The QRPer Board

How much do you trust that an EFHW will have good SWR when using a rig that doesn’t show SWR such as the TR-35. I’ve heard people say that they don’t worry because the ant supposed to be resonant on 40m & 20m. I’ve always used an ATU when using my TR-35.

Max - WG4Z

wg4z wrote: ↑Mon Dec 05, 2022 11:26 pm How much do you trust that an EFHW will have good SWR when using a rig that doesn’t show SWR such as the TR-35. I’ve heard people say that they don’t worry because the ant supposed to be resonant on 40m & 20m. I’ve always used an ATU when using my TR-35.

Max - WG4Z

Hi Max,

I home brewed the linked EFHW that I use with my TR-35. I set it up in my normal inverted V configuration for tuning using an antenna analyzer. I trimmed each section for minimum SWR at the center of the CW portion of each band. 30 and 17 are set by separate links that were tuned individually. 40 was tuned at the full length, and 20 was verified to work well as a harmonic of 40m. While I recognize that soil conditions can vary, I just set up the antenna in my normal inverted V, and run with it. I carry no tuner or analyzer in my field kit.

Note that I do not push output power hard, my target is 5 watts. I use a 13.8V LiFePO4 battery, but keep the power knob about 60% of full scale. So far, results have been good: plenty of contacts and no smoke.

Best 73 de Brian - K3ES

Same answer as Brian K3ES. I have checked it several times since I built it a couple years ago, including most recently when I added a link for 30m, but it's always been good enough (less than 1.8) and don't worry about it in the field.

However, if you're finicky, note that an EFHW might not have the same SWR across all bands. Mine's trimmed to be real good on 20m (<1.2 across the entire band), but is slightly higher on 40m (but <1.5) and gets up to 1.8'ish on 10m. (FYI, it's also <1.2 on 30m if I pull the link.) I'm not sure if that's because of slight differences in the multiples in the relevant band portions or due to the way 49:1 windings actually work, but in any event some people with perfectionist tendencies will tweak the length slightly depending on the band of interest. In any event, my antenna has been way good enough for me and I don't worry about it.

73 Skip K4EAK

I almost always use a tuner with my EFHWs and the TR-35, but not because I'm concerned about SWR. My little rig will put out 8 watts or more at full power with 13.8 volts. I run a lot of QRP events and 8 watts ain't QRP. I want all of 5 watts out, and the tuner keeps me good to QRP standards.

I use an ATU-40 I picked up on eBay. I like it so well that I bought a second one. Cheaper than either ATU-10 or ATU-100 and works great with my QRP rigs.

72,

Don, K9DRP

I use a 40m efhw at home, and one in the field. My rig has a built in SWR meter and tuner, but I have never needed the tuner on 40, 20, 15, or 10.

John WA4RXO