[Linrad] Re: Map65IQ and softrock V9

[Jeremy Alexander <w7eme.org; jeremy@xxxxxxxxxxxxxxxx>]

Hi Ed,

If one might be contemplating spending even $2000 towards good rx on 2m, Leif's WSE converters and a good sound card would be the place to drop your money, as then LinRad, MAP65 and plenty of support exists already. Plus the simplicity of hardware, you then also have just One software to deal with as far as the receivers.

Doing this myself I had a Huge learning curve, but once the stitches healed, I couldn't think of using anything else currently available. Plus - oh my gosh the cw ability with these things. 

Jeremy w7eme


--- On Thu, 3/26/09, Edward Cole <kl7uw@xxxxxxxxxxxxx> wrote:

> From: Edward Cole <kl7uw@xxxxxxxxxxxxx>
> Subject: [Linrad] Re: Map65IQ and softrock V9
> To: linrad@xxxxxxxxxxxxxxxx
> Date: Thursday, March 26, 2009, 7:58 AM
> 
> At 03:04 AM 3/26/2009, you wrote:
> 
> >Hi Dom, Edward and all,
> >
> > > >in fact , to obtain full adavanrage what we
> need is a design able to use
> > > >fully Linrad , I mean V and H simultaneously
> and being able to get optimum
> > > >signals any time. WSE RX is perfectly OK ,
> but a bit too expensive for the
> > > >average ham.We need a " dual channel system
> for the poor ham"
> >It should be trivial to modify the Softrock so two of
> them
> >use the same LO. The second thing needed would be one
> more
> >144 to HF converter that is modified to use the same LO
> as
> >the other 144 to HF converter.
> >
> >Why not phase-locking two 144 MHz converters as well as
> two
> >Softrocks to a common reference oscillator with very
> good
> >stability. That would solve two problems at the same
> time:-)
> >
> > > It is true that MAP65IQ only decodes a single
> polarity, but if you
> > > have a dual-pol antenna system, you can switch
> pol on the nezt
> > > sequence and capture any signals that are coming
> in on that
> > > polarity.  I would guess that one would
> sample the spectrum with
> > > MAP65 every 5-10 minutes else you would have
> information
> > > overload.  Activity would not change that
> rapidly that one needed to
> > > capture everything in one minute. 
> Obviously, not as sophisticated as
> > > WSE Rx into dual channel Linrad, but I think it
> is workable.
> >Yes. The problem is that you will loose 3dB at times
> when the
> >signal level is the same in both polarisations. The
> loss is
> >a cosine function with -3dB at 45 degrees. Someone
> might compute
> >the percentage of time you will loose more than 1 dB. I
> would guess
> >it comes out as more than 50%.
> >
> >In a contest the time loss will matter. Weak stations
> that answer
> >your CQ may have to be much more persistant when you
> listen
> >in the wrong polarisation 50% of the time and sometimes
> loose
> >3 dB.
> >
> >There is another thing. In case your noise floor is
> somewhat
> >degraded by high rates of interference pulses, you
> might find
> >that the noise blanker becomes more efficient when it
> can
> >use the information from two antennas.
> >
> >73
> >
> >Leif / SM5BSZ
> 
> Yes, the ability of Linrad to receive H/V inputs and
> display to the 
> resultant pol is an real advantage.  I may end up with
> two 144/28 
> convertors that may be PLL slaved to my 10-MHz Rubidium
> Ref.  Too bad 
> that the SDR-IQ appears to be too difficult to lock to an
> external 
> ref., else I could obtain a second unit.  But if I
> only run one 
> SDR-IQ behind Linrad with full dual-pol input I would be
> able to see 
> display of all signals, but still have the 3-dB penalty for
> decoding 
> JT65 or MAP65iq when pol=45/135.
> 
> My real experience is that doesn't occur 50% of the
> time.  However, 
> when Faraday is very active on 2m considerable percent of
> the time it is.
> 
> I am considering obtaining a K3 with dual Rx.  The
> problem is 
> obtaining wideband output as the final SDR baseband is 
> 18-KHz.  Taping the 1st IF of 8.2 MHz would work but
> this still 
> leaves one with the need for a dual channel SDR-IQ or
> such.  Probably 
> simpler to go straight from 28-MHz into a dual SDR like you
> 
> suggest.  Or i could be satisfied only sampling 18-KHz
> of spectrum vs 
> 95-KHz that MAP65 can do.
> 
> More study needed ;-)
>   73, Ed - KL7UW
> 
> 
> 
> > 
> 

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