and since the idea has been whirling in my head for some time now, I decided to run a little "experiment" regarding the (not so) "random" antennas, for such a purpose I created a model in 4NEC2 describing a somewhat typical "portable random" setup, in short the starting point was a random antenna with a 41ft radiator and a 17ft counterpoise, in the the model, the antenna feedpoint is at 5ft from ground, the radiator is sloping up with an endpoint at 20ft (which I considered reasonable for portable operations) and the counterpoise is just dropping down to ground and is then laid in the same direction as the radiator, now, the idea was to try and find if a particular combo of counterpoise length and transformation ratio could achieve a good SWR over the 7 to 30 MHz range and below you'll see my findingsIn short the image below shows three NEC "scans" for SWR over the 7 to 30 range, the top one shows the original antenna fed using a 9:1 UnUn, as you can see, while the SWR is below 10:1 it isn't exactly optimal, so I started raising the counterpoise length until I reached the same length of the radiator, and the middle part of the image shows the curve of the same antenna but using a 41ft (instead of a 17ft) counterpoise, it's easy to see that things seem to have improved a bit, but I wasn't still satisfied, so I decided to replace the 9:1 UnUn with a 16:1 one (800 to 50) and the bottom part of the image shows the results, the max SWR is 6:1 at 12 MHz, but it stays at or below 2:1 on most frequencies and the second peak, at 4:1 is around 25MHz, so overall it seems to me it may be considered a good match, not only the mismatch with the coax feeded will be reduced, but even a "poor" antenna matching unit should be able to easily find a match
Nothing special, but I hope it may be useful (note: right click and open image in new tab to see it a full res)
