Scratchbuilding an AM receiver--maybe a replica TR-1?

[cat6]

Hey Everybody,

I'm a computer science student doing the dreaded "today you know nothing about electricity. In 3 months you must be able to build a computer from the transistor level up" class. Anyway, the one redeeming thing about this class is that we get a very open-ended choice for our final project. I figured building a transistor receiver would address the tech in the course while being a boilerplate enough project that the hazards of pure experimentation would be minimized.

Since I enjoy technological history, I thought maybe building a device electronically equivalent to the Regency TR-1 (the first handheld transistor radio ever) would be cool. I found an awesome tech manual for the device here: http://www.regencytr1.com/images/TR-1_tech_serv_man.pdf and couldn't believe my luck when a full circuit diagram was in the back. (Anybody take a look at the wordless 3-page 'manual' that came with their ipods lately? Things have changed a lot.)

I haven't asked extensively yet, but I'm pretty sure that building from kits will be disallowed. That said, I already cleared the idea of a transistor radio with my prof as a potential project, soo....time to investigate. I really found this video helpful:

... since the builder did a good deal of research and improvement on the initial design after encountering problems and documented his work with links.

At the moment I'm looking for the best resources and advice I can muster before really planning this project out. I'm especially interested in knowing if anybody's done a 'replica' TR-1 and/or what challenges are involved in such a project. Regardless, any and all newbie radio-builder advice is hereby solicited.

Cheers,

Brian

 

[BobK]

Sourcing the components for that might be a bit difficult...

Bob

 

[cat6]

Sourcing the components for that might be a bit difficult...

Bob

Why's that? What's changed so much that I can't do a prototype board build of this sort?

 

[BobK]

Electronic components come as go over time. It is highly doubtful that you will be able to find any of these:

1. the transistors (these are probably germanium)
2. the tuning capacitors
3. the IF transformers

Radios today are built completely differently, so there is no longer a need for many of the components used back then.

Bob

 

[cat6]

Electronic components come as go over time. It is highly doubtful that you will be able to find any of these:

1. the transistors (these are probably germanium)
2. the tuning capacitors
3. the IF transformers

Radios today are built completely differently, so there is no longer a need for many of the components used back then.

Bob

Awww..that sucks. Thanks for the info, though. I won't even ask if it's just possible to supplant period electronics for modern parts.

 

[davenn]

Awww..that sucks. Thanks for the info, though. I won't even ask if it's just possible to supplant period electronics for modern parts.

Hi Brian
welcome to the forums

The really difficult part are the coils, the oscillator and IF coils. They wouldnt be available
there are modern equivelents but they are all designed for a radio operating on 9V or much less ... a couple of 1.5V AA cells ... NOT a 22.5V battery as this one is.

Transistors in modern radios are all silicon rather than germanium.

You do some searching, and I will do the same for you, and see if we can find something a bit more modern, with components that should be relatively readily available


Dave

 

[davenn]

Brian,

been looking through lots of circuits, and even in more modern radios, the coils are still going to be the main hassle.
The only way you would build a radio receiver is to buy a kitset that has all the required components.
You then have the challenge of learning to solder to a good standard and construct the kit, tune it up and make it work

I was rereading you opening statement ...

I'm a computer science student doing the dreaded "today you know nothing about electricity. In 3 months you must be able to build a computer from the transistor level up" class.

thats a major project, and no one would even consider building a computer with discrete transistors, the physical size of the project alone would cover several bench tops. Hence why microprocessor chips are used that contain the 10's of 1000's to millions of transistors in a tiny package.
Can you clarify if they really expect you to build a computer, and if so using what sort of technology.

If you really do, then maybe you initial project should be digital based as a lead in to the computer project, rather than a totally unrelated technology such as a radio receiver

cheers
Dave

 

[CDRIVE]

Rf & IF transformers and coils are still available from many sources. It's true that technology has changed but radios still use them.

http://www.ebay.com/itm/J-Tran-455-...134?pt=LH_DefaultDomain_0&hash=item4607ce5006

At this link you will see a number of small IF cans made by Toko. These cans were the most popular cans found in just about any receiver, including marine VHF transceivers, for many decades. I don't know if these are new or new old stock but I see no reason, even with today's technology that IF cans would no longer be manufactured. I left the marine electronics business about 20 years ago and they were common then. My bet is they still are.

http://www.surplussales.com/inductors/Ind-SmAdjRF/Ind-SmAdjRF-1.html

There are also quite a few websites devoted to all kinds of radio related projects, including Crystal, Regen, Superhet.

Google is your friend.

Chris

 

[CDRIVE]

Here's a few more.

http://www.elexp.com/cmp_6irf.htm

http://www.mouser.com/ProductDetail/Xicon/42IF301-RC/?qs=sGAEpiMZZMsX0CFs5rpLHmvHZHglO8mC



Here's some application info..

http://hem.passagen.se/communication/ifcan.html

Home brew for Vacuum Tubes/Valves but I see no reason that cans have to be made this large for silicon transistors, or even tubes for that matter.

http://www.lindsaybks.com/bks7/rexp5/index.html

Chris

Edit: I found this from a link in this discussion...

http://www.antiqueradios.com/forums/viewtopic.php?t=124477

 

[cat6]

Thanks for all the input, guys. I'm really impressed with the feedback.

As far as course expectations are concerned, that's actually what were were more or less told in the first lecture. I know it's a silly impractical thing build a computer with such simple equipment, and the prof added that it wouldn't be a very good computer, but....it's one of those courses. I wouldn't be surprised if the pedagogical sentiment was "They're not going to learn anything more about electrical engineering after this credit, so just stuff everything there is to know in there!". Even our prof was depressed and apologetic about how hard this course is going to be.

I'm somewhat enamored about the idea of building from a kit, but I'll have to see how acceptable that will be and how much "design" I'll be required to input myself. I can solder just fine and have done lots of kits in the past, have my own equipment, etc., so that's not a problem.

Can anybody recommend a good transistor radio kit to build from? I'd like to not make any purchasing mistakes given the loss of time and money that buying a bad one could produce.

 

[CDRIVE]

A crystal set is dead simple to build. Add an OpAmp for an audio amplifier to drive 1000 ohm earphones or add an AF power amp chip and you have a viable AM radio.

Chris