So today is a random day off for me, and so I figured that after my interview was done this morning, I would take advantage of some time away from work to play radio. I stopped by the local electronics store to pick up some SO-239 connectors and some 3.5mm plugs.
Once I arrived back home, I brought my mobile rig inside and decided I would try loading what was supposed to be a 220MHz (originally intended as a CB) whip antenna. I was told that Canadian Tire was selling a certain CB antenna which would load up well on 220MHz so I picked this little gimmick up for $15. I figured, well CB radio is essentially 11m so this should work okay(ish) on 10m with the aid of an antenna tuner.
Well, as you could imagine, when I tried listening on 10m not much was heard. I tried switching over to 20m and using my MFJ-902 tuner to match the impedance. I had a few weak stations coming in, but nothing spectacular. At least this was a start! But I knew there was a better way, and perhaps that just might be a dipole cut for 20m!
In my recent acquisitions of things related to radios, I picked up a “Wonderpole” which is a collapsible fishing rod which is 20′ long. I also acquired some end-strain insulators at a recent ham fest. Ah, now we have the workings for a dipole!
I looked around for some spare coax but was unable to come up with anything. I then looked slyly over at the cheap-o Canadian Tire antenna and marched over with my wire-cutters in hand. Without second thought or remorse, I had liberated the RG-58/U cable from the pathetic magnetic whip antenna. Then I was horrified to find that the percentage shielding was perhaps 10% optimistically.
Next, I cut two pieces of 18-gaugue insulated wire at approximately 16’6″ to start the trimming process. In hindsight, I should have cut the wire longer, though I figured the velocity of propagation and the extreme coupling to near-by objects would give a closer match. The two wires were then soldered to the coax, one side to the center conductor, the other to the shield. I had also run the wires around the insulator to act as strain relief – I will do a better job later, this was j-ust done in the spirit of Field-Day type projects (just to get on the air.)
With the coax connected to the two poles of the antenna, it was time to string it up and give it a try! I tied a nylon rope to one side of the antenna and fastened it to our apartment door. The other side of the antenna was attached to the Wonderpole and stuck out out 16th floor window. I should note that I took additional precautions by tying the Wonderpole to our couch to prevent it falling in the event of any failure of the system.
Once it was strung up, I tested out the system and found that the SWR was a bit high on the low side of the band and low on the high side which indicates that the antenna is too short for where I want it (14.07 MHz). Oh well, I’ll suck it up for now – or use the existing wires for 15 or 17m.
I should note that I am using an excellent HF low-pass filter to prevent RFI for my neighbours. I’d like to perhaps add a balun to the system to mitigate any common-mode current in the antenna system.
With everything in place, I was now picking up distant signals like I had a beam antenna! I could not believe my eyes! I quickly fired up JT65-HF and started decoding signals right away. Lo and behold, I made contact with Billy (ZS1BAA) in South Africa !! Our signal managed to traverse 12917.0 km and our reports were -12 (mine) and -19 (his). Not too bad for an apartment dweller!!
So there we have it. Real DX on 40W and a home-made (poorly tuned) dipole antenna, half strung out my 16th floor window. Man I love this hobby!