开云体育

Single Messages Topics Expanded Polls

Re: WSPR on 28MHz

Hans Summers #1134 Hi Andy Thanks for doing the experiments. But can you confirm pls -? 1) On 10MHz (or some frequency where we think it is working Ok), you should see a ramp which goes from 0Hz shift to 5.5Hz shift, in 12 steps of 0.5Hz height, and 5 seconds duration. Then the cycle should repeat.? 2) So what we should expect to see on 10m is something similar - but you're saying that we don't, we see some number of discrete tones, which seems to depend also on the frequency.? Is my understanding correct? If so, and particularly given that the tones seem to depend on what frequency you are sending, it seems to imply some sort of numerical precision issue in the arithmetic. Which at least tells me where I need to be looking, in the code, so this is very useful. Regarding the frequency counter - I went through all this in my testing, and for a while I thought that I had made some mistake in the code etc., the frequency counter looked unstable.? Yes, in the U1 it will glide. The reason is that in the U1 the frequency shift is kind of generated in an analog way - there is a Pulse Width Modulated output from the processor, which is averaged in a resistor-capacitor integrator, and applied to a varicap diode (reverse-biased LED) to create the frequency shift. The resistor-capacitor averaging makes the frequency SLIDE to its new value, not cut suddenly. In the U2, the frequency is generated digitally in the DDS. When the frequency is changed, there appears to be a short gap in the output of the DDS while the new frequency is being updated. The gap is very short. But if you are very local, i.e. blasting your receiver from right next to it, then yes, you will hear the click. And see it on Argo. I puzzled over strange frequency counter readings for a while, but I was able to prove conclusively that the frequency counter is only jumping around because of that frequency transition being sudden, not smooth.? I may be wrong, but my feeling currently is that the "sudden" frequency transitions are not a problem. Yes, you can hear the click when receiving a local transmitter, and yes the frequency counter jumps, and yes it isn't like the smooth glide on the U1. But I don't think any of these things are unexpected, or unreasonable, or unacceptable when it comes to WSPR decodes etc. Furthermore I don't see any way around it anyway! 73 Hans G0UPL toggle quoted message Show quoted text On Sun, May 19, 2013 at 9:33 AM, andyfoad@... <andyfoad@...> wrote: ? --- In QRPLabs@..., Hans Summers wrote: > So it should be 050123456789AB for the described ramp. I've done the ramp test. Results are here: It only confirms my previous findings :-( 1) At one chosen frequency in 28Mhz I see 4 tones, but they done ramp. The final one goes lower. 2) I then choose another random 28Mhz frequency up about 10Khz (not really counting) and now I get only TWO tones. 3) A third random frequency gives me an even weirder result. Three tones but one look like it's being split up if that makes sense. So it does look like all the observations about not seeing certain bit streams (I'll call them that for now) in WSPR look to be true. I have not exhaustive tests yet but I tried - 30m, I saw four tones that seemed quite ok. Got superb on air results! 17m, I saw three tones. 10m, I saw all sorts of tones depending upon the selected frequency. One other thing I note. I have a frequency counter here which I use to also set up the U1. When that changes frequency, as FSK or WSPR my counter `glides` to the required without any problems. The same cannot be said about the U2. During frequency changes it has trouble keeping steady. A sort of electronic Delirium Tremens, which probably explains the spikes that me and Eddie see on our traces. Hope this helps Hans. 73 de Andy

View All 13 Messages

#1134

Join [email protected] to automatically receive all group messages.