MK484 single chip AM radio question [Repair]

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From: Albert on 4 Apr 2005 11:53

I hope to use the MK484 single chip AM radio at 20 kilohertz for a
very low power receiver. The spec sheet says it only goes down to 150
kilohertz however.

Has anyone used the MK484 chip below 150 kilohertz?

I know it works well at lowfer frequencies...it runs circles around my
ICOM receiver! But, I'm not sure about the minimum usable frequency.

I have the spec sheet for it (and it's more modern variant, the
MLF501), if anyone wants a copy, please speak up.

Any comments appreciated.

A

From: Highland Ham on 8 Apr 2005 09:12

From: Dale Parfitt on 8 Apr 2005 10:02

<Albert> wrote in message news:1mn251h6aip5lcirupgoooumiaeh90krnr(a)4ax.com...
> I hope to use the MK484 single chip AM radio at 20 kilohertz for a
> very low power receiver. The spec sheet says it only goes down to 150
> kilohertz however.
>
>
> Has anyone used the MK484 chip below 150 kilohertz?
>
>
> I know it works well at lowfer frequencies...it runs circles around my
> ICOM receiver! But, I'm not sure about the minimum usable frequency.
>
>
> I have the spec sheet for it (and it's more modern variant, the
> MLF501), if anyone wants a copy, please speak up.
>
>
> Any comments appreciated.
>
Hi Albert,
What is the upper freq limit on this chip? I am always looking for a good AM
dtector. 9MHz is current interest.

Thanks,
BTW, if you are the same fellow asking about wire gauge- a
micrometer/calipers is by far the more accurate method. The gauges just do
not work well for small diameters. And, you'll find lots of other uses for
the calipers.

73,
Dale

From: John Woodgate on 8 Apr 2005 10:09

I read in alt.binaries.schematics.electronic that Albert <?@?.?.invalid>
wrote (in <1mn251h6aip5lcirupgoooumiaeh90krnr(a)4ax.com>) about 'MK484
single chip AM radio question', on Mon, 4 Apr 2005:

>I hope to use the MK484 single chip AM radio at 20 kilohertz for a very
>low power receiver. The spec sheet says it only goes down to 150
>kilohertz however.

Is there any reason to suppose it contains a coupling capacitor or
something that would limit the low-frequency response? It seems rather
unlikely. But the definitive test invokes a little-used technique in
these days of calculations and simulations. It's known as 'trying it'.
(;-)

It isn't as if testing at 20 kHz is rocket science, after all.
--
Regards, John Woodgate, OOO - Own Opinions Only.
There are two sides to every question, except
'What is a Moebius strip?'
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

From: Chuck Harris on 8 Apr 2005 11:06

John Woodgate wrote:
> I read in alt.binaries.schematics.electronic that Albert <?@?.?.invalid>
> wrote (in <1mn251h6aip5lcirupgoooumiaeh90krnr(a)4ax.com>) about 'MK484
> single chip AM radio question', on Mon, 4 Apr 2005:
>
>> I hope to use the MK484 single chip AM radio at 20 kilohertz for a
>> very low power receiver. The spec sheet says it only goes down to 150
>> kilohertz however.
>
>
> Is there any reason to suppose it contains a coupling capacitor or
> something that would limit the low-frequency response? It seems rather
> unlikely. But the definitive test invokes a little-used technique in
> these days of calculations and simulations. It's known as 'trying it'. (;-)
>
> It isn't as if testing at 20 kHz is rocket science, after all.

Since this is a superhet chip (IIRC), the problem is more likely one of LO
bleed through into the IF. The LO frequency would have to be on the
high side of the receive frequency, so in this case, with a 455Khz IF,
the LO would be at 475Khz. The LO signal bleeding through the IF filter
would probably be as strong, or stronger than the 20KHz signal you were
intending on receiving.

-Chuck

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