[time-nuts] GPS down converter question

[paul swed]

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 <magnus at rubidium.dyndns.org
> 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
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