[Moon-Net] IQ+ PREAMP GAIN NEEDED

Edward R Cole kl7uw at acsalaska.net
Wed Nov 2 19:16:43 CET 2016


Serge,

First off the preamp gain is labeled 26-dB?  How high does s-meter 
read with preamp on?

90-foot of 1//2-inch hardline is 0.88 dBx0.9=0.79 dB loss (not 3-dB) 
so you should have 25-dB net gain at the 3-dB splitter and 22-dB to 
each receiver (quite adequate for most radios - Alex will have to 
respond about needs of the IQ+).  I seem to recall that one needs 
minimum of 17-dB gain ahead of the IQ+ (which you have).

Have you ever run MAP65 with the IQ+?  What audio level is seen in 
the vertical bar meter on left side of MAP65 main window?  If at 
least 20-dB its is sufficient gain .  Have you ever compared MAP65 
with WSJT7?  Have you tried WSJT10?

I stopped using WSJT7 probably 6 or more years ago.  I run WSJT10 
r4336 on both 6m & 23cm, and run MAP65v2.4.1, r2587 on 2m.  All 
decode to -28 and occasionally down to -30.  All dependent on local 
noise and sky temp.  When my local noise runs S8 even -1 signal will 
not decode (normal reading with my preamp on is S3).

6m is run with aggressive deep search with averaging since I have 
very small antenna for that band.  On other two bands I have both 
tried deep search and without DS, seeing no significant difference in 
decoding ability.  My call3.txt is several years out of date which 
probably why.

Without knowing how you performed setting up the IQ+ not much we can 
tell you.  Decoding JT65 signals depends on statistics (simple 
answer) so you roll the dice and one receiver gets snake eyes and the 
other seven or eleven (don't ever invite me to throw the dice for you 
at Las Vegas).

73, Ed - KL7UW

At 08:38 AM 11/2/2016, serge wrote:
>Hello Folks over the years folks have been telling me I need at 
>least 26db at the input of the IQ+ i only have at the most 20db & 
>the IQ+ rarely decodes below -28db. I am using WSJT7 as well which 
>decodes more often than the IQ+ but NOT ALL THE TIME.
>So on the same computer i have the IQ+ with delta 44 & WSJT with the 
>signalink sound card to receive & who ever decodes first i TX with & 
>it is OK. I could put an extra preamp in line before the splitter 
>but then i would need probably a 15 to 20db attenuator not to 
>overload the IQ+ & WSJT it just does sound practical.
>I would like to get feedback from people who use the IQ+.
>I have a 26db preamp to 90 feet 1/2" hardline to receive It goes to 
>a splitter so i loose 3db plus the loss in the cable & connectors 
>may be at the most 2 to 3db so i am left with 20db at the input of 
>the IQ+ may be not enough
>
>The eternal question has been for me WHY is WSJT7 decodes lower & 
>more often than the IQ+?????????????
>BUT not always. Sometime the IQ+ will out decodes WSJT so i guess 
>you have to have both
>Serge VE1KG
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73, Ed - KL7UW
http://www.kl7uw.com
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