[Moon-Net] IQ+ PREAMP GAIN NEEDED

Alex Artieda hb9dri at emeham.com
Fri Nov 4 05:42:48 CET 2016


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

-----Original Message-----
From: moon-net-bounces at mailman.pe1itr.com
[mailto:moon-net-bounces at mailman.pe1itr.com] On Behalf Of Paul Andrews
Sent: Donnerstag, 3. November 2016 21:46
To: serge
Cc: Les Listwa; Moon-Net
Subject: Re: [Moon-Net] IQ+ PREAMP GAIN NEEDED

Serge,

I think I have the same 2M receive setup as you.   I have dual
polarization antennas (XP28s) and I use the dual channel IQ+ for
adaptive receive feeding MAP65.    I am using WA2ODO high gain (30 db
gain) preamps and 3db splitters to feed my 2M transceiver.  I use WSJT
v10 and sometimes v9.7 for a sanity check.  My transceiver soundcard
is SignaLink.   My IQ+ soundcard is Delta44.   My WSJT v10 runs on a
Win7 PC with i7 CPU.   MAP65 runs on WinXP with older Core2Duo CPU.

I was using an FT-847 but will soon be using a TS-2000X.   I have a
manual switch to feed RX-V or RX-H directly to the transceiver.   I
can also use a manual switch to select TX-V or TX-H.  MAP65 helps me decide
which is best.

I have an uncalibrated version of Linrad but it does not improve the receive
performance of MAP65 because I do not have an impulse noise problem and my
linrad is not calibrated.  :)

----------------------------

Summary - After my 1000+ QSOs on 2M EME during the past year - I am very
often surprised by which system decodes first but I'm learning why this
happens.  MAP65 will decode first if my transceiver is on the
wrong polarization.   IQ+ MAP65 will decode first if the receive
signal is sitting at 45 degrees (-3db).   When the receive signal is
pure V-pol or pure H-pol WSJT will sometimes report a better signal than
MAP65.

For some reason I am always very happy when IQ+/MAP65 and WSJT v10 report
the same signal level because that means (to me) that the IQ+ is set up
properly.

My FT-847 has AGC that can not be defeated without modifying the
radio.   The IQ+ has no AGC and is an excellent receiver for reporting
station noise floor issues.   I have a better 2M EME station because
the IQ+ doesn't lie to me.    If the IQ+ is happy - I'm happy.    If
the IQ+ is happy - MAP65 reports decoded signal reports at very similar
levels to WSJT during Co-Pol receiving.

IMHO - WSJT v10 has the advantage when I'm trying to dig out very weak
traces using Tol 10 Hz.     In my system, I see a significant decode
performance improvement when using Tol 10 Hz or 25 Hz.   Using Tol 10
/ 25 Hz on MAP65 does not seem to provide the same magic.

I'm a believer that WSJT v10 and MAP65 decode with equal performance given
an equal signal.  I am also convinced after a 1000+ QSOs and a
1000+ hours of operation that setting up MAP65 / IQ+ / Preamps /
Splitters / Delta44 and all the associated cables is more susceptible to
noise issues.

My cards are on the table.  Read'em and weep.

73 - Paul - W2HRO   (soon to be QRV - 23cm QRP)























On Thu, Nov 3, 2016 at 4:36 PM, serge <ve1kg at eastlink.ca> wrote:
> Les i have private emails of people who have the same problem as i 
> have with the IQ+ & MAP65.  i am not alone.
> My system is very simple: Preamp to a 90 FT of over kill coax & a 
> Splitter one side goes to IQ+ the other side goes to my 40 years old
transceiver.
> That is it.
> My system works VERY well i am just intrigued why MAP65 & IQ+ does not 
> decode as well as WSJT & My 40 years old receiver that is all.
> I will do the test that Leif suggested & i will have a better idea on 
> what is going on.. Some people have added small rf amplifiers to make 
> up for the losses & to get enough gain to the IQ+.
> I do not use Linrad it is above my level of comprehension so i accept 
> the fact that i have reached my level of incompetence. Having said 
> that even with my somewhat messy set up as you described it I do not 
> miss too much off the moon.
> See you off the moon hopefully
> 73 Serge VE1KG
>
> ----- Original Message -----
> From: Les Listwa
> To: moon-net at mailman.pe1itr.com
> Sent: Thursday, November 03, 2016 7:22 PM
> Subject: Re: [Moon-Net] IQ+ PREAMP GAIN NEEDED
>
> Serge,
>
> There is a less costly alternative to running WSJT and Map-65 at the 
> same time, especially in your case where you are horizontal only and 
> can not take advantage of adaptive polarization.  Right now you are 
> using your Icom for WSJT and the fabulous IQ+ for Map-65 and its  a 
> complicated mess, with a splitter, an addtional relay(?),  and coax  
> adding additional losses, which requires more gain from the preamp, 
> which you dont have unless you replace it.
>
> Learning from W3SZ,  I  use my IQ+ to "drive"  both Map-65 and WSJT at 
> the same time using the magic of Linrad and VAC with the help Trackbox 
> for frequency control. No 2nd receiver or additional hardware needed.
>
> 73
> Les
> W2LPL
>
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