ARRL

Secure Site Login

Forum Home - Rules - Help - Login - Forgot Password
Members can access, post and reply to the forums below. Before you do, please first read the RULES.

End Feed Half Wave Antenna Problems

Aug 3rd 2015, 14:39

AB2WS

Joined: Dec 14th 1998, 00:00
Total Topics: 0
Total Posts: 0
I am trying to construct a 40m End Feed Half Wave Antenna (EFHWA) for QRPp that doesn't need a tuner, but am seeing very high SWR in the 40m band. I have read what information I could find in these forums and on the net (http://www.aa5tb.com/efha.html).

The antenna was constructed for the 40m CW band as follows:
(1) 67' of 24 AWG insulated stranded wire for the radiating element [468/7.0 Mhz= 66.8' which is 1/2 wavelength]
(2) ~7' [0.05% of a wavelength] or 34' [1/4 wavelength] of same wire for counterpoise- I tried 2 lengths
(3) 9:1 UNUN toroid wound matching unit using a junk box toroid. I used 3 conductor ribbon cable for the winding (http://vk6ysf.com/unun_9-1.htm).
(4) 6' BNC-BNC RG58 coax jumper from rig to UNUN

I tested the UNUN by putting 470 ohm resistor across the terminals, patch cable to IC-7000; It showed low SWR accross 40m.

I tossed the 67' radiator out my 2nd story window in a slight inverted V configuration and tested with no counterpoise, 7' counterpoise, and 34' counterpoise. In all cases the SWR was off scale for 40m; however, it showed low SWR on 80m.

Since 67' is 1/4 wavelength on 80m I reconfigured antenna as 34' radiator, 7' counterpoise with UNUN and this tunes up on 40m. It seems I am making 1/4 end feed antennas?!? What is the radiation pattern of a 1/4 wave end feed antenna and can anyone explain why the 1/2 wavelength antenna isn't working?

Thanks,

James
Aug 3rd 2015, 17:43

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
The fact that its working where it shouldn't suggests some sort of wiring error.

Zack Lau W1VT
ARRL Senior Lab Engineer
Aug 13th 2015, 12:57

K3DRJ

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
How about trying to shorten the 67 foot element 33.5 feet and making the "counterpoise" 33.5 feet and making it look like a center fed halfwave dipole in an "L" configuration?
- Jim -

Back to Top