Wednesday, December 4, 2019

Four crystal super VXO pulls 5 kHz higher

Those who tinker often like to squeeze the best performance out of their creation. It might be accelaration or fuel economy from their vehicles, output power from a linear amplifier or gain from an antenna. 

Something else in this category is pulling range with a variable crystal oscillator (VXO). Normally they can only be shifted by a few kilohertz. However there's ways, from keeping capacitances down, adding series inductance to using parallel crystals, that extend pulling range. The cnallenge in this case is to maximise pulling range while keeping your signal acceptably stable. And pulling above a crystal's marked frequency can be harder than pulling below it. 

This video is of a VXO experiment.  I use 7.023 MHz crystals, a frequency commonly supplied with the cheap 'Pixie' QRP transceiver kits. 

Have you ever built a VXO? What pulling range did you get? Please let me know in the comments below. 

PS: Find hints and tips for working DX in Minimum QRP. It's the top-selling manual on the equipment, antennas, operating and strategy of successful QRP operating. And its techniques work for 100 watts as well. It's available for under $US 5 each in electronic form. Or you can get a paperback version. Visit VK3YE Radio Books to find out more. 

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