Though it might seem a bit daunting, modifying the frequency of your Hulda Clark Zapper is actually quite simple.

Before we get started on what to purchase for your variable Zapper, we need to make sure you've got the right equipment. Since the electronic components involved in the making of any given Zapper can vary in values by up to 10%, depending on what you purchase, your main concern for getting exactly the right frequency is going to be having some kind of reliable frequency meter. We typically use an oscilloscope to read out the frequency of our units, but there are meters available to read frequency as well. You won't be able to get lab-level precision from these, but you'll at least be able to get in the ballpark where you can test out frequencies for yourself. 

What you need to vary frequency (roughly between 15Hz and 100kHz):

  1. CD4069 Chip.
  2. 200k potentiometer.
  3. Several capacitors:
    1. .1uf for low ranges
    2. .005uf for mid ranges.
    3. 100pf for high ranges.
  4. Resistors listed on the Zapper schematic:
    1. 1k.
    2. 1M.

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Once you've put it all together, just hook up power, connect the output to your frequency counter, and tune in the frequency using the potentiometer. 

If you've got some experience with a soldering iron or a breadboard, it's pretty straightforward. It's worth mentioning, that if you wanted to, you could modify our existing model to be a variable Zapper. So if you are looking for a specific frequency, you could purchase our model replace a couple of parts, and tune in whatever frequency you want. 

Modifying the existing Zapper for specific frequencies:

If you've already purchased a Zapper from Zapperplans, or have built one from the plans using the 220k resistor and 100pf capacitor, you can modify your model to find specific frequencies. Again, you'll need something to read off the frequencies, but here are some quick ways to get some common frequencies:

  1. 30kHz - Place a 200k potentiometer in parallel (that means connect it to the same solder points) with the 220k resistor, then tune in the frequency.
  2. 2.5kHz - Replace the 100pf capacitor with a .005uf. At this point, the most precise way to get your frequency will be to replace the 220k with a 50k potentiometer and tune in the frequency. However, your 200k should be able to get you in the ballpark.
  3. 15Hz - Replace the 100pf capacitor with a .1uf. This will already get you close to 15Hz, however, you could replace the 220k with a 300k potentiometer to get closer. 

Keep in mind that not all electronic components are equal, so some experimentation with various increases or decreases in values of the potentiometer will be needed if you're trying to get really close to a specific frequency.