Uploaded March 2019 | Updated September 2026, 2 weeks ago
PART 2 HEATHKIT HM9 QRP WATTMETER SWR
I spent a lot of time with the Heathkit HM9 QRP wattmeter and swr meter installed all the parts in it for HF use when it came it was built for 6 meters and I need it for use on the HF bands . The whole story is on the video here . One last comment I found the SWR set pot to be very touchy when checking swr you are supposed to pull the swr knob out , turn it for full scale then push the swr knob in to see the reflected power ratio . I found that when measuring SWR when I turned it up to full scale it would JUMP way over full scale . That is because I was at the end of adjustment of the cheap 200 k pot and the pot wiper was touching the contact at the end of its travel . I decided to leave this as it is and when measuring SWR just turn the pot up to 40 on the scale rather than full scale this works not as accurately but ok for most uses . I would like to have tried some different pots but I do not have any with a push pull switch and decided I could tolerate it working this way . Note that I discovered by accident adding the 25 PF capacitor ACROSS the entire toroid winding caused the null circuit to work GREAT I thought I had tack soldered that capacitor to one side of the toroid and was very pleased to see how nicely the SWR null capacitor adjusted the null right down to zero then when Soldering it in permanently I found I the capacitor across the entire toroid winding I wonder if this will work on other HM9 units or was this something peculiar to just this one HM9 due to tolerance of the toroid or ?? at any rate it works great now on HF . NOTE the ticking noise or pecking noise you hear is in my camera it is the auto focus circuit pulsing the lens focus motor I see on the internet other people are having this problem too .The cure is to use a camera with an external microphone something I do not have . Heathkits forever ! Bob
PART 2 HEATHKIT HM9 QRP WATTMETER SWR
I spent a lot of time with the Heathkit HM9 QRP wattmeter and swr meter installed all the parts in it for HF use when it came it was built for 6 meters and I need it for use on the HF bands . The whole story is on the video here . One last comment I found the SWR set pot to be very touchy when checking swr you are supposed to pull the swr knob out , turn it for full scale then push the swr knob in to see the reflected power ratio . I found that when measuring SWR when I turned it up to full scale it would JUMP way over full scale . That is because I was at the end of adjustment of the cheap 200 k pot and the pot wiper was touching the contact at the end of its travel . I decided to leave this as it is and when measuring SWR just turn the pot up to 40 on the scale rather than full scale this works not as accurately but ok for most uses . I would like to have tried some different pots but I do not have any with a push pull switch and decided I could tolerate it working this way . Note that I discovered by accident adding the 25 PF capacitor ACROSS the entire toroid winding caused the null circuit to work GREAT I thought I had tack soldered that capacitor to one side of the toroid and was very pleased to see how nicely the SWR null capacitor adjusted the null right down to zero then when Soldering it in permanently I found I the capacitor across the entire toroid winding I wonder if this will work on other HM9 units or was this something peculiar to just this one HM9 due to tolerance of the toroid or ?? at any rate it works great now on HF . NOTE the ticking noise or pecking noise you hear is in my camera it is the auto focus circuit pulsing the lens focus motor I see on the internet other people are having this problem too .The cure is to use a camera with an external microphone something I do not have . Heathkits forever ! Bob
