Strange K2 Behavior?
Locked
 
|
So I am patiently waiting for my K3 to ship (katiegram came end of last week, Woohoo!) and so I have been using my K2 as the main station radio after selling my IC-756Pro (still a great radio in its own right...)
Anyway, this evening I was trying to update my records after my latest batch of bureau cards came in, and tuning along a mostly quiet 20m band. Worked a mobile station in TX, and then casually tuned up the band. I actually tuned out of 20m by a little bit up to 14359 (14359.03 on the display to be exact) and BAM! I got an S9 tone. It goes from totally quiet to S9 as soon as the tuning display hits 14359.03. happens with no external antenna. It obviously must be an internal birdie, but I don't ever remember one that seems to be so abrupt - it's like something breaks into oscillation right at that point. It is totally repeatable. If I continue tuning up, it just drops in frequency and goes out of the passband. But tuning up to it from lower in frequency, it is not there at all, and then THERE! Everything else about the rig seems fine, so I am not sure this is even a problem. But I am kinda curious to know if this is 'normal' behavior, or what. I don't normally tune out of the ham bands on the K2 (not much point to it) so I just stumbled onto it. No idea if the radio has always done this or not. Any ideas as to what this is, and if it represents any kind of an issue? 73 de KE0MF/Mike _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
On Wed, 2008-10-15 at 19:34 -0600, Michael Lewis wrote:
> band. I actually tuned out of 20m by a little bit up to 14359 > (14359.03 on the display to be exact) and BAM! I got an S9 tone. It > goes from totally quiet to S9 as soon as the tuning display hits > 14359.03. happens with no external antenna. I just tried it and I get the same thing. Starts at exactly: 14359.03 USB (I assume you were using USB?) 14360.80 CW 14359.25 CW reverse 14361.74 LSB 14361.50 RTTY 14358.53 RTTY reverse It behaves exactly as you described. It always starts suddenly then gradually tapers off in strength while tuning to higher frequencies. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
|
|
Mine does that too. The VCO for a frequency around 14.360 MHz should
be running aabout 19.274 MHz and the reference oscillator runs at about 12.096 MHz. 2*19.274-2*12.096 = 14.356 MHz, so that seems to be the culprit. It pops in because of the way the VCO is tuned. When you get to the edge of the fine tuning, the U4 tunes the VCO to the next 5KHz coarse step and U5 changes the reference oscillator back to the beginning of a fine step. For the previous coarse step the birdie is not heard, but for this coarse step the two oscillators are tuned so that it is. On my K2, with the way I have RTTY set up, I can hear it pop in on RTTY at 14361.5 and then it pops out at the next coarse step at 14366.5 73 Kevin w9cf
|
|
|
In reply to this post by Michael Lewis-3
Michael Lewis wrote:
> Worked a mobile station in TX, and then casually tuned up the band. I > actually tuned out of 20m by a little bit up to 14359 (14359.03 on the > display to be exact) and BAM! I got an S9 tone. It goes from totally > quiet to S9 as soon as the tuning display hits 14359.03. happens with no > external antenna. It obviously must be an internal birdie, but I don't I suspect the design policy was that the spurious responses should not be controlled outside of the amateur bands, and this one may have dictated things like IF frequencies specifically to avoid its being in band. > ever remember one that seems to be so abrupt - it's like something The reason for abrupt changes is that the K2 steps the synthesizer ratio relatively infrequently and interpolates by pulling the reference oscillator frequency. The sudden onset probably corresponds to a synthesizer step and corresponding jump of the reference oscillator frequency to the other extreme. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Strange K2 Behavior?
|
|
In reply to this post by w9cf
With respect Kevin the 'culprit' responsible for this birdie in my K2 is the
(LO + IF) / 2 spurious response of the receiver which can 'hear' the PLL reference oscillator. When the receiver is tuned to 14.360 MHz the frequency of this particular response, assuming a 4.914 MHz IF, is (19.274 + 4.914) / 2 = 12.094 MHz, moving down to 11.914 MHz as the receiver is tuned down to 14.000 MHz. 73, Geoff GM4ESD Kevin W9CF wrote on Friday, October 17, 2008 at 8:29 AM > Mine does that too. The VCO for a frequency around 14.360 MHz should > be running aabout 19.274 MHz and the reference oscillator runs at about > 12.096 MHz. 2*19.274-2*12.096 = 14.356 MHz, so that seems to be the > culprit. It pops in because of the way the VCO is tuned. When you get > to the edge of the fine tuning, the U4 tunes the VCO to the next 5KHz > coarse step and U5 changes the reference oscillator back to the beginning > of > a fine step. For the previous coarse step the birdie is not heard, but for > this coarse step the two > oscillators are tuned so that it is. On my K2, with the way I have RTTY > set up, I can hear it pop in on RTTY at 14361.5 and then it pops out at > the next coarse step at 14366.5 > > 73 Kevin w9cf _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Strange K2 Behavior?
|
Administrator
|
In reply to this post by Michael Lewis-3
This is a known out-of-band birdie on the K2 and has always been there.
Part of our design goal on the K2 was to place any strong mixing products lile this outdie the ham bands. All superhet receivers will have birdies. Fortunately most are quite weak and are usually covered by band noise. This strong one was unavoidable and we purposely adusted the synthesizer and bfo parameters to place it outside the ham band. 73, Eric WA6HHQ _..._ -----Original Message----- From: w9cf <[hidden email]> Date: Friday, Oct 17, 2008 12:29 am Subject: Re: [Elecraft] Strange K2 Behavior? To: [hidden email] Mine does that too. The VCO for a frequency around 14.360 MHz should be running aabout 19.274 MHz and the reference oscillator runs at about 12.096 MHz. 2*19.274-2*12.096 = 14.356 MHz, so that seems to be the culprit. It pops in because of the way the VCO is tuned. When you get to the edge of the fine tuning, the U4 tunes the VCO to the next 5KHz coarse step and U5 changes the reference oscillator back to the beginning of a fine step. For the previous coarse step the birdie is not heard, but for this coarse step the two oscillators are tuned so that it is. On my K2, with the way I have RTTY set up, I can hear it pop in on RTTY at 14361.5 and then it pops out at the next coarse step at 14366.5 73 Kevin w9cf Brian Mury-3 wrote: On Wed, 2008-10-15 at 19:34 -0600, Michael Lewis wrote: > band. I actually tuned out of 20m by a little bit up to 14359 > (14359.03 on the display to be exact) and BAM! I got an S9 tone. It > goes from totally quiet to S9 as soon as the tuning display hits > 14359.03. happens with no external antenna. I just tried it and I get the same thing. Starts at exactly: 14359.03 USB (I assume you were using USB?) 14360.80 CW 14359.25 CW reverse 14361.74 LSB 14361.50 RTTY 14358.53 RTTY reverse It behaves exactly as you described. It always starts suddenly then gradually tapers off in strength while tuning to higher frequencies. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- View this message in context: http://n2.nabble.com/Strange-K2-Behavior--tp1339332p1344229.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |