I agree with you I sent a private email to him stating that the switches are not fast enough.
They would be usable in the circuitry to turn front end components on and off such as a prea-mp or doing TR switching. At 11:02 AM 10/23/2005, KY1K 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.pdf > > > >73 Alberto I2PHD > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > >-- >No virus found in this incoming message. >Checked by AVG Free Edition. >Version: 7.1.361 / Virus Database: 267.12.4/146 - Release Date: 10/21/2005 Cecil Bayona KD5NWA www.qrpradio.com I fail to see why doing the same thing over and over and getting the same results every time is insanity: I've almost proved it isn't; only a few more tests now and I'm sure results will differ this time ... ------------------------ 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/
