Hi Frank, thanks for clarifying your question
--- In [email protected], FRANCIS CARCIA <[EMAIL PROTECTED]> wrote: > > Hi, > I was thinking about discrete switching devices like a good fast transistor that operates at a lower base voltage rather than logic levels. I do not know but you need good fast switching transistors in a single chip. Probably you will need power to drive them and maybe they will not have a low Ron... maybe some other problems too. > Another thing I was considering was going back to using an SD5000 with two AC cmos gates driving a transformer in bridge mode to get higher gate swing rather than 7 volts on a flip flop. frank Well you can try .. the SD5000 was replaced by the FST3125 because it was needing a very high switch on gating voltage, a substrate voltage and it had a very had conversion loss over 8dB plus complex gating balance adjustment. Not a hot front end ... FST3125 gives the H-Mode Mixer (and others) a KISS solution, simple driving no adjustment except squarer balance unless IP3 around >+35dBm vs 40+ is OK you can avoid balance adjustment, and vy important a very low conversion losses <5dB !!!! and lower noise than SD5000 solution. Finding a better solution is welcomed ... that's why we should share ideas .... The QSD did get a benefit by my idea of using Fast Bus Switches for mixers. 73 Gian I7SWX > Giancarlo <[EMAIL PROTECTED]> wrote: > --- In [email protected], FRANCIS CARCIA <carcia@> wrote: > > > > Anybody ever try using 2N5109s in an Hmode mixer with RF drive. > Frank WA1GFZ > > > > Hi Francis, > > I am not sure I understood your question... do you mean if anybody > has tried an RF amp at the H-Mode Mixer RF input? > > If this is the question.... an H-Mode Mixer is a Hot device (vy low > conversion losses <=5dB. In low HF bands you do not need preamp as > the requirements vs band noise are strong to IMD. In high HF bands > you may be OK with a preamp where you may require also sensitivity > and you can be OK dropping the IP3 from +40dBm(+/-) to >+30dBm. > A low noise lossless feedback RF amp using 2N5109 should be OK. Keep > gain not higher than 10dB and with the highest IP3 possible. > I have an low noise RF preamp in my overmodified IC751 with a 14dB > gain replacing the original Icom pre- using 2x BFR91 in parallel. No > problems... I usually keep it off. > > 73 > > Gian > I7SWX >
