Re: [Elecraft] K2 S/N 4787 First QSO
The Sherwood Engineering data says that for the 2 kHz spacing dynamic range test, the K2's performance was limited not by nonlinearity (intermodulation distortion) but by the K2's oscillator phase noise sidebands. The same table says the same thing about the Ten Tec Orion's performance in the 10 kHz spacing dynamic range test, and it is listed as the top performer in their table. I think this data speaks more to the excellent wide dynamic range performance of these radios more than to the inferiority of their phase noise performance. The Sherwood "Receiver Test Data Table" has a column labeled "LO Noise Spacing" and another column labeled "kHz" immediately to the right. For the K2 data near the top of the spreadsheet, I interpret the entries in these columns as meaning that the single sideband phase noise power (in a 1 Hz bandwidth) for the K2's oscillator spectrum is -123 dB relative to the oscillator carrier power at 10 kHz away from the carrier frequency (someone please tell me if I'm wrong). This is not too shabby considering the price of the K2. Cost is an important consideration. Poseidon Scientific Instruments of Perth, Austrailia builds sapphire loaded cavity resonator microwave oscillators which are quite popular with high resolution, high dynamic range radar system designers. These sport SSB phase noise performance of better than -145 dBc/Hz at only 1 kHz from the carrier at 10 GHz carrier frequency! These can be used with regenerative frequency dividers to produce even more phenomenal performance at lower (read HF) frequencies, since the phase noise sideband spectrum extent also gets divided by the same ratio as the carrier frequency. If you plan to get one to replace your K2's oscillator, you might wish to know that they cost more than $100k each. You might also wish to know that if you actually want to measure the phase noise of one of these, you'll need another oscillator phse locked to the first one, with as good or better phase noise performance, not to mention a pretty fancy low frequency spectrum analyzer and a few other peripherals, which means you'll need to spend more than $200k. Given that I'm only looking for weak CW signals on 40 Meters in the presence of QRM from another ham a mile away from me, and not trying to extract the doppler shifted radar pulse echo of a gnat at 200 miles range from that of the mountain behind him, I'll stick with my original K2 oscillator at about 0.5% of the cost. Bob WB4TGG [EMAIL PROTECTED] wrote: In a message dated 16/03/05 22:48:02 GMT Standard Time, [EMAIL PROTECTED] writes: The K2's I've tested fall down on LO phase noise performance. Also note that the K2 measurements on the Sherwood web site state that the receiver performance is limited by phase noise. I agree the RX works very well, but I've attracted comments on the air (when running QRO) re transmitted phase noise. I wonder if there is an obsession with numbers. To place the matter in perspective, the Sherwood Engineering web site does list the K2 which is serial #3170 or about 2 years old? as being the 7th from the top of all the ham radio receivers tested. The aspect of the effects of phase noise being only one of many parameters that determine the final result. I would presume that to measure phase noise needs the resources of a well equipped professional lab. Whilst personally I am well equipped to carry out servicing of radios from HF through to UHF, cannot even really scratch the surface in terms of measuring phase noise. The professional communications systems servicing organisation I worked for despite being well equipped for testing from HF though to microwave in the field had little that could be used seriously for testing phase noise except for probably some rather expensive HP spectrum analysers that were issued only recently to maintain a new 8GHz digital microwave system. Before slagging the K2 one should take more seriously what it represents in terms of outlay, costing only a fraction of cheapest HF transceivers available on the market. Admittedly you have to build it yourself, but still the performance of the K2 as what it was primarily designed for, a QRP CW transceiver takes a heck of a lot of beating. There are shortcoming that occur with the additional added components, though even these have been mitigated by later modifications. Do the persons reporting phase noise on K2 TX really know what they are talking about or just pushing out some mumbo jumbo that just happens to be the popular quotation of the day? To be frank most hams including myself would probably not be be aware what phase noise is even if it jumped out and bit them. Bob, G3VVT K2 #4168 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list.
