Just one caveat on this procedure (thanks Guy!) -- make sure you have CWT turned OFF; otherwise, SPOT will not do what you want it to. (It will attempt to retune the VFO.)
Bill W5WVO -----Original Message----- From: Guy Olinger K2AV Sent: Friday, December 03, 2010 13:38 To: [email protected] Cc: Elecraft List Subject: Re: [Elecraft] Determining zero-beat Set mode to CW. Set width to 200 Hz. Do a HOLD on MON. Set level to 20-25. Tap MON to turn off beat. Tune to 10.000.000. Tap SPOT. Should hear a beat, albeit a slow one. Advance or retard AF gain to get the obvious beat. In CONFIG: go to REF CAL. This will have turned off SPOT. Tap it again. Adjust VFO A to get slowest beat. With some patience and careful listening this is usually clearly a specific setting, in my case 49.379.737. You will find that the beat frequency wavers around due to changing propagation path length so you have to listen for a while. Having accounted for the variation in propagation it is quite clear in my case, albeit subtle, that 738 is too high, and 736 is too low. It is also more clearly heard at some times of day on a given frequency than others. There are also times where there is a fast QSB on the signal that can be confusing and you may just have to wait until the signal steadies. When you have it spot on, there will be periods of several seconds or more where the beat does not vary, something which does not happen nearly as much up or down one Hz on the REF CAL frequency. After this adjustment it is clear that my K3 is within +/- 0.5 Hz at 10.000000 MHz with no drift, probably within +/- 0.2 Hz though I won't claim that. I have the KTCXO3-1 option in mine. It may be that a K3 without it may be a bit more cranky, I would imagine so, but I'm not pulling it out to see :>) 0.5 Hz at 10 will be less than 2.5 Hz at 50, though I don't know the formula. It's not a straight multiply because of the conversion scheme. With this adjustment in the menu, the chief contribution of the KTCXO3-1 is no drift, not an absolute accuracy. My K3 is way more accurate than they spec, and accurate enough to show up the propagational variations in the WWV frequencies. I would think that if you have left it on for a while, and calibrate it before an "exercise", you can count on it for spot on. 73, Guy. On Fri, Dec 3, 2010 at 6:09 AM, Pete Smith <[email protected]> wrote: > I want to use my K3 to calibrate the QS1R receiver used here as part of > the Reverse Beacon Network. For technical reasons, it's desirable to > calibrate the QS1R at as high a frequency as possible, so I wanted to do > so in the 6-meter band. I thought that if I knew how accurate the K3's > frequency display was at 10 MHz WWV, I'd know whether I needed to > compensate for any systematic error when comparing the two up on 6M. > > Here's where the problem comes in. AM mode isn't usable for finding > zero-beat, of course. On CW, it appears that the zero-beat frequency is > displayed as 10 MHz minus the "pitch" frequency (which can only be > adjusted down to 300 Hz). I'd like to know the frequency accuracy of > the K3 within 20-30 Hz if possible for this exercise. > > How to proceed? > > -- > 73, Pete N4ZR > > The World Contest Station Database, updated daily at > www.conteststations.com > The Reverse Beacon Network at http://reversebeacon.net, blog at > reversebeacon.blogspot.com, > spots at telnet.reversebeacon.net, port 7000 > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > 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:[email protected] 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
