beat freq method
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Trying to set the freq cal for the reference using method 2 since I do not have a freq counter. I may be tone deaf or something but I am not sure what the beat-freq sounds like. Wish someone would post or send a sound file demonstrating the beat freq when off, close and good sounds like. I tried setting it on 15mhz and thought I was close but when listening to WWV on 10mhz had to go down 300 hz to understand the voice transmission. Also 15mhz voice was "fuzzy" until I tuned off freq about 100hz. Guess I am confused at this point. I do understand that this really just adjusts vfo's so when at band edges I do not go out of band. However when using DX spots with N3FJP auto tune clicks I am off freq. Have to dial around to get clear signal so if I don't then they do not hear my calls well. Am sending this message to K3 support a well but appreciate any responses from the community.
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If your tone perception needs assistance, try using an audio spectrum
analyzer on your computer - I use Spectrogram (download from Tom Hammond's website www.n0ss.net), but others like Specravue or Spectrum Lab will work just as well. Tune in WWV - make certain you are tuned to the carrier - use CW mode (you will not be able to understand the voice in CW mode), and adjust the VFO so the carrier is quite near the audio pitch of your sidetone. Now turn on the sidetone, and adjust the AF gain so the sidetone level is about the same as the tuned carrier. You will see both tones on the audio Spectral display - when they are close to each other, listen for the 3rd tone. Its pitch will be the difference between the other two and results in a slow rising and falling in amplitude of the other two tones. When that rising and falling slows to zero, that is zero beat. Once you know what it sounds like, do the Ref Cal as indicated in the manual. 73, Don W3FPR On 3/28/2011 1:31 PM, jrstorms wrote: > Trying to set the freq cal for the reference using method 2 since I do not > have a freq counter. I may be tone deaf or something but I am not sure what > the beat-freq sounds like. Wish someone would post or send a sound file > demonstrating the beat freq when off, close and good sounds like. I tried > setting it on 15mhz and thought I was close but when listening to WWV on > 10mhz had to go down 300 hz to understand the voice transmission. Also > 15mhz voice was "fuzzy" until I tuned off freq about 100hz. Guess I am > confused at this point. I do understand that this really just adjusts vfo's > so when at band edges I do not go out of band. However when using DX spots > with N3FJP auto tune clicks I am off freq. Have to dial around to get clear > signal so if I don't then they do not hear my calls well. Am sending this > message to K3 support a well but appreciate any responses from the > community. > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/beat-freq-method-tp6215961p6215961.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by jrstorms
Hello jrstorms,
> Trying to set the freq cal for the reference using method 2 since I do not > have a freq counter. I may be tone deaf or something but I am not sure what > the beat-freq sounds like. Wish someone would post or send a sound file > demonstrating the beat freq when off, close and good sounds like. ... You could not hear a beat frequency. Noboby can hear it. But you can locate it. Turn your VFO/BFO slowly around the target frequency (up and down). If you VFO/BFO frequency was higher than the target frequency you can hear the tone/frequency goes lower and lower. At one point you can't hear it. If you turn the VFO/BFO in the same direction, so you can hear the tone/frequency again, but the frequency goes now higher. The area, at which you can't hear the tone, that is the beat frequency. -- 73/72 de Ingo, DK3RED - Don't forget: the fun is the power! www.qrp4fun.de - [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by jrstorms
What you are doing (in CW mode) is matching the sidetone of the carrier to that
of the K3 internal side tone. You cant hear the beat tone when they are close together, BUT, when they are VERY close the tone VOLUME will go up and down. Going either side of zero beat the volume will rise and fall faster. You want to tune very slowly and get the RISE/FALL of volume level to a null in the middle. Other freqs you can check your calibration is CHU at 7850.000 or 14670.000 or at night 3330.000kHz. Use CWT and SPOT while tuning the reference signal in the CW Mode. With the freq. set to FINE, it will display the to nearest Hertz and you can see how close you got the reference oscillator. AM signals will sound good when the tuned frequency (USB) matches the carrier frequency. 73, Mike AC5P ________________________________ From: jrstorms <[hidden email]> To: [hidden email] Sent: Mon, March 28, 2011 12:31:40 PM Subject: [Elecraft] beat freq method Trying to set the freq cal for the reference using method 2 since I do not have a freq counter. I may be tone deaf or something but I am not sure what the beat-freq sounds like. Wish someone would post or send a sound file demonstrating the beat freq when off, close and good sounds like. I tried setting it on 15mhz and thought I was close but when listening to WWV on 10mhz had to go down 300 hz to understand the voice transmission. Also 15mhz voice was "fuzzy" until I tuned off freq about 100hz. Guess I am confused at this point. I do understand that this really just adjusts vfo's so when at band edges I do not go out of band. However when using DX spots with N3FJP auto tune clicks I am off freq. Have to dial around to get clear signal so if I don't then they do not hear my calls well. Am sending this message to K3 support a well but appreciate any responses from the community. -- View this message in context: http://elecraft.365791.n2.nabble.com/beat-freq-method-tp6215961p6215961.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
It seems there's a common misconception that one has to have some sense of musical pitch to use this method. Especially with the K3, using CWT, it's completely unnecessary. If you can hear the volume (not the pitch) of the tone going up and down, that's all you need. Using an oscilloscope, you wouldn't have to hear at all.
