[Elecraft] Dummy load (with light bulb) doesn't work

[Don Wilhelm]

Jeff,

If you MUST use a light bulb, a higher wattage bulb would present a load
much closer to 50 ohms than a 40 watt bulb - the one I just measured showed
only 25 ohms cold resistance, so 2 of them in series would be a bit better.

Be aware that a light bulb will have a lot of inductance - so expect the SWR
to be high because of that even if the resistance is correct.  Light bulbs
make very POOR dummy loads at RF frequencies, and they change resistance as
the element heats.

Bottom line - almost any form of 50 ohm resistor would make a better dummy
load than a light bulb, but wirewound resistors are not very good either
because of the inductance.  The Elecraft DL1 is a good investment if you
need a dummy load, and there are other sources too.  Every ham shack should
have some type of good dummy load.

If need be, borrow a good 50 ohm resistive dummy load if you can to complete
your alignment - your K1 (and you) will be happier for it.

73,
Don W3FPR

----- Original Message ----- 

> I'm ready to align and test a K1's transmit side.  And I need a dummy
> load to do it so...
>
> My first attempt at a homemade dummy load went like this:
>
> A light bulb socket (with 40 watt bulb in it) on a plastic stand was
> connected on the underside to two pieces of about 9" insulated wire (wire
> is about 18 gauge, I'm guessing).  The positive wire I soldered to the
> center of an SO-239 (female) connector, the negative wire I soldered to
> the outside (threaded) part of the same connector.  That connector has a
> BNC type connector at its other end, and I attached that to the K1
> antenna jack.  When I turned the rig on, the output wattage said 2.0, but
> the BAND button would not give me either band, just the reading P=0 on
> the screen, which I know means that no power is going out.
>
> How can I change the dummy load to make it work?
>