Posted: 8/19/2026 3:09:21 PM EDT
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A couple of years ago I built an 40-10m EFHW. It was designed for the low ends of the bands for cw and ft8 work, and it has worked great with low swr readings almost flat on 40,20,15 and about 2:1 on 10m. Perfect for what I need. I have room to extend the length of the antenna to make it 80-10m. My primary reason to do this is not so much picking up 80m as much as it being resonant on 30m. My question is if I cut the antenna for the low end of 80m am I going to see low swr readings on the rest of the bands. I have no need to add coils that expand the coverage into the phone portion of the bands. Your ideas appreciated. |
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It's been my experience that you won't get 30m resonance on a 75/80m EFHW (I have two of them in use at the house currently) unless you do something I haven't done with the value and position of the loading coil to get it there. The coil is used to dial in resonances on the higher bands, so I've never chased resonance on 30m. My Xiegu G90 tuner doesn't care, and the IC-73 will tune both antennas to 30m in emergency mode (50W peak output). If you want 30m to be natively resonant on the EFHW, I believe you will have to cut the wire for 90 rather than 80 meters. IMO it's a situation where chasing after perfect is the enemy of good enough. Also, I'm not a CW or digital guy anymore, so haven't been on 30m in about 40 years and my opinion should not count 
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Originally Posted By Prolix: It's been my experience that you won't get 30m resonance on a 75/80m EFHW (I have two of them in use at the house currently) unless you do something I haven't done with the value and position of the loading coil to get it there. The coil is used to dial in resonances on the higher bands, so I've never chased resonance on 30m. My Xiegu G90 tuner doesn't care, and the IC-73 will tune both antennas to 30m in emergency mode (50W peak output). If you want 30m to be natively resonant on the EFHW, I believe you will have to cut the wire for 90 rather than 80 meters. IMO it's a situation where chasing after perfect is the enemy of good enough. Also, I'm not a CW or digital guy anymore, so haven't been on 30m in about 40 years and my opinion should not count |
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Yeah, after posting this I did a little more research and found I'm not going to get 30m coverage. I borrowed a MFJ tuner and that worked so I may just have to buy one or forget 30m. Another solution I was thinking about is to run another wire cut specific for 30 and just alternate between connecting it or the 40-10m antenna to the matching transformer. This is kind of an experiment because I don't know how much activity is on 30m anyway. Since I'm running low power I'd like to know more about running the IC7300 in emergency mode. Doesn't seem like a good idea on a permanent basis. |
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An EFHW cut for 3.7MHz will work swell on 17 and 12m. One cut for 7.2 - probably going to need a tuner. All a matter of what's harmonically related. E-mode for the IC-7300 just limits power to 50W out, and the tuner then has a much larger matching range. It's just a menu selection to get in and out of the restriction - didn't take long to memorize the steps. |
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Originally Posted By supercrew: Yeah, after posting this I did a little more research and found I'm not going to get 30m coverage. I borrowed a MFJ tuner and that worked so I may just have to buy one or forget 30m. Another solution I was thinking about is to run another wire cut specific for 30 and just alternate between connecting it or the 40-10m antenna to the matching transformer. This is kind of an experiment because I don't know how much activity is on 30m anyway. Since I'm running low power I'd like to know more about running the IC7300 in emergency mode. Doesn't seem like a good idea on a permanent basis. yep, nevermind. I was wrong. |
Mach
Nobody is coming to save us.
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Nobody is coming to save us.
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