We have a Panasonic 1300W microwave oven. It causes a tremendous amount of static in weak (5000W) AM radio stations. Even on a battery operated portable playing in the other end of the house. Is this an indication of a problem with the microwave, or it's normal, is there a trap, or something that can be done to eliminate the interference?
Sounds like leakage, usually around the door. Use the portable radio as a detector, put the oven on low power, the radio tuned away from a station, and move it all around the oven, esp. the edges of the door. If it's the door, it's either not closing properly, or food particles are preventing a good seal.
Why low power? Microwave Ovens actually only have one "power" - the lower settings merely cycle the Magnatron on and off. You should never run a microwave while empty, in any case. Put a bowl of water in it.
BB
My four year old Panasonic (full size) microwave oven causes no such interference with AM signals. Put a cup of water in the oven and listen the static when the oven is on full power and on low power. If you hear a modulated sound on low (rapid pulses of static) then there is likely a poorly bonded connection in the path between the magentron and the oven chamber. The intense microwaves will cause arcing at any point where there is a sufficiently poor bonding (electrical connection) between any of the metal parts involved in the microwave path. This arcing will create a spark oscillator type source of broad band radio noise which can get into the house mains or directly radiate from the metal cabinet.
Fixing the problem by trying to filter out the noise created by a defective oven would appear to be the wrong solution, better to eliminate the source. Since microwave ovens are so cheap now I would just get another one and relegate this one to the junk pile or someone you have a grudge against.
Regrads,
John
Really? Please tell me where I can find out more about this.
Thanks, BB
I have had two over the range Microwave ovens, a Quasar and recently a GE Profile. When running either they create noise on the AM of my old 1972 Panasonic tabletop radio on the top of the fridge.
The current crop of dept store AM/FM radios are known to have crummy AM reception. It is just built in so they can say it is an AM/FM model. The designs are not very good at rejecting noise.
My easy solution is to turn off the radio when the microwave is on.
If you have to listen to it with the microwave on you can try the following..
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Low Noise Antenna Connection From: snipped-for-privacy@space.mit.edu (John Doty) Newsgroups: rec.radio.shortwave Subject: Low Noise Antenna Connection Date: 26 Nov 1993 16:55:24 GMT
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BinaryBillTheSailor@Sea++.com wrote in news: snipped-for-privacy@4ax.com:
Panasonic Inverter technology.They use a switching power supply to generate the voltage for the Magnetron,and can vary the output DC voltage,thus changing the power the tube generates.This also eliminates an expensive iron core transformer,and reduces the weight of the oven.
Try the Panasonic website for info on this.
Only drawback I can think of is that the switching PS is more failure- prone;more parts,more complexity= less reliability,and more vulnerability to surges on the mains.
Switching power supplies are notorious sources of birdies at every harmonic of their (not very high) operating frequency, even when there's been some effort to suppress them in design. I doubt a microwave oven has much suppression.
Try plugging the radio into an outlet that's on a different circuit, you may find one that's more isolated from the microwave. Or if possible, run the radio from batteries, and see if that makes a difference.
vulnerability
My old microwave oven had a strong arc and died. I replaced it with a Panasonic which uses the "inverter" technology. They must have done something clever to reduce noise from the switching power supply because there is no noise on any of the nearby radios or cordless phones etc. The oven also performs as advertised regarding thawing and cooking. Their claim is that thawing is uniform and that the edges of food are not overcooked as compared to an oven which uses PWM.
"George" wrote in news:ltfXa.2809$ snipped-for-privacy@news1.news.adelphia.net:
Regular MW ovens don't use PWM control,they vary the duty cycle of the magnetron,on for 50%,off for 50% for half-power,for example,or 25/75% for
1/4 power.The magnetron runs at full power for the time it's on.Those ovens use an iron-core transformer and rectifier to generate the HV for the tube.HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.