Saturday, February 13, 2021

Built the QRPKits BLT+ Z-match antenna tuner

Locked down here in Melbourne it seemed like a good time to build a little antenna tuner. This is the Balanced Line Tuner Plus (BLT+) from Pacific Antenna or QRPKits.

As the radios I'll be using this have built-in SWR measurement I chose not to build the LED SWR indicator that's included.

The kit went together easily and the case is really excellent.

The manual, with circuit diagram, is available here

I tested it by throwing some wire out over the clothes line and running a counterpoise on the ground. The two controls interact a lot and you must adjust one and then the other and then the first.... but in the end it gets there and I'm happy with the result.

One minor note is that my kit came with version 2 of the SWR indicator but the link to the construction notes re-directs to version 3 which is a different circuit. This was enough discouragement for me to skip it.


After a gentle prod from veteran home brewer, John, VK2ASU, I went back and completed the built-in SWR indicator.

Tuning for a dimming or extinguishing of the LED does work but the meter on the radio is much easier to work with. The LED SWR indicator is worth having for simple QRP gear so I'm glad I've now put it in. It can be switched out of circuit of course.

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