Mystery 660kHz signal - Page 1
Forum section: electronics / general

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 06, 2016, 08:20:32 pm
content: I was running a couple of test earlier and ended up using my analogue oscilloscope (a Hameg 203-6) as I needed the extra channels.At the end of the test I powered everything down and the oscilloscope was last to go off...And that's when I noticed... the signal.I ran to my car, threw my laptop in the back seat and had a pretty intense moment driving towards the Very Large Array in new mexico. Unfortunately, Jodie Foster and Matthew McConaughey wanted their movie back, so I had to give up on the chase.I did however spend a good five minutes trying to figure out where the signal was coming from, and a further half hour trying to get it to come back after it vanished.Signal was at 660kHz, about 50mV peak to peak, and appeared any any channel - was picking it up on the coax cables used in the test jig. Turned off everything in the lab save the oscilloscope - still there - tried adding a 50ohm terminator which attenuated it a little, but it was still there.After five minutes, the signal vanished - and I've no idea where it came fromCan anybody think of common appliances or bands that use the 660kHz range? I've seen a couple of DC-DC converters that work in that sort of range, but if they're radiating that much emf I'd be kind a surprised. Any other ideas where it might have came from, or will I be left blaming it on the aliens?

author: Zero999
author_rank: Super Contributor
timestamp: August 06, 2016, 08:22:28 pm
content: Could it be a radio station? Did you try tuning in to it?

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 06, 2016, 08:34:59 pm
content: Just tried there - no luck I'm afraid!According to the internet, 657kHz and 666kHz are both BBC local radio bands in the UK for local stations a few hundred miles down south.Signal I saw was a 660Hz with very little variation in amplitude (less than 5mV, down in the noise) and the frequency was pretty stable - which is why I never checked the actual radio in the first place!I'm wondering if it might have been a walkie-talkie; though I'm pretty sure they're up in VHF and UHF bands.I wish I had plugged it into the Rigol scope and got a capture of it! Oh well, will need to remember that next time!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 06, 2016, 09:08:14 pm
content: Could've been someone else testing something nearby. Potentially not very "near" at all if it was commercial power level. Pretty rare that that would be the cause, I think, but who knows.Now, where did you add the terminator? Was that a tee against the scope, or did you unplug the coax and terminate the empty scope input?What is the test jig setup, and how are the cables arranged? Was the amplitude the same on all channels? Did it vary by the locations the cables connected to, or how much exposed lead length, or loop length, they enclose, on the jig?Tim

author: Ampera
author_rank: Super Contributor
timestamp: August 07, 2016, 03:18:22 pm
content: You said that it was on any channels at 660Khz.Maybe a jamming attempt? To me it seems like that could do it. Other than that I can't think of anything, and I am not very well versed in radiocommunications.

author: SeanB
author_rank: Super Contributor
timestamp: August 07, 2016, 06:28:36 pm
content: Was this at around dusk when a lot of street lights ( in the UK at least) are turned on in blocks by a group controller, which uses a tone transmitted over the MV feeder to control the local lighting relay in your local substation. Used so as to have group switching and to compensate for inclement weather by turning on early, or to compensate for seasonal variance, without having to have a local clock in each substation. Also used to turn off the lights at midnight in some areas to reduce power consumption and increase lamp life considerably.

