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#15
November 16th 14, 02:52 AM
posted to rec.radio.amateur.antenna
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It is a truism
On Saturday, November 15, 2014 7:01:13 PM UTC-6, FBMboomer wrote:
On 11/15/2014 6:23 PM, wrote: On Saturday, November 15, 2014 5:25:01 PM UTC-6, FBMboomer wrote: Yes, smaller is better. I strongly encourage you to use 1/4 inch antennas. It is like homeopathy, less is more powerful. Getting your antenna length down to microns is the answer. Are you suggesting I use a 33 ft tall mobile antenna? Or are you just being silly because you have no other alternatives? If a short antenna is just as good as a full size dipole, than why not use a 1/4 inch antenna. Or might there be something said for large full size antennas? Or could it be, size actually matters. Who ever said a short antenna is just as good as a full size version? Certainly not I. I only corrected your confusion about the reason for a lack of system efficiency with the usual garden variety G5RV. And it's not the first time I've attempted to correct your false ideas concerning that particular antenna. It seems to enter into one side of your brain pan, and exit the other side in an awful quick hurry, without bearing any fruit in the middle. Trust me, the shortcomings in using a G5RV on 75m CAN be corrected if one does away with the lousy method many use to feed them on that band. The garden variety G5RV fed in the usual manner was never really intended to be used on 75m in the first place. But you CAN change the feed method so it can be quite efficient on that band. The slightly shorter length of the radiator is not the reason for the usual lower *system efficiency* with the typical "designed for 20m" G5RV being used on 75m, vs a full size dipole. You could use a 130 ft full size radiator, but if one feeds it in the same perverted manner IE: coax to choke to ladder line, it will suffer excess feeder losses also, same as the 102 ft G5RV radiator. On 75m, I use full size dipoles or turnstiles fed with coax. An *antenna system* so efficient it really can't be beat unless you used a tuned open line feeder with no antenna tuner involved. The differences between the two would likely be undetectable on the air on that band. On VHF/UHF, you would notice more of a difference, with the tuned open wire feeder being the most efficient system by a noticeable amount. You can feed a full size loop in the same manner, with the same high system efficiency on the band it's cut for. You might need to add a short length of 75 ohm coax as a series transformer to better match the slightly higher 75-100 ohm feed point if one has a picky transmitter, but coax series transformers add very little loss in such a case. The main reason I use full size dipoles is not some magical property with that length radiator. It's because it allows me to use a highly efficient method of feeding, with no tuner involved to add loss. Which means that most of my power makes it to the radiator, instead of turning into heat on the way to it, as with the usual improperly fed G5RV many try to use on 75m. In the past, you admitted you don't know too much antenna theory, but like the one who shalt not be mentioned, you seem to have a problem taking the the advice of people who do, and instead retort with pure silliness. |
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