+++++++++++++++++ Date: Mon, 25 Nov 2002 09:04:58 -0500 (EST) From: kc4kgu at ENTERZONE.NET To: Dave Sergeant Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Re: Noise level on 160m On Mon, 25 Nov 2002, Dave Sergeant wrote: > On 25 Nov 2002 at 4:01, LA3ZA wrote > > > I notice that the band is very noisy, but my K2 behaves in a strange way as > > I have to work it with the Attenuator on and RF gain in the 10 or 11 o'clock > > position to get rid of a kind of noise that makes it almost impossible to > > copy anything. The Noise Blanker makes it a little bit easier, otherwise the > > RF gain has to be turned down even more. The noise seems to come as the RF > > gain crosses a threshold and then it will distort the received CW also. To > > me it seems like some sort of overload or oscillation in the RF/IF part of > > the receiver. I have also noticed this kind of behavior on 80 m from time to > > time. > > I also suffer from very similar noise on top band and to a lesser > extent on 80m. I had originally thought it was local noise to me (and > was certainly not there some years ago when I was more active on the > band). It is certainly not generated internally in the K2 and was > completely absent when we used my K2 in the RSGB Field Day in June. > It is also usually absent during daytime and the early morning hours. > I rather suspect it is from the increasing use of computer and TV > devices (ADSL springs to mind as well). A month or so ago, I chased a noise on 75/80 + 160m here at my shack. Strangely, for the first two days or so, I thought that it was atmospheric garbage or that the band(s) were just poo-poo. It sounded like a wind storm on the K2 and on the TS-2000. Then, one night, I was monitoring the 75m wind storm while I was working on some power runs (installing some new lighting) in the house. I wasn't sure which breaker was which (they're now labled) so, I simply broke out the flashlights and killed the main power. The shack has a large battery for backup so, the radios stayed on. Much to my amazement, the "wind storm" went away and the band was VERY good. After I completed the electrical work, I started tracking the noise source down. I live about 500yds from a sub-station and I had this sinking feeling that I was going to be in for a long drawn out battle with the folks at AEP over something at the sub-station causing noise on the lines. I grabbed my portable receiver and walked outside. The noise was louder on the ground floor then in the basement where the shack was. I was getting even sicker. Then, as I walked towards the sub-station, the noise got softer. The further I got from the house, the less noise I heard. I finally tracked the circuit that was causing the noise down to my upstairs office. Then it dawned on me. A week earlier, I had brought a "retired" machine home from our datacenter to use in the office. I hadn't been on the air for a couple of days after bringing the machine home so, the "cause and effect" relationship didn't stick out in my mind. I turned the office breaker back on - the noise came back. I powered the computer down and the noise went away. It was the computer. I haven't powered it back up since then. I'm fairly certain it is the power supply. You can literally hear the HD spin up on the air when it is powered up. So, if you have introduced something new to your environment, look there. I've not had PC noise issues ever before. I've even operated portable from just outside of our datacenter with no issues. This one machine caused quite a racket though! I'm just glad it wasn't the refrigerator or heat pump! 73 de John - K4WTF +++++++++++++++ Reply-To: From: "Sverre Holm - LA3ZA" To: Subject: RE: [Elecraft] Noise on 160m Date: Tue, 26 Nov 2002 09:25:49 +0100 Thanks to those who responded to my question. It turned out that the noise source was sitting right under my desk - a little embarassing perhaps, but it is a switching power supply! With a battery, the noise goes from S9++ to S1-2 in day-time on 160 m 73 Sverre LA3ZA +++++++++++++++ Reply-To: From: "Sverre Holm - LA3ZA" To: "'Dave Hottell'" , Subject: RE: [Elecraft] Noise on 160m Date: Tue, 26 Nov 2002 19:18:04 +0100 My switchers are both local brands and have probably been used for powering the old style car phones (NMT 450 system). The best one with respect to noise and which runs from 90-230 V is a 13.5 V/5A switcher made by www.mascot.no, model 8620 (no longer in their line of products). It will only give noise if the K2 is powered by it, not if it idles and the K2 runs from batteries. The worst one generates noise on idling, which is radiated. It is labeled Powerest 0588A. But, having modified my K2, why not modify the power supplies, along the lines of http://focus.ti.com/docs/apps/catalog/resources/appnoteabstract.jhtml?ab stractName=sbva012 ? Sverre LA3ZA ++++++++++++++