author: System Error Message
author_rank: Frequent Contributor
timestamp: August 07, 2016, 07:40:05 pm
content: I also have the same issue.The UK residency areas are considered packed, many sources of interference. You have various radios and low band stuff like radio clocks and other stuff, cell phone towers, possible ground interference. Space is a premium in the UK.If you can at least make a small faraday cage you could try having your oscilloscope inside, that could help as long as the cage doesnt act as an antenna. You will still get noise on the inputs when you use the probes to measure but you do want to see noise when measuring because thats the noise the equipment you measure has to deal with.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 08, 2016, 07:19:09 am
content: Quote from: SeanB on August 07, 2016, 06:28:36 pmAh! I can't remember the exact time, but it was in the region of 1930 - so it may very well have been the streetlights! I shall investigate tonight and see if I can pick up the signal again.Quote from: evb149 on August 06, 2016, 11:32:23 pmFluorescent bulbs may be the culprit - I'm in a mid-terraced house, and the kitchens used to have fluorescent strip lights in them - again, will investigate tonight to see if my light does it.According to the interwebs, induction cookers tend to be in the tens of kilohertz range, with "high frequency" variations going to the region of 100kHz (but these are uncommon). I also came across a whole forum of people worrying that the induction cookers were giving themdisease Xwith its electromagnetic radiation (they claimed all EM radiation was bad (I suspect it was because it contained the word "radiation"))I'm wondering if a laser printer of photocopier was to blame actually - they're quite power hungry when printing - not sure what sort of noise they produce though. I have a (rather crappy) dell laser printer - willtestthat tonight as well.Quote from: T3sl4co1l on August 06, 2016, 09:08:14 pmA commercial test may be possible - there's a big civilian transmitter/repeater (right next to a Ministry of Defence antenna station) a few miles south of me, and they've been expanding the local cell phone network (though I'm not sure why they'd be transmitting in an MF band? I've never really poked around with telecommunications I'm afraid!)The test jig was not my proudest moment - imagine cutting a ball of elastic bands - it sort of looked like that but with four oscilloscope probes and a bodgy PCB with some BNC connectors on it - but it workedThe minimum setup to pick up the signal was an unterminated (1 meter) coax cable coming off the scope - I couldn't get a trigger without the coax or flying leads. When the coax was linked straight from the oscilloscope to the frequency counter, the signal amplitude decreased slightly (about 5mV total) but was otherwise unaffected.The frequency counter could pick it up if you turned the sensitivity up with nothing attached to the input. Again, a flying lead or unterminated coax gave a stronger signal.I turned off everything except the oscilloscope and then turned back on the frequency counter - so that particular room doesn't seem to have been the source.Quote from: System Error Message on August 07, 2016, 07:40:05 pmAye, you can see it everywhere! I was fascinated by all the noise I was able to see when I got my new Rigol scope - I actually discovered my mid-priced wall Worts pump out a surprising amount of RF noise (not at 660kHz mind you)The plan:-observe at dusk and see if the noise coincides with the streetlights start-up-measure when laser printer is printing-measure when fluorescent strip light is starting up / running-capture the waveform on the DSO if possible.Just out of curiosity, what sort of gear would I need to pick up and record an intermittent signal like this over a long period of time? (wait, is that even legal?) I mean, granted, I can take snapshots of it with the DSO - but that requires me to be there to start the recording and I can only capture a few seconds of the signal at most: how do radio analysts and organisations like SETI record things like this? Is it essentially just a fancy (or perhaps fairly simple) trigger circuit and amplifier recording straight onto a hard drive (with or without compression or mathematical transforms)?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 08, 2016, 07:27:57 am
content: A logging spectrum analyzer would be the way to go -- probably an RTL-SDR thingy tuned to that range.Tim

author: System Error Message
author_rank: Frequent Contributor
timestamp: August 08, 2016, 01:45:51 pm
content: some oscilloscopes like my GW instek can capture waveforms over a period of time.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 08, 2016, 01:57:33 pm
content: Quote from: System Error Message on August 08, 2016, 01:45:51 pmMy Rigol 1104Z can probably capture over a long period and dump it onto USB actually - not sure I fancy leaving it on for that long though =/ I can probably also link it up to a raspberry pi or something via it's networking and just configure it to periodically dump a waveform to the USB (or to an external hard drive)..... I wonder if my oscilloscope features wake-on-LAN actually... might be a fun project for the future.I've never really had cause to measure a waveform over more than an hour before - for the sake of tracking down a mystery noise source I'm not sure I can be bothered!

author: tszaboo
author_rank: Super Contributor
timestamp: August 08, 2016, 03:32:58 pm
content: 660 KHz can be an SMPS. They easily work in that range. Maybe a ceramic cap is gone inside the scope. Or BBC.

