an email from my friend Pete Zenner in Sioux Falls, South Dakota asking
me if I had ever engineered any custom fm or vhf receiver circuits? I
responded by telling him that I had engineered a single fm receiver
circuit years ago using a TDA7000 chip that Radio Shack had started
selling and had put my Mark 8 fm receiver circuit plan on the market
using that chip.
The only problem was that a few months later Radio Shack discontinued
selling the TDA 7000 chip and their answer was that some manufactured
had bought the rights to its entire stock. I wound up refunding a lot
of money after that since nobody could buy the chip. He informed me
that you can find them on ebay and a few other places now so I am
adding my Mark 8 fm receiver circuit here.
answer was and has always been that it is much cheaper to modify or
detune any receiver into any custom band rather than engineering one
from scratch plus it is cheaper to buy one rather than build one.
His response was that a lot of people would like to learn more about receivers by actually building one rather than buying one.
I totally agree with him. If you want to learn how to build an fm or
vhf receiver circuit, study front end rf amplifiers, IF strips and why
they are used, both 10.7 MHz and 455 kHz – Demodulators and last basic
audio amplifiers. Below is a scan of my original Mark 8, FM Receiver
Circuit. Enjoy, John.