Very Low sYnus Ocs

Hi all

I need to design and buid a very low freq synus oscilator/ It showld work at less then 1Hz .

How this would be done ?

Thanks BarNash

Reply to
BarNash
Loading thread data ...

Do you mean a sinus generator? There are many informations missing for a useful answer:

- do you need just a fixed frequency? If not: the exact frequency range and how do you want to adjust it?

- the maximum allowed harmonic distortion

- output: voltage or current? If voltage, how much current do you need?

- how exact do you need the frequency? Longterm stability? Temperatur stability?

A very simple generator with a PIC (you can use nearly any PIC for this simple program), adjustable with a trim-pot, but maybe not very exact:

formatting link

It's in German, but the Google translation is not too bad:

formatting link

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
Reply to
Frank Buss

I need this oscilator for controling a volume output of a MORSE code parctrice oscilator.

The idea is to simulate real fading in CW receivers in real time .

Thanks BarNash

"Frank Buss" ??? ??????:1fdcyrdf1bx22$. snipped-for-privacy@40tude.net...

Reply to
BarNash

I don't know how the fading looks like, but the spectrum in the article in Wikipedia looks more complicated than a simple sine wave:

formatting link

But you could use a microcontroller to create random numbers, which are fed to a digital lowpass filter and which is used for a PWM, like used in my sine generator. This could be a more realistic fading simulator.

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de
Reply to
Frank Buss

If you intend to model selective fading, in which the components from different paths cancel out each other briefly, the abs(sin(x)) would be more realistic than just sin(x). The abs(sin(x)) will create nice deep narrow nulls.

Taking the unfiltered PWM from a MCU could be used to chop the audio path so no voltage controlled amplifier is required.

Paul

Reply to
Paul Keinanen

If you use just a sine wave to modulate the audio tone, then you should use a 4 quadrant multiplier (such as 1496) as the signal is muted at sine wave zero crossing, and the audio tone will reappear with inverted phase for negative values of sin(x).

Attenuating the audio tone may be a realistic alternative for receivers without AGC (such as most home brew direct conversion receivers), in which the audio level drops, when the signal level drops.

However, a receiver with good AGC will keep the audio tone more or less constant, fading can be detected by the increase of the noise level, which will finally swamp the audio tone. To simulate a receiver with good AGC, let the audio through and amplitude modulate a noise source with something like (1-abs(sin(x))), which will give strong noise bursts, when the signal drops very low.

Paul

Reply to
Paul Keinanen

border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.de!t-online.de!news.albasani.net!weretis.net!feeder2.news.weretis.net!feeder.erje.net!195.197.54.118.MISMATCH!feeder2.news.elisa.fi!uutiset.elisa.fi!7564ea0f!not-for-mail

Real CW ops don't use AGC. They turn AGC Off, Turn the AF Gain all the way up and control the volume with the RF Gain. They put the phones on their head in front of, not on, their ears. Their attention focuses on the pitch of the signal which they follow right down through the interference and into the noise. Volume doesn't matter.

Ken Fowler, KO6NO

Reply to
Ken Fowler

It's easy to build a triangle-wave oscillator, at this frequency range, and one can play tricks (like the XR2206 waveform generator chip does) to make it more sinusoidal.

True sinewave generators are tricky; the classic HP200 generator, for instance, won't work well at such a low frequency. Digital synthesis (using a lookup table, counter, and DAC) is possible, of course.

Reply to
whit3rd

border1.nntp.dca.giganews.com!nntp.giganews.com!newsfeed00.sul.t-online.d= e!t-online.de!news.albasani.net!weretis.net!feeder2.news.weretis.net!feed= er.erje.net!195.197.54.118.MISMATCH!feeder2.news.elisa.fi!uutiset.elisa.f= i!7564ea0f!not-for-mail

way

their

pitch

You are describing accomplished operators. The device described is for training beginning to early intermediate operators. I think that the varying S/N ratio is a better approach though.

Reply to
JosephKK

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.