Looking for guidance with radio design

[Jon Yaeger]

I'm interested in building a miniature AM broadcast band radio and would be
interested in any broad brush solutions for eliminating the large LC tuning
circuit that is typically part of an AM front end.

Thanks in advance,

Jon

 

[Fred Bloggs]

I'm interested in building a miniature AM broadcast band radio and
would be interested in any broad brush solutions for eliminating the
large LC tuning circuit that is typically part of an AM front end.

The actual tuning circuit is not so big as the antenna. To which are you
referring?

 

[Jon Yaeger]

The actual tuning circuit is not so big as the antenna. To which are you
referring?

A ferrite coil and 365 pf variable cap are typical parts.

 

[Fred Bloggs]

A ferrite coil and 365 pf variable cap are typical parts.

Well- if small is what you want then block convert it upwards by x100
and then do the channel selection.

 

[PN2222A]

I'm interested in building a miniature AM broadcast band radio and would
be
interested in any broad brush solutions for eliminating the large LC
tuning
circuit that is typically part of an AM front end.

R-C anti-alias filter
Fast ADC
Single-Chip DDS.
Audio Driver.
Done.

PN2222A

 

[Joerg]

R-C anti-alias filter
Fast ADC
Single-Chip DDS.
Audio Driver.
Done.

But don't even think about battery operation and be prepared to shell
out several times the dough that you'd pay for a nice AM radio.

If I had to do it I'd upconvert like Fred suggested, but not by 100
times. Somewhere to an IF where you can buy a cheap filter of less than
a 100kHz BW. 10.7MHz would be really low cost and small here. Then
downconvert to 455kHz and use the usual 455kHz stuff. Done

Regards, Joerg

 

[Phil Allison]

"Jon Yaeger"

A ferrite coil and 365 pf variable cap are typical parts.

** That " ferrite coil " IS the damn antenna - dickhead.

If you use an external antenna, the RF stage can use the same mini size
coils as the IF does - circa a 6 mm cube.

If you have NO antenna - you will get no reception !!


......... Phil

 

[DaveM]

Well- if small is what you want then block convert it upwards by x100 and
then do the channel selection.

Use a varicap, or several in parallel, in place of the 365 pf variable
capacitor. The ferrite coil is the antenna.. . the radio not gonna work to
pretty good without it!!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!

 

[Glenn Gundlach]

"Jon Yaeger"


** That " ferrite coil " IS the damn antenna - dickhead.

If you use an external antenna, the RF stage can use the same mini size
coils as the IF does - circa a 6 mm cube.

If you have NO antenna - you will get no reception !!


........ Phil

What? Designing a radio isn't dangerous?
GG

 

[The Real Andy]

"Jon Yaeger"


** That " ferrite coil " IS the damn antenna - dickhead.
YAWN.....


If you use an external antenna, the RF stage can use the same mini size
coils as the IF does - circa a 6 mm cube.

If you have NO antenna - you will get no reception !!


........ Phil

 

[Phil Allison]

"The Real Andy"


** Run out of little kiddies to molest have you - Andy ??

Or just getting over another MONSTER hangover ???

Or is it both ??




......... Phil

 

[Frank Raffaeli]

I'm interested in building a miniature AM broadcast band radio and would be
interested in any broad brush solutions for eliminating the large LC tuning
circuit that is typically part of an AM front end.

Thanks in advance,

Jon

Do you want to use a magnetic (coil) antenna, or do you have a
connector feed from somewhere else? ... like in a car.

http://www.google.com/search?hl=en&q="One-chip+AM"&btnG=Google+Search

Thanks

Frank Raffaeli
http://www.aomwireless.com/

 

[The Real Andy]

"The Real Andy"


** Run out of little kiddies to molest have you - Andy ??

Or just getting over another MONSTER hangover ???

Or is it both ??




........ Phil

YAWN....

 

[John Jardine.]

I'm interested in building a miniature AM broadcast band radio and would be
interested in any broad brush solutions for eliminating the large LC tuning
circuit that is typically part of an AM front end.

Thanks in advance,

Jon

AM has lots of atmospheric noise and relatively strong signals. Maybe just
use a couple of feet of wire and go straight into a mixer, having volts of
dynamic range (eg ..4066 etc). Feed mixer with square wave local oscillator
at AM frequency of interest. Filter and amplify the resulting audio.
Most of this stuff can be done nowadays with standard opamps.
john

 

[Druso]

John said:

AM has lots of atmospheric noise and relatively strong signals. Maybe just
use a couple of feet of wire and go straight into a mixer, having volts
of dynamic range (eg ..4066 etc). Feed mixer with square wave local
oscillator at AM frequency of interest. Filter and amplify the resulting
audio.

OK, but why a square wave? I do not see the adavntage on a sysnusoidal one.

thanks

Leo

 

[Rich Grise]

John said:


OK, but why a square wave? I do not see the adavntage on a sysnusoidal
one.

thanks

Leo

Think of it as a chopper, that samples the input at F times per second,
with a 50% duty cycle. Another example would be a "Lock-In Amplifier" or
"Synchronous Detector"

Draw a graph of your incoming modulated RF carrier, and chop it so that
every other half-cycle doesn't exist - voila! Detected audio! (once
you get in sync, of course. )

Hope This Helps!
Rich

 

[Ken Smith]

AM has lots of atmospheric noise and relatively strong signals. Maybe just
use a couple of feet of wire and go straight into a mixer, having volts of
dynamic range (eg ..4066 etc).

You can make 3 balanced mixers out of a CD4053 at modest frequencies.

 

[John Jardine.]

You can make 3 balanced mixers out of a CD4053 at modest frequencies.

Indeed yes!. One useful earner, needed two long wave down converters and a
switch to swap between them. Bingo! CD4053. Could not have asked for better
capability, even if in custom Silicon.
john