Tech: I want to build an AM tube radio

Subject: Tech: I want to build an AM tube radio
From: DonMeixner
Date: 14 Dec 06 - 06:27 PM

As a New Age Luddite I have thought it would be fun to build a radio. I had thought that in the age of electrons and the InterWeb this would be an easy thing. Not so. But I'm convinced it is a language thing.

I know Tuner = Radio (Sort of) for the most part but thats about as far as I go.

Any ideas?

Don

Subject: RE: Tech: I want to build an AM tube radio
From: Bill D
Date: 14 Dec 06 - 06:44 PM

find someone (online) who supplies vacuum tubes. The usual hobby is repairing old AM radios...I'm not sure where you'd get tuners.

Subject: RE: Tech: I want to build an AM tube radio
From: jeffp
Date: 14 Dec 06 - 07:02 PM

A tuner is a part of a radio. The radio is basically a power supply, a tuner section, an amplifier section, and a speaker. The tuning is accomplished with a variable capacitor (condensor). This consists of a series of metal plates separated by either air or mylar with every other plate fixed and the remainder attached to a shaft which can be rotated to increase or decrease the overlap between them.

That's about all I know about the subject. Good luck finding parts. The chassis will present a real problem. You will probably have to fabricate something.

Sounds like a fun project. Keep us posted on your progress.

Jeff

Subject: RE: Tech: I want to build an AM tube radio
From: Stewart
Date: 14 Dec 06 - 07:06 PM

As a kid about 50+ years ago I built my own short-wave radio receiver from instructions in the Amateur Radio Handbook, using the schematics and a list of parts, and a trip to the local electronics parts store (long before Radio Shack). I'm not sure you can do that anymore (that is, buy all the individual parts). You might try Edmund Scientific for a kit.

Good Luck

Cheers, S. in Seattle

Subject: RE: Tech: I want to build an AM tube radio
From: Q (Frank Staplin)
Date: 14 Dec 06 - 07:40 PM

You should be able to find circuit diagrams in old radio magazines or books.
I have a couple, one AM, the other a communications receiver for the short wave bands, but I bought them, one at a house sale, the other at a war surplus long ago. Try advs in Pop Sci Pop Mech type magazines for tubes.

Subject: RE: Tech: I want to build an AM tube radio
From: Sandy Mc Lean
Date: 14 Dec 06 - 07:46 PM

When I was a young lad studying electronics one of our exams required that we draw a schematic of a workable 5 tube AM receiver, from memory. You had to know the location and value of each critical part.
I made my living for about 30 years maintaining telephone company microwave installations. I changed one hell of a lot of tubes in my day!
Anyways have fun Don but don't go with AM because AM transmitters are becomming dodo birds just like myself. :-}

Subject: RE: Tech: I want to build an AM tube radio
From: Mooh
Date: 14 Dec 06 - 09:23 PM

I can't help you at all, in spite of having made several in high school where I was a wizz-bang radio guy. Can't believe I've forgotten EVERYTHING!

Gotta love tubes though, like the Sovteks in my old Fender Champ 12. What tone!

Peace, Mooh.

Subject: RE: Tech: I want to build an AM tube radio
From: Leadfingers
Date: 14 Dec 06 - 10:57 PM

AM radio is most definately on the way out - And valves (Tubes in YOUR funny version of the language) are NOT as easy to find these days ! Best of luck though , Don . I got out of electronics thirty years ago !!

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,.gargoyle
Date: 14 Dec 06 - 11:48 PM

Try a "crystal set" for AM. Old Cub-Scout books will tell how. A thousand and one websites will explain (Do NOT buy web kits) for less than 10 US you can get the parts at radio shack (crystal, wire, resister, paper roll, ear-phone, connectors) ...but scrounging the GoodWill stores and Dollar stores will yield an ear-phone for a buck.

