Thursday 11 February 2016

Switching Bilateral Amp

The January number of QRP-ARCI's QRP Quarterly just landed here at m0xpd...

It contains the usual mix of neat stuff - all presented in a superbly produced, large-format journal, between full-color (it's American!) covers.

This issue is marred only by the inclusion of an article in which I've described an idea about how to electronically switch a bidirectional amplifier using FETs, rather than the usual relays, as shown below...

The QQ article goes on to use a pair of the amplifiers, sharing a single direction controller, either side of a parallel pair of IF filters to form a new 'Parallel IF Board' for Ben, kk6fut and Pete, n6qw's 'LBS' transceiver project.

Here's the initial 'ugly' development version of that system, in which the shared direction controller is using the SMD FETs you can see mounted on the green SOIC carrier close to the centre of the image...

The 'complementary' FETs used in the construction example in QQ are leaded components, to match the single-sided, through-hole PCB design I've presented there: 2N7000 / ZVP3306 (although if you are willing to use surface mount devices, there's a wider range of options available for the P-channel device).

If you're not a member of QRP-ARCI, I recommend it - despite the occasional dodgy article from yours truly!

...-.- de m0xpd

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