Some simple math:
4 harmonics -> 4 x 3 db = -12 db
12 V -12 dB = 750 mV over any wiring carrying the load.
If the length of the wiring comes anything close to the wavelength, half
or quarter of the comm freq's, adding a working antenna to this
transmitter design, you might be a nuisance to anything in quite a
reasonable range in addition to your own problems. Bypass capacitors?
Will load (overload?) the square wave generator.
Jos Okhuijsen
irampil@notes.cc.sunysb.edu wrote:
>
>
>All that you say is true under those circumstances.
>Another approach might be:
> no more than 2 leds in series since if one goes, they
> all stay dark
> I put bypass caps on anything with sharp transitions,
> and we are talking 10
>4 harmonics to the nav/com
> range
> Course, ADF would be more likely affected, but I
> would not consider putting such an Antique Direction
> Flubber in my plane ;-)
>
>
>
>
>>Yes super bright LEDs are available, too bright for me to look at when
>>on with 15 ma, but they do get brighter still with pulsing. I don't think
>>10 kHz is going to interfere with much on an aircraft.
>>
>>Ira N224XS in paint shop
>>
>>
>
>I wouldn't bet on that! A square wave is the fundamental freq plus the
>sum of all harmonics, each 3dB down I recall. If used to pulse a series
>string of LEDs, and say a voltage swing of 10V, you can easily get a few
>microvolts in the harmonics to annoy a VHF receiver whose antenna is a
>few feet away.
>
>Fred F.
>
>
>
>
|