really old magazine article on diy modem

[Brad]

Hi all,
I'm trying to find an article I read about 30 years ago or so. It was
a diy project for a low speed modem. It was in Byte, Kilobaud or
Popular Electronics. Do any of you happen to know where this article
might have been?

If I recall, the modem was like 300 baud or maybe only 110. I'm doing
a little project that could use a dirt cheap modem, and signalling
speed is not an issue. Slow is fine, cheap is better

Or, if anyone has a more up to date approach I'd be glad to look at
that too. I've come across a few half-way described implementations of
modems using PICs, but I don't have the time to figure out the missing
details.

Regards, Brad

 

[Homer J Simpson]

Hi all,
I'm trying to find an article I read about 30 years ago or so. It was
a diy project for a low speed modem. It was in Byte, Kilobaud or
Popular Electronics. Do any of you happen to know where this article
might have been?

IIRC it was Popular Electronics and it was an acoustic coupler.

Look on eBay for an old Radio Shack modem.

 

[Tom Bruhns]

Or, if anyone has a more up to date approach I'd be glad to look at
that too. I've come across a few half-way described implementations of
modems using PICs, but I don't have the time to figure out the missing
details.

Google "modem IC" and you'll get quite a few hits. Search for "Bell
103 modem IC" and you'll get things more targeting what you are asking
for. There are other ways to phrase the search that will become
obvious from the hits you get on those. I suppose some of the slow
modem ICs are still available. MM74HC943 seems to not be made by
National now, but perhaps someone has stock.

Cheers,
Tom

 

[Ross Herbert]

Hi all,
I'm trying to find an article I read about 30 years ago or so. It was
a diy project for a low speed modem. It was in Byte, Kilobaud or
Popular Electronics. Do any of you happen to know where this article
might have been?

If I recall, the modem was like 300 baud or maybe only 110. I'm doing
a little project that could use a dirt cheap modem, and signalling
speed is not an issue. Slow is fine, cheap is better

Or, if anyone has a more up to date approach I'd be glad to look at
that too. I've come across a few half-way described implementations of
modems using PICs, but I don't have the time to figure out the missing
details.

Regards, Brad

If cheap is what you want there will be literally thousands of unused
dial-up modems lying around which can be had for a few dollars if not
for free. These are tried and proven so you won't have to spend time
developing and proving a design either... why re-invent the wheel?

 

[Eeyore]

If cheap is what you want there will be literally thousands of unused
dial-up modems lying around which can be had for a few dollars if not
for free. These are tried and proven so you won't have to spend time
developing and proving a design either... why re-invent the wheel?

Heck, even I've given some away and I'm the ultimate hoarder. I'm sure I must
have a rather nice 33.6k one somewhere still around.

Graham

 

[Jeff Findley]

If cheap is what you want there will be literally thousands of unused
dial-up modems lying around which can be had for a few dollars if not
for free. These are tried and proven so you won't have to spend time
developing and proving a design either... why re-invent the wheel?

I've found old RS-232 modems (often 9600 baud and higher) at places like
Goodwill, garage sales, and etc. for $5 or so. You might even try eBay.
You can get just about anything on eBay.

Jeff

 

[GregS]

I've found old RS-232 modems (often 9600 baud and higher) at places like
Goodwill, garage sales, and etc. for $5 or so. You might even try eBay.
You can get just about anything on eBay.

36 years ago I was troubleshooting modems made from 7400 series
chips. I didn't really know how the whole thing worked but I could fix
bad logic. That was at DEC.

greg

 

[Homer J Simpson]

Heck, even I've given some away and I'm the ultimate hoarder. I'm sure I
must
have a rather nice 33.6k one somewhere still around.

IIRC I have 5 of the RadShack 300 baud models NIB.

 

[Brad]

IIRC I have 5 of the RadShack 300 baud models NIB.

I appreciate the advice and offers of cheap modems. I am not
interested in obtaining a modem. I am interested in information
presented in that specific article.

So, if anyone knows where the article was, I'm still looking......

 

[Homer J Simpson]

I appreciate the advice and offers of cheap modems. I am not
interested in obtaining a modem. I am interested in information
presented in that specific article.

