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[Linrad] Re: MAP65 and the SDR-IQ


Even without capture of polarity data, I should be able to capture 
all stations on either pol by switching on alternating 
measurements.  Certainly not as good as the full dual pol receiver 
system, but usable for us SDR-IQ users.

Ed - KL7UW

At 05:40 AM 2/19/2009, Joe Taylor wrote:

>Hi Dom and all,
>You are 100% correct that a big part of the value of MAP65
>is its polarization-matching capability, separately matched
>to the exact polarization angle of every received JT65
>signal.  As has been discussed on this list in the past, in
>some detail, a single channel receiver like the SDR-IQ
>cannot provide such capability.  [Of course, two SDR-IQs
>would also not work, because they could not be properly
>Nevertheless, there is great interest in having a
>single-channel version of MAP65 that is capable of working
>with the SDR-IQ.  There are several good reasons for this:
>1. At 1296 MHz and above, nearly everyone uses circular and
>therefore polarization diversity is not required on receive.
>2. On 144 MHz many people have single-polarization antennas
>and nevertheless want to have wideband panoramic reception
>of JT65 signals, even if it does not have the
>polarization-matching capability.
>3. The SDR-IQ is well engineered, highly capable, and
>relatively inexpensive.
>These are the principal motivations that have encouraged me
>to make a "MAP65-lite", which I have called MAP65-IQ.  The
>program is now happily running in my lab, receiving very
>weak JT65B signals from a QRPP transmitter about a mile
>away, on the dead 10-meter band. A few more details to be
>improved..., but it works very well!  :-)
>The MAP65-IQ screen display looks almost exactly like those
>of MAP65:
>... except that the "measured" polarization angles are
>always zero.
>         -- 73, Joe, K1JT
>f6dro wrote:
> > Hello Joe,
> >
> > in my idea , the greatest interest to use MAP-65 , is when a dual polarity
> > system is  the antenna is use , then , a dual RX system is 
> necessary. I dont
> > think it is possible to use 2 SDR-IQS for dual polarity. If I 
> recall rigth ,
> > even using  commons LO on the V/UHF converters and SDRIQs  , is 
> not enougth
> > , am I rigth? I recall I've asked abt this in a mail a long time ago , and
> > have been replied " common LO's not enougth3 , there are some issues in
> > SDR-IQ ( software , DIGITAL CONVERTERS or what?)
> >
> > 73
> > DOM
> >
> >
> >
> > >

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