Re: Building the 'Minimod' AM modulator-questions!
Hi Howard,
I would definitely recommend building this. I'm not an RF sort of person and didn't want a design where I had to get involved winding coils. Being able to buy them easily and cheaply was the deciding factor for me.
I kitted up to build three units so I ordered 6 coils (90UOL is the stock code), 3 BF256B FET's and 3 BC109 plus 10 390R resistors from Spectrum. Total cost including postage was £8.45 and their service excellent.
All the caps, apart from the polystyrene ones, came from RS Components. They are great as there is no minimum order & free postage. Anyone can set up an online account. I can give you all the stock codes if that would be useful?
Ebay was the most economical source for the polystyrene caps.
If you get the FET from Spectrum, the pin out given in David's picture above is correct. Be sure to take on board the correct connections for L1 & L2: I got confused about L2!
By design, this is a low powered device so you won't be able to receive it all round the house. It's aerial needs quite close coupling with the radio's aerial. I simply twisted a few turns of both aerial wires together and it works well.
I only need this to work with single sets so that's fine for my needs.
The perf board works well as you just use the component leads as connecting wires. No risk of forgetting to cut tracks like with Vero board!
Hope that helps,
Cheers
Nick
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