Here is the procedure I recommend: 1. Select fine VFO resolution (1 Hz). 2. Select CW mode and set bandwidth to 500 Hz. (You don't have to have a CW xtal filter.) 3. If using WWV, do the calibration only when the carrier is unmodulated. If you try it when there are audio tones, you may end up tuning to one of the sidebands. 4. Using CWT, tune to the calibration signal. This will get you very close to zero beat. 5. Locate CONFIG:REF CAL. 6. Tap SPOT to enable the sidetone, and adjust its level to be about the same as that of the signal. You should hear the "beat", a fluctuation in volume. If necessary, adjust the sidetone level for the strongest beat. (If you can't hear it when adjusting the sidetone level, shift the VFO a few Hz.) Tune the VFO for the slowest possible fluctuation, probably less than 1 per second. 7. Note the VFO display frequency. If it isn't within 1 Hz of the calibration signal, adjust the REF CAL frequency in small increments, always retuning the VFO for zero beat as above, until the VFO display reads with 1 Hz of the calibration frequency. 8. Using the K3 utility, save the configuration. (Or record the REF CAL value.) 9. Cancel SPOT and exit the menu. Note to Wayne and Eric: Feel free to use this. 73, Scott K9MA > > On 3/28/2011 1:31 PM, jrstorms wrote: >> Trying to set the freq cal for the reference using method 2 since I do not >> have a freq counter. I may be tone deaf or something but I am not sure what >> the beat-freq sounds like. Wish someone would post or send a sound file >> demonstrating the beat freq when off, close and good sounds like. I tried >> setting it on 15mhz and thought I was close but when listening to WWV on >> 10mhz had to go down 300 hz to understand the voice transmission. Also >> 15mhz voice was "fuzzy" until I tuned off freq about 100hz. Guess I am >> confused at this point. I do understand that this really just adjusts vfo's >> so when at band edges I do not go out of band. However when using DX spots >> with N3FJP auto tune clicks I am off freq. Have to dial around to get clear >> signal so if I don't then they do not hear my calls well. Am sending this >> message to K3 support a well but appreciate any responses from the >> community. >> Scott Ellington Madison, Wisconsin USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
A couple of hints:
1. You must be in CW mode with three digits showing to the right of the decimal point in the freq display. It helps a lot to narrow the WIDTH to 200 Hz or even less. You won't hear [or at least be able to understand] the voice announcements, and the second "ticks" will sound strange. Set VFO A to the exact WWV frequency [e.g. 15.000.000] in the display. I suggest you start this whole procedure during one of the minutes when WWV does *not* have the tone on, assuring you are listening to the CW beat note from the carrier. If you are close and your BW is less than 200 Hz, you may not hear the tone when it comes back on. 2. You "turn on the sidetone" by doing a HOLD on the MON knob ["CMP PWR"] You'll hear the sidetone at whatever you have the PITCH set to. 3. The knob now adjusts the level of the sidetone in your phones. For this to work, that level needs to be approximately equal to the level of WWV in your phones. You can equalize them with either the MON knob or the AF gain, or both. 4. When you're in CONFIG:REF CAL, as you tune VFO A, the pitch of WWV will vary, the sidetone will remain constant. Your goal is to get WWV exactly the same pitch as your continuous sidetone. If it is a bit off, you may actually hear the very low beat note. If it is close, you'll hear the combined audio signals fading up and down rather than a "beat note." That fading *is* the beat note but it's too low a frequency to hear it as a tone. 5. As you close in on a match between WWV and your sidetone, the in and out fading will slow down, almost stop, and then begin to speed up again as you move past zero beat. It takes a bit as you are right at the zero beat point to find the absolute slowest in and out fading. 6. Although you can't tell when your K3 is in FINE tuning rate, the frequency is moving step-wise when you tune. You'll find as you approach zero beat, the in and out fading will slow, and then speed up a tiny bit, most likely never really stopping. That's because one DDS tuning step was just a tad below exact, and the next DDS step was just a tad above exact. Pick the step with the slowest rate. If you actually get the in and out fading to stop, you should buy a Power Ball ticket immediately :-) 7. The fading you hear is actually the individual cycles of the "beat note." When you're very close, you can count the number of peaks in some period, say 30 sec, and divide that count by the length of the period you used [in seconds]. The quotient is the beat note frequency. Mine is about 0.1 Hz which translates to 0.1 Hz frequency error when receiving. 