Johan, I took a quick look at the Maxim chip.
It looks like the user of this chip is limited to THEIR built in VCO electronics, meaning it might not be suitable for weak signal amplitude modulated signals, but that it is more suited for FM (where the signals tend to be MUCH stronger). Maxim makes some outstanding products, but in the true Maxim style, it appears that they have integrated to many building blocks into the chip, which limits it's application to exactly what they specify and little else. I sure wish they would run inputs and outputs to the outside world so the users could elect to use the chip as Maxim intended or to allow the user to 'roll their own' ...using all or part of the chip if the user needs the additional integration. If that chip had 10 or 12 more inputs and outputs, the users who wanted to use it in CDMA could interconnect the sections of the chip as needed with a simple jumper between adjacent pins. It would also allow us to access the needed sections more directly. That's just my personal opinion, and I don't mean for it to be critical. If I was building an FM rig, I'd probably be overjoyed with the chip as it stands. Thanks for pointing it out though, clearly they do have an integrated QSD that is capable of operating at vhf frequencies.....which is good to know! Art At 12:38 PM 10/23/2005, you wrote: >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 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/