The web explanation for a WWII set made with a razor blade....gave me enough information to understand "jamming" of of cell-phones so they render Zero-Bars within a 30X30 room. This information you must learn on your own - I will not share - but it is VERY easy....and VERY cheap (far from the 250 pounds requested by French/Swiss companies) Be careful, correctly done OK, however, US law will identify the French verions as illegal.

Sincerely,
Gargoyle

A "Trans Oceananic" Tube receiver (circa 1938) has brought my family hours of enjoyment.

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,.gargoyle
Date: 14 Dec 06 - 11:52 PM

To clarify - receivers A-OK (you can even tune to your neighbor's cordless phone) and listen without "wire-tap" supeina

Jammers - viewed by FCC as illegal since the 1920's in the USA.

Sincerely,
Gargoyle

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,MGJohn
Date: 15 Dec 06 - 04:11 AM

The Radio Society of Great Britain has a website (WWW.RSGB.ORG) which might prove useful. The society also has a Journal (RadCom) which is published monthly. Many adverts. appear in it both for equipment for sale and also wanted items including details of vintage equipment.
Another source might be for you to visit your nearest Maplins store or the website.
If you happen to know of a Radio Ham living in your area he or she will probably know of a local Radio Amateurs club whose members might be able to help.
Good Luck

Subject: RE: Tech: I want to build an AM tube radio
From: John J
Date: 15 Dec 06 - 04:53 AM

I gather you are in USA, if so try the ARRL which is the US version of the RSGB.

A simple valve / tube AM tuner isn't difficult to make if you're handy with a soldering iron, the hardest bit will be sourcing a suitable HT transformer with LT windings for the heaters.

A suitable circuit is here: http://www.localhistory.scit.wlv.ac.uk/Museum/Engineering/Electronics/history/valvedetails.htm

Good luck,

John
G4WQD

Subject: RE: Tech: I want to build an AM tube radio
From: skipy
Date: 15 Dec 06 - 04:58 AM

Making an AM radio receiver
To make an AM radio, we need to have five basic parts:

1) An antenna, to receive the electromagnetic waves and convert them back to electrical signals

2) A tuner, to select out the particular carrier frequency that we want, corresponding to a particular radio station that we are interested in listening to

3) A detector (diode) , to get rid of the high-frequency signal but keep the low-frequency part.

4) An amplifier, to make the signal bigger

5) A speaker, to produce the sound that we can hear

Here are descriptions of the individual parts:

1) The antenna: To make an antenna, all we need is a long piece of wire. Ideally, this should be very long (like 50 feet), but something shorter will work pretty well. We will connect this antenna to a coil of wire that is wound around a piece of plastic tubing. The photograph below shows one that is almost exactly what yours will look like. This coil is about 3 inches high and 1.5 inches in diameter.

                     

2) The tuner: The job of the tuner is to select which radio station we want to listen to. Each radio station broadcasts at a different carrier frequency. Our tuner uses a coil of wire (called an inductor) and a capacitor. The combination of inductor and capacitor makes something called a "resonator"-- it is a circuit that throws away all the unwanted signals, and keeps only the one that we want.   The resonator resonates (obviously...) at a particular frequency that is determined by the size of the inductor (its "inductance", measured in "henries") and the size of the capacitor (its "capacitance", measured in "farads") .    The little figure below shows that electrical symbol for the inductor and capacitor that make up the tuner.

   

In our radios, we will use a capacitor that has a fixed size, and we will "tune" the radio to different stations by changing the size (the "inductance") of the inductor. The photo below shows the inductor (coil), which is about 5 inches long. It looks a lot like the antenna coil, except that it is longer.



The tuner coil has about 200 turns of wire with a thin red insulation on it. The insulation is scraped away on the top. To tune the radio, we will use a brass strip with a contact on the end that will make electrical contact at different points along the coil, where the insulation was scraped away. By pivoting the brass strip about a screw, the sliding contact will move across the coil, changing its inductance. When the contact is near one end the inductance will be very small, and the circuit will tune in radio stations whose carrier frequency is very high. When the contact is near the other end, the inductance will be large and the circuit will tune in radio stations whose carrier frequency is very low.

