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Author Topic: The amazing MPF102 VHF FM receiver!  (Read 5843 times)
BRIANCAMBRE
Member

Posts: 29




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« on: February 09, 2002, 12:26:16 AM »

Hello all,

I thought it would be a wise idea to put this out
on as many forums as I possibly can....referring
to those who like to homebrew RF!

I have just spent a few weeks modifying an old
regenerative VHF receiver...to the lowest component
count ever!  In fact, this could be world's
lowest compoents count in making an FM receiver!

I am still fascinated by the end project.  I listen
to it every night, just for the fact that FM
music is coming out of it.

The mighty MPF102 is the heart of the system...

All parts scan be purchased at Radio Shack...I kept
this in mind experimenting all thru this project...
for a relaxing week-end...one would not have to
order something by mail....and wait....heck, the
week-end would be over. Right?

And so, my friends, I have the complete plans, from
beginning to end on it.

I call it The Radio Shack Special...because all of the
parts can be purchased there...except for the tuning
capacitor...which can be salvaged from an ole' AM/FM
tuning radio.

While I type, there are about 15 people, right now,
making it.  I have been getting about 2 e-mails a day
on it, from novices to HAM's.  I don't know why it is
working....FM was always a difficult and lengthy
circuitry....but it is surely giving big brother (TDA7000) a run for the money!

My e-mail address is   braincambre500@yahoo.com

I just wanted to get this out to as many people as
possible.  I know that it is the small projects that
become the best!

   I again, thank you for your time reading this.

                             ...your friend, Patrick
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BRIANCAMBRE
Member

Posts: 29




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« Reply #1 on: September 13, 2016, 07:42:30 AM »

Hello again dear friends,

Patrick here. I am the one who designed the Radio Shack Special.

I am currently making a new website for the updated 'Radio Shack Special 2016'

Later in the year 2016, I should be finished with the new website.

The website is at http://www.the-radio-shack-special-project.com

thank you again for all that have looked at the project.

sincerely, Patrick
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VK3YE
Member

Posts: 180


WWW

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« Reply #2 on: September 17, 2016, 01:47:17 PM »

Super-regen receivers are a lot of fun.  

Hissy, sometimes unstable, sometimes difficult to tune for minimum distortion but a great entertainment to knock together.

A couple of points on the circuit for would-be builders:

1. The symbol for the 4.7 pF capacitor is shown with a wire going through the middle.  

This might confuse some people since it depicts a special type of capacitor known as a 'feedthrough capacitor'.  These are useful for RF decoupling the supply rails of sensitive stages - eg RF oscillators or low level RF amplifiers.  And they are quite rare components.  Fortunately only an ordinary 4.7pF disc ceramic is suitable for this part of the circuit and those redrawing the diagram may care to route the gate lead differently.  

Feedthrough capacitor: As per https://upload.wikimedia.org/wikipedia/commons/3/32/Feed_through_capacitor_symbol.png

2.  Pin 7 of the LM386 in the diagram has no connection.  Often, to aid stability it has a capacitor to ground (I've seen values of around 10uF).

As a short-cut, you can buy cheap LM386 modules for a couple of dollars or less on ebay. Then you just need to build the MPF102 stage.  That's so simple it's not worth making a printed circuit board.

The sensitivity of these circuits is high for a 1 transistor circuit. Only a few cm of wire is needed to pick up FM stations.

Here's some videos of a similar superregen receiver tuning the FM broadcast band.

https://www.youtube.com/watch?v=tbKffpfe9_s

https://www.youtube.com/watch?v=tYc4x9JXqyU

As the title says - it's amazing and you should build one or similar!


(MODERATORS - is it possible to move this thread to the Homebrew section?)
« Last Edit: September 17, 2016, 01:49:56 PM by VK3YE » Logged

Peter VK3YE

TOP-SELLING QRP BOOKS $US 5 EA: 'Minimum QRP' & 'Hand-carried QRP antennas'. 
See http://home.alphalink.com.au/~parkerp/vk3yebooks.htm or search title in Amazon.
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