27-04-2024, 07:04 PM
The Minicircuit VCOs have 3 or 4 varicaps. One is the VCO and the others are part of a pi or similar LPF. They use the osc varicap voltage as the series Ls are appropriately chosen and a LPF isn't so critical in component values for such an application.
I've made copies on Stripboard with copper foil on the plain side and all the SMD parts on the track side. A track cut slightly less than half width , using a part to side of the holes can work at GHz tuned by the varicap as the oscillator. Below 800 MHz coils are simpler.
Three early prototypes without the low pass filter and a commercial filtered one at 850 MHz
Bottom left is mad "veroboard" stripline at GHz (I forget frequency)
Top two are VHF
Bottom right is the Minicircuits filtered VCO on vero/strip as a DIL adaptor.
Each homebrew VCO using I think 4 GHz or 6 GHz transistors.
They were used with NS synth chips, early prototype controlled by bit banging on PC parallel port. Later PIC18F series using JAL to program. Much superior to assembler, BASIC or C for the PIC family.
Pity the internal VCO varicap voltage isn't on the MC44CC374, unless the external loop filter has a version of it that could buffered/scaled for the two varicaps in a three series coils LPF.
I've made copies on Stripboard with copper foil on the plain side and all the SMD parts on the track side. A track cut slightly less than half width , using a part to side of the holes can work at GHz tuned by the varicap as the oscillator. Below 800 MHz coils are simpler.
Three early prototypes without the low pass filter and a commercial filtered one at 850 MHz
Bottom left is mad "veroboard" stripline at GHz (I forget frequency)
Top two are VHF
Bottom right is the Minicircuits filtered VCO on vero/strip as a DIL adaptor.
Each homebrew VCO using I think 4 GHz or 6 GHz transistors.
They were used with NS synth chips, early prototype controlled by bit banging on PC parallel port. Later PIC18F series using JAL to program. Much superior to assembler, BASIC or C for the PIC family.
Pity the internal VCO varicap voltage isn't on the MC44CC374, unless the external loop filter has a version of it that could buffered/scaled for the two varicaps in a three series coils LPF.