The photograph below shows a blowup of the sliding contact.   You can see the individual turns of wire, and you cansee that the red insulation is scraped away where the brass nut touches it. The brass nut is connected to a wire to carry away the electrical signal, and the brass strip acts like a spring to make sure the brass nut is pressed against the coil.





The detector: The detector is something called a "germanium diode". The germanium diode lets electricity flow in one direction but not in the opposite direction. The germanium diode looks like a little glass cylinder with metal wires coming out each end.



The electrical symbol looks like an arrow with a line at the end. The electricity through a diode flows in only one direction – the direction the arrow points in. The diode itself has a little black line or a dark stripe at one end to tell you which direction the electricity flows in. The photo above shows the electrical signal for the diode at the left, and a photograph of a diode exactly like the one you will be using on the right. The diode is quite small, not much bigger than the size of a grain of rice.

4) The amplifier: The signals that we pick up with the antenna and tuner are very small -- maybe only a few thousandths of a volt. (A regular flashlight battery is 1 ½ volts). So, the amplifier makes the signal bigger. In our radios, we will two little things called "integrated circuits", or "chips", to make the signal bigger.   There are a lot of different kids of integrated circuits. The kind that we will use are called "op-amps", or "operational amplifiers". Each op-amp looks like little spiders with 8 legs ! We will use 2 of them in each radio.

They will be mounted on a circuit board that will look sort of like the one below.

This board is about 2.5" long and 1.5" high. The electrical symbol for an op-amp is a triangle with two wires on one side (these are the inputs) and a line coming from the point of the triangle, which is the amplified output signal.




5) The speaker. The speaker is the thing that actually makes sound. It takes the electrical signal and uses a tiny electromagnet to move a piece of plastic or paper back and forth, making sound that we can hear. The speakers that you will use a just small versions of the speakers that you might have in a radio, stereo, or television in your home. The figure at below left shows the electrical symbol for a speaker, while the photograph a below left shows the real thing.

   

When we connect all these together in the right way, we get a complete radio !



To summarize the entire process: The antenna picks up the signal and brings it to the antenna coil. The antenna coil is brought close to the tuner, and the electrical signal in the antenna coil transfers to the tuner coil. The inductor (coil) and capacitor that make up the tuner select out the particular carrier frequency of the radio station we want to listen to. The detector (diode) gets rid of the very high frequency, but keeps the low-frequency signal that corresponds to the "sound" that we want to hear. The amplifier makes the signal bigger, and the speaker converts the electrical signal back into sound!


Skipy

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,Ted
Date: 15 Dec 06 - 05:06 AM

The British Vintage Wireless Sociey (http://www.bvws.org.uk/) looks like a good starting point; I'd guess there is a US equivalent - not sure where you are, Don. Other than that, Googling 'vintage wireless' or 'vintage radio' produces quite a lot of hits for people who like these devices. As with most things that have been out of production for a few years, it's probably worth joining a club, then you've got lots of help & experience on tap.
Maybe worth looking through some back issues of the hobby magazines of 40-odd years ago (always liked the "Radio Constructor" as a kid), as they regularly published details as Stewart suggests above. The only obvoius problem I can see is getting some of the more specialist RF valves new; there's a limited range of AF valves still available as some people prefer them for HiFi applications.

Good luck, anyway

Ted

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,Mark Oney
Date: 15 Dec 06 - 05:08 AM

Crystal Sets

Simple tube radios

Have fun!

Subject: RE: Tech: I want to build an AM tube radio
From: JohnInKansas
Date: 15 Dec 06 - 05:58 AM

The last more or less "official" report I heard was that there are NO TUBE MANUFACTURERES IN THE "WESTERN" WORLD. The last operating tube maker was somewhere in the Soviet region, producing a very limited selection of tubes.

