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Old 11th Oct 2017, 1:18 pm   #1
David G4EBT
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Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default 'I.F Alignment Aid'

I mentioned in another post that I spotted a neat little circuit on internet for an I.F Alignment Aid'.

I don't need one, and it has its limitations, but as it uses only two ICs and two transistors, it may have some appeal to anyone who is sans signal generator. Because it's an American design, it's for 455 kHz - not 465 kHz. What determines the frequency is a ceramic resonator and a ceramic filter. There is a trimmer which can pull the frequency about 5 kHz max, so for 465 kHz, it would need the resonator and filter to be for 465kHz.

Cricklewood stock the resonator, (only £1.30) but not the ceramic filter.

https://www.cricklewoodelectronics.com/D465.html

I've scoured internet and all I can find is 455 kHz filters, which abound, such as this one:

https://www.aliexpress.com/item/Cera...053_10052_1033

Hence, unless I can find a source of 465 kHz filters this little project is destined to only be a paper exercise. (In any event, it was designed in 2004 and specified a Toko filter and they're no longer available even for 455 kHz). I've amended the original circuit by adding a 6V regulator and provision for an LED and have designed a PCB for it, albeit I've not yet checked it for errors.

If anyone knows of a source of three terminal ceramic filters, I'd appreciate a link.
(I saw one from Italy with a 30 Euro min order plus VAT, plus post, so discounted that).

The original design is here:

http://electronbunker.ca/eb/SignalGen455.html

First pic below is the amended circuit after I tweaked it.
Second pic is the component overlay of the PCB I've designed.
Third pic is the track side of the PCB.

It's kept me occupied on a rainy day - it's nice and toasty, sat here flying a desk!

Memo to self: Stop poking around on internet - it's the thief of time.

"Use what talents you possess; the woods would be very silent if no birds sang there except those that sang best".
Henry Van Dyke. (He was clever).
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