19-10-2023, 05:29 PM
The IP3 spec of an SA612 is only an issue on receive before an IF. I'd use a quad FET switch mixer for applications in front of IF filter and receive. The best IM performance sets you can buy use the quad switch (a similar idea to a ring diode mixer). I built many PCBs in 1970s using the MC1496. It's not got the frequency response of an SA612, carrier 300MHz, signal 80MHz @ -3dB Transadmittance.
mc1496.pdf (Size: 208.59 KB / Downloads: 0)
But feel free to build a clone of a Swan.
Schematic here
16 valves: 6EW6 12BE6 6GK6 6LQ6 6LQ6 12BZ6 12BE6 6EW6 12BA6 12AX7 6BN8 6GK6 7360 12BA6 12AX7 0A2 12BA6
I'm very fond of my portable valve SSB /AM/CW receiver and it does beat cheaper transistor / IC sets. Hallicrafters S72 I never figured why the BFO works fine on the replica battery pack (Alkaline D cells and AA cells) but doesn't oscillate on mains via 230 to 115V transformer. The voltages all check out. Someone had swapped the original audio op transformer and wired the phone socket wrong, which puzzled me for a while. Otherwise it was mostly replacing dodgy caps. My first "serious" SWL set was an R1155 in 1966.
A friend living about 20 minutes drive away has either an RA17 or RA117. He specialised in collecting old valve vintage Commercial sets. Also has a bunch of Eddystones & Collins (some of which I've restored) Replacing paper caps under the switch units on an Eddystone needs special tools, dexterity and patience. Replacing the drive cord on some isn't much fun either.
mc1496.pdf (Size: 208.59 KB / Downloads: 0)
But feel free to build a clone of a Swan.
Schematic here
16 valves: 6EW6 12BE6 6GK6 6LQ6 6LQ6 12BZ6 12BE6 6EW6 12BA6 12AX7 6BN8 6GK6 7360 12BA6 12AX7 0A2 12BA6
I'm very fond of my portable valve SSB /AM/CW receiver and it does beat cheaper transistor / IC sets. Hallicrafters S72 I never figured why the BFO works fine on the replica battery pack (Alkaline D cells and AA cells) but doesn't oscillate on mains via 230 to 115V transformer. The voltages all check out. Someone had swapped the original audio op transformer and wired the phone socket wrong, which puzzled me for a while. Otherwise it was mostly replacing dodgy caps. My first "serious" SWL set was an R1155 in 1966.
A friend living about 20 minutes drive away has either an RA17 or RA117. He specialised in collecting old valve vintage Commercial sets. Also has a bunch of Eddystones & Collins (some of which I've restored) Replacing paper caps under the switch units on an Eddystone needs special tools, dexterity and patience. Replacing the drive cord on some isn't much fun either.
