I recently purchased some of these low-cost 433 MHz SAW transmitter and receiver pairs for a current project.

The receivers work as advertised.

The transmitters?
Obviously dispatched from the factory, never tested, and without a QC inspection


How do I know this?

None of the three FS1000A transmitter boards had L2 fitted ex the factory

A rudimentary un-skilled 2 second inspection would have revealed the [obvious] missing component.

With L2 missing, there are no DC volts applied to transistor VT1’s collector. It couldn’t possibly work.

The fix, albeit annoying, was relatively easy using some enameled copper wire that was on hand and similar in gauge to L1.

Using a screwdriver as a 4mm diameter mandrel, I wound three turns and filed/tinned the ends appropriately, for soldering to the PCB.



The transmitters now work as they are supposed to.

I brought this to the attention of the eBay seller ‘eshop5may’ and they offered a $3.00 refund. The original purchase price was $6.88, so the three pairs ended up costing me $3.88 delivered (from within Australia via a slow boat).


When purchasing ‘cheap Chinese crap’, be prepared to fault find and repair!