author: HighVoltage
author_rank: Super Contributor
timestamp: August 08, 2016, 05:40:14 pm
content: I had a situation with a much higher frequencyAnd it took me a while to figure it out, I had to get the government involved with their fancy measurement cars.Read here:https://www.eevblog.com/forum/chat/43-mhz-burst-noise-every-63us-in-the-lab-%28how-to-find-the-source%29/

author: hammy
author_rank: Unknown
timestamp: August 08, 2016, 10:20:13 pm
content: Quote from: cprobertson1 on August 08, 2016, 07:19:09 amA spectrum surveillance monitor.http://www.ke5fx.com/gpib/ssm.htmI made this several times in the past. You need a huge amount of time, recorded samples, a big Excel sheet.You want to find out what type of modulation it is, if there is modulation at all.You want to know if some sort of pattern/regularity emerges.The direction it comes from is important - RF finding with an automated system or your fellow hams around.Patience ;-)

author: vk6zgo
author_rank: Super Contributor
timestamp: August 09, 2016, 06:56:14 am
content: Quote from: cprobertson1 on August 08, 2016, 07:19:09 amGrab an ordinary MF AM radio,tune it to 660kHz & listen---if there is programme content,it is a radio station,or a mixing product from two such stations---it does happen,I remember chasing a mixing product between my employer's staion & another MF station,which unfortunately had our modulation on it.It will be hard to record the actual RF long time,but any modulation could be recorded by connecting the radios audio to the sound card of your computer.Listening to the demodulated signal will be useful,even if it is from some non-broadcast source such as a SMPS,or whatever.If the MF radio is a portable,you can hunt the signal down with it--remember the "loopstick" ferrite rods on these things are directional.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 09, 2016, 07:20:33 am
content: Quote from: vk6zgo on August 09, 2016, 06:56:14 amTried it on Saturday - didn't have any luck. I've picked up the signal once since then, and only for about 30 seconds (that was at around 2000).Will keep the radio handy in case I pick it up again in the near future though!My weekends investigation:Quote-no signal at dusk nor at streetlight start up (will check next time I see them coming on early as well)-nothing from (my) laser printer-nothing from (my) fluorescent strip light-failed to capture waveform on DSO (didn't start it up in time!)Quote from: hammy on August 08, 2016, 10:20:13 pmI wouldn't mind playing around with a spectrum analyser at some point - wish I had a real purpose to actually buy one (rather than just "having it to play around with")I should probably try and get in touch with some of the local hams - I've never really seen or heard of the local hammers (but then again, you can't usually identify a ham just by looking at them.... though there are exceptions)In fact, I might even look into joining them - I've always wanted to try my hand at ham radio - nearest club is a few miles away by train - a bit of a nuisance, but it would be a good excuse to get out more and expand my analogue circuit knowledge while I'm at it!I shall continue the hunt for the mystery signal though. Long-term recording on a radio tuned to that frequency is probably the easiest way - that way I can get an idea of how often it crops up and more importantly, when

author: CJay
author_rank: Super Contributor
timestamp: August 09, 2016, 09:37:06 am
content: It's not Starlord messing around with that ropey class D amplifier design of his is it?

author: System Error Message
author_rank: Frequent Contributor
timestamp: August 09, 2016, 04:39:06 pm
content: well here in the UK i get noises on various frequencies and the usually occur above 1Mhz. If i set the frequency filter to block all frequences higher than 1Mhz i get very little noise. The noises are very regular in nature like some modulated signal.

author: station240
author_rank: Unknown
timestamp: August 10, 2016, 09:03:40 am
content: Wondering if this could be a radio link, I know some sewer monitoring devices use antennas to communicate back to head office.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 10, 2016, 11:31:00 am
content: 660kHz is within the upper sideband of the 657kHz radio station and the lower sideband of the 666kHz one.(That is a very strange set of allocations,as somewhere the sidebands will interfere with each other).There is a possibility that your 'scope input circuitry is being overloaded bytwo or moretransmitters with a 660kHz frequency spacing.Years ago,when I worked at a TV transmitter site,we were troubled by faint vertical ljnes appearing on our transmitted signal.It wasn't present directly out of the Studio to Transmitter Link (STL) but was,at the outputs of the Vision Distribution Amplifiers (VDAs) fed by the STL.We looked at the VDA output with a Spectrum Analyser,& found carriers at 800kHz,1600kHz,& 2400kHz.It turned out that several of the FM stations on our own,& adjacent,sites had spacings of 800kHz or multiples.The signals around 100MHz mixed in the VDA input stages,producing the much lower frequency signal interfering with the video.A small capacitor across the VDA input got rid of the VHF signal,with no measurable affect upon the required signal.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 11, 2016, 05:34:41 am
content: Managed to get arecordingof it yesterday - signal came in two bursts of around about 10 seconds, a bit of crackle when the signal started and stopped. (660kHz, AM, at 1928)Reminds me of a steam trainI'd be inclined to say its a local noise source rather than a deliberately transmitted one - but, I might be wrongWill keep listening and see what I find!

