Whatever happened to the LM3820 AM radio chip?

[Joerg]

Just curious: When checking my parts inventory I saw that I still have a
few LM3820 radio chips and was looking for the data sheet on the web.
Zilch. National does not even recognize the part and Alldatasheet
doesn't find it either.

What happened to it? Was this chip just a sparkler that whizzed away
into the night?

Regards, Joerg

 

[Leon Heller]

Just curious: When checking my parts inventory I saw that I still have a
few LM3820 radio chips and was looking for the data sheet on the web.
Zilch. National does not even recognize the part and Alldatasheet doesn't
find it either.

What happened to it? Was this chip just a sparkler that whizzed away into
the night?

They made several interesting radio chips that sank without trace, like the
LM373 IF amp/detector.

Leon

 

[Tom Torfs]

Just curious: When checking my parts inventory I saw that I still have a

few LM3820 radio chips and was looking for the data sheet on the web.
Zilch. National does not even recognize the part and Alldatasheet
doesn't find it either.

Datasheet can be found online at: http://www.bgmicro.com/pdf/lm3820.pdf

greetings,
Tom

 

[Gary Lecomte]

I have most of the Old Data Books from Various IC Manufacturers and I
do Have the documentation for this LM3820.

So if you need it, Just Email me.
But you MUST put the word "Electronic" in the "Subject" Line or it
automatically get filtered as JUNK MAIL.

Take care........Gary
***********************************************************************

 

[Joerg]

Hi Gary,

Thanks to all of you. I do have the data sheet but was just wondering
why such chips vanish so fast. At least they could leave legacy data
available.

Regards, Joerg

 

[Tim Shoppa]

Just curious: When checking my parts inventory I saw that I still have a
few LM3820 radio chips and was looking for the data sheet on the web.
Zilch. National does not even recognize the part and Alldatasheet
doesn't find it either.

What happened to it? Was this chip just a sparkler that whizzed away
into the night?

The LM3820 was great for analog-tuned AM receivers, but since those
days a few gotchas:

1. Everything is digitally tuned today
2. Everything is FM with AM only added on as an afterthought

Basically, nobody's interested in buying good AM receivers any more,
they're only interested in digital readouts and FM. (That's not
stricly true, auto radios still have passable AM sections, but they
aren't as good as they used to be.)

There are exceptions (GE SuperRadio, etc.)

Automotive OEM AM receivers from the 70's and 80's are wonderful machines.
Especially the slug-tuned ones. They work in the cold and the hot, they
have tuned antenna input stages, etc.

At some point in working with a young web developer in the 90's I realized
that kids today don't know what "radio buttons" actually refers to.

The NE602/NE612 is not exactly a drop-in equivalent to the LM3820 but
it's respectable in its own ways (a pretty good mixer in particular).
It doesn't have an IF stage so most of the schematics you find using
it as a direct conversion receiver, but there's nothing stopping you
from using it differently.

Tim.

 

[SioL]

At some point in working with a young web developer in the 90's I realized
that kids today don't know what "radio buttons" actually refers to.

The NE602/NE612 is not exactly a drop-in equivalent to the LM3820 but
it's respectable in its own ways (a pretty good mixer in particular).
It doesn't have an IF stage so most of the schematics you find using
it as a direct conversion receiver, but there's nothing stopping you
from using it differently.

Tim.

I have fond memories of the TCA440, I have built a multitude of all kinds of
receivers from these. I wonder if these are still out there. I remember the
mesmerising sounds of SW/MW AM HAM and CB radio stations in the distance...

I think I am getting old, I long for those days of early starts in electronics.

I got the GRUNDIG Yacht Boy 80 recently, fine radio, but its just not the same.....

SioL

 

[Joerg]

Hi Tim,

The LM3820 was great for analog-tuned AM receivers, but since those
days a few gotchas:

1. Everything is digitally tuned today
2. Everything is FM with AM only added on as an afterthought

3. Almost everything has sub-optimal FM performance and outright lousy
AM performance.

At some point in working with a young web developer in the 90's I realized
that kids today don't know what "radio buttons" actually refers to.

My impression is that young engineers just don't know how to build a
good tuner, whether that is AM or FM. Or a good IF section for that
matter. The newer a radio is the worse it gets. Our latest one has great
sound but simply doesn't work on AM and the FM IF filter is so sloppy
that some stations can be 'received' over more than 500KHz.

The NE602/NE612 is not exactly a drop-in equivalent to the LM3820 but
it's respectable in its own ways (a pretty good mixer in particular).
It doesn't have an IF stage so most of the schematics you find using
it as a direct conversion receiver, but there's nothing stopping you
from using it differently.

Yes, these are nice chips. Still, when I build a receiver I usually
throw in a nice DBM and a good IF filter right before the first amp.
These would be the only expensive parts and when rolling your own DBM
even that can be had for under $2.

Regards, Joerg

 

[Mark Zenier]

Hi Gary,

Thanks to all of you. I do have the data sheet but was just wondering
why such chips vanish so fast. At least they could leave legacy data
available.

Regards, Joerg

Isn't that a second source of a Cherry or Sprague part? (I've got
a Sprague databook that lists a ULN-3820, but says contact the
mfgr. for data).

One of the big guys in car radios probably wouldn't use it unless
there was a second source, and when they quit using it ...

Mark Zenier [email protected] Washington State resident