So, if anyone knows where the article was, I'm still looking......

Early '80's IIRC.

 

[Roger Hamlett]

I appreciate the advice and offers of cheap modems. I am not
interested in obtaining a modem. I am interested in information
presented in that specific article.

So, if anyone knows where the article was, I'm still looking......

I have a memory of an article like this, when the AM7910 was fairly new.
Possibly in EDN?.

Best Wishes

 

[Michael Black]

I've found old RS-232 modems (often 9600 baud and higher) at places like
Goodwill, garage sales, and etc. for $5 or so. You might even try eBay.
You can get just about anything on eBay.

You're paying too much. I paid five dollars for my used 2400 baud external
modem back in 1995.

I paid ten dollars for an external 33.6K modem some years back. And I
got my 56K external modem for five dollars last year.

MIchael

 

[Michael Black]

I appreciate the advice and offers of cheap modems. I am not
interested in obtaining a modem. I am interested in information
presented in that specific article.

Your vague reference means nothing. DO you really think there was
only one modem described in all those magazines? Do you really think
it matters that much whether or not you get the very same article if
all you need is a modem? Do you really think that you can build a 30
year old design without having to dig to get the ICs that it used?

IN the very first issues of Byte magazine, in the fall of 1975, there
was a series of excerpts from Don Lancaster's "TV Typewriter Cookbook".
I can't recall whether those covered building modems, but the book does,
even if they aren't construction projects.

There is nothing special about a modem, and so some of those early schemes
for saving programs to cassette tape were basically modems. There was
an article, I think it was in "73", that used the Digital Group cassette
interface as a teletype modulator/demodulator for use on radio, and it
was a modem minus the interface circuitry.

Lee Felsenstein described his "Pennywhistle" modem in early 1976 in Popular
Electronics.

Steve Ciarcia eventually described a modem, using PLLs, in his "Circuit
Cellar" column in Byte. ANd then some years later, revisited the topic
once or twice as ICs became available that provided the whole modem
function in one package.

It goes on and on.

Michael

 

[Michael A. Terrell]

Hi all,
I'm trying to find an article I read about 30 years ago or so. It was
a diy project for a low speed modem. It was in Byte, Kilobaud or
Popular Electronics. Do any of you happen to know where this article
might have been?

If I recall, the modem was like 300 baud or maybe only 110. I'm doing
a little project that could use a dirt cheap modem, and signalling
speed is not an issue. Slow is fine, cheap is better

Or, if anyone has a more up to date approach I'd be glad to look at
that too. I've come across a few half-way described implementations of
modems using PICs, but I don't have the time to figure out the missing
details.

Regards, Brad

Find a large library with old magazines on microfilm, and start
looking. There were dozens of those articles, and most used now
obsolete ICs. There is a company in Ann Arbor, Michigan that made those
microfilms. I think it was connected to the university. They used to
advertise in '70s and '80s magazines.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Mark Zenier]

I appreciate the advice and offers of cheap modems. I am not
interested in obtaining a modem. I am interested in information
presented in that specific article.

So, if anyone knows where the article was, I'm still looking......

"Build the Pennywhistle - a hobbyists modem"
Lee Felsenstein*
Popular Electronics, March 1976

*(the desiger of the SOL computer).

As I remember it, it didn't have a great reputation.

Suggestions:
In ham radio circles, Buzzwords would be "RTTY" and "Terminal Unit".
Try looking up the XR-2211 FSK receiver chip.

Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)

 

[Ross Herbert]

SNIP

I am not interested in obtaining a modem. I am interested in information
presented in that specific article.

It sounded awfully like you wanted to obtain or build one;

"I'm doing a little project that could use a dirt cheap modem, "

 

[Jan Panteltje]

Suggestions:
In ham radio circles, Buzzwords would be "RTTY" and "Terminal Unit".
Try looking up the XR-2211 FSK receiver chip.

Mark Zenier [email protected]
Googleproofaddress(account:mzenier provider:eskimo domain:com)

TCM3105 100% integrated 300 Baud modem, used for amateur packet radio.
Needs a 4.43 MHz xtal

This is a very good chip though, even with bad signals, build in filtering,
carrier detect, hardly any external components.