About a month ago (4 March), I posted about a newly hatched business plan of mine and referred to a cage dipole that sold for $350 and had 5dBd claimed gain. There was possibly an implication in my p
Whoops, probably did it again. I'm bad at this tiptoeing around in forums stuff. Please read this as "It is my opinion that" any such antenna is impossible. Apologies again. 73 Dan __________________
Hardly impossible, Dan. All you have to do is model the subject antenna over ground with NEC (e.g. engineering analysis) and then compare that field strength to a free-space dipole reference (2.15dBi
Any chance that individual is willing to post said engineering analysis to his company's web site? It might be amusing to read. 73, Dave AB7E _______________________________________________ _________
The website doesn't claim the gain was based on analysis, as a matter of fact they say you can't get the correct gain with your modeling program. (I wonder if they have a custom modeling program writ
Dan- If it means anything and will remove any blame he wants to heap on you, I can assure him (and you may quote me) that your opinion did not influence me at all. I knew all long that his "Engineeri
If it is truly a cage dipole then it has no gain over a regular dipole or 2.2 db gain over an isotropic source. I've not seen the literature the other company has so they may not have a true "cage di
Thanks to the link that was provided I did go to the page advertising the antenna. Basically I agree with their statements *except* for the gain. Most could really do away with the tuner, but with a
Put simply, for such claim to be valid the feed impedance of the cage dipole would need to be substantially less than 50 Ohms such that the total current flowing in the cage elements was approximate
Increasing the current while maintaining the distribution of current along the antenna does not produce "gain" provided that the applied power is held constant. Directive gain can be realized only if
Only if you mount the cage dipole in free space! Any dipole mounted somewhere above a good ground, could have some gain in some directions ... compared to a dipole in free space ... and so it would
exhibit a positive dBd number. And many do. There is no snake oil in that. Really? Do you know of a product that would allow me to mount my comparison dipole in free space for tests? To use dBd to r
But this is MARKETING, they thrive on things like that. No one says you have to be able to measure it, or that it could even be compared to anything buildable on earth. Manufacturers have quoted gai
But that is EXACTLY what it means!!! Anything else is inexact science, not even science, and would require a disclaimer that all numbers have an error tolerance of +/- 10 dB or so because we don't r
But they are comparing it to something buildable on earth by saying "We list it as having a 5dbd (yes thats dbd) gain over a dipole." I think it is fair to assume that the reference dipole has the sa
Dan, More eloquently put than I could have - I agree entirely! The 5dBd figure can't be passed off by saying they might be referencing a dipole in free space. Take a look at the advertising. The 5dBd
I agree, Steve. My read of the advertising is that it is conveying the notion that when the cage is substituted for a single-wire dipole at some reasonable height the cage will increase signal streng
Andy, I don't know how you arrived at that conclusion. It simply isn't true. Dbd "could" be referenced to a dipole in free space if so noted, but there is no convention that says it always is, or tha
Whilst you are technically correct (and the ARRL Antenna Book agrees with you - 21st Edition page 11-2), I think Tom W8JI covered this fairly well back in 2004 in his posting "dBd vs dBi misuse" and
True, but I'm using the standard comparison numbers which are about as real as an isotropic source. The numbers are strictly as a reference, that they do vary a bit is mostly irrelevant for this disc