Interesting RFI Pulse

Hi all, I just got a hold of a hand-held battery powered theremin from Burns. While riding in an SUV tonight, I noticed a strange RFI PULSE that occured at 4 pulses per second. I had the driver rev the engine, but there was no change in the pulse rate. I tried moving the theremin around the cabbin, but thee was no change in intensity. But, when the engine was shut off, the pulse stopped. I wonder what part of the vehicle could cause that? A computer system? radar system? Don't know.

These days I would imagine damn near everything in a vehicle emits some sort of RFI.

You need to call the fellows from Car Talk ;)

Yeh, lol. What was so interesting is the pulse sounded as if one were playing dipping grace notes. Kind of cool.

Weird. I wonder it it would continue if the ignition key was in the ON position but without running the engine? If it did, you could systematically pull fuses one at a time until it stopped.

Thomas:

Do you know if all the Burns instruments use the same sound-producing circuitry? I recall seeing (on one of the forums here) that a regular B3 will run on a 9v battery. Are they all the same inside?

4Hz is about what one would expect for non-critical scanning - things like checking that doors are closed, or for general system updates..

Not having worked on any vehicle radar or proximity sensing, I have no idea what the update rate for these would be.. but I would think 4Hz is possibly a bit slow - at high speed (100mph) one can travel about 10m (32') in 250ms (if my quick calculations are right! ;-)

A regular B3 will run on a 9V battery, but it will be unstable. The recommended supply voltage is between 14 and 24V to give some headroom to the internal 78L12 voltage regulator.

So the best is taking 2 9V block batteries in series. I had a client from Switzerland who asked me at first to modify his B3 with a power plug instead of the attached 110 to 16V transformer. I did that and sent him an European 230V to 16V power supply together with his "universalized" B3 and also an adapter cable with the same DC plug on one side and two battery clips for 9V block batteries on the other side. He told me that he could play more than 40 hours with two alcaline LR6 batteries.

As far as I know all the B3s use basically the same circuit but with some additions in case of the Pro version.

[i]A regular B3 will run on a 9V battery, but it will be unstable. The recommended supply voltage is between 14 and 24V to give some headroom to the internal 78L12 voltage regulator.[/i]

Merci, Thierry!

I have the B3 Deluxe (which already has a DC power plug) but I thought the adapter supplied with it was kind of wimpy, and I was getting what sounded like a bit of ground hum, so I substituted an Hewlett-Packard 18V 2.2A power supply (model 0950) that is socketed for an IEC AC mains lead with grounding pin, and can use any AC voltage input from 110v to 240v. It seemed to solve the hum problem.

It also has a nice little green LED on the DC power plug itself, so I can easily confirm that AC power is hot (or if the converter is malfunctioning.) And the DC plug itself is an [i]exact[/i] match to the power jack in the B3 Deluxe.

The B3 really likes the 18v - I think it has a bit less residual noise than it had with the tiny unregulated, ungrounded 12v "wall-wart" that came with it.

I understand why Dan Burns sells the B3 with the small adapter - he's trying to keep the price down, and a similar HP power adapter runs about US$50 all by itself. (Luckily I had it left over from an old HP printer that had died.)

Hi Joe Max, Sorry I'm so late getting back here.

Yes, B3s all use the same circuitry, but I'm not certain about the handheld / pitch only theremins.

I didn't think to have my friend take the key out of the ignition. Next time he gives me a lift to opera rehearsal (tomorrow night), I'll take the handheld theremin along again, and try that.

Have your friend just turn the key to the 'on' position without starting the engine (so like, the radio will come on). If it's an electrical device in the car the interference should kick in.