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To Whom It may Interest:

I am working on a high altitude balloon tracking project using the firmware of this project. The mock-up of the circuitry includes the Arduino/SI5351 with a uBlox GPS receiver.

To test the mock-up the SI5351 antenna output feeds to an RTL-SDR.com USB TV receiver at 20m/14MHz. GQRX is my SDR receiver software, feeding WSJTX. I believe my computer time is correct.

When I connect the RTL-SDR to a rooftop antenna, I receive and decode WSPR from several locations, including Europe; I am near NYC. However, when I connect the RTL-SDR directly to my SI5351, I seem to receive the signal all the way through to WSJTX, but it doesn't get decoded.

I'm not sure where to go from here, what to change, or what to test. Any help is appreciated. Some screenshots to settings and current results are attached.

FWIW, Some of the things I have tried:
- calibrating WSJTX to RTL-SDR: slope and intercept
- GQRX Input Hardware AGC and LNA adjustments (off and 0 for direct to SI5351)
- GQRX Audio Gain adjustments (-50dB, 0dB, 50dB)
- GQRX Receiver AGC adjustments (fast and off)


Thx,
Jeff

Hi, it looks like you are listening in on the 10th overtone or something, thats usually what it looks like then, also its way out of wspr band pass but that will probably sort when you get it going like it should be.

Dont know gqrx but as you can decode other stations thats a good indicator that your rx is correctly setup.

First thing that comes to mind, what speed of the xo for the 5351 are you using?? have you checked you have it corresponds to the speed set in the ict fw?

/Mikael

Hi Jeff. //Harry

Hi Mikael,

Thanks for your time.? I think the xo speed was a good hint.? I'm doing a mock-up using the Adafruit SI5351 breakout board.? The board has a 25MHz TXCO, but I noticed that the HABalloon code was set for 27 MHz.? So I made that correction.? Also, someone mentioned that my signal seemed off target frequency, so I looked through the code and found WSPR_FREQ set for 14000000 MHZ, so I adjusted that to be 14095600.? Now I get a signal that seems to be in the filter frequency path.? I believe it may be WSPR, but not sure as I can't seem to find a good Waterfall diagram of a WSPR signal, online.

Still not decoding in WSJTX, however.? Looking at the waterfall, it appears to me that I may be overdriving the receiver, particularly considering the receiver and SI5351 are directly connnected, no antennas.? I'm going to try an attenuator and see what happens.

In the mean time, here are some updated pics of waterfalls.? Thanks for your time.

TY,
Jeff

Hi Harry,

Thank you for your time and response.?

It seems that my signal wasn't at a WSPR frequency, but rather at 14MHz.? I failed to change WSPR_FREQ in the HABalloon code.? Once updated it appears I have a signal right at about 14.0956 MHz.

Screenshots of the updated results are in another posting, if your interested and have the time.

Thank you,
Jeff

Hi, its always hard do say what to do just seeing some pictures but I notice two things, first it looks to me you have to set the correct wspr freq, 14095600 is the dial freq, the transmitted signal is 1400-1600hz up so you need to set something like
#define WSPR_FREQ? ? ?14097120UL, secondly it looks to me the wspr tx is to long, longer then the ca 2min it should take to tx a wspr frame, check that you have set the CTC setting to corresponds to the speed of the xo driving the 328,?

#define WSPR_CTC? ? ? 1334? // CTC value for WSPR //? 10672 @ 16Mhz //5336 @ 8Mhz //2668 @ 4Mhz //1334 @ 2Mhz //667 @ 1Mhz

/M

I heard a program on NPR yesterday about a bunch of scientists using trackers on birds. He said they use a store and forward method using a cell fone chip to dump a days worth of data in a text message to the scientist. It sounded like they were battery powered and used a GPS chip like we do,

Thanks for responding Ken. I'll look more closely at my setup and see if I need to adjust transmit frequency to be in band.