to my childhood happiness.

Well, that and solvents.
-- MaxwellBuchanan, Nov 02 2015


LM386 note posted for audio amp.
-- travbm, Nov 02 2015


//With me it was the LM3909//

LM3909?? Luxury, mate, sheer luxury.
-- MaxwellBuchanan, Nov 02 2015


Anyway Mouser electronics has a bit of good stuff. Unless you prefer something like Electronic Goldmine.
-- travbm, Nov 03 2015



random, halfbakery