Digital phase/frequency detector as a dedicated PCB.
I will probably use this one since it takes up less space than the original ugly version.
This is a shared (public) design at OSHPark
Since this circuit block more or less never changes and is not one that can be improved upon
via experimentation, it is therefore one that really supports the idea of a dedicated PCB.
Real estate can be reduced with SMD components.
SMD 4 section Sallen-Key audio filter.
This was inspired by coming across about 100 cheap (free?) OP074 SOIC op amps.
This is a shared (public) design at OSHPark SMD Audio LPF
If you decide to build this make sure to keep your resistance values in k Ohms, not 100s of Ohms.
Many of the low power OP Amps cannot drive low impedances.
Diode ringe balanced modulator for generating DSB.
This is a shared (public) design at OSHPark MOD_BALMOD1
The pot is for carrier suppression, aka balance. Si Schottky diodes tend to be matched well enough that
they will perform well with no carrier balance adjustment for unwanted sideband suppression.
This is a nice compact broad band amp PCB designed around the TO-92 MPSH10 NPN.
MPSH10 has fT=650 MHz and is relatively cheap and easy to find.
With 350mW power dissipation and Ic=50mA (max) it is a great device for most HF applications.
Bias stabilization at DC is accomplished with emitter degeneration and AC coupled emitters
to parallel the devices at RF. This allows a lot of flexibility on the board for loading 1 to 4
transistors depending on how much power out one needs or an IMD agenda.
MPSH10s in this board work well out through 6m. Note that MPSH10 pin out is not the same as most NPN
in the TO-92 pkg.
4 devices at 250mW each will provide >+20dBm useful Pout for class AB SSB driver applications
or a superhet RX front end mixer post amp. The benefit of running at 250mW or less is not needing any
form of heat sink!.
Another option for this board is to bias for class AB, maybe 5mA per stage (min) and use it as a QRP final
at 1W out.
This design has a wide range of options for gain and power out depending on feedback and emitter resistor
values and bias setting on the base.
This is shared (public) at OSHPark BBAMPx4