While this thread isn't much to do with Flex Radios, it is interesting and caught my attention. Being an ex-sound engineer, I am sensitive to sound and so, I'll chime in a bit.
I find that the most annoying thing in my shack is the oscilloscope fan, due more to the higher frequency of the sound than the loudness. Next on the list perceptibly, it is a toss-up between my F3K and the computer's large, but slow, 200mm fans, except that the 3K fans are higher pitch and hence, a bit more annoying. (Which is why it resides buried on a shelf.) The exception is when I am running my F3K on 100% duty cycle modes and I push it to near full power, then the fan kicks up in the Flex relatively loud. I have several power supplies, including my old linear Astron, which is my permanent install supply in the shack. The Astron's hum is VERY soft compared to even the quiet tower computer that sits beside my desk. If you run a desktop/tower computer, a linear Astron supply that uses no fan won't be perceptible above the computer. Due to this thread, I decided to do some exercises on what is the loudest in my shack by itself and overall sound levels. It is important to understand several things about noise in a room: 1 - Different frequencies are more annoying than others. In general, the higher the frequency, the more annoying. 2 - Sound pressure is cumulative. If you have 10 very soft things running, the overall sound level is going to be higher than the loudest item. 3 - Empty room with hard floors = noisy, due to high reverberation and no absorption. Carpet, textured ceiling and furniture quite things down considerably. I place a calibrated sound meter set to ANSI C-Weighted on the corner of my desk pointing toward the shelves my equipment is setting on. This is closer than my ear would be to the equipment by about 2-3 feet. (You can see a photo of my shack at QRZ with me near the operating position.) These are the results of my not-so-scientific-but-close-enough testing. 38 db - Nothing running 42 db - All equipment off, A/C running in house, so slight sound of blower in ductwork. 42 db - Astron power supply running. I can hear the very slight hum of the transformer. Placing meter on shelf the Astron is on, it reads 46 db. 49 db - computer only 49 db - F3K only. Noticeably higher in pitch than the computer. Placing meter on shelf within 12" of F3K, it reads 60 db. 46 db - oscilloscope (Tektronix 2230) only. Placing meter on shelf within 12" of scope, it reads 56 db. IT is perceptibly quieter than the F3K at the operating position. 51 db - AL80B amplifier only - transformer hum and fan. Placing meter on shelf within 12" of amp, it reads 63 db. The AL80B is considered a quiet amplifier. 54-55 db - All equipment running simultaneously measure at edge of desk. You can see how the sound is cumulative. 51-52 db - All equipment running simultaneously, as measure from operating position. 60 db - All Equipment running, F3K in 100 watt two-tone test, fans running at max speed, measured at edge of desk 72 db - Same as above in two-tone test, with meter 12" from F3K on shelf (Obviously, placement of F3K is key so this doesn't drive you crazy.) And the loudest thing in the shack, my Palstar DL2K dummy load, with fan on 61 db - from operator position 74 db - with meter within 12" on shelf by DL2K Luckily, I RARELY run the dummy load long enough to get the fan to kick on. For reference 64 db - desk chair wheels rolling on floor 72-74 db - Talking in a normal voice about 12" from meter I do own two switching supplies that utilize variable speed fans. (Both happen to be Jetstreams which I won as door prizes. They work quite well and self-protect for short circuits, which the Astron does not other than a fuse.) While I didn't test them for sound levels, I can tell you they are very quiet and not as loud as the computer or F3K. If I push them hard, I can make the fans spool up to high speed and then they are relatively annoying. But I never push a power supply above 50% of its rating as a normal practice based upon experience, as this will shorten any power supply's life, regardless of the rating claims. I could drop the sound pressure levels down a bit in my office/shack by putting a sound treatment behind the equipment, so the sound is not reflected off the back wall. Also, putting acoustic treatment in the room to reduce the reverberation level in the room would also help. But I would not call my shack loud by any stretch. That's my 50 cents on the subject. 73, Scott AC8DE -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Tim Taylor Sent: Tuesday, June 21, 2011 12:24 PM To: [email protected] Subject: Re: [FlexEdge] O/T - Need Power Supply Suggestions (Please Read MyRequirments) Silent (adj)-(def) inaudible. Can not be heard. Does not bug the operator. I am mainly trying to get away from loud fan noise. I find the noise from computer fans, power supply fans, amplifier fans, etc can be quite annoying after a while. How loud is too loud? Well, when you finally turn it off and you are struck by an over whelming sense of quiet, then it was too loud. I guess the good news about growing older is that I am getting deafer. Right now, when I am chasing weak signals, I use Bose noise cancelling headphone. They are very expensive, but they work great. 73, Tim -----Original Message----- From: Peter G. Viscarola [mailto:[email protected]] Sent: Tuesday, June 21, 2011 11:02 AM To: Tim Taylor; [email protected] Subject: RE: [FlexEdge] O/T - Need Power Supply Suggestions (Please Read MyRequirments) >My requirements: >1. Its operation is SILENT!!!! Can you further define "silent", please? Because, even if conductively cooled, a linear power supply is going to hum. The Astron linears certainly make quick a pronounced hum in my shack. Does hum count in your definition of silent, or are you just concerned about fan noise? Peter K1PGV _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software. _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
