The VCOs are the heart of the jammer, they generate the ultra high frequencies that we sweep through the RF bands we are jamming. One can build a VCO from raw parts, but its rather painful and I find that if its your first jammer and you dont have a spectrum analyzer, buying is the way to go. I use Minicircuits because they are high quality, wide bandwidth, easy to buy and somewhat low cost. However, Z-Comm, Micronetics and Crystek (available at Mouser) are also possible. If you're going with different VCOs, check the following specifications:

• Vtune: the voltage range required to tune. Wideband VCOs need 15-30V.
• Frequency range: Obviously, you want to make sure you can cover the desired bands.
• Output power: 6dB to 10dB is nice. Above 8dB you'll want to attenuate the output before pushing it thru the gain stage (with the tee network provided onboard).
• Vcc: This board design assumes 12V. Many use 5, 8 or 10V. You can overdrive a little but too much and you'll fry it.
• Case: the pads on the board are for 0.5"x0.5" VCOs, a common size.

The power switches are there to keep power down when using only one VCO at a time. They are not essential and may be jumpered if you know what you are doing. YMMV.