[time-nuts] 4 KV Power Supply Recommendations

Bob Camp lists at cq.nu
Mon Jan 18 23:15:16 UTC 2010


Hi

My guess is that your VHF antenna is far from perfect at 2.4 GHz. The power seen by the antenna *should* be significantly less than the oven is actually leaking. The same could be said about the connectors and cable used (loss at 2.4 GHz).  Assuming there's not a gotcha in the setup or calibration of the spectrum analyzer, that microwave is putting WAY more than it should.

Bob 
On Jan 18, 2010, at 5:10 PM, Didier Juges wrote:

> I could not resist, so I checked my relatively expensive Sears/Kenmore
> microwave oven.
> The results are there:
> http://www.ko4bb.com/Test_Equipment/Microwave_oven_leakage/
> 
> In one word, dismal. Almost 1W peak power leakage at 1 foot, and almost
> 100MHz occupied bandwidth.
> 
> I looked with a crystal detector driving a scope, and it is obvious the unit
> is driven from a 60Hz transformer with half wave rectification, and has no
> filtering whatsoever, like the first Microwave oven I have ever opened (a 20
> years old model long dead).
> 
> Didier KO4BB
> 
> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com 
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Chuck Harris
>> Sent: Monday, January 18, 2010 8:28 AM
>> To: Discussion of precise time and frequency measurement
>> Subject: Re: [time-nuts] 4 KV Power Supply Recommendations
>> 
>> As I understand it, the supplies are 100KHz, and have no 
>> significant filtering at HV.  They modulate the magnetron 
>> with the 100KHz PWM mess.  As long as the signal doesn't 
>> leave the rather wide ISM band, they are under no obligation 
>> to filter anything.... routers, etc. are squatters on the IMS 
>> band, after all.
>> 
>> I am sure that some brands are better than others, but then 
>> some brands are only $50.
>> 
>> I don't have any of the new ovens as yet... My old beaters 
>> from the early '90s are still running strong.  I have no 
>> neighbors, so their choices are not an issue.
>> 
>> -Chuck Harris
>> 
> 
> 
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