Hi, I found recently a chip of maxim; the max2314.
Input is possible from 40 -150 Mc and delivers an IQ signal. Maybe this will help in getting to VHF. 73 Johan PA3GSB --- In [email protected], KY1K <[EMAIL PROTECTED]> wrote: > > Hi Alberto, > > I've seen that switch, and it looks like the dead short or the 50 ohm > termination is a problem. Since the switch does not present a high > impedance during the time it's open, there is no way to avoid having > it discharge (or drain) the integrating caps, so they can't function > as a sample and hold. > > Also notice that the turn on vs turn off time varies, it turns on in > 3.6 nS and it turns off in 5.8nS. This isn't going to work well since > 1 cycle of 144 MHz is 7 nS. While the switch passes 144 MHz, it won't > turn on and turn off fast enough to be usable at 144 MHz. > > IF (and it's a big IF) we could slow down the on time transition, it > might be usable. If it would turn on in 5.8 nS and turn off in 5.8 > nS, it would be good, provided the other switches could operate with > the same on and off times (switching times are all consistent). > > I've chatted with AD about these issues, there is no way to burn out > the 50 ohm resistors to effectively remove them from the circuit. > There is no comparable analog switch made by them that does function > properly (for us). They are NOT planning or designing a suitable switch. > > I talked to a friend who designs cmos about the consistency problem. > It is a relatively simple task to equalize the switching times IF > 'adjustability' is a design goal. But, it is very expensive to make > the masks necessary to do the fabrication of the parts. Without a > major demand for switches with consistent (equalized) on/off times, a > suitable switch will never be built. > > I have some ideas about how to control the switching speeds and would > love to chat with anyone interested in QSD at vhf. Talk to me off > list, as the subject might be off topic for this group. > > Art > > > At 06:13 AM 10/23/2005, you wrote: > > >I know that a few of you are considering the idea of building a QSD > >directly at 144 MHz. I have just received an Analog Device bullettin > >with the specs of a new high speed analog switch. > > > >Maybe it is worth investigating its suitability for that application. > > > >http://www.analog.com/UploadedFiles/Data_Sheets/847169922ADG901_2_b.p df > > > >73 Alberto I2PHD > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