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 16, 2016, 07:45:49 am
content: Found it! I was measuring some stuff on my test jig in the lab - and everything was going well. Made a few changes, put in the new uC, pottered about - and then the neighbour turned on some music next door - and I didn't think anything of it.A few moments later, reflashed the uC with the latest version of my code, and... there it was, a sine wave on the signal line going to my 433MHz transmitter? Well surely I had done something wrong? The oscillator should have been at 60kHz, and it shouldnt even have been active: maybe I was doing something daft?Turned on the the other scope (I was already using the four channels on my rigol) and right before I hooked it up - I noticed the 660kHz signal. Measured the signal that was in the circuit, and sure enough, 660kHz.And then it dawned on me - "neighbour playing music..." - so I went and politely queried him!Found it! I know none of you are excited by this, but it's been annoying me that I couldn't track it downThrough the wall of my lab is the neighbours man-cave - and he has a big-*** 20A powerbrick on the other side of the wall (no, seriously, it's literally the size of a brick) for his masterclass audiophoolery grade hifi (which, to be fair, looked the part - it even hadrealvalves and was shiny and silvery with blue LED strips all over it - AND A WINDOW OMAGOD - with more blue LEDs inside the window to make it sound better)The neighbour was pretty kindly in letting me poke around with my oscilloscope - though I may have snickered a little when he mentioned the following:- Low noise amp (£500)- Low noise potentiometers (£50 each)- Low noise Gold Caps (£30 each - and he had like twenty of them)- Low noise cables (£100)- Low noise perspex window to let the noise in (£40)- Low noise blue lights on the inside to make it sound better (£10)- Low noise 660kHz Noise (£150 power brick)Now, to be fair, he did let me have a listen (he had a REALLY expensive set of earphones (like, in the thousands of pounds region)) - and it did sound awesome... but I listen to music on my £20 headphones on my Ipod, so obviously a hi-fi is going to sound better with an even half-decent set of earphones......but I didn't tell him that partNow the real question is: how do I deal with the noise source - I can't exactly say "Haw, mate - yer fusking power brick's cucking out cloffing noise in the 660kHz range you shote! Gonna no dae that and buy a skanking new one your prunk!?" - given that he spent £150 on it.Will a clip-on ferrite on the lead reduce the noise a bit - or will I have to get a metal box for him to put his PSU in?I mean, it's not a big nor constant signal, but it can be a nuisance (especially if i confuse it with my oscillator breaking!)

author: Kilrah
author_rank: Unknown
timestamp: August 16, 2016, 08:04:28 am
content: Should be a piece of cake, he's seen the noise, and should easily understand how bad his "low noise" PSU actually is! Take advantage of his audiophoolery, go to his place with a clean supply and connect it to his system instead of his crap, and persuade him of how better it sounds. Then sell it to him for £200-300 (it has to be more expensive than the other one of course, otherwise it can't be better)

author: StuUK
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:11:06 am
content: And while you're at it can you tell him i've got some replacement blue lights at a slightly different wavelength and emit even less noise but they are £30 each!