That report may have slightly stretched the truth of the situation, but the simple truth is that it's almost impossible to buy a new tube, so to make a "tube type" radio you'll need to get friendly with those who salvage and sell them, or someone who collects them and might have come across some "spares."

Since nobody makes tubes any more, nobody makes tube sockets to plug them into. See above junk dealer.

Since the AM Broadcast Band is at a very low frequency (for radio) the variable capacitors need to be much larger than the things people are still using, so finding one in the right size range again will almost certainly take you deep into someone's junk bin. There is some AM broadcasting still at "Short Wave" frequencies, but at these higher frequencies having exactly the right components and assembly becomes much more critical.

Homebuilts that people made in the olden times could get by with an RF amplifier stage and a rectifier - basically two or sometimes 3 tubes; but with the amount of "noise" around now an AM radio is going to be virtually worthless unless it's a "superheterodyne" circuit. You're unlikely, with any simpler circuit to be able to "lock" onto any broadcast frequency other than strong local stations with sharp enough drop off on either side of the carrier frequency to avoid picking up more noise than signal.

IF you want to "go classic style" you'll need batteries of two or three different voltages. Since they don't make 'em any more in the voltages required, you'll need to hit Radio Shack or similar place for "battery holders" that you can use to wire piles of little ones into the appropriate big 'uns. (Common tubes used 37.5 V plate voltages, so you'll need 25 1.5V flashlight batteries in series. There are 15 V tubes, but they were less widely used, and only late in the "vacuum tube era" so they're likely to be hard(er) to find.)

An old ham radio handbook (called the ARRL Handbook in the US, for the Amateur Radio Relay League) might give you enough info to whip up a workable circuit, if you can find one that dates to the 1960s or before - preferably before.

The instructions that Skipy posted for a crystal set are fairly complete, although if a link had been posted you could see the pictures. (or maybe he scanned it from his old boy scout "merit badge book").

In crudest form, one doesn't even need a capacitor. One layer of B&S #28 wire wrapped around the cardboard tube from the center of a roll of toilet paper (US style at least) with the turns cemented in place with "Duco" cement painted on with a brush after winding very carefully and evenly will have enough "self capacitance" to tune, with the right number of turns, to the US AM Broadcast band. A wire wrapped around a piece of graphite pencil lead and twiddled against the sharp edge of an old carbon steel double-edge razor blade, with the blade connected to one lead of a high impedance earphone, will give (if you twiddle right) enough rectification to extract hearable audio from a reasonably strong station. I used one I built like that ca. 1948, with only a coathanger for an antenna, for a couple of years (in the bedroom after lights out) before it got trashed. Of course I probably just got lucky with the windings etc., and trying again might not work at all.

IFF you want to build anything with tubes in it, you'll want to search the junk sales for a copy of the "RCA Vacuum Tube Handbook." They quit publishing it in the 1960s¹, I think, but by then it had all the tube types that ever would be built, with the few "properties" you'll need to know to substitute what you can find for what think you want.

¹ The "Sylvania Transistor Handbook" came out only a little before the Tube book ceased being published. It was similarly "thorough," but was published for less than a decade because integrated circuits drove the "discrete transistors" pretty quickly out of widespread production. Now you buy a chip, connect it to your earphone, slap on a battery, and you're up and running. (only slightly kidding.)

John

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,Cathode Ray
Date: 15 Dec 06 - 06:03 AM

there are NO TUBE MANUFACTURERES IN THE "WESTERN" WORLD
Here's one in Huntsville AL.

Subject: RE: Tech: I want to build an AM tube radio
From: John J
Date: 15 Dec 06 - 06:33 AM

If using a TRF design and for general AM reception at up to a couple of mhz (ie medium wave) you can use audio valves for RF applications, the inter-electrode capacitances won't be too much of a problem at these frequencies. I have used 6V6 and EL34 for transmitting applications at 2mhz with very good results.

