There seems to be something floating around that if there's noise, it must be the K3's fault. While EME frequencies have very little ambient noise unless the antenna is aimed at the sun or some known noise source, for MF and HF, there is plenty of ambient noise that will come in on any antenna.
At my location near Raleigh, NC, on 160m in the daytime, using 500Hz bandwidth the ambient noise is always 3 uV to 5 uV coming in on my 160 transmit antenna, now and then in the 30-70 uV range (source unknown). On ten meters the ambient noise is around 0.2 microvolt with my beam pointed NW. On ten when I disconnect the lead to the antenna, the noise drops another 11 db, meaning that the K3's internal noise is the equivalent of 0.06 uV coming off the antenna. With K3 preamp on, no ATT, AGC off and RF gain to max, the K3's internal noise is a mild "white" noise. When I reconnect the antenna, the noise jumps up to mid-range comfortable audio level, there is "stuff" in the noise including some component of 120 cycle hash. It's not a hiss anymore. Stuff coming off the air. Switching back to 160m, to get the same "pleasant" level of noise audio, I have to turn off the preamp, turn on the attenuator, and back off the RF gain to 2pm to reduce the overall gain of the K3 to get the outside ambient noise to match the sound level I want. This is NOT engaging the AGC. I have reduced the overall gain of the RX to match the band. In older radios that seem quiet on 160, the gain is either intentionally reduced on 160, or the RX just didn't have the gain on any band, and the performance on the high bands really stunk. RX gain (RF gain +PRE) that is comfortable for 10 meters will not work for 160. In the absence of a louder signal, 5 uV noise will be set to regular signal level by the AGC, the same level it would have put the way in the clear 5 uV signal on 10m. In the FT1000MP there was a default menu setting to reduce the radio's overall gain as the frequency went down. In contests we generally turned that off, preferring to handle gain controls ourselves because we had quiet listening antennas for low bands and occasionally quiet conditions on big antennas. The K3 has left those decisions to us so I can use the RX preamp on BOG listening antennas to make up for that antenna's natural loss. I like that. It gives *ME* the choice on how to set the gain instead of forcing me to supply a switchable preamp to make up for an artificially reduced gain For 160 listening on the transmit antenna it's preamp OFF, ATT ON, and RF gain backed off to 2 or 3 pm. For the BOGs on the RX ANT port it's still RF gain at 2pm, but ATT off and preamp ON. No roaring noise, I can copy all the signals clearly AND use the AGC to keep the 20 over 9's from blowing off my ears. I backed off the RF gain to place the ambient noise at the audio level I'm willing to put up with. Using that procedure, I DO NOT have to jockey RF as I tune across signals. I DO NOT have noise roaring in my ear. I set it for the band and the setting suffices for the evening. In the Orion, the RF gain was not a dedicated knob. It was a menu item set by band. One owner (who had had it for over a year) brought one to a contest, and everybody was complaining about the AGC bringing the noise up to a roar on the low bands. The ONE change that was made? Set the by-band-by-mode digital RF gain in the menu down from 100 (pedal to the metal max) to a number that left the band noise at a tolerable level. End of problem. End of complaints. It was fine after that. Very interestingly, the owner could not understand our complaints and had never done that himself. Took a room full of hollering peers to get him to even look at it. Even then it was a guy who had never used an Orion before that figured it out. 73, Guy. On Thu, Jan 7, 2010 at 9:11 AM, Wes Stewart <[email protected]> wrote: > Doug, > > It's been a long time since I was on EME and time has marched on to where the > current ops are using digital modes to pull signals from below the noise and > calling them "contacts". But when we actually listened for signals, hours > were spent listening to noise and I can assure you that distortion, artifacts > and whatever else you want to call stuff that shouldn't be there all > contributed to fatigue and the ear-brain's ability to discern signals. > > Wes N7WS > > --- On Thu, 1/7/10, DOUGLAS ZWIEBEL <[email protected]> wrote: > >> From: DOUGLAS ZWIEBEL <[email protected]> >> Subject: [Elecraft] three recordings - say what? >> To: "Elecraft Reflector" <[email protected]> >> Date: Thursday, January 7, 2010, 6:40 AM >> Excuse me, but are all of you guys >> listening to NOISE ONLY? I >> mean...noise WITHOUT a signal? What good is >> that? Sorry, but I never >> listen to noise on purpose. >> >> I cannot see any practical value in such a "test." >> >> de Doug KR2Q > > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
