Change WSPR Receive window -Question

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Change WSPR Receive window -Question

Postby VK2XTC » Sun May 10, 2015 12:08 pm

Hopefully this is a quick answer,

How do I change the WSPR receive window so that I can decode outside of the normal WSPR band ?

I have a signal coming up on 6M that is very local to me and I would like to work out who it is.
It's outside of the WSPR "Green" receive band.

How do I wary the Receive band so I can decode this signal?

Picture Attached .
Screen Shot 2015-05-10 at 11.59.51 am.png
6M signal on WSPR Freq - Who is it ?


Brian

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Re: Change WSPR Receive window -Question

Postby VK3ZTE » Sun May 10, 2015 12:34 pm

G'day there Brian

I may be missing the point, but have you tried simply tuning your receiver down a couple of hundred Hz?

Hoping I'm not telling you how to suck eggs.

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Re: Change WSPR Receive window -Question

Postby VK2XTC » Sun May 10, 2015 12:52 pm

As soon as you hit enter you get that thought , "maybe if I did ...."

Well I answered my own question. change the RX BFO and the window adjusts accordingly.

Screen Shot 2015-05-10 at 12.46.23 pm.png


Grant, good answer , that would have done it also. (yes, I hadn't thought about that !)

But , I thought the RX window for WSPR was a convention , else we wouldn't hear each other and the spots would not have been reported.
I though the default of 1500 was the norm.

Did I have that wrong ?


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Re: Change WSPR Receive window -Question

Postby VK3ZTE » Sun May 10, 2015 2:32 pm

Yes Brian, my understanding is that SSB BFO frequency offset of 1500Hz is pretty much universal in commercial transceivers. On the related issue, however, from what I've seen (on 2m at least) there is the odd transmission that falls significantly outside the designated 200Hz WSPR window and if we are to decode it, we need to compensate one way or another at the receiver. Seems like, providing the off frequency WSPR transmission is within the rx IF, moving the BFO will do the job. If it is falling outside the IF passband, then retuning may be required.

hoping this doesn't sound like nonsense

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Re: Change WSPR Receive window -Question

Postby VK2XTC » Sun May 10, 2015 4:33 pm

Grant,

No that sounds fine. I still wonder why send a WSPR signal outside the decode band, when the purpose it be be heard and decoded. Everyone else would be using the default.
I've been able to decode it and sent a PM to them to ask.
They may end up here to answer it.

It's a Big signal , odd harmonics , the trace seems to have an arm, you can see images of the trace higher and lower than the original in the waterfall.
I wonder if thats my receiver or the transmitter that's effecting signal purity.
I've not seen my transmit signal so don't know what it looks like. It may be my setup.

Anyway, it's been answered for now.


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Re: Change WSPR Receive window -Question

Postby VK3ZTE » Sun May 10, 2015 4:59 pm

No worries Brian. As regards transmitting off frequency, more than likely, it's not intentional. Calibration errors of up to 50Hz seem relatively common, and I suspect some kit is worse still. Not sure if yours is locked to a high accuracy standard such as GPS? If not, it's possible that part of the error you are seeing could be at your end? And, regarding your comments about the big trace having an arm, that sounds like it might be an aircraft reflection showing some Doppler. Finally, on the image traces, on big signals I often see images at +/- 50Hz (ie above and below) the real trace. I put it down to funny business in my sound card although backing off the audio level doesn't seem to help greatly so I don't really know. I suppose too, it could be in the sound card at the source end!

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Re: Change WSPR Receive window -Question

Postby VK2KRR » Sun May 10, 2015 7:15 pm

Yep, as Grant said, I would just use the radio's RIT control to tune the rig up or down slightly on RX to find out who it is.

As the WSPR window is only 200 Hz, some radios will not be accurate enough to be inside the window. Need a good calibration or accurate 10 MHz lock. Alternatively if you know someone whos rig is GPS locked you can check how accurate your rig is when receiving their sig or getting them to decode you.

Also the signals you see on your graph angled off from the main signal are reflections from aircraft flying between you and the TX station. So the TX station should be within about 500 Km I'd say to see signals with those doppler shifts.
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