If you are going to use a superhet circuit, you really need to use a decent valve designed for the mixer / osc (eg ECH80), although you may be able to get away with something like an ECL80 if you know what you're doing. I wouldn't worry about the other sections. For the rectifier don't bother with valves, a couple of 1N4007 silicon diodes will do the job nicely. For the detector just use a standard signal diode....provided there's no HT across it.

John

Subject: RE: Tech: I want to build an AM tube radio
From: JohnInKansas
Date: 15 Dec 06 - 07:15 AM

Cathode Ray -

Of course I could have added the qualifying "except for a few makers of commercial/broadcast-power tubes."

I find only about 5 "products" listed at Western, and they all appear to be for that "last remaining hole in the wall" of BROADCAST applications, - i.e. Kilowatt power. Hardly suitable for use in an AM Receiver, and of no use to someone who wants to build one.

Another exception that I "glossed over" is the Cathode Ray tubes used in TVs and lots of lab equipment applications. Technically, yes, they're "vacuum tubes," but so specialized to the particular application that they have a separate category that customarily is omitted from "talk about tubes" among people interested in signal level receiving, amplifying, modulating, and detecting EM emanations applicable to public communications.

"Tubes" of the kind Western lists in their product line were much more slowly replaced by other kinds of devices, mainly because of the inability of solid state replacements to handle the power levels. In a few places, TWTs (it is pronounced "twats") have poked into the market, and MASERS and other device types are getting in, but most of the high-powered stuff that could be used in place of the kinds of "tubes" Western is making are better suited to higher frequencies than the older public broadcast bands - so Western still has a market. Many of the newer devices use high vacuum, but nobody much refers to them as vacuum tubes.

Delco Electronics, for many years, claimed to use more than 90% of all "electronics grade" silicon processed worldwide, just making a sparse line of simple diodes. Of course they were making "simple diodes" capable of rectifying multi-hundred ampere currents at near kVolt breakdowns - almost exclusively for Turboelectric/Turbodiesel railroad tractors (engines) - mostly for General Electric. (And they weren't selling large numbers of them.) I think Delco is still in the business, but haven't checked lately. I'm not sure about GE (in the train business).

John

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,HughM
Date: 15 Dec 06 - 08:13 AM

AM on its way out? How else could I get Radio Scotland or Radio Eireann here in northern England (apart from on the Internet)? My wife asked me if I wanted a digital (DAB) radio, and I said no! If I want to hear Ceilidh House, or Take the Floor, or Travelling Folk I need AM.

If you use 1N4000 series rectifiers or something similar instead of a double diode vacuum tube for your power rectifier, you will get more voltage than the transformer maker quotes, so this should be borne in mind if you put silicon rectifiers into a circuit designed for tubes. The smoothing capacitor will be charged to (root 2) x the r.m.s. voltage from the transformer. Normally much of the excess voltage would be dropped across the rectifier tube.

Subject: RE: Tech: I want to build an AM tube radio
From: DonMeixner
Date: 15 Dec 06 - 09:32 AM

Thank you everyone. I know this is the place to ask just about anything!

Don

Subject: RE: Tech: I want to build an AM tube radio
From: JohnInKansas
Date: 15 Dec 06 - 09:39 AM

HughM -

In the US, when one says "AM Radio" most people will think of the US AM Broadcast band where the licensed (mostly) commercial stations broadcast. There still are a lot of AM stations around, but their listener base is declining (probably) in many areas because of interference between stations and from "industrial sources."

Even at the top end (~1.6 MHz) signals can follow earth curvature via "ground wave" far enough to fill in the gaps to the next skip, so a station can interfere with a lot of other stations outside their nominal broadcast area, and there is a lot of station/station interference anywhere that the signal strength isn't extremely good. (Broadcast) AM in the US may not actually be dying, but it's sort of sickly in most places outside a few big metro areas.

