MK 484 Radio - Tuning Capacitor Value?

[Dave.H]

I found a website that has construction details for a radio using the
MK 484 IC. The site doesn't seem to say what variable capacitor value
to use, I happen to have a fairly new 365 pF unit lying around, that I
could use. I would also want to know if any type of ferrite coil
would work, or would it be better to wind my own?

Thanks, Dave
Australia

 

[Dave.H]

The component values depend on what frequency band you wish to tune.

Here's a link that may help you.

http://www.rapidonline.com/resources/docs/82-1026.pdf

Note that the MK484 IC is rated only to 3 MHz.

I want to tune the AM band 530 kHz too at least 1500 kHz. There's not
too many AM stations in the high end of the band, (highest one is at
1431 kHz, the one I usually listen to) so I'm not worried about the
radio tuning any higher than 1500 kHz

 

[ian field]

I want to tune the AM band 530 kHz too at least 1500 kHz. There's not
too many AM stations in the high end of the band, (highest one is at
1431 kHz, the one I usually listen to) so I'm not worried about the
radio tuning any higher than 1500 kHz

Pinch the tuning cap and ferrite rod out of an old transistor radio.

 

[Dave.H]

You could use the ferrite coil from a junk AM radio, or wind the one shown
in the link. The author of the publication used a 120pF cap, but your 365pF
cap will do fine; the lowest frequency will be achieved with the plates
about 1/2 meshed unless you use fewer turns. If you wind the coil on a
ferrite rod, I suggest you tap it every 10 turns and experiment.

Don

I've got an old AM/FM radio I don't use any more, I might pinch the
tuning cap and ferrite coil from that, and save the 365 pF cap for a
tube regen I'm planning. I forgot to post the link where I found the
schematic, http://bellsouthpwp2.net/w/u/wuggy/mk484.htm