8. Use the highest frequency WWV you can hear. Even without the KBPF3, I could hear 2.5 [at night], 5 [most of the time], and 15 and 20 during the day. For the record, I've done this several times figuring the K3 will drift. So far, I cannot detect any drift and my REF CAL frequency hasn't changed since I first calibrated. Be sure your K3 FP temp has stabilized before starting [tap DISP and use VFO B to find "FP" followed by a temp]. OK, I lied, that's 8 hints and one hint-let. 73, Fred K6DGW Auburn CA On 3/28/2011 5:45 PM, Don Wilhelm wrote: > Tune in WWV - make certain you are tuned to the carrier - use CW mode > (you will not be able to understand the voice in CW mode), and adjust > the VFO so the carrier is quite near the audio pitch of your sidetone. > Now turn on the sidetone, and adjust the AF gain so the sidetone level ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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This brings up an interesting point, though it doesn't affect the method at all. The "beat" Fred refers to results from adding of the sidetone to the signal tone: When they happen to be in phase, the volume goes up 6 dB, when they are exactly out of phase they cancel, so you hear the volume go up and down. It is a completely linear process.
This is not what produces the sum and difference "beat frequencies" in a mixer, which requires nonlinearity or multiplication. If you look at the audio coming out of a receiver with a spectrum analyzer, with two audio tones present, you will see only those two frequencies, not sum and difference frequencies. (Except for some tiny traces due to inevitable distortion.) So, for example, if you tune in a signal for a 400 Hz tone, and the sidetone is 600 Hz, you will NOT hear a 200 Hz beat, unless you turn the volume up so high that your receiver and/or ears produce distortion products. (Don't do that!) When you get close, though, you will hear that fluctuation in volume, which we can use to match frequencies. 73, Scott K9MA On Mar 28, 2011, at 2:18 PM, FredJensen wrote: > If it is close, you'll > hear the combined audio signals fading up and down rather than a "beat > note." That fading *is* the beat note but it's too low a frequency to > hear it as a tone. Scott Ellington Madison, Wisconsin USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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There's a reason why mathematicians speak with equations rather than
words. ;-) Scott is entirely correct, the sidetone signal and the audio signal add linearly in the K3 audio amplifier stage(s) and what you hear is their algebraic sum. If my choice of words implied that the effect was non-linear mixing, it was unintentional. Being an OF from the days of receivers, transmitters with VFO's, and modulators, often on separate chassis', getting on someone's frequency entailed turning your VFO [only] on, and adjusting it until its signal, as heard in your receiver, added algebraically with the AM carrier or CW tone until the exact effect in REF CAL took place ... as the VFO approached the audio tone of the signal, they began to fall in and out of phase with each other slower and slower, and you heard the "beat" [or slow pulsing in amplitude] between them. When that "beat" stopped [or got very slow], your VFO was "Zero Beat" and you would transmit on the same frequency as the other station ... if you transmitted fairly quickly ... VFO's in those days tended to drift around some unless they were built by Art Collins. And, thus the origin of the term "Zero Beat." Let's assume your VFO signal was 250 cycles higher than the frequency of the other station. You would then hear it, the other station, and a 250 cycle component from the algebraic sum of the two, just as you would hear a 1 cps "beat" as you got the VFO within 1 cycle. I suppose a musician with a very good sense of pitch might be able to identify the three frequencies involved [other station's note, VFO note, and 250 cps sum], but I can't. What I can tell is that there is a component in there and which way to move the VFO to achieve zero beat, and nearly everyone else can do that as well. That's all that's required for the Method 2 REF CAL. If you are deaf, just hang an analog AC multimeter across the headphone leads and you can watch the "beat" on it. Method 2 is an example of a very simple, test equipment-free mechanism that can achieve a really amazing frequency accuracy for your K3. I used the terms "cycle" and "cps" in this because Hz hadn't been invented in the ancient era I was drawing my example from, and the term "zero beat" that originated from it can be both a verb phrase or a noun phrase. I hope this clears up any misunderstandings I might have left about REF CAL Method 2. 73, Fred K6DGW Auburn CA On 3/28/2011 7:41 PM, Scott Ellington wrote: > This brings up an interesting point, though it doesn't affect the method at all. The "beat" Fred refers to results from adding of the sidetone to the signal tone: When they happen to be in phase, the volume goes up 6 dB, when they are exactly out of phase they cancel, so you hear the volume go up and down. It is a completely linear process. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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