[Moon-Net] IQ+ PREAMP GAIN NEEDED

serge ve1kg at eastlink.ca
Fri Nov 4 15:52:40 CET 2016


Alex & Roger
I agree that you cannot compare apples & oranges. However if you have 2 
systems & one decodes better & more often
than the other one! you will pick the one which works  best for you for what 
ever reason.
So I am simply comparing RESULTS.
Now i may have a problem with not enough gain at the input of the IQ+ & will 
check it out today. I live in a noiseless location & i mean NO NOISE only 
get noise on very low declinations & the antenna is beaming towards the 
house.
To add to the confusion they will be times when the IQ+ & MAP 65 will decode 
when WSJT & my 40 year old receiver will not. WHY? i have no idea &  that 
iswhyi needboth  systems
Will let you know  RE: gain at the input of the  Q + . that may be an 
important factor as well.
Now as to the many versions of  WSJT . I prefer WSJT 6,WSJT7, WSJT 9.03. As 
to  WSJT 10 i do not like it because it seems to hesitate to decode at .52 
second & if it decodes 2 or more signals it is even worth.
See you on 144MHZ soon on what ever system you use
Serge VE1KG

----- Original Message ----- 
From: "Roger Rehr W3SZ" <w3sz73 at gmail.com>
To: <moon-net at mailman.pe1itr.com>
Sent: Friday, November 04, 2016 12:42 PM
Subject: Re: [Moon-Net] IQ+ PREAMP GAIN NEEDED