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:26:55 am
content: Quote from: Kilrah on August 16, 2016, 08:04:28 amHahaha! It's a 50V, 20A supply - I don't have any replacements kicking about (Though, I could just buy a generic supply and put it in a metal box so the noise is low...Let's see, a CNC PSU should suffice - £50, metal junction box - £30, engineering - £150, testing - £100, Lifetime return-to-base Warranty - £200, Installation - £20, disposal - £5... - so that's £555 - which means I can pick up a cheap-o arbitrary function generator instead of the crappy one I built myself - coincidentally, with a 555 timerQuote from: StuUK on August 16, 2016, 08:11:06 amOh no man, can't do that! You'll ruin the noise immunity!Mycold-cathode blue lights run at a lower temp than your LEDs, and provide a more even light spread than LEDs - which are a group of discrete light sources, which, as you know means there will be less spot-heating and radiation absorption by the circuit board - which, of course, means lower noise susceptibility from your circuitry. Also, lower ESI, ESR and Capitance - those are all real terms. WouldI lieto you?...I'm just wondering if he'll complain once I start transmitting at up to 10W on my foundation ham license next week xD...and even worse, in a few months time once I've got the intermediate license and build a big-*** antenna on the roof, oh he'll love it!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 16, 2016, 08:34:15 am
content: He might get a noise filter, which is a real thing that exists, though without standards, a $500 audiophool model may not do any filtering at all. (It also may not be the kind of filtering that's needed.)It may be enough to simply replace the power supply with one worth more. But if they aren't doing basic EMC testing of most any of those kinds of products, it may not accomplish anything.Unfortunately, to do it with ferrite beads, you'd need a stack of about a hundred. The frequency is too low. Not practical.Tim

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 16, 2016, 08:46:01 am
content: Quote from: T3sl4co1l on August 16, 2016, 08:34:15 am...does that mean I can sell him 100x clip-on ferrites?Aye, good point - I've got two noisy wall-warts on my bench (25-50kHz range - which spend most of their time unplugged for obvious reasons) - I've also got a literally noisy (as in audible) wall-wart from 1995: I'll do some experimentation and see if I can cut their EMI with metal shielding (I'm thinking adhesive aluminium used for ducts - followed by metal junction boxes tied to earth if the foil isn't enough (which I don't think it will be unless I ground it))I've never really had to deal with electrical noise before - the circuits I make are either working at a low enough frequency (sub 100kHz range) or are adequately designed (i.e with some light shielding) that they just don't have problems. I might deliberately design something high frequency and bad EMC and then try to fix it, just for practice (nothing like a practical learning experience!)

author: CJay
author_rank: Super Contributor
timestamp: August 16, 2016, 09:17:24 am
content: Quote from: cprobertson1 on August 16, 2016, 07:45:49 amActually, I'd do almost exactly that, if that signal is large enough to cause you that sort of headache, ask him to imagine how much of an effect it's having on his hifi. Plant the seed of doubt and let his head do the rest.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 17, 2016, 12:32:36 pm
content: Quote from: CJay on August 16, 2016, 09:17:24 amGood news! He done it on his own accord... his new, custom-built-in-Japan, £400 power supply with integral wifi and both active AND passive noise suppression will arrive in about 4 weeks, and it even...."...wait, did I hear that right? It has wifi?"- MeYes... you read that right. His... his power brick has a wifi connection - but dissapointingly, it's only for connecting to a home automation system (which he doesn't even have)But, that gave me an AWESOME idea to make me A LOT OF MONEY.I'm going to build a simple, moderately low-noise switchmode power supply and what it's going to do is tie up (via the wifi) with a simple web interface that logs the voltage, current, power consumed, and any noise going in / out of the PSU - I'm then going to gold-plate the shielding, add a platinum IEC connector, and sell them for £2000 each. I might even put some basic filtering on it so the audiophiles can have a super clean signal - they will even be able to see the before/after filtering readout so they know they're getting their money's worth!

author: hammy
author_rank: Unknown
timestamp: August 17, 2016, 12:46:40 pm
content: Quote from: cprobertson1 on August 17, 2016, 12:32:36 pmExcellent Idea!Interestingly he directly bought a new power brick after he got the info there is "something wrong/660kHz/the neigbor measured something". Obviously they just need a lurking doubt and they buy it new.Cheershammy

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 17, 2016, 01:02:09 pm
content: He must have had money to spare, I suspect he was just looking for an excuse - "but the dude next door who's a scientist says it's emitting lots of radiation, we need to get a new one!"Aye, as I said - he said he's having it custom-made for him by... Nagasawaya Kiwaki?? Somebody Japanese-sounding at any rate - I was too busy being shocked by the wi-fi addition...He's invited me over to have a listen when it arrives... I might have a bit of fun and tell him it sounds terrible and that he should get a refund--EDIT--Quick addendum, he said he's planning to sell on his old power supply - I hope it doesnt go to somebody with an EE-inclined neighbour

