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Old 5th Jun 2017, 4:21 pm   #8
David G4EBT
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Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,737
Default Re: FM to AM Converter?

Quote:
Originally Posted by Argus25 View Post
They can of course be used with any AM radio.
As they require direct connection to the radio's aerial socket, not to vintage radios which don't have an aerial socket, often for good reason - in addition to having an internal am aerial, they are AC/DC live chassis so external connects must not be made to the chassis. Some AC/DC sets do have socket for an external aerial and RF earth isolated by capacitors, which these days would need to be Y Class.

The constructional article on the scanning FM/AM radio converter in the Summer BVWS Bulletin has the merit of not requiring any direct connection to the set. It just has two aerials - one to receive the FM signals - the other to transmit it on MW to the adjacent AM receiver so FM on a DAC90A or other live chassis sets isn't a problem. (For the duration of FM transmissions that is - however long that continues, but don't let's go there!).

Given how many threads there have been along the lines of "I've got this Bush DAC90A off eBay and I'd like to rip the insides out and fit a DAB/Bluetooth jobby in it", I imagine that the article will prove quite popular and deservedly so, because not only does it facilitate reception of FM stations on AM only radios, as a constructional project, it overcomes two obstacles which some constructors would otherwise come up against: Namely, though it's PIC-based, programmed pics are available from the author, and secondly, it's built on strip-board so obviates the need for a PCB.

The RX FM modules are cheap too - £2.19 for two post free from a UK ebay supplier.

From my perspective in reading the article, the stripboard layout (Fig 2 on page 25) is rather small and indistinct. Also there is no underside view of where the strips need to be cut or the mounting of the momentary switch used for scanning and setting stations. The close-up on the upperside of the stripboard give little hint of the switch which is hidden on the underside. That won't be a problem for experienced constructors who will sort that out by reference to the circuit, but might baffle or deter inexperience constructors.

Not in any way wanting to sound critical of this ingenious little gizmo - just saying that anyone inexperienced wishing to build it will need to exercise some care and will need to carefully compare the tracks with the circuit to make the necessary nine cuts in the tracks, as explained by the author in the text. The mounting of the FM module on ten tinned wires will call for some care too.

Won't be long I think before we have steady stream of 'success stories' as has been so with the highly popular mini-mod.

Early days, but I think this thread has legs and will run and run!
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