K3 10-meter sensitivity
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Yesterday, in the 10-meter contest, I noticed that some other stations (using comparable antennas) within a very few miles of me were working stations that I could barely detect, or not even hear, on my K3. In itself that is not too unusual, but I had another radio in the shack, a Yaesu FT-900, so I connected it to the K3 for some comparative receiver testing.
What I discovered was rather disappointing. About half the time, there seemed to be no difference in the ability of the two receivers to pick out very weak signals at or near noise level. The other half of the time, the old FT-900 seemed just a bit better. NEVER was the K3 better at digging out the weak ones. What are other people's impressions of the K3's sensitivity on 10 meters? This is a K3 that was in Aptos a few months ago and came back "within spec". Does the K3's 6-meter sensitivity problem extend down to 10 meters? Comments, anyone? 73, Tony KM0O |
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Hi Tony,
I used my K3 this year and did not notice the problem Tony. Last year, I used an FT-900 for an hour and gave up on it because the inter modulation products were so bad and used my Kenwood TS-850. Signals were very weak this year with rapid fading. It would be very possible for two stations near each other to be hearing different signal strengths. Only a few signals were strong and those were only on Sunday afternoon for me. I did notice some distortion on the very strong signals when slightly off frequency which I do not have on the TS-850. My non-contest comparisons with weak signals between the TS-850 and the K3 are that signals that are Q3 on the TS-850 are Q4 on the K3. Does not sound like much, but is the difference between QSO and no QSO. Willis 'Cookie' Cooke K5EWJ Willis 'Cookie' Cooke K5EWJ _______________________________________________ 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 Tony - KM0O
I have the same experience. *Without* the preamp the K3 sensitivity is excellent but turning the preamp on, the improvement in sensitivity is disappointing, in my case as little as 3dB (for 11dB more gain). My K3 has also been back to the factory (primarily for mods), and came back with the statement that it meet specs.
I wonder if others have toyed with the idea of replacing the K3 preamp with a broadband low noise preamp with 11dB gain. I want it in *place* of the K3 preamp so that it will be behind the RF BP filters and thus protected. An outboard preamp in the RX antenna loop is not an option since it would have to be band selected in order to retain good IM. A small well shielded unit should be possible to wire in with a few trace cuts on the main circuit board. With a 1-2dB NF we should be able to lower the MDS by close to 10dB relative to what the typical K3 preamp provides (they seem to vary a bit)
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Re: K3 10-meter sensitivity
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In reply to this post by Tony - KM0O
1. The K3's sensitivity in manufacturer’s specifications for BW=500Hz is equal to -136dBm. If we will recalculate sensitivity for SSB BW=2800Hz we will see only -128dbm. 2. If we will see measurements from ARRL Lab for K3 and ProIII (for example), we will see that ProIII has better noise floor (MDS): for 14MHz -141dBm for ProIII (PreAmp2=On) and -138 for K3 (PreAmp=On) for 50MHz -142dBm for ProII (PreAmp2=On) and -136 for K3 (PreAmp=On) For 28MHz we don't have the results from ARRL. :( 73! Alex UR5LAM Tony - KM0O пишет: Yesterday, in the 10-meter contest, I noticed that some other stations (using comparable antennas) within a very few miles of me were working stations that I could barely detect, or not even hear, on my K3. In itself that is not too unusual, but I had another radio in the shack, a Yaesu FT-900, so I connected it to the K3 for some comparative receiver testing. What I discovered was rather disappointing. About half the time, there seemed to be no difference in the ability of the two receivers to pick out very weak signals at or near noise level. The other half of the time, the old FT-900 seemed just a bit better. NEVER was the K3 better at digging out the weak ones. What are other people's impressions of the K3's sensitivity on 10 meters? This is a K3 that was in Aptos a few months ago and came back "within spec". Does the K3's 6-meter sensitivity problem extend down to 10 meters? Comments, anyone? 73, Tony KM0O _______________________________________________ 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 Tony - KM0O
During a serious effort this week end in the 10 meter contest and
fighting snow static I had a lot of experience with the pre-amp and snow static and the NB! We had a blizzard here all Saturday night and Sunday and a bit below zero and lots of snow blowing around so I really could only use the 5 element at just below 200 feet which was pretty much above the blowing snow. Early on when it was still dark on Sunday morning it was snowing some and even the NB did not take care of it. For those of you down south when it is cold the snow is "dry" and the snow static is much worse. Anyway I had to turn the pre-amp on and off depending on the snow static noise. Several times I was having trouble hearing people and I would notice the pre-amp was off and would turn it on and be able to copy them. Before turning the pre-amp on I had the volume really cranked up and when it was quiet I would turn the volume down and turn on the pre-amp and it definitely made a difference. What I am saying is that I could copy signals with the pre-amp on that I could not copy with the pre-amp off no matter what I did if I did not have the snow static. The bottom line is I had the pre-amp on as much as I could. For me I had more trouble with what I would called NB induced splatter than on 160M CW but I think it was a factor of the wide filter 2.8 khz and the DSP at 2.1. I tried the 1.8 filter a few times but I seemed to have trouble hearing the weak ones and when you are trying to survive it is not the time to be learning how to use your radio. We had great success using the 1.8 khz filter in SS but 10 meters with trying to copy weak signals and having someone strong right next door and using the NB and Pre-amp I just did not get it figured out how to use the 1.8 filter. I will have to try and learn this summer during the better sporadic "E" season but it is nearly impossible to simulate the 10M contest. I have a lot of people calling me that I just can not pull out. The truth is with 1500 watts it is impossible to hear someone running a few watts if they are just barely hearing me. I am sure there were a lot that called that I did not hear and there were others I just could not copy calls, etc. I do everything I can with having quiet rcv conditions and 7/8" heliax but the heliax just makes me louder on transmit so really no help there on hearing the weak ones. Anyway last year before the K3 arrived this summer I used the FT-1000D for a number of years and previous to that a TS-950SDX and the K3 is much better on 10 meters than they were. On another note I did notice the K3 puts out full power on 10 meters which a lot of radios do not. I was amazed at how cool the K3 stays. FWIW I operated split in the contest a lot as it is a lot easier tuning for those off frequency of which there seems to be a lot on 10 meters than using the small RIT knob. The RIT on the K3 is better than other radios I have used but going split is a lot better. Just like the FT-1000D tuning the "SUB" in the right ear is not the most "FUN" with the small knob. I see that physically there is room for a bigger knob. Is there someway one could but your "CQ" frequency in memory and use the main knob for the "SUB". I think I am dreaming but with the firmware lots of things are possible. For those in the NE my heart goes out to you with the "ICE". I have had ice here and it causes a lot of work to be destroyed in a short time!!! Ed W0SD _______________________________________________ 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 Tony - KM0O
Hi Tony following you post I did 10mt MDS calculation on my K3 sn1118 @400hz and I found that the MDS W/O preamp is only -127dBm and -131 with Preamp. I'm also a bit disappointed of this low sensitivity on 10mt and I agree about little gain of the preamp on this band. On the other bands the MDS is into specifications and the preamp gain is about 6dBm. Max IW0GXY |
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Max,
This is unusually low MDS on 10 m for the K3. It should be more like -136. Either your K3 isn't properly aligned, or you're injecting a smaller signal than you think, or there's a problem. Please email k3support so Gary can help you with it. 73, Wayne N6KR Max iw0gxy wrote: > Hi Tony following you post I did 10mt MDS calculation on my K3 sn1118 > @400hz > and I found that the MDS W/O preamp is only -127dBm and -131 with > Preamp. --- 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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