Hi Here’s sort of a backwards look at it:
Do you *need* an IF filter in the downconverter? By that I’m asking about a filter better than a simple LC tank. Did they put the filter in the downconverter or in the main box? I would think that putting a fancy filter up by the antenna would have been a less likely thing to do than putting it down in the main box. Bob > On Dec 1, 2015, at 9:48 AM, paul swed <[email protected]> wrote: > > Thanks everyone. The Meinberg is nice and maybe available from Ebay by > Alex's link. But its 35.42 much as the Odetics down converter. I am looking > to create a 75.42 Mhz IF. > Mini-circuits makes just the right parts. But had several IF bandwidths > available. > So will go with the 2 or so MHz filter as suggested. > > I have the typical GPS better quality high gain antenna 1/2" Heliax feed to > a low noise gain block that makes up for the loss of a 8 X splitter. > I may add a 1575 filter ahead of the 10 db amplifier and then hit the > mixer. I think I have a filter. I actually question that I need the filter > or 10 db amp. May build without it to see what happens. Can easily add it. > The LO will be a mini-circuits dsn-2036 followed by a 10 db amp to drive > the mixer another mini-circuit DBM. The IF drives a bpf-a76+ and then will > follow that with 30 db of gain at 75 MHz. > At least thats my thinking. > Regards > Paul > WB8TSL > > On Tue, Dec 1, 2015 at 1:36 AM, Magnus Danielson <[email protected] >> wrote: > >> Hi, >> >> This is a side-track to Pauls original question, but maybe a nice little >> point to make now that Peter touched on the subject. >> >> To elaborate a little on C/A and multipath surpression. >> The multipath surpression of the receiver depends on code rate, bandwidth >> and correlator spacing. P-code is able to surpress more, and the C/A code >> errors look about the same as the P-code, but scaled accordingly. >> Increasing the bandwidth helps to reduce the C/A errors, but taking the >> next step of using narrow correlators further reduces the error. This is >> shown already in the classical Spiliker book, but further readings from >> Novatel could be nice. >> >> Increasing the bandwidth and narrowing the early and late correlator taps >> both have the effect of reducing the time over which energy goes into the >> E-L difference, and hence reducing the impact of multipath into the >> solution. >> >> Cheers, >> Magnus >> >> >> On 12/01/2015 06:00 AM, Peter Monta wrote: >> >>> >>>> What should the IF pass band bandwidth be? >>>> >>>> >>> For GPS C/A with wide correlator, about 2 MHz; if you want Galileo BOC and >>> (eventually) GPS L1C, or legacy C/A with narrow correlator, about 8 MHz; >>> for GPS P code about 20 MHz. Books on GNSS software receivers will detail >>> the many tradeoffs available---if you're starting out with a >>> proof-of-concept lab receiver, go for 8 MHz. >>> >>> Cheers, >>> Peter >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
