[Lowfer] WSPR-15 tonite

Wed Feb 6 13:46:27 EST 2013

I've been watching this thread for a while now ... here's my 2 cents. BTW, I've changed the subject 
line to one more in line with the discussion.

No, Pat, I don't think you have a screw loose ;~) ... don't forget I'm in the 'near field' of this 
signal and see 'crushing' levels as well ... even with directional antennas pointed the other 
direction!

First a comment about receiving setups. It really shouldn't make any difference whether one uses the 
R-75 for direct reception or a setup using the converter ahead of the receiver ... at least as far 
as WSPR overload is concerned. The 200 Hz WSPR bandwidth is contained within the boundaries of both 
the R-75 roofing and i-f filters. The overload is occuring within this area. In terms of the 
likelyhood of what's causing the problem I'd guess ... E probe (not likely), converter (not likely, 
but not completely ruled out), R75 (not likely especially since the K3 produced similar results), 
A/D (possible depending on wherther it is a quality external sound card or 'onboard' audio junk) and 
software (probably the most likely). This assumes that no noise blanking, noise reduction, clipping, 
compression etc is in use - these are known bad things that cause overload.

If there are visible 'phantom' products in the waterfall (as I sometimes see here) this overload is 
probably some sort of IM or 'image', and it should be possible to make two tone measurements to 
determine the offending component by inserting attenuation between each of the major system 
component and observing the overload level.

Jay W1VD  WD2XNS  WE2XGR/2

----- Original Message ----- 
From: "pbunn" <pbunn at matrixei.com>
To: "Discussion of the Lowfer (US, European, &amp; UK) and MedFer bands" <lowfer at mailman.qth.net>
Sent: Wednesday, February 06, 2013 9:57 AM
Subject: Re: [Lowfer] WSPR-15 tonite

> John,
>
> There seems to be a problem with strong signals and WSPR.  Eric has emailed me and seems to think 
> that the problem is with my R75 but I don't think so. I realize that an R75 has poor strong signal 
> performance but I have a very strong receive converter ahead of my R75. I use a mini circuits +17 
> DBM with a 7 pole filter in front and a GPS disciplined LO followed by a good diplexer and a 
> Norton lossless FB post amp. Last night I could clearly hear a weak XSH/6 QRS3 in the background 
> when Bob was transmitting. I made an audio recording of it. Bobs signal was not blocking.
>
> My WSPR panel gain had to be set  to where I had no green bar at all in order to decode Jay and 
> Eric. The background was jet black.
>
> I have a K3 that I could use as a receiver but in tests I see little difference. Jay asked me this 
> weekend why I was transmitting WSPR -15 at 468 KHz and I responded to "get away from the strong 
> signals"
>
> I think he thinks that I have a loose screw, but from my experience, if you have powerful signals 
> in the band pass or nearby, WSPR does not perform well.
>
> Thanks for the comment. This sure is fun. More fun than I have had in a long time with radio.
>
> Pat
> N4LTA
>
>
>
> -----Original Message-----
> From: lowfer-bounces at mailman.qth.net [mailto:lowfer-bounces at mailman.qth.net] On Behalf Of John 
> Andrews
> Sent: Wednesday, February 06, 2013 9:45 AM
> To: Discussion of the Lowfer (US, European, &amp; UK) and MedFer bands
> Subject: Re: [Lowfer] WSPR-15 tonite
>
> Pat,
>
> I had something similar with Jay last evening. Very strong signal, and several missed decodes. At 
> least one was in a period where XGR/6 was off. Was running AGC on the R75, so it certainly wasn't 
> a receiver overload issue.
>
> John, W1TAG
>
>
>
> On Feb 5, 2013, at 10:58 PM, <pbunn at patbunn.com> wrote:
>
>> I have been running WSPR-15 since last night. When Gary noted that
>> someone was in the middle with a drifting signal, I went out to the
>> shop to see if I could see the signa
>>
>> What I saw was a surprise. I have not touched any gain setting since
>> last night and have been getting good decodes until recently.
>>
>> The screen shot shows what I found and shows where I reduced gain to
>> the point that very little noise is showing ( and very likely no weak
>> signal would be seen)
>>
>>
>> The screen can be seen at
>> http://i620.photobucket.com/albums/tt286/n4lta/wsprscrn_zps392e4d37.gi
>> f
>>
>> The screen is split between when I first found it first smeared in
>> red, my first gain reduction and then a further adjustment.
>>
>> The far left is Bobs WSPR 2 signal
>>
>> There is no noise here tonite to speak of. The S meter on the R75 is
>> below
>> S1 (no bars on the S meter) and goes to S4 when Bobs signal comes on.
>>
>> The gain setting was initially set last night and worked fine all
>> night with numerous decodes.
>>
>>
>> Something is unusual with WSPR and strong signals, and I am pretty
>> certain it is not my receiving equipment. I can hear the WD2XSG/6
>> beacon in the background at the same time Bob is transmitting. He is
>> not blocking the radio front end.
>>
>> Pat
>> N4LTA
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