Outside the US, there still are lots of AM signals to be heard. My impression is that mostly they use the "shortwave," or at least higher, frequencies, where ground wave isn't much of a factor (although skip can be). In US coastal areas, there's a lot of "interesting" chatter on marine bands, and at higher frequencies one can pick up quite a few "foreign" broadcasts with reasonable clarity.

I suspect Radio Scotland et. al. are at somewhat higher frequencies than the US Broadcast AM band, where among other things there's a lot less "industrial" interference. The differences in regions and usages should have been recognized, and/or discussion related more clearly to the particular kind(s) of AM meant.

Apologies for "talking provincially."

John

Subject: RE: Tech: I want to build an AM tube radio
From: Stilly River Sage
Date: 15 Dec 06 - 10:26 AM

I have the Hallicrafter that was in the family kitchen when I was a child. I had it repaired about 20 years ago but the tubes used or fixed then have lost it again. Last time I tried it could only pick up one very nearby station.

Maybe once you learn to build one on your own you can tell me how to repair mine!

SRS

Subject: RE: Tech: I want to build an AM tube radio
From: John J
Date: 15 Dec 06 - 11:48 AM

Radio Scotland is on 810khz, and as HughM says, it's quite audible here in the North of England (Manchester), as is RTE on 567khz. Reception of both these is via skywave.

With regard to interference,in USA stations are separated at 10khz intervals, in Europe the spacing is 9khz. The main problem is probably going to be cross-modulation but that's only likely to be apparent with solid-state receivers, valve stuff tends not to be bothered with this.

John

Subject: RE: Tech: I want to build an AM tube radio
From: WFDU - Ron Olesko
Date: 15 Dec 06 - 11:56 AM

Don, there is a great company that supplies parts called Antique Radio Supply. Their web address is
www.tubesandmore.com

While they mainly supply parts for people who fix old time radios, I am sure they would have just about everything you need or could point you in the right direction.

Subject: RE: Tech: I want to build an AM tube radio
From: DonMeixner
Date: 15 Dec 06 - 12:00 PM

Thanks Ron.

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,HughM
Date: 15 Dec 06 - 06:34 PM

I can get Radio Scotland during the day, though the signal is quite weak. I suppose that would be ground wave. The same goes for RTE (Radio Telefis Eireann). At night there is sometimes interference from foreign stations on the same channels as JohnInKansas describes.
   If the radio is a portable one with a ferrite rod antenna, sometimes it's possible to boost the wanted signal and cancel the unwanted one by placing the radio next to a vertical conductor such as a water pipe. Of course, the signals have to come from opposite directions for this to work.

What I should have pointed out before is that when using silicon rectifiers in a circuit designed for tubes, it is necessary to put some series resistance between the rectifiers and the smoothing capacitor. Otherwise when the supply is connected there will be a huge surge of current which could destroy the rectifiers. The 1N4000 series can take a 50A surge for 1 cycle of 50Hz. if the power transformer gives 250v r.m.s. output, the peak voltage will be around 350. Therefore a resistance of 350/50 = 7 ohms is needed. To be on the safe side I'd double it, which would give 14 ohms, and use the nearest preferred value, 15 ohms.
   The problem doesn't arise with valve (tube) rectifiers because the current builds up slowly as the tube warms up. Consequently a valve radio (or amplifier) should not be turned off and immediately turned back on again as there will be a current surge which will shorten the life of the rectifier.

Subject: RE: Tech: I want to build an AM tube radio
From: Peace
Date: 15 Dec 06 - 07:13 PM

This site's jus' watcha need, Don.

Subject: RE: Tech: I want to build an AM tube radio
From: Peace
Date: 15 Dec 06 - 07:14 PM

That'll give you the basics and then you can build one with tubes that Marconi woulda bin proud of.

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,DonMeixner
Date: 15 Dec 06 - 07:21 PM

Thanks Bruce, that looks a gas. I hope I never grow up.

