It turns out I was using the wrong modulation envelope for the phase transition. The best IMD figure I could get with it was -18dB. This has now been fixed (program attached). The signal (all zeroes) now shows an IMD of -42dB:
Another issue was signal level. At full scale, the Propeller audio output will overdrive the PC's line-level input and get clipped. So I added an attenuator to the PASM code. The IMD figure was obtained with a 12dB attenuation setting in the program.
As it turns out, doubling or quadrupling the sample rate and interpolating the table values had no benefit. But I've left the interpolation code in the program to experiment with.
-Phil
_
Post Edited (Phil Pilgrim (PhiPi)) : 1/24/2010 6:22:20 AM GMT
Well I was called out too much lately but I got around the stuck point, using memory relative to the stack
instead of DAT. I'm not transmitting yet but certainly thinking about a standalone QRP rig. The tables are
synthed but according to the display, well, there are two issues. At the moment the display is a good
representation of the synthed signals because the 128 points fit on screen. Upon seeing the results I
want more definition, even though the quantization noise probably won't get through the filter.
I didn't have to waste time on the gui display style because I already made it for a sci-fi control panel.
But I don't think it is of any use to post my code yet until it transmits, since it is a mess.
I meant to say that upon seeing the results, everything is redundant, and I can make a cleaner signal
with even less memory because everything is just upside down and backwards of everything else.
I think the display is nice but not sure if it is better with or without it IF I FINISH THE RADIO.
Until then, it is good for debugging the math, and in using the radio it would be great to have a spectrum
to pick signals with, so I would like to try to do that.
Still don't wait for me, lets all make our own, because the more radios in the shack, the better.
I assume that the signal tends to be in one phase but switches to the other and back every time a
zero is sent? I'm still not sure but that's my guess. It might be easier to see how others implement
receiving also, instead of guessing how it's done. If only zeros are out of phase, and the message
is biased (not a fair coin) then it is probably doing something like locking to one phase and detecting
out of phase. I guess I'll be looking that up. Anyway here is what I did so far, only synthed the signal
phases into memory and plotted them on a TV screen. Sorry, the cam has less picture quality than
the TV does. I hope I attached something because there is no indication on this post itself that it is
attached (photos only). Not looking good on preview. Attachment manager says it it there though,
so here goes it.
Para ti no habrá sol, para ti no habrá muerte, para ti no habrá dolor, para ti no habrá calor, ni sed,· ni hambre, ni lluvia, ni aire, ni enfermedad, ni familia.Nada te causara temor, todo ha terminado para ti, excepto una cosa: HACER TU TRABAJO. En el puesto que has sido asignado, ahí te quedaras para la defensa de tu nación, de tu gente, de tu raza, de tus costumbres, de tu religión.! Juras cumplir con el divino mandato AHUI....!
Comments
http://www.moetronix.com/ae4jy/winpsk.htm
Thanks!
-Phil
Another issue was signal level. At full scale, the Propeller audio output will overdrive the PC's line-level input and get clipped. So I added an attenuator to the PASM code. The IMD figure was obtained with a 12dB attenuation setting in the program.
As it turns out, doubling or quadrupling the sample rate and interpolating the table values had no benefit. But I've left the interpolation code in the program to experiment with.
-Phil
_
Post Edited (Phil Pilgrim (PhiPi)) : 1/24/2010 6:22:20 AM GMT
instead of DAT. I'm not transmitting yet but certainly thinking about a standalone QRP rig. The tables are
synthed but according to the display, well, there are two issues. At the moment the display is a good
representation of the synthed signals because the 128 points fit on screen. Upon seeing the results I
want more definition, even though the quantization noise probably won't get through the filter.
I didn't have to waste time on the gui display style because I already made it for a sci-fi control panel.
But I don't think it is of any use to post my code yet until it transmits, since it is a mess.
I meant to say that upon seeing the results, everything is redundant, and I can make a cleaner signal
with even less memory because everything is just upside down and backwards of everything else.
I think the display is nice but not sure if it is better with or without it IF I FINISH THE RADIO.
Until then, it is good for debugging the math, and in using the radio it would be great to have a spectrum
to pick signals with, so I would like to try to do that.
Still don't wait for me, lets all make our own, because the more radios in the shack, the better.
I assume that the signal tends to be in one phase but switches to the other and back every time a
zero is sent? I'm still not sure but that's my guess. It might be easier to see how others implement
receiving also, instead of guessing how it's done. If only zeros are out of phase, and the message
is biased (not a fair coin) then it is probably doing something like locking to one phase and detecting
out of phase. I guess I'll be looking that up. Anyway here is what I did so far, only synthed the signal
phases into memory and plotted them on a TV screen. Sorry, the cam has less picture quality than
the TV does. I hope I attached something because there is no indication on this post itself that it is
attached (photos only). Not looking good on preview. Attachment manager says it it there though,
so here goes it.
a few days i found a good tool for·the math for analyze audio, and a good spectrum viewer
·http://www3.cs.utwente.nl/~ptdeboer/ham/basicdsp/
thats is free, and work great.
Yo can make radio decoder i/q, filter
Maybee can usefull for you.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Juramento YAQUI.
Para ti no habrá sol, para ti no habrá muerte, para ti no habrá dolor, para ti no habrá calor, ni sed,· ni hambre, ni lluvia, ni aire, ni enfermedad, ni familia.Nada te causara temor, todo ha terminado para ti, excepto una cosa: HACER TU TRABAJO. En el puesto que has sido asignado, ahí te quedaras para la defensa de tu nación, de tu gente, de tu raza, de tus costumbres, de tu religión.! Juras cumplir con el divino mandato AHUI....!
Luis C. Yepiz
XE2NBW
·