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QMX thoughts

Bojan Naglic All Messages By This Member #108823 Hi Hans, I see my QMX as a very well thought out rig. Works nice. FT8 and CW. I built it for +12V. But the "too" small PCB means there is no place for an additional dedicated GPS connector for instance. And also no place for some improvements on BPFs and LPFs if needed. OK, this is perhaps marginal.?But about the two SMPSs, I think you could live with just one. If you would supply the MC?permanently with the 3V3 LDO and than switch its input from +12V at powerup to a stable +5V SMPS it would be beneficial. Than you would have to deal with just one SMPS's interference. On a cost of a bit larger supply current. A win-win. Just my thoughts. 73 Bojan S53DZ PS: Why do I have a feeling that the QMX Volume control encoder would be better to work counter-wise and not the opposite? The frequency is increasing in that direction and the volume is decreasing.
Hans Summers All Messages By This Member #108827 Hello Bojan Operation of the volume?control is a known firmware issue I need to address.? Yes one could have designed it with a single SMPS regulator, at the expense of higher supply current. Though this is a "trade-off" not a win-win (higher supply current being a bad thing!). It would simplify the circuit but it would not achieve much else; the two SMPS are synchronous anyway so on the same interference?schedule.? 73 Hans G0UPL toggle quoted message Show quoted text On Wed, Aug 30, 2023 at 4:02?PM Bojan Naglic <bojan.naglic@...> wrote: Hi Hans, I see my QMX as a very well thought out rig. Works nice. FT8 and CW. I built it for +12V. But the "too" small PCB means there is no place for an additional dedicated GPS connector for instance. And also no place for some improvements on BPFs and LPFs if needed. OK, this is perhaps marginal.?But about the two SMPSs, I think you could live with just one. If you would supply the MC?permanently with the 3V3 LDO and than switch its input from +12V at powerup to a stable +5V SMPS it would be beneficial. Than you would have to deal with just one SMPS's interference. On a cost of a bit larger supply current. A win-win. Just my thoughts. 73 Bojan S53DZ PS: Why do I have a feeling that the QMX Volume control encoder would be better to work counter-wise and not the opposite? The frequency is increasing in that direction and the volume is decreasing.
Bojan Naglic All Messages By This Member #108830 Hans, ok, I understand your point of view. By win-win I meant a better and less risky MC supply. A bit more mAmps doesn't hurt much either. GL with your upcomming new challenges. 73 Bojan S53DZ
Bojan Naglic All Messages By This Member #109050 Hi, what I think it would further improve the functionality is: - an AGC ( fast or medium one) for the CW?reception (already mentioned elsewhere), - if?the volume control would followed a logarithmic law rather than a linear one (smaller steps at lower volume). 73 Bojan S53DZ
Bojan Naglic All Messages By This Member #109908 Hi Hans et al, ? My QMX is working fine. Leave it as it is then? Hmmm, as I see supplying the MC from 3V3 SMPS controlled by MC too risky (although it works well, I have to admit!!!) I want to try supplying it from a linear regulator at all times. ? So if the 78M33 would withstand continuous dissipation (bigger heatsink, +12V to +3V3, @ 100 mA) I would try this on PSU#2 board: 1. Put a diode 1N4004 across the Q102 2. Remove Q109 and Q113 3. ADC_3V3 line will be served through a reverse diode inside the Q111. ? Would the MC and the FW be happy with that? In this light I would appreciate a choice of using a second type PSU board #2 instead of PSU#2. Comprising of only a linear regulator for 3V3 rail. ? 73 Bojan S53DZ ?
Chris, G5CTH All Messages By This Member #109909 开云体育 I'm currently running my QMX on two linear regulators, a L7805CV for the 5V and a LD33CV for the 3.3V, both TO-220.? This is built onto a small veroboard which just about fits.? I don't have power control but it does work.? Current is 220 mA with the backlight on, 200 with it off. I'll live with that for the sake of reliable power supplies. Chris, G5CTH On 13/09/2023 22:47, Bojan Naglic wrote: toggle quoted message Show quoted text Hi Hans et al, ? My QMX is working fine. Leave it as it is then? Hmmm, as I see supplying the MC from 3V3 SMPS controlled by MC too risky (although it works well, I have to admit!!!) I want to try supplying it from a linear regulator at all times. ? So if the 78M33 would withstand continuous dissipation (bigger heatsink, +12V to +3V3, @ 100 mA) I would try this on PSU#2 board: 1. Put a diode 1N4004 across the Q102 2. Remove Q109 and Q113 3. ADC_3V3 line will be served through a reverse diode inside the Q111. ? Would the MC and the FW be happy with that? In this light I would appreciate a choice of using a second type PSU board #2 instead of PSU#2. Comprising of only a linear regulator for 3V3 rail. ? 73 Bojan S53DZ ?

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