Erik, Yes, that is why you cannot use a single signal (tone) when aligning the filters. The use of a broadband noise source and an audio spectrum analyzer application running on the computer soundcard will make K2 filter setup easy and uncomplicated.
73, Don W3FPR On 4/30/2012 2:49 AM, Erik Linder wrote: > Aha! Then I did not fully understand the inner workings of the K2. > I just looked att the schematics and noticed the BFO and the mixer. Out of > that I made the conclution that the BFO value must change the pitch. > > So what you are saying is: > During filter setup, it is normal for the pitch to change but when I press > XFIL the save-routine inside the K2 is compensating for the change and > restores the pitch to its original position? > Is that correct? > > Which in practice means that I cannot adjust the pitch manually (like on an > old radio), it's up to the K2 routine to set the pitch. > > ./Erik > > 2012/4/29 Don Wilhelm<[email protected]> > >> Erik, >> >> The K2 will preserve the pitch when the BFO is changed. Of course, if >> you move the BFO enough, the signal will no longer be inside the passband. >> >> You must move the VFO to change the pitch, just changing the BFO will >> not do it. The filter passband edges will change, but the pitch of a >> tuned signal will not. That is why it is important to use a broadband >> noise generator (often band noise will do) and some type of audio >> spectrum analyzer (I use Spectrogram) to view the shape of the passband >> - you can see when it is centered at your target pitch. Use no signals >> in the passband when changing the filters, having signals present will >> only confuse your view of the passband shape and positioning. >> >> If you need Spectrogram, you can find it on my website www.w3fpr.com - >> look near the bottom of the opening page. >> >> 73, >> Don W3FPR >> >> >> On 4/29/2012 4:40 PM, Erik Linder wrote: >>> Don, tnx for the answer. >>> >>> Yes, the difference was small. Tnx for the info about 20 Hz, then I now >> the >>> limitation of the construction. >>> >>> Yes I can use the FL1 (open) as both TX and RX (well of course TX is >> alway >>> using FL1). But if I want something more narrow I like to use FL2 - FL4. >>> And now I know that I can get in 20 or so Hz if I work hard enough. :-) >>> >>> But the main problem here is that I cannot adjust my filters at all right >>> now. :-( >>> I can move the BFO (change the pitch) as long as I am in cal fil but as >>> soon as I save the filter and return to listen the pitch has changed to >>> "default". The BFO-value _has_ changed, it _has_ been saved. (I see the >>> display showing BFO freq for a short time). >>> But still - the pitch is where it was before I changed the BFO-value. >>> >>> And I have changed it much - like 50 to 100 units. USB, LSB, CW - the >> mode >>> does no difference. >>> >>> So: >>> Received pitch of the signal transmitted from my 2:nd TRX: 1500 Hz >>> The BFO value is (lets say) 128 >>> I change the BFO value too 100 >>> I hear (and see on the waterfall) that the pitch is changing. >>> I press XFIL (to save) >>> Display shows BFO freq for a short time. >>> I press XFIL a couple of times to "get round" to FL1 again. >>> The pitch has now jumped back to 1500 >>> The BFO-value is at it's saved 100 >>> >>> I can now lower the BFO value once more and when I come around the pitch >>> will be 1500 and the BFO is saved with the new value. >>> >>> Isn't it suppose to work like: >>> Change the BFO to get the correct pitch >>> Save >>> Return to the filter and the pitch is where you programmed it to be. >>> >> ______________________________________________________________ >> 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
