20-05-2012, 08:57 AM
Put the new arrangement through its paces last night, the results were very good although not much DX around, managed to copy a W2 from long Island and several UK QRPer's (England & Scotland)
The addition of a tuned RF amp has enabled me to drop the tunable IF down in frequency and still retain a reasonable image ratio, the tunable regen det now tunes from 2 to 2.5 mhz,
The lower resulting L/C ratio has enable me to increase the value of the regen grid coupling capacitor from 4.7 pf to approx 27 pf whilst still maintaining no discernable frequency drift when going in and out of full regen (important for SSB)
I have also used a screened lead from the regens grid coupling capacitor to it's top cap grid in order to reduce the inherent hum pickup which is inevitable in a test bed lashup job. The down side of this is that it forms a capacitive divider for the grid input so some attenuation is present but it has only a small effect on the receivers performance, if a G1 top cap valve is used in the final design then that whole section can be screened so no problems.
If I get time I will post up the latest circuit.
Lawrence.
The addition of a tuned RF amp has enabled me to drop the tunable IF down in frequency and still retain a reasonable image ratio, the tunable regen det now tunes from 2 to 2.5 mhz,
The lower resulting L/C ratio has enable me to increase the value of the regen grid coupling capacitor from 4.7 pf to approx 27 pf whilst still maintaining no discernable frequency drift when going in and out of full regen (important for SSB)
I have also used a screened lead from the regens grid coupling capacitor to it's top cap grid in order to reduce the inherent hum pickup which is inevitable in a test bed lashup job. The down side of this is that it forms a capacitive divider for the grid input so some attenuation is present but it has only a small effect on the receivers performance, if a G1 top cap valve is used in the final design then that whole section can be screened so no problems.
If I get time I will post up the latest circuit.
Lawrence.
