Re: Output power

Terry Morris

I have a 5 watt dummy load consisting of 5-1 watt carbon resistors, gold band, soldered into a PL-259 connector circa 1970's. It was given to me from an elderly ham, now SK. He learned I was starting the hobby with a QRP kit built HW-9. He told me he tried QRP once but it was too difficult making contacts. Thought I would like the low power heater. I do.

Terry - KB8AMZ
Brimfield Twp, OH  USA
Linux User# 412308, Ubuntu User# 34905

On Wed, Jun 20, 2018 at 7:13 PM brad martin <emclinux@...> wrote:
Thank you all for the replies. Unfortunately my idea on paper does not look like it’s going to work out based on my experiments last night. My idea was that I have a cb type swr meter and I was going to make it into a digital swr and power meter and well being that it’s not for Hf the output voltage of the meter didn’t line up with output power. .6v on 80, 1v on 40 and 30 and 1.5v on 20. So oh well on that one. I have Arduinos all over the place so using a mega for this is not a loss for me. I almost use them as coasters at this point. I would see a deal on them and get them over the last few years and as far as time goes I always try to make time for my hobbies because life is short right :).

I have seen the dummy load with a cap and diode before and have been planning on adding that to my dummy load as well. When choosing the diode what properties are you looking for?

I have a goal most people would probably say I’m crazy for doing. The plan is that my first HF contact will be done using things I have made, built, or repaired. So far everything I have (power supply, uBITX, antenna, CW paddle, dummy load, and other random stuff) and the swr meter is the only thing I have left that has not has been modified.

On Wed, Jun 20, 2018 at 3:39 PM Jerry Gaffke via Groups.Io <> wrote:
The BAV21 is not a bad choice for the dummy load dectector.
Very cheap, which is of course my primary criteria.

Forward voltage drop appears to be around 0.5v at 0.1ma from their graphs,
the detector would have a much smaller current going through it.
So should still be able to measure 10mW into the dummy load,
though factoring in that drop to the calculations becomes more important than with the 1n5711. 

I'd still use the 1n5711 for the diode RF probe.


On Wed, Jun 20, 2018 at 12:27 pm, Jack Purdum wrote:
We use a BAV21 diode in our design, which is rated at 250V.

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