02 March 2013

Cedar Lakes Gauteng end-fed-half-wave (efhw)

At 13:30 local, I walked out from our apartment a distance of about 500 metres to the upper corner of our Cedar Lakes gated community. There I located a nice tree to sit under which was right under the electric fence. Well lets see what I can hear! My Inventory for this trip consisted of the following:

  1. Small backpack
  2. K2 with internal battery, carried in purpose built case
  3. mini-Palm paddles
  4. 7.020Khz (20.32m) long 0.5mm pvc covered wire
  5. EFHW antenna tuner
  6. Coax connector from K2 to tuner
  7. Antenna launcher consisting of a 10m long cord tied to a yogurt bottle filled with sand.
  8. Leatherman
  9. Earplugs
  10. Electrical tape
  11. Waterbottle
  12. Notebook and pen
  13. Hat (on my head)
Using my sand filled yogurt bottle antenna launcher, I was able to get my EFHW up into the tree about 8 metres after two throws. I then strung the wire across to a branch in my shade tree up about 2.5 metres and routed it down to the tuner which was sitting on the ground near the radio. After setting up the K2 and bypassing the internal ATU I was able to tune the wire to an SWR of 1:1 with ease using the efhw little tuner and about 400mW. Based on the marked spot on the tuner dial I could see that the system was operating correctly and there was no noticeable coupling to surrounding objects. I then touched the K2 chassis and noted no change in SWR. I figured that a counterpoise (other than the chassis and metre long connecting cable) was unnecessary. This antenna loves it when the rig is on the ground. I was QRV after a 15 minute set up time and turned the power up to 5 watts. I immediately heard ZS4SFon 7020KHz. I called om Monk in Welkom FS and had a wonderful 40 minute rag chew with him. We QSY'd down to 7015KHz due to a net starting up at 14:00hrs. He gave me a solid 599 report and he was 599+20dB. I was absolutely amazed at how good this efhw worked. I could hear the electric fence but was able to eliminate the QRM completely by using my noise blanker on setting 2. The wx was looking threatening so I packed up after making a few CQ's with no answer and walked the 500m back to the apartment. I reckoned this trip was a great success and I look forward to more QSO's with Monk in the future. It sure was nice to do a bit of qrp/field/cw on a lazy saturday afternoon!

Improvement opportunities:
Cerdar Lakes, Fourways, behind our apartment
  1. I need a cw rig for 40m with built-in batteries. 2 watts. Rockbound on 7020khz.
  2. Built in LED type swr meter in the tuner altoids tin.
  3. The efhw wire can be much smaller gauge
  4. Use a fishing weight as the launcher
  5. Get a miniature notebook
  6. Use smaller coax for the feeder line.
  7. Try to tune the EFHW using the built in K2 tuner (however I will be surprised if it works since the EFHW exhibits an end impedance of about 5kohms??
  8. A small towel to sit on to prevent 'ants in my pants!' 

40m EFHW + Antenna launcher. Too bulky!

EFHW tuner showing expected tune mark on 40meters

EFHW tuner. A parallel tuned circuit with 5K to 50 ohm transformer


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