President Himalaya base antenna

[freecell]

it would appear that even w8ji was not immune to the hype and propaganda. stating gain figures for any radiator without factoring in the radiation efficiency does not provide an accurate gain figure at any radiation angle.

G = η • D | the (G) gain of any radiator @ any radiation angle is equal to the (η) radiation efficiency of the antenna multiplied by the (D) directivity of the radiator. commercial manufacturers of antennas ignore the radiation efficiency of the radiator because they know that anything less than 100% Reff. will detract from their stated (advertised) gain figure. all antennas are (more or less) assumed to have a Reff of 100% by default.

an antenna with an advertised gain of 3 dB. is reduced to 1.5 dB. with a radiation efficiency of 50%. unfortunately most end users and hobbyists have no way to determine the radiation efficiency of either commercial or home brew antennas.

radiation efficiency (for end fed / base fed radiators) is equal to radiation resistance divided by radiation resistance + radiation loss. radiation losses are a major contributing factor to lower and wider than normal radiator swr bandwidths.

 

[The DB]

it would appear that even w8ji was not immune to the hype and propaganda. stating gain figures for any radiator without factoring in the radiation efficiency does not provide an accurate gain figure at any radiation angle.

He modeled that antenna. The modeling software takes into account radiation efficiency. While EZnec doesn't show the efficiency data directly (at least I don't think it does, @Marconi can you confirm this for me), the 4nec2 software, which uses essentially the same engine, does. Any model made with any of the nec engines will take into account antenna efficiency when creating their outputