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Author Topic: Convert Kit Transceiver to other band or multi-band?  (Read 643 times)
KX4QP
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Posts: 396




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« on: March 13, 2019, 03:19:47 PM »

Yes, I know, to change a QRP crystal CW transceiver from one band to another, I need to change the crystal and the resonant frequency of the tank circuits, but when the coils aren't accessible to change...

I've got a kit on the way, the Four State QRP Group Cricket 30.  I really wanted a 40 m or 80 m TRX, but the Hilltopper was too much money, and the Cricket seems to be available in only one band at any given time (40 and 80 are long gone), so I bought what I could afford.  This is the kit with the required inductors etched on the circuit board, so no coil winding is needed -- but changing a coil value or tapping a coil is relatively difficult.

It occurred to me, though, since I'll be building the thing anyway, can I reasonably come up with a way to plug in auxiliary caps in parallel with the tuning caps in the oscillator and receive tuner, to be able to switch crystals and caps and cover more than one band?  Going to higher frequency, like 20 or 15, could be a problem (or maybe not -- I might be able to provide for series as well as parallel caps to shift the tuners that direction).  I know I've seen references to Pixie and Cricket transceivers being band shifted during construction -- but how well does this work?  Or is it easier than I think to tap the etched-on-board coils to raise frequency?
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KD0REQ
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« Reply #1 on: March 13, 2019, 07:57:11 PM »

if the schematics for the others are on line, you'll find the values of the parts you need.
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KX4QP
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« Reply #2 on: March 14, 2019, 02:48:07 PM »

if the schematics for the others are on line, you'll find the values of the parts you need.

Aha!  The assembly instructions (which include board locations and values) are surely online for the other band versions.  Only question is whether they all use the same etched coils, or if those were changed for the different bands.  Shouldn't be impossible to figure out from the capacitances.
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