Re: [Elecraft] K2 S/N 4787 First QSO
On Mar 16, 2005, at 8:09 PM, [EMAIL PROTECTED] wrote: Admittedly you have to build it yourself, but still the performance of the K2 as what it was primarily designed for, a QRP CW transceiver takes a heck of a lot of beating. I figure about $300 of what I spent on my K2 (which is waiting for me at home having just been delivered) was for the privilege of being able to build it myself! Great post. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 S/N 4787 First QSO
In a message dated 16/03/05 22:48:02 GMT Standard Time, [EMAIL PROTECTED] writes: The K2's I've tested fall down on LO phase noise performance. Also note that the K2 measurements on the Sherwood web site state that the receiver performance is limited by phase noise. I agree the RX works very well, but I've attracted comments on the air (when running QRO) re transmitted phase noise. I wonder if there is an obsession with numbers. To place the matter in perspective, the Sherwood Engineering web site does list the K2 which is serial #3170 or about 2 years old? as being the 7th from the top of all the ham radio receivers tested. The aspect of the effects of phase noise being only one of many parameters that determine the final result. I would presume that to measure phase noise needs the resources of a well equipped professional lab. Whilst personally I am well equipped to carry out servicing of radios from HF through to UHF, cannot even really scratch the surface in terms of measuring phase noise. The professional communications systems servicing organisation I worked for despite being well equipped for testing from HF though to microwave in the field had little that could be used seriously for testing phase noise except for probably some rather expensive HP spectrum analysers that were issued only recently to maintain a new 8GHz digital microwave system. Before slagging the K2 one should take more seriously what it represents in terms of outlay, costing only a fraction of cheapest HF transceivers available on the market. Admittedly you have to build it yourself, but still the performance of the K2 as what it was primarily designed for, a QRP CW transceiver takes a heck of a lot of beating. There are shortcoming that occur with the additional added components, though even these have been mitigated by later modifications. Do the persons reporting phase noise on K2 TX really know what they are talking about or just pushing out some mumbo jumbo that just happens to be the popular quotation of the day? To be frank most hams including myself would probably not be be aware what phase noise is even if it jumped out and bit them. Bob, G3VVT K2 #4168 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 S/N 4787 First QSO
Fraser G4BJM wrote: Sorry, I don't understand this point. The K2's I've tested fall down on LO phase noise performance. Also note that the K2 measurements on the Sherwood web site state that the receiver performance is limited by phase noise. I agree the RX works very well, but I've attracted comments on the air (when running QRO) re transmitted phase noise. Surely the good receive performance is primarily due to having good selectivity near the front end. Phase noise seems to be a taboo subject on here... Is there a way to bring it in line with other top rigs? --- You're the first that I've heard to make such comments, Fraser. I have not tested the K2 myself. I was referring to the design approach the K2 uses that allows for lower phase noise than a fully-synthesized oscillator, but at the cost of somewhat less absolute frequency stability and dial accuracy. As you know, reducing the frequency at which phase correction is applied to a PLL reduces the phase-generated sidebands or "phase noise". If you have a fully-synthesized oscillator must stay within 1 Hz of the reference oscillator, it has to be corrected often enough that it will never drift more than 1 Hz or it'll start "walking" across the band in 1 Hz steps. That involves very frequent corrections and resulting noise. Elecraft uses a PLL that tunes in only 5 KHz steps. It does not need to correct nearly as often as a fully synthesized oscillator, hence less phase noise. Of course, a local oscillator that tunes in 5 kHz steps isn't very useful on the Ham bands so, instead of using a very precisely controlled reference oscillator, the K2 uses a variable frequency oscillator for the reference oscillator. More accurately, it uses a variable frequency *crystal* oscillator, or VXO, for the reference oscillator. The VXO is tuned by a varicap over a 5 kHz range to fill in the gaps in the PLL tuning. The result is a very quiet PLL with continuous frequency coverage. The down-side of that approach is that because the reference oscillator is