Items of Interest

There are a couple of areas that has sparked my interest lately, I'm burning out with software projects.

  1. Parametric amplifiers, mixers, and oscillators.
  2. Tunnel diodes used as amplifiers and oscillators, supplies of available parts are all but gone. May be a moot issue if item #3 works out.
  3. Experiment with Lambda diodes as substitutes to Tunnel diodes in new designs.
  4. Anti-Parallel diode sub-harmonic mixers.
  5. Regenerative Receivers
  6. Use some of these older devices and techniques with Software Defined Radios.
  7. Linear RF Power Amplifiers

One project that I will try to do is creating a replacement for the the SoftRock radio using parametric mixers instead of FET commutating switches, the advantage besides simplicity is the frequency range possible with a parametric mixer which can be easily into the Microwave range.

Another area to be explored is using anti-parallel diodes as the mixers of a SDR receiver. Towards that end I have acquired a large NOS supply of Agilent (HP) dual matched diodes that are very fast. A quick prototype yielded a 6M receiver that worked quite well considering the time spent on it, shortly I will begin experimenting with a 2M version. Dual matched anti-parallel diodes as available for $1 that can reach 10's of GHz.

Another area to explore is using FET switches to implement an equivalent to the anti-parallel diodes, the advantages are that the clock circuitry can remain digital while the clocking speed is 1/2 the normal clocking speed

I have bought a good supply of 27pf, 45pf, 90pf, and 420pf high Q Varactors in lead packages which should be useful at HF, VHF, and UHF frequencies but I'm looking for an inexpensive source of higher capacity units( 220 pF ) for use at HF frequencies. One source that looks promising is Power Schoktty Diodes, I have about a dozen different devices that I need to test in an actual radio, they range in value from 80pF to 700pf at 1V bias while having 10,000V dv/dt capability so they should work great in the HF bands.

Other items that I have acquired lately in anticipation of having additional time and room available are several RF Power Transistors that I was able to buy in large quantities and are available in my store for less than $1 in quantity 1.