RSGB RadCom K3 review posted on RSGB Members web page
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RSGB RadCom K3 review posted on RSGB Members web page
 
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For those who are RSGB members, see:
http://www.rsgb.org/membersonly/publications/reviews/index.php The K3 review by Peter Hart has just been posted. As it is copyright RSGB, so I can't quote much of it, but Peter concludes with: "The K3 is an impressive radio, which has attracted much interest and orders. One of the leading radios for close-in dynamic range and with excellent features, it is an ideal radio for use at home, field day or DXpeditions" 73 Dave, G4AON K3/100 #80 _______________________________________________ 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 |
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Dave G4AON wrote:
>For those who are RSGB members, see: > >http://www.rsgb.org/membersonly/publications/reviews/index.php > >The K3 review by Peter Hart has just been posted. > >As it is copyright RSGB, so I can't quote much of it, but Peter >concludes with: > >"The K3 is an impressive >radio, which has attracted much interest >and orders. One of the leading radios for >close-in dynamic range and with excellent >features, it is an ideal radio for use at home, >field day or DXpeditions" Hopefully Elecraft will obtain permission from RSGB to post the review publicly, as happened with the QST review. Most of the five pages are taken up by a description of the K3, which will be very familiar to existing users. The really interesting parts are towards the end, the on-air impressions and the measurements - although here too, many of the issues are familiar. One important thing to add is that the review would have been written *before* the major MCU 1.87 / DSP 1.69 update released on May 3rd, so Peter did not see the K3 in its current state of performance. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek _______________________________________________ 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: RSGB RadCom K3 review posted on RSGB Members web page
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In reply to this post by Dave, G4AON
Interesting review.
Considering IMDDR3 it seems like one should stay way from the 500 Hz filter, looks like the 400 Hz is the filter to get. Also the TX probably shouldn´t be cranked up to 120W but instead 100W should be maximum. 73 Jim SM2EKM ------------------------------------------------------ Dave G4AON wrote: > For those who are RSGB members, see: > > http://www.rsgb.org/membersonly/publications/reviews/index.php > > The K3 review by Peter Hart has just been posted. > > As it is copyright RSGB, so I can't quote much of it, but Peter > concludes with: > > "The K3 is an impressive > radio, which has attracted much interest > and orders. One of the leading radios for > close-in dynamic range and with excellent > features, it is an ideal radio for use at home, > field day or DXpeditions" > > 73 Dave, G4AON > K3/100 #80 > _______________________________________________ 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 |
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Hmmmm! Makes me feel like I knew something when I decided to get the 400 hz
filter instead of the 500 hz filter! As far as power settings, I usually like to follow a self imposed rule of never running a transceiver at more than 85% of "maximum". It probably is meaningless in many cases as far as really being a safety valve, but I figure that less than maximum strain ought to have some beneficial effect on the finals, etc. It probably sounds very arbitrary, but I follow this same rule in lots of things--even other than ham radio. In golf, for instance, I find that swinging the club at about 80-85% of what might be my maximum results in better contact and consistency. As far as the receiving station is concerned, 80 or 85 watts vs. 100 watts should be imperceptible. Although the K3 may not be one of them, there are lots of rigs out there that are very closely spec'd, either as to the finals, or the filters, etc. Some rigs have lots of "cushion"--the older TS-50 comes to mind, which apparently could easily run 200 watts or more with the finals in that rig. Some folks were actually cranking them up to that or higher! But nobody seemed to be too concerned about what the bandpass filters could handle, etc., and that bothered me enough to resist the temptation. So, I usually set my K3 at around 85 watts if I'm running QRO. Ignorance is bliss sometimes! Dave W7AQK ----- Original Message ----- From: "Jan Erik Holm" <[hidden email]> Cc: <[hidden email]> Sent: Monday, June 16, 2008 10:19 PM Subject: Re: [Elecraft] RSGB RadCom K3 review posted on RSGB Members web page Interesting review. Considering IMDDR3 it seems like one should stay way from the 500 Hz filter, looks like the 400 Hz is the filter to get. Also the TX probably shouldn´t be cranked up to 120W but instead 100W should be maximum. 73 Jim SM2EKM ------------------------------------------------------ Dave G4AON wrote: > For those who are RSGB members, see: > > http://www.rsgb.org/membersonly/publications/reviews/index.php > > The K3 review by Peter Hart has just been posted. > > As it is copyright RSGB, so I can't quote much of it, but Peter concludes > with: > > "The K3 is an impressive > radio, which has attracted much interest > and orders. One of the leading radios for > close-in dynamic range and with excellent > features, it is an ideal radio for use at home, > field day or DXpeditions" > > 73 Dave, G4AON > K3/100 #80 > _______________________________________________ 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 |
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In reply to this post by Jan Erik Holm
