2020-05-01, 10:09:00
Rob, a EFHW is a really good antenna to use. Mine is just that. I have attached some pictures to show you my installation. The near end is supported at about 18 feet on 5 sections of fibreglass camo pole (Princess Auto). The wire actually droops down the pole to the 49:1 transformer inside the grey plastic box on the fence. If your wire runs from your tower you may have to mount the transformer at the top of the tower to prevent the tower detuning the antenna.
A couple of notes about my 49:1 transformer:
1. I used a single ferrite core, FT240-43 (Mouser Electronics Kitchener, ON depot. Ordered online, delivered by Canada Post the next day). Some EFHW experts (e.g. Steve Ellington, N4LQ) recommend 3 cores. I never use more than 100 watts and have found that a single core works just fine. If you plan on using an amplifier you should probably use 3 cores.
2. I used thinner enamelled wire for the windings than is recommended. It was all that I had. I checked the current ratings and calculated that it should be easily sufficient for 100 watts. I have built another 49:1 transformer for use when camping in my trailer and used stiff insulated wire; it works too.
3. It is recommended that you use a high voltage capacitor across the coax input "to improve performance on the higher bands". I found that to be true for a 66ft wire (half-wave on 40m) but it made no difference for a 132ft wire (half-wave on 80m). Also, the Mouser part number for the part was no longer available when I tried to order it. My home antenna is 132ft (more or less) so I omitted the capacitor. My camping antenna is 66ft and, since I didn't have the right capacitor, I substituted a 4ft section of RG-58 coax, open at the far end, which has a capacitance of 25pF per foot. I tuned the length to get resonance on the 20m band - works like gangbusters.
The far end of my wire is supported at about 30ft on a tree at the back of my yard. I found that I had to adjust the length of the wire to get it resonant on the frequencies I like to operate. For me that is the CW portion of 40m and 80m. I bypass my tuner and get near perfect SWR. When I check into the GBARC HF net higher up the band I have to use my tuner. I also need to use my tuner for 20m. The antenna also tunes up OK on 30m - surprisingly.
One further note; the coax feeding the antenna MUST be perpendicular to the antenna wire for as far as possible. That's not just theory - I proved it in practice. I originally had my coax running parallel to the antenna (but about 20 feet away) and the induced RF in the coax braid brought RF right into my shack and caused tuning problems! If you run your wire from the top of your tower and bring the coax down the side of the tower you won't have that problem.
John, VA3KOT
A couple of notes about my 49:1 transformer:
1. I used a single ferrite core, FT240-43 (Mouser Electronics Kitchener, ON depot. Ordered online, delivered by Canada Post the next day). Some EFHW experts (e.g. Steve Ellington, N4LQ) recommend 3 cores. I never use more than 100 watts and have found that a single core works just fine. If you plan on using an amplifier you should probably use 3 cores.
2. I used thinner enamelled wire for the windings than is recommended. It was all that I had. I checked the current ratings and calculated that it should be easily sufficient for 100 watts. I have built another 49:1 transformer for use when camping in my trailer and used stiff insulated wire; it works too.
3. It is recommended that you use a high voltage capacitor across the coax input "to improve performance on the higher bands". I found that to be true for a 66ft wire (half-wave on 40m) but it made no difference for a 132ft wire (half-wave on 80m). Also, the Mouser part number for the part was no longer available when I tried to order it. My home antenna is 132ft (more or less) so I omitted the capacitor. My camping antenna is 66ft and, since I didn't have the right capacitor, I substituted a 4ft section of RG-58 coax, open at the far end, which has a capacitance of 25pF per foot. I tuned the length to get resonance on the 20m band - works like gangbusters.
The far end of my wire is supported at about 30ft on a tree at the back of my yard. I found that I had to adjust the length of the wire to get it resonant on the frequencies I like to operate. For me that is the CW portion of 40m and 80m. I bypass my tuner and get near perfect SWR. When I check into the GBARC HF net higher up the band I have to use my tuner. I also need to use my tuner for 20m. The antenna also tunes up OK on 30m - surprisingly.
One further note; the coax feeding the antenna MUST be perpendicular to the antenna wire for as far as possible. That's not just theory - I proved it in practice. I originally had my coax running parallel to the antenna (but about 20 feet away) and the induced RF in the coax braid brought RF right into my shack and caused tuning problems! If you run your wire from the top of your tower and bring the coax down the side of the tower you won't have that problem.
John, VA3KOT