author: CJay
author_rank: Super Contributor
timestamp: August 17, 2016, 02:24:55 pm
content: Quote from: cprobertson1 on August 17, 2016, 01:02:09 pmYou'd have to be an evil person to exploit vulnerabilities in the WiFi and provoke random power downs.y'know, just kinda speculating about the sort of thing a nasty hacker might do.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 17, 2016, 02:38:04 pm
content: Quote from: CJay on August 17, 2016, 02:24:55 pmMan, that'd be cruel!I hear a lot of these easy-install video-doorbells are easy to get the mac address off, you can just lift them off the wall and read the back.Or better still, just steal somebody's doorbellThey can even watch you doing it on their mobile phones.

author: CJay
author_rank: Super Contributor
timestamp: August 17, 2016, 02:52:09 pm
content: Quote from: cprobertson1 on August 17, 2016, 02:38:04 pmYou don't even need to do that, you can sniff the MAC address off the air when someone rings their doorbell.Apparently. So I'm told.

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 17, 2016, 03:01:32 pm
content: Now, see, I read it from a.... not-so-reputable newspaper, so I'm assuming it was just their usual scaremonger B.S. (bovine stercus), like how drones are being used by criminals to steal toupes and how mobile phones cause mucus cancer...I'm guessing the idea of using packet sniffers didn't occur to them - or that home Wi-Fi isn't inpenetrable by any stretch of the imagination.Anyways, we're now drifting off the topic that we drifted off fromThe 660kHz signal will just have to be tolerated for the next 4-ish weeks, and then I get to witness what a £400 custom made wifi-enabled passive AND actively filtered power supply looks like

author: CJay
author_rank: Super Contributor
timestamp: August 17, 2016, 04:50:40 pm
content: Out of interest do you know what make the offending item was?And fingers crossed the new one doesn't spew interference over an even more broad bandwidth

author: Brumby
author_rank: Unknown
timestamp: August 18, 2016, 06:02:11 am
content: Quote from: CJay on August 17, 2016, 04:50:40 pmI'd suggest making yourself available to check out the new power brick when it arrives. I have a feeling you might get asked to test it....

author: Srbel
author_rank: Frequent Contributor
timestamp: August 18, 2016, 06:52:30 am
content: Buy some proper power brick, and give it to him as a gift, to use it instead of the old one. And yes, tell him it costs about 300 quid and it has 2 times less noise, but you got it for free as a sample or something.

author: Brumby
author_rank: Unknown
timestamp: August 18, 2016, 07:13:34 am
content: ... but will it have the polished onyx case and gold terminals?

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 19, 2016, 09:18:38 am
content: Quote from: CJay on August 17, 2016, 04:50:40 pmIt was marked with "Naim Audio" but I suspect it may have been counterfeit (I also can't find power bricks on their websites, just bench units - well, Hi-Fi units, it's what I'd call a bench supply) - he bought it from "Illumen" (ill-omen) Audio Specialists, which I also can't find -.-Quote from: Srbel on August 18, 2016, 06:52:30 amThat's not a bad idea xD Not sure I can be bothered sourcing one though. Having said that, a CNC PSU will probably suffice for about £50 - put it in a nice metal box, earth everything, stick some gold leaf on it... aye, if I had money to spare that'd be a planQuote from: Brumby on August 18, 2016, 06:02:11 amAye! Fingers crossedI suspect you're right with getting asked to test things! I should offer a "once over" where I check it's susceptibility to RF interference and see what it emits for £40 or something. I'd settle for £30 and a crate of beer. (cheaper than my usual rate)

author: cprobertson1
author_rank: Frequent Contributor
timestamp: August 19, 2016, 09:21:51 am
content: Quote from: Brumby on August 18, 2016, 07:13:34 amYou just gave me an awesome idea... a lot of very pretty rocks contain metal flecks and could make a decent attenuater at certain frequencies - and look awesome when polished.Line it with aluminium and shove a hi-fi all up inside it - very expensive, very pretty-looking audiophoolery grade gear: I reckon you could sell each one for £20k-30k for some of the more exotic minerals, maybe £10-20k for standard materials like black granite or schists xD Could beverylucrative, especially with a good marketing managerI wonder if it's amoral to rip off audiophools like that