Sunday, 5 December 2010

Band Switching Arrangements

Having enjoyed little success with diode switching for the multi-mode beacon's band-pass filter, I've crossed over to a simple relay-based switching arrangement.

Each of the three bands in the unit under development has its input and output switched by a single-pole change over relay, as shown below...

The relays are switched by the circuit below (only one channel shown)...


I might not have used this design - but for the fact that it inherits much of its circuitry from the failed diode-switching circuit - indeed, I've actually stolen the components from the "diode" board!

The cold weather has been in remission today, such that I felt able to get out to the
PCB etch tank (which lives in what used to be the children's play house - now its just another "shed"). I made the re-designed PCB, drilled the myriad holes, populated and tested.

Here's the partially completed board...


I've populated two bands - for 40 and 30 m (these being the most popular QRSS bands at the moment). I've just got to wind and fit the toroids.

I'm going to leave the third channel unpopulated for the moment until I decide which other band to use.

The weather forecasters are suggesting it is going to get cold again - good job I got the PCB made today!

...-.- de m0xpd

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