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Sbitx Amplifer Relay Output
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First effort at a better amplifier relay control output.? ? Previous work with an older vacuum tube SB-200 amplifier consistently showed the tuned circuits in the amplifier actually improved the signal!? (With the amplifier, you can get 200-300 or so watts output.? ?There is no need for ALC from the amplifier, because full output from the sBITX simply isn't enough to saturate the SB-200 amplifier.? ?The same sort of result should generally apply with commercially provided 811A or 3-400Z 3-500Z etc amplifiers.? ? This will likely also work with solid state amplifiers, but those don't provide much in the way of signal "cleanup," like the older vacuum tube amps with their tuned circuits do!? ?? However, learned the hard way NOT to use the switched +12V analog since this is involved in small signal stage power.... Much safer to utilize the digital TX signal from the Raspberry Pi.? ?However, this is a modest current +3.3V output.?? To avoid significant loading on this signal, used a 2N7000 enhancement mode N-channel MOSFET (same idea as Ashhar's design uses repeatedly) to turn on current through a commercially available optocoupler PC817 available as a small breakout board from Amazon:? ? This optocoupler doesn't have much "gain". The typical modifified SB-200 with solid state input (instead of the high voltage -170VDC input that would destroy most newer transcerivers if connected by the unwary ham!) -- open circuit relay voltage of 1.58 V, and short circuit current of 4.8 mA.? ?Most of that current is required to turn on the T/R relay in the SB-200. I changed the 1000 ohm resistor in the breakout board to a 200 ohm so it could be driven by a 5V supply with about 10mA -- so that the output optotransistor can conduct 5 mA without any problem. Tapped into signals: TX Digital -- pin 5 of an IC controlling the relays Ground -- pin 8 of the same IC +5.1 VDC -- scraped the +5V trace to gain this voltage, soldered. Haven't fully tested, but it does go ON and OFF properly and it did positively and correctly control the T/R relay system in my SB-200.? (Remember:? this has a SOLID STATE MODIFIEED input) There is less room available in the harrdware of the V2,, so this breakout board idea may have to be disassembled a bit, but the basic idea should still work.? ?Will test this more thoroughly to verify spectrum is unaffected and operation OK with full RF flowing.? ? Those tests haven't been done yet. 73 Gordon KX4Z |
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1.? V2 software doesn't seem to decode /cwdelay command....I need to figure that out.? ?Managed to adjust it in the lini file -- we have to rrun our CW training net SLOW so needed longer "hang
2.? With a "hang" of 900 I was able to run the CW tranining net on 3.560 for half an hour with about 100+ watts output from the SB-200 -- the relay control output worked FINE the entire time. Gordon KX4Z |
开云体育Gordon KX4Z:? Was wondering, did you just use you Sbitx with the SB 200 or did you also use the Ubitx? 73 Dave WD8AJQ ? SE? On Nov 24, 2023, at 12:32?PM, Gordon Gibby <docvacuumtubes@...> wrote:
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There is a good?likelihood that? in the past I have also fired up the SB-200 with output from a uBitx, but I'm so busy with so many pursuits it has been a looong time since I worked with a ubitx.? ?The principle should be the same -- avoid using analog voltages that have anything?at all with amplifying stages to control output, instead take digital outputs from the arduino, buffer with a MOSFET or something, control an optoisolator for further separation. I think the gain of a lot of older amps is about 7dB.? ?However,? I *do* remember one experiment where I drove the grid of a 6146 inside a HW-100 with the output from a ubits....I used a swamping resistor on the grid and I think I used a 49:1 transformer to increase the voltage from the ubitx to drive the grid and wow!? ?I? could get close to 90 watts or more output.? ? Back then I did not have a spectrum analyzer?but I would bet it was pretty clean anyway since the HW-100 has tuned pi network for output. Lots of cool things you can do once you have a little RF with which to work! Gordon KX4Z On Sat, Nov 25, 2023 at 11:03?PM David Barber <wd8ajq@...> wrote:
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I'm pretty sure that Allison gave me some pointers on how to connect to the 6146 grid.? ?I would hazard a guess at a 2K-4K swamping resistor on the grid, and a 49:1 transformer feeding it from 50 ohm output of qrp radio.? ? ?It might still be somewhere on this site. Gordon KX4Z On Sat, Nov 25, 2023 at 11:44?PM Gordon Gibby via <docvacuumtubes=[email protected]> wrote:
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开云体育Gordon KX4Z: I use to have a HW 100. That was back in the 1980. Then I move up to a Drake TR 7. Not sure what happen with it from my many moves. The Ubitx V6 with Reed B N’s accessible firmware is my path back to the HF bands. As a Blind individual, its nice having an affordable HF rig that I don’t have to adapt myself to it. ?? One day I hope to purchase a HF amplifier for use with my Ubitx V6. Eventually, I will need to seek assistance in making miner modifications to my Ubitx.? Thank you For your Info Reply: 73 Dave WD8AJQ ??? SE? On Nov 25, 2023, at 11:43?PM, Gordon Gibby <docvacuumtubes@...> wrote:
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