designed to change frequency, it will tend to drift. A fully-synthesized PLL can use exotic crystal oscillators in temperature-controlled ovens to provide a much higher degree of stability than any variable-frequency oscillator can achieve. So, in terms of absolute frequency stability, the K2 is not as stable as some fully-synthesized rigs. Still, in my experience, the K2 needs offer no apologies for frequency stability, even in very demanding situations such as PSK31. If you are experiencing phase noise problems in either transmit or receive, I'm sure Elecraft would like to hear about it. I'm not personally familiar with the Sherwood web site. I've never seen a subject relating to Elecraft equipment that wasn't eagerly discussed and dissected here on the reflector, although comments do get missed from time to time. Certainly, no such queries are "taboo". Indeed, a great many of the design improvements to the Elecraft rigs have come directly from initial criticisms published right here, followed by a lot of discussions about ways to improve the rigs that eventually led to a design change. Moreover, every time such a change was made, an upgrade kit was also made available to all current owners so their rigs could keep pace with the performance of the very latest new units being built. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 S/N 4787 First QSO
Sorry, I don't understand this point. The K2's I've tested fall down on LO phase noise performance. Also note that the K2 measurements on the Sherwood web site state that the receiver performance is limited by phase noise. I agree the RX works very well, but I've attracted comments on the air (when running QRO) re transmitted phase noise. Surely the good receive performance is primarily due to having good selectivity near the front end. Phase noise seems to be a taboo subject on here, attracting only personal replies. Is there a way to bring it in line with other top rigs? 73 Fraser G4BJM One of the features that gives the K2 receiver its 'edge' in hearing weak signals over many of the other rigs is that the K2 does *not* use a fully-synthesized local oscillator. With that superior receive performance comes a trade-off: the K2 simply is not as stable as those other rigs with fully-synthesized L.O.s in crystal ovens. Still, current K2's are very, very good, but it deserves a good 15-minute warm-up. _ Want to block unwanted pop-ups? Download the free MSN Toolbar now! http://toolbar.msn.co.uk/ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 S/N 4787 First QSO
Thanks Ron, You've gave me some good information. Now I remember the filter and processor settings. I'll have to go tweak them and see what we get. I'm hoping the 12 uhenry inductor will give more range and will help stablize the frequency. Support also stated they had gotten some crystals that were not "rubber" enough and recommended replacing the associated inductor. I'm going to print your response and put it with my K2 fact folder. Thanks again, Jim, AB0UK --- Ron D'Eau Claire <[EMAIL PROTECTED]> wrote: > Jim, AB0UK wrote: > > Got the SSB and NB installed and decided it was time > for that first QSO. A friend across town was happy > to > oblige. He was impressed with the audio. He > recorded > it and it sounds nice when played back. Received > audio sounds a little tinnymaybe it is just my > headphones and the tiny speaker. > - > > With my K2 set for optimum xmit audio, I find the > receive audio tends to cut > off more of the "lows" than I like on some signals. > The ideal bandpass > definitely changes with the voice on the other end. > So I have FL2 set using > the OPT1 filter for a BFO frequency that shifts the > bandpass slightly to > produce more bass in the signal (bandpass closer to > the carrier freq). That > gives me way to shift the tone of the received > signal by changing filters. > The settings for FL1 are *always* used for xmit, no > matter what filter > position you are using for receive, so adjusting the > other filter positions > to suit your taste will not have any affect on your > transmit audio. > > Jim wrote: > During the qso I > realized that either there is no mike gain adjust or > it's buried in a menu that I can't remember. Anyone > know where that might be? > > > Mic gain is set via an attenuator and then > automatically adjusted in the > speech processor I.C. The mic attenuator control is > available under MENU > option SSBA. SSBA 1 attenuates the audio by 10 dB. > SSB 2 or 3 provides full > gain with no attenuation. > > Jim wrote: > > I've realigned the 4 mhz and PLL three times against > WWV and my friend says I am still 20-30 hz off. > Does > it settle down at some point or do I need to chase > it > every few days? > > > > One of the features that gives the K2 