Subject: RE: Tech: I want to build an AM tube radio
From: Peace
Date: 15 Dec 06 - 07:30 PM

I think you will have a blast, Don. My grandfatehr was forever foolin' with the radio. He did amazing things with it by getting it to work often. (The reason it didn't work was because he was always doing wonders with it, but we had fun.) All the best with your project.

Subject: RE: Tech: I want to build an AM tube radio
From: bobad
Date: 15 Dec 06 - 07:41 PM

That brings back lots of memories to when I received a crystal radio set one Christmas. It opened up a whole world in my bedroom at night. I lived near a canal and bridge and locks and would receive communications
from ships to shore and vice versa over my radio set - very romantic stuff for a 9 year old kid.

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST
Date: 15 Dec 06 - 08:52 PM

The Pirate Radio Handbook - admittedly oriented towards building transmitters - observed that it wasn't much trouble to modify old (not that outdated, actually) military tube transceivers such as the KWM-2A to broadcast on the AM frequency.

If that's the case then it shouldn't be too much trouble to modify one to receive on the same AM band.

Knowing a ham radio enthusiast or going to a hamfest would be extremely helpful.

Subject: RE: Tech: I want to build an AM tube radio
From: The Fooles Troupe
Date: 15 Dec 06 - 09:59 PM

http://www.siliconchip.com.au/

Is an Aussie print publication.

They recently had some articles on building a valve AM radio using the low plate voltage (12-35V) bottles which seem to be readily available - at least in Australia - they also have links to kit suppliers - they also set about doing some articles on valve radio power supplies, how to restore old radios, etc. I do not have my physical copies to hand, so I can't quote issue details at the moment.

You must remember that 30-40+ year old valve sets should NOT just be switched on - the capacitors may be leaky, resistors gone out of spec, - all sorts of things will cause it to 'blow up' and damage an otherwise perfectly good set (including damaging perfectly OK valves!) - that just needs a bit of 'TLC' to get it working - if you don't know what to do, you should do some research, or get an experience friend to assist... it's lke trying to drive an old car that has no oil in it... KaBOOM!

Googling http://www.google.com.au/search?hl=en&q=silicon+chip&btnG=Google+Search&meta=cr%3DcountryAU
will get you to an interesting page that will show you all sorts of relevant links too.

You can search the site easily - round about Dec 2001 they had some articles about what tools and methods you need to check out old valve radios, for etc.

The Historical Radio Society of Australia (HRSA) is the national association of vintage radio enthusiasts in Australia, with approximately 1100 members. It is by far the largest group representing vintage radio enthusiasts in Australia.

You might try looking for similar local groups - or even contact the HRSA (on the web) and ask them to help you find local groups. I'm sure they will be only too happy to foster interest in 'naive' newcomers!

Oh, there is also a Europe/English mag (published in several languages) called Elektor Electronics which is one fo the other few current relevant publications.

I would recommend you first start playing around with 'crystal sets' - they are great fun and cheap - that link from Peace above is a great place to start.

Subject: RE: Tech: I want to build an AM tube radio
From: GUEST,.gargoyle
Date: 15 Dec 06 - 10:31 PM

For - non-violation jamming of cell-phones (two, one, and zero bar signal responce to cell tower units) the white "magnetic paper" for printers and intended for white boards.... cut into lengths and placed on the metal strips of suspended in-door-room ceilings does a superior job and they blend into the decor. A scattered few on a whiteboard's edges also help. Incoming are not always blocked but the receiver must leave the room to respond.

Sincerely,
Gargoyle

Radio, television and computer (hard wired) are not affected.

Subject: RE: Tech: I want to build an AM tube radio
From: Peace
Date: 15 Dec 06 - 10:37 PM

Some flypaper company is gonna capitalize on that idea.

Subject: RE: Tech: I want to build an AM tube radio
From: Stilly River Sage
Date: 16 Dec 06 - 05:15 PM

There are devices used for blocking phones, but they're not legal here. I've heard about South American cities where they are popular, such as in movie theaters.

SRS