Re: Transmit indicator light.
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Roy? WA0YMH
Yes.? It works fine with just a couple inches of twisted hookup wire between toroid
and LED.? Adjust the number of turns for slightly less than full brightness at full
power.? FT37-43 cores work well, but for 40M you can use one of the clip-on ferrites
or the green core liberated from a dead CFL light bulb.?
This is not a particularly new or original idea.? It has been floating around the airwaves
for many years.?
Arv? K7HKL
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Arv, so you have used this method in a QRP transceiver? Did you run the wire to the LED as a simple twisted pair or a piece of mini coax?
Roy WA0YMH
Roy WA0YMH
Probably could use a diode rectifier and filter cap at the toroid location and run
DC to the front panel LED.? I have never tried that because radiated RF inside
the chassis has never been a problem.
Using a rectifier and filter cap could also let you measure RF current on an ADC
input of the Arduino.? Interesting thought that if you measure RF current and RF
voltage at the antenna jack it might be possible to calculate antenna impedance.
Arv? K7HKL
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The following is a question not a statement.
Typically the ant lead is at the back of a radio case and the LED indicator would be on the front panel. Wouldn't running the wires feeding the LED that distance cause a potential of rf radiation into the radio?
Roy WA0YMH
On Mon, Jun 18, 2018 at 8:07 AM Praba Karan < vu3dxr@...> wrote: Circuit diagram to enable this idea?..
On Sat, Apr 21, 2018, 3:51 AM Don, ND6T via Groups.Io <nd6t_6= [email protected]> wrote: In my opinion, the very best LED transmit indicator was the one that Derry Spittle (VE7QK [SK]) used in his Epiphyte QRP SSB series. That was just a 470 ohm quarter watt resistor through a small toroid and attached to a panel-mounted LED at each leg. The lead to the antenna passed through next to that resistor. That was it! When RF went to the antenna, it lit. You could easily tell if you were speaking loudly enough into the microphone, etc. Fast response, little panel space, and EASY. 73, Don
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