The Pancake Antenna
by Gil Lappay, 4F2KWT
On many DXpeditions we’ve done the problem of antenna size and weight plus installation options have always posed a modicum of difficulty. The VDA (Vertical Dipole Array) is a new innovation that has been employed by many successful DXpeditioners. The Pancake Antenna, so named because it mimics the visual display of that breakfast mainstay, has been the talk of many people lately. Curious on how it performs I embarked on a project to test it. Who knows, I could just take it along on one of our next trips to some exotic island.
The support system consists of PVC pipes so configured to accept the pattern of the number 12 magnetic wire that I used. The 2 inch diameter boom is 32 inches long while the half inchers are 35 inches in length. Holes drilled into the crossed half-inch pipe made easy assembly of the antenna. A center antenna connector with about a foot of copper wire on each side was attached to the magnetic wire. It came together rather nicely and at the end of two days worth of work at two hours per day soon produced something. How well would it radiate?
It was 4pm when the antenna found itself mounted at the top of a 20 foot iron pipe. The antenna is cut for 40M which means that each side of wire is 33 feet long, initially. SWR was 3:1 right off the bat and I determined that the wires were too long so some trimming had to be done. Sure enough, 5 trips of nips and tucks brought the SWR down to an agreeable 1.4:1 on 7.015 MHz.
Because it was still broad daylight there were only weak signals to be found on the CW portion of 40M. A JA was calling CQ so I dialed down to zero beat and purposely set power to 25 watts as I answered his call. Twice I sent my callsign at a speed closely matching his. He came back to me! Gave me 559 and his name. Acknowledging, I sent him 579 plus my name and we closed the QSO after one more set of returns. The antenna worked!
Ok, 3000 kilometers is not exactly nearby but how about farther away? Soon, VK9DWX on Willis Island was in the band with the attendant pile up. Well, if the antenna would punch through then I would be truly convinced of its efficacy. Because the wall of callers was mildly thick the amplifier was fired up and tested for 200 watt output. A call was put forth and… nothing. Again I sent my call twice at about 25 WPM. He heard me. Man oh man, the operator was really smoking. We exchanged 599s, it is always this way, though he really was a hairline over signal 9. The test is consummated, and how!
Using the automatic tuner on bands higher than 40M saw a quick match every time. The antenna is worthy of being brought along on a DX trip I think. The next trick is to cut it up into parts readily put together as needed. That should not be too hard. The pancake antenna is neither too heavy nor bulky and if it works wonders on a future trip then that will be a story worth telling.
© Philippine Amateur Radio Association, Inc. 2008