Tom & Don,
Tom, When the antenna is connected and disconnected the noise floor moves just barely. You can tell, but it requires a critical ear. >No, I'm not talking about "antenna noise." I'm talking about >signals, in particular at 21.150. Using the pre-amp makes signals >that are unreadable jump out clearly above the K2's noise floor and >turns them into arm chair copy. >A note about my antenna. It is a HyGain 5BDQ trap dipole and the >SWR on it is 1.2:1 into about 200' of LMR240. _____________________________ Don, 3dB does NOT explain the improvement in the copy of signals received, it is more like 7 or 8 S units, signal to noise. A quantum improvement ! Warren ________ OK, that helps explain a bit - 200 feet of LMR240 has more loss at 15 meters and above than what I find is acceptable for me. At the shack end, on 10 meters, the RF voltage is only about half that which is at the antenna base - approximately 3 dB loss. Your preamp is making up for that feedline loss. LMR240 is good feedline, but at higher frequencies and long lengths, I prefer to use something with less loss - I usually use LMR400. >>However, the sensitivity of a properly working K2 on 15, 12 and 10 >>meters is sufficient to make a -136 dBm or lower level signal stand >>out well above (greater than 3 dB) the internal noise of the K2. I >>have measured many, including yours. >> >>Normally the atmospheric noise on those bands is low, especially >>during the current (and extended) sunspot low period, and that >>allows a preamplifier to be of value. >> >>The other thing to consider is the antenna (and feedline loss). If >>there is not an increase in noise (due to the presence of >>atmospheric noise) when you connect the antenna to the K2 (or any >>other radio), then a preamp will help. >>If there *is* a noise increase when the antenna is connected, then >>*usually* a preamp will not help - it will make the atmospheric >>noise heard in the audio output greater, but that is not a signal - >>we normally do not copy signals buried in the atmospheric noise - >>although a few ops have excellent ears for doing just that. >>Warren & Barbara Reese wrote: >>>Dear fellow Elecrafters, >>> >>>I want to report the stunning success the PT-3 has had on the >>>upper bands. Especially 15 and 10 meters. I have long held the >>>suspicion that the K2 is deficient in sensitivity on these bands >>>and the PT-3 confirms it in spades. Stations that are >>>indecipherable now stand out clearly in arm chair copy. >>> >>>Let me recommend to others to try the PT-3 ! >>> >>>BTW, my K2 has been back to both Gary and Don and has been checked >>>on the higher bands for sensitivity. It has returned both times >>>with a testimonial as to it's being OK. >>> >>>TR, K6GC, the Great Circle Station >>>in the State of Jefferson. >>>http://www.ijpr.org/Page.asp?NavID=1033 >>> >>>K2/100/KAT S/N 838, Updated with all the new mods. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
I built a KX-1 with the antenna tuner over the Winter. I don't use it much so I
thought someone else would like to give it a try. Well built; works perfectly. I just tested it using 2 pieces of 24ga hookup wire lying on the and draped over furniture in the living room. tuned up fine and I was able to do a few quick QSO's on 20. $320 shipped USPS First Class CONUS. Doug -- K0DXV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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