I haven't read the review but he must have had a bad 500 Hz filter from what I've heard reported (i.e. the 2.7k better than the 500 Hz). That makes no sense and is contradictory to previous measurements by both Elecraft and Sherwood: Elecraft: Filter 20kHz 10kHz 5kHz 2kHz 200 Hz, 5 pole 100+ 100+ 100+ 95 250 Hz, 8 pole 100+ 100+ 100+ 95 400 Hz, 8 pole 100+ 100+ 100+ 95 500 Hz, 5 pole 100+ 100+ 100+ 94 1 kHz, 8 pole 100+ 100+ 100 94 2.7 kHz, 5 pole 100+ 98 92 n/a 2.8 kHz, 8 pole 100+ 100 93 n/a http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters Sherwood: Filter - IMD @ 2 kHz 500 Hz - 95 dB 400 Hz - 96 dB 200 Hz - 101 dB* *I listed the 200 Hz because it's a 5-pole filter (just like the 500 Hz) in case some believe there is an inherent problem with 5-pole filters. http://www.sherweng.com/table.html It's odd but Peter Hart reported something similar when he did Orion's review. The 2.4k filter was much better than the 1.0k, which again makes no sense unless the 1.0k was defective. I'm sure Peter reported what he measured but common sense would dictate that one should suspect something was wrong with the filter and request another when anomalous results like this are measured. It also reminds me when ARRL once reported better IMD performance with Preamp ON versus Preamp OFF. Common sense would say "TILT"! 73, Bill W4ZV |
Re: RSGB RadCom K3 review posted on RSGB Members web page
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Yes something isn´t right. This was his measurements:
CLOSE-IN INTERMODULATION ON 7MHz band,500Hz bandwidth, CW preamp off 2.7 kHz roofing 1.8 kHz roofing 500 Hz roofing 2kHz +19dBm 101dB +12.5dBm 96dB +2.5dBm 88dB 3kHz +19dBm 101dB +12.5dBm 96dB +2.5dBm 88dB 5kHz +22dBm 103dB +12.5dBm 96dB +8.5dBm 92dB 7kHz +22dBm 103dB +12.5dBm 96dB +13dBm 95dB 10kHz +22dBm 103dB +12.5dBm 96dB +17.5dBm 98dB 15kHz +22dBm 103dB +12.5dBm 96dB +22dBm 101dB 20kHz +22dBm 103dB +12.5dBm 96dB +25dBm 103dB 30kHz +22dBm 103dB +12.5dBm 96dB +26.5dBm 104dB 40kHz +22dBm 103dB +12.5dBm 96dB +27dBm 104dB 50kHz +22dBm 103dB +12.5dBm 96dB +27dBm 104dB He also wrote this: Third order intercept and dynamic range results were excellent, but results were a little dependent on which roofing filter was in circuit (see table). With the stock 2.7kHz filter, the intermodulation limited dynamic range held at over 100dB (in 500Hz DSP bandwidth) down to 2kHz spacing, probably the highest figure I have ever measured at this spacing. However, with the 500Hz 5 pole roofing filter, a degradation was seen at close spacings and non-linear effects such as hysteresis were also observed. A step drop in performance was triggered as the spacing was reduced, which did not follow the reverse pattern as the spacing was again increased. Now if something similar did happen in the Orion case a measurement error can be suspected. It isn´t logical to think two bad filters. de SM2EKM ............................................................. Bill W4ZV wrote: > > Jan Erik Holm wrote: >> Interesting review. >> >> Considering IMDDR3 it seems like one should stay >> way from the 500 Hz filter, looks like the 400 Hz >> is the filter to get. >> > > I haven't read the review but he must have had a bad 500 Hz filter from what > I've heard reported (i.e. the 2.7k better than the 500 Hz). That makes no > sense and is contradictory to previous measurements by both Elecraft and > Sherwood: > > Elecraft: > > Filter 20kHz 10kHz 5kHz 2kHz > 200 Hz, 5 pole 100+ 100+ 100+ 95 > 250 Hz, 8 pole 100+ 100+ 100+ 95 > 400 Hz, 8 pole 100+ 100+ 100+ 95 > 500 Hz, 5 pole 100+ 100+ 100+ 94 > 1 kHz, 8 pole 100+ 100+ 100 94 > 2.7 kHz, 5 pole 100+ 98 92 n/a > 2.8 kHz, 8 pole 100+ 100 93 n/a > > http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters > > > Sherwood: > > Filter - IMD @ 2 kHz > 500 Hz - 95 dB > 400 Hz - 96 dB > 200 Hz - 101 dB* > > *I listed the 200 Hz because it's a 5-pole filter (just like the 500 Hz) in > case some believe there is an inherent problem with 5-pole filters. > > http://www.sherweng.com/table.html > > > It's odd but Peter Hart reported something similar when he did Orion's > review. The 2.4k filter was much better than the 1.0k, which again makes no > sense unless the 1.0k was defective. I'm sure Peter reported what he > measured but common sense would dictate that one should suspect something > was wrong with the filter and request another when anomalous results like > this are measured. It also reminds me when ARRL once reported better IMD > performance with Preamp ON versus Preamp OFF. Common sense would say > "TILT"! > > 73, Bill W4ZV _______________________________________________ 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 |
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Yes, and also the 8-pole 1.8k should be better than the 5-pole 2.7k. Some very strange results indeed but I'm sure Peter is reporting what he's measuring. I cannot find his original Orion review but I recall it showed the 2.4k 4-pole and 1.8k 8-pole to be much better than the 1.0k 4-pole at 2 kHz spacings, which again did not make sense unless the 1k filter was defective. 73, Bill |
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I don't understand why the IMD figures worsen as the roofing filter narrows. Also I've always been led to understand that the signal spacing likely to cause IMD problems is roughly 0.25 of the roofing filter bandwidth assuming a narrow final passband. On this basis, and even allowing for responses down to the -60dB level (say 5kHz for the 2.7K filter...) none of the quoted signal spacings should be 'getting through' any of the roofing filters listed. So at these spacings the IMD response should be a function only of the pre first mixer circuitry which doesn't explain (to me!) the significant variations with roofing filter.
I'm sure I'm missing something here, perhaps about how these things are actually measured; anyone care to put me right....? Stewart Rolfe, GW0ETF (K3/100 #145)
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