After reading many positive comments here about the QRPGuys vertical tribander I decided to get one. It went together quickly and after a little adjustment got it working with very low SWR on 20 and 30 meters. I was using the built in SWR meter on my YouKits HB-1B. I know not the most accurate but it's what I have for QRP levels. Resonate on 40 meters was way to low so I wound up removing 2 wraps from the inductor and that got it up to where I need it. I was using just a short 3 foot coax jumper to connect to the rig. I decided to add 6 feet of coax to make sure it doesn't change anything. On 20 and 30 it didn't change much but on 40 it is now resonate way up in the voice part of the band with the extra length of coax attached. That is, unless I have my hand under the back of the rig, then the resonate freq comes back down to the CW part of the band. I'm thinking that I will probably operate this antenna with longer pieces of coax since I don't want to be tethered so close the the base of the antenna to operate. I can add a wrap or two back onto the toroid since I haven't yet snipped off the excess I had after taking two wraps off but that part of the wire is no longer insulated. What happens if uninsulated magnetic wire rests against the toroid? It will be fine as long as it doesn't come into contact with uninsulated wrap right next to it right?
Hi, I think it will be fine, I don't think these inductors are conductive..
I put one wrap back on the inductor and tried it with both lengths of coax and my HB-1B. It seems that I can operate the lower part of the CW portion when using 3 feet of coax 7.025-7.055 and I can operate the upper portion of the CW band with 9 feet of coax 7.055-7.100. Have other people experienced such a narrow Q on 40 meters? Perhaps I should buy QRPGuys QRP tuner and use that when using this antenna on 40 meters. I don't think I will use my MTR3B on 40 meters with this antenna without a tuner. I can't risk running a high SWR and not know it with that rig.
You can also try a clamp-on toroid on the coax and slide it back and forth for best SWR...
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Good idea Gil!
I'll try that today.
Gil, Thanks so much for pointing out what should have been obvious. I feel like a fool for not thinking of it myself. It works like a charm. If I run the coax inside the bead without any loops I have to have the bead up by the base of the antenna. If I loop it through just once (like in the photo) it gives me perfect SWR on the HB-1B meter no matter where it is on along the coax. It even shows low SWR over a much wider range of the band.
Glad it helped :)