K-2 vs SDR-1000
Locked
 
|
Have there been any lab tests published comparing the SDR-1000 against the K-2? Carry on Bill_Harris _______________________________________________ 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 |
|
Administrator
|
Hi Bill,
The ARRL has not published lab tests on the SDR-1000 to my knowledge, but I do have one here in the lab. Its an interesting approach for a 100% computer based rig and in general its RX performance is not too bad, but is is well below the K2 for IMD dynamic range and Blocking dynamic range. It relies on the sound card in the PC to do all of its filtering, which makes it's performance quite variable depending on what quality sound card is in use and how it is set up by the user. In any case though, the current PC sound cards do not have enough A/D input range to get the same dynamic range performance as rigs (like the K2, Orion. etc) that use narrow crystal filtering at their first IF. It also uses a direct DDS based local oscillator (without a following PLL to clean it up) for its VFO, which will have numerous significant off freq spurious responses in the -80 to -90 dB range that will mix off frequency signals onto your listening frequency. These spurious receive components absolutely can not be canceled out by the DSP once they occur. They look identical to legitimate on-frequency RX signals to the DSP. As a comparison, the K2 and other top performing rigs have local oscillator noise (with no spurs) at -125 to -130 dBc range five to ten kHz from the carrier. A big difference. Even more important, the direct DDS approach creates the same DDS off freq. spurs on transmit. Not a great idea then running 1KW etc. 73, Eric WA6HHQ Bill_Harris wrote: > Have there been any lab tests published comparing the SDR-1000 against the K-2? > > Carry on > > Bill_Harris > _______________________________________________ > 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 |
|
|
On Wed, Feb 16, 2005 at 11:51:53AM -0800, Eric Swartz - WA6HHQ, Elecraft wrote:
> Even more important, the direct DDS approach creates the same DDS off > freq. spurs on transmit. Not a great idea then running 1KW etc. Something to think of before hooking the output of your KX-1 to an Alpha 77! Bob, N7XY _______________________________________________ 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 |
|
|
In reply to this post by Eric Swartz - WA6HHQ
In results obtained by me with Leif Asbrink on 14 Mhz,
the IP3 is over 10dBm <IF> you set the thing as it should be. The Elecraft K2 is 20+ dBm with preamp off at 5 Khz. SDR-1000 BDR is 105 dB, the Elecraft K2 is 135 dB It IMDDR3 is 99 dB, the Elecraft K2 is better. The DDS does produce spurs BUT the DDS is not directly driving the mixer. This is often misunderstood. The DDS output does not even touch the mixer. The DDS output is hard limited and that hard limited signal is using to drive a switched capacitor network. What spurs there are, are CONSIDERABLY better than driving it directly. In this regard Eric is slightly off in his implications in that if driven directly by the DDS, the mixer would be a mess. The worst spurs are "buffered" away from us. On the other hand, some spurs get through as phase modulation on the bus switches driving the switched capacitor front end. I know this well. I spent months perfecting this ingenious method for escaping the AM spurs and the PM SPURS are what is getting through!! These spurs are annoying and I hope that Gerald in his "next radio" or next generation boards (whatever) finds a way to clean this up. That said, what spurs there are, are way down and on transmit, even with the 100w amplifier these transmit spurs are so far below legal limit as to be not a thing to worry about. On receive, they are annoying because Gerald has built too much sensitivity into the receiver. With everything flaming, he has < -140 dBm as the MDS. This is about 15 dB too sensitive for HF work and of course you can raise the IP3 and BDR WITH A GREAT SOUND CARD by attenuating the front end. With a great sound card, I raised the BDR by 15 dB while keeping the MDS the same even though I put another 6 dB of attenuation inline! I was able to increase the IMDDR by changing the roofing filter (switched capacitor filter values) and increased the IP3 to TOP OF CLASS, BETTER THAN EVERYONE EXCEPT THE IC7800 with a change of front end device! By the way, my sound card cost $1000. SO, you can take your knife and soldering iron and make it a great receiver. NOT FOR EVERYONE! The League recently purchased one for review. Their results will be interesting to see but the K2 will remain the king. I would take away from this discussion that the Elecraft K2 is and will be at the top of the heap in these raw numbers. The SDR-1000 in my view is about 4-th or 5-th on the "Elecraft receiver comparision chart" as it comes from the shop. I can make it almost best on the chart with surgery. So the SDR-1000 is for those who do not mind a never ending beta project. It really is interesting and I have spent hundreds of hours programming the DSP for it along with AB2KT. It is in the spirit of the tinkering amateur radio operator who doesn't mind modifying their existing radio to make it better. SOUND FAMILIAR? On Field Day, I supplied to W2GD, Elecraft K2's for our QRP FD (2A Battery) and we came in sixth overall. I own three transceivers. Elecraft K2, SDR-1000, and FT1000MP. The FT1000MP has not been here for months because it is at my contest multi-multi site (N3NGE's house) as the two meter radio (with transverter). The K2 and the SDR-1000 are fantastic radios but it pays to investigate what is right for you. If you are interested in an open source project that is really interesting and will continue to be interesting for a while, SDR-1000 is a really good radio. It is NOT the "best radio" in what would be most people's estimation. Gerald has been in business for two years and has probably learned a lot from this experience. He has sold over 500 of the radios and has had 5 returned. Three of those folks didn't know they needed a computer! Two of them could not download new software. I don't think he has had a truly disatisfied customer. The SDR-1000 is a real darling of many bleeding edge types in the EME community. It does things others cannot do (some of these ideas stolen from Linrad, etc.) That said, it is a radio in training and Gerald's next offering whatever that is and whenever it will be is likely to be a really nice one. In my mind, the Elecraft K2 is at the top of the heap for best receiver. It never ceases to amaze me that Wayne and Eric put together a kit that continues to put the big boy's to shame. My Elecraft K2 and SDR-1000 sit side by side and they fight daily for my attention! 73's Bob N4HY _______________________________________________ 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 |