18-10-2023, 04:53 PM
I'd use an SA612 which replaces two 7360, takes much less power, lasts well, lower noise and better frequency response. It was a last gasp of valves in early 1960s. Sixty years ago. Nuvistors were an RCA idea nearly obsolete from the start.
An original Luddite was wanting a share of the profits and advantages of the new technology. They were not anti-advancement. They thought that instead of worse pay, worse conditions that the x1000 increase of profits of the cloth producers should be shared more equitably. It was only when the mill owners refused to negotiate that riots and machinery destruction ensured.
FPGAs and SDR designs, and PIC programming are specialist skills. But DDS is pretty simple to apply and gives crystal stability without the noise (and phase jitter) of a VCO and PLL. The PLL, no matter if valved or whatever, or a Wadley loop, is progressively worse the smaller the channel step and faster the channel step. In contrast the DDS can implement fractional Hz steps at almost no penalty and can even have any kind of modulation. Having perfect I Q (90 degree shift) for mixers (up or down conversion) is also trivial.
Commercially produced radios may have been using DDS instead of a VCO or tuning PLL for nearly thirty years. Certainly more than twenty (FT817). Such sets used the PLL synth essentially to replace the band crystals on 1980s and older sets.
In most cases the only reason now to use valves is either more than 100W (typically 500 to 1000W) of home brew HF Linear Amp or nostalgia (fun). You don't need to use BGAs, which is needing good PCBs and BGA heating / reflow gear, though the gear isn't that expensive now.
I've assembled SMD on Vero/Stripboard by cutting down either side of holes so each track is two tracks. Also adaptor to 0.1" PCBs are cheap for up to 64 leg insects. Tin PCB and a regular clean dry 3mm tip iron to reflow. I might use a dab of glue for awkward devices. I've made LNAs, mixers, VCOs, (up to 2.5GHz) IF amps, FM Radio with SMD tuner, SMD stereo decoder, SMD audio amp, DIL RDS decoder, PIC & LCD display with keypad all on stripboard. Beats tag strips and fitting valve bases (which I started with in late 60s and early 1970s). Also made a 30MHz to 1GHz noise generator to see filter responses on an HP 141T spectrum Analyser. After me restoring it in 2004 it finally packed in a couple of years ago and I replaced it with a new Rigol, which has the tracking generator built in. I never had that for the HP. The noise generator is some zener diodes from a clean supply with a high pass filter driving two stages of SMD Microwave IC amps. Nice flat noise jump from 30MHz to 800MHz on the Rigol input!
I've restored / repaired much valve gear from 1928 to 1960s to 1980s hybrid. But now I've not the enthusiasm to build more than some basic accessories.
An original Luddite was wanting a share of the profits and advantages of the new technology. They were not anti-advancement. They thought that instead of worse pay, worse conditions that the x1000 increase of profits of the cloth producers should be shared more equitably. It was only when the mill owners refused to negotiate that riots and machinery destruction ensured.
FPGAs and SDR designs, and PIC programming are specialist skills. But DDS is pretty simple to apply and gives crystal stability without the noise (and phase jitter) of a VCO and PLL. The PLL, no matter if valved or whatever, or a Wadley loop, is progressively worse the smaller the channel step and faster the channel step. In contrast the DDS can implement fractional Hz steps at almost no penalty and can even have any kind of modulation. Having perfect I Q (90 degree shift) for mixers (up or down conversion) is also trivial.
Commercially produced radios may have been using DDS instead of a VCO or tuning PLL for nearly thirty years. Certainly more than twenty (FT817). Such sets used the PLL synth essentially to replace the band crystals on 1980s and older sets.
In most cases the only reason now to use valves is either more than 100W (typically 500 to 1000W) of home brew HF Linear Amp or nostalgia (fun). You don't need to use BGAs, which is needing good PCBs and BGA heating / reflow gear, though the gear isn't that expensive now.
I've assembled SMD on Vero/Stripboard by cutting down either side of holes so each track is two tracks. Also adaptor to 0.1" PCBs are cheap for up to 64 leg insects. Tin PCB and a regular clean dry 3mm tip iron to reflow. I might use a dab of glue for awkward devices. I've made LNAs, mixers, VCOs, (up to 2.5GHz) IF amps, FM Radio with SMD tuner, SMD stereo decoder, SMD audio amp, DIL RDS decoder, PIC & LCD display with keypad all on stripboard. Beats tag strips and fitting valve bases (which I started with in late 60s and early 1970s). Also made a 30MHz to 1GHz noise generator to see filter responses on an HP 141T spectrum Analyser. After me restoring it in 2004 it finally packed in a couple of years ago and I replaced it with a new Rigol, which has the tracking generator built in. I never had that for the HP. The noise generator is some zener diodes from a clean supply with a high pass filter driving two stages of SMD Microwave IC amps. Nice flat noise jump from 30MHz to 800MHz on the Rigol input!
I've restored / repaired much valve gear from 1928 to 1960s to 1980s hybrid. But now I've not the enthusiasm to build more than some basic accessories.