receiver its > 'edge' in hearing weak > signals over many of the other rigs is that the K2 > does *not* use a > fully-synthesized local oscillator. With that > superior receive performance > comes a trade-off: the K2 simply is not as stable as > those other rigs with > fully-synthesized L.O.s in crystal ovens. Still, > current K2's are very, very > good, but it deserves a good 15-minute warm-up. > > One other issue that affects your frequency readout > is the ability of the K2 > to reset the oscillators to a specific frequency. > When you calibrate your > K2, the analog voltages used to tune the oscillators > are converted into > digital values and stored as digital data in memory. > When you tune in a > specific frequency, the logic looks up those digital > values and converts > them back into the proper analog tuning voltages. > This conversion back and > forth is done by "Digital to Analog Converters" or > DACs. DACs have a > specific amount of accuracy. More accuracy requires > bigger numbers and more > memory. The tradeoff that Elecraft used between > memory and accuracy puts the > K2 within about 20 or 30 Hz of the expected > frequency. > > That said, one might ask how accurate the other > guy's rig is. A quick check > for you is to tune in WWV. Give your K2 a 15 minute > warm-up at least, then > zero beat WWV's carrier and check your K2's > frequency display. I just turned > on my K2 a few minutes ago and it's showing WWV at > 1.01 kHz right now - > 10 Hz high. > > Ron AC7AC > > > > __ Do you Yahoo!? Yahoo! Mail - Helps protect you from nasty viruses. http://promotions.yahoo.com/new_mail ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: [Elecraft] K2 S/N 4787 First QSO
Jim, AB0UK wrote: Got the SSB and NB installed and decided it was time for that first QSO. A friend across town was happy to oblige. He was impressed with the audio. He recorded it and it sounds nice when played back. Received audio sounds a little tinnymaybe it is just my headphones and the tiny speaker. - With my K2 set for optimum xmit audio, I find the receive audio tends to cut off more of the "lows" than I like on some signals. The ideal bandpass definitely changes with the voice on the other end. So I have FL2 set using the OPT1 filter for a BFO frequency that shifts the bandpass slightly to produce more bass in the signal (bandpass closer to the carrier freq). That gives me way to shift the tone of the received signal by changing filters. The settings for FL1 are *always* used for xmit, no matter what filter position you are using for receive, so adjusting the other filter positions to suit your taste will not have any affect on your transmit audio. Jim wrote: During the qso I realized that either there is no mike gain adjust or it's buried in a menu that I can't remember. Anyone know where that might be? Mic gain is set via an attenuator and then automatically adjusted in the speech processor I.C. The mic attenuator control is available under MENU option SSBA. SSBA 1 attenuates the audio by 10 dB. SSB 2 or 3 provides full gain with no attenuation. Jim wrote: I've realigned the 4 mhz and PLL three times against WWV and my friend says I am still 20-30 hz off. Does it settle down at some point or do I need to chase it every few days? One of the features that gives the K2 receiver its 'edge' in hearing weak signals over many of the other rigs is that the K2 does *not* use a fully-synthesized local oscillator. With that superior receive performance comes a trade-off: the K2 simply is not as stable as those other rigs with fully-synthesized L.O.s in crystal ovens. Still, current K2's are very, very good, but it deserves a good 15-minute warm-up. One other issue that affects your frequency readout is the ability of the K2 to reset the oscillators to a specific frequency. When you calibrate your K2, the analog voltages used to tune the oscillators are converted into digital values and stored as digital data in memory. When you tune in a specific frequency, the logic looks up those digital values and converts them back into the proper analog tuning voltages. This conversion back and forth is done by "Digital to Analog Converters" or DACs. DACs have a specific amount of accuracy. More accuracy requires bigger numbers and more memory. The tradeoff that Elecraft used between memory and accuracy puts the K2 within about 20 or 30 Hz of the expected frequency. That said, one might ask how accurate the other guy's rig is. A quick check for you is to tune in WWV. Give your K2 a 15 minute warm-up at least, then zero beat WWV's carrier and check your K2's frequency display. I just turned on my K2 a few minutes ago and it's showing WWV at 1.01 kHz right now - 10 Hz high. Ron AC7AC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