> Hi All,
>
> I second everything that Alex sent.  Two of his points bear re-emphasis:
>
> 1.  If you are not using identical hardware feeding identical data to
> both programs when comparing MAP65 with WSJT, then you are NOT really
> comparing MAP65 with WSJT.  You are comparing (hardware-1 and MAP65)
> with (hardware-2 and WSJT), and may get different results than if you
> were truly comparing MAP65 with WSJT.
>
> 2.  If you don't have your hardware optimized then your comparison won't
> reflect what the system in question is really capable of.  Specifically,
> if you don't feed the IQ+ with the signal levels it was designed to use,
> it won't perform optimally.  Running it with inadequate signal levels
> and then being disappointed in the result is like buying a Lamborghini
> Aventador and then running it on diesel fuel and wondering why it
> doesn't perform properly.
>
> I would also add a third comment:
> 3.  I am not aware of anyone who has performed a comparison between
> MAP65 and WSJT using identical hardware feeding identical data to both
> programs who has published data showing a significant difference between
> the MAP65 and WSJT decoding results.  That is not to say that at
> individual stations differences may not be seen between results with
> these two programs.  But it suggests that the differences that these
> stations see is not necessarily due to differences between MAP65 and WSJT.
>
> As most of you know, I did a study using data from the 2012 ARRL EME
> contest which I published online in 2013 including a total of 8805
> decodes that showed what Alex described, namely that the MAP65 and WSJT
> decoders performed similarly.  I went into some detail, and the results
> are still online at:
> http://www.nitehawk.com/w3sz/LinradMAP65Statistics.htm
>
> Alex was too modest to post the link to his excellent paper from this
> year's EME contest, but the slides are online here:
> http://www.eme2016.org/wp-content/uploads/2016/08/EME-2016-ZS6EME-Presentation.pdf
> and the paper is in here, on page 39:
> http://www.eme2016.org/wp-content/uploads/2016/08/EME-2016-Complete-Proceedings.pdf
> I encourage all to read both of these excellent documents.
>
> My results from 2012 are now obsolete because they used WSJT with the
> old KV decoder.  I have started a new analysis using data from this
> year's ARRL EME contest, where I used WSJT-X with the new Franke-Taylor
> decoder instead of WSJT.  Because MAP65 still has the old KV decoder,
> one would expect that there might be a different result from this
> analysis than the result I obtained with the 2012 data.  We shall see :)
>
> This new comparison is of course in one respect comparing apples (KV
> decoder) to oranges (Franke-Taylor decoder). But the comparison is
> really of what the available version of MAP65 will be able to do for a
> user compared to what WSJT-X will be able do for a user.  In that
> respect the comparison is of apples to apples.
>
> Of course, this new analysis will also become obsolete when the
> Franke-Taylor detector is added to MAP65 or its updated replacement, and
> then another analysis will need to be done.  I hope that the need for
> that analysis will be very soon!
>
> 73,
>
> Roger Rehr W3SZ
>
> On 11/4/2016 12:42 AM, Alex Artieda wrote:
>> Dear Friends
>>
>> With great interest I'm following this post and with special attention 
>> the
>> observations done by Serge, Les and both Rogers, this topic is not new, 
>> for
>> that reason during the las EME Conference in Venice I present a properly
>> setup to compare WSJT vs MAP65 or any other software.
>>
>> I will not re-write what is already printed in the proceeds of the
>> Conference but I will point to some key elements:
>>
>> 1) Again "IQ+ DONT DECODE" is just the receiver presenting the Analog 
>> signal
>> properly amplified to your ADC, means your audio card.
>> 2) The IQ+ is designed to lift the noise floor 16dB when a preamp with 
>> 26dB
>> gain is in front, the properly test is remove the antenna from the preamp
>> input and place a 50ohm dummy load on the preamp input, if you power 
>> on/off
>> the preamp under this condition the noise floor MUST lift 16dB, if not: 
>> your
>> preamp is defective or has not enough gain, your attenuation after the
>> preamp is too high, your audio levels in your audio card are not properly
>> adjusted or your internal preamp in the IQ+ is defective. Could be just 
>> one
>> or more or all this options together.
>> 3) Splitting your RX line can be done always with a CERO DEGREE 2 way
>> splitter, you must split the signal preserving phase and resulting with 
>> same
>> amplitude on both output ports, normally 3dB less. A simple BNC TEE; IS 
>> THE
>> WORST, DONT USE THAT.
>> 4) The properly setup is if you use Linrad as input and then you send the
>> digital signal to MAP65 and WSJT, then your comparison will be valid 
>> because
>> you are presenting the same signal coming from the same receiver.
>> 5) Here are my conclusions presented in the EME Conference in Venice 
>> after
>> many years of observations and thousands of QSO in 144Mhz with both 
>> systems
>> running in parallel n HB9Q:
>> ___________________
>> IS WSJT BETTER THAN MAP65?
>>
>> I don't' think so, what I believe is both programs behave (in terms of
>> decodes) pretty much the same and if exist a difference is not more 
>> than1%.
>> How both software can decode "the same" when WSJT is looking just for 
>> 4KHz
>> of bandwidth and MAP65 90 KHz.? I think exist a trade-off compromise 
>> about
>> Wide-decoding, sensitivity and confidence to avoid false decodes.
>> Maybe is a matter of interpretation and your goals you establish about
>> performance. What is clear is sometimes WSJT decodes when MAP65 doesn't 
>> but
>> I see many times the inverse relation when MAP65 beat WSJT in very low 
>> SNR
>> ratios, is very difficult (and non-professional) to just assume WSJT is
>> better than MAP65.
>> I think, and this needs to be confirmed in the next years (when enough 
>> data
>> is collected and analyzed properly with the correct Methodology and
>> Metrology), in some specific cases WSJT, under Multi-polarization
>> configuration, decodes when MAP65 not. These specific cases are
>> statistically very small (less than 1% for SNR -27 to -30dB) but if those
>> particular cases are in relation with a new DXCC or rare grid then the 
>> value
>> to implement such a complex system is tremendous and corresponds to each
>> individual to evaluate and balance the cost/benefit of this system. Not
>> because the differences are less than 1% we will neglect that differences
>> exist, especially when pushing to the limits our software and Hardware 
>> could
>> be translated in just 1 DXCC more in your list, is a matter of individual
>> decision I guess.
>> __________________
>>
>> 73 de Alex, ZS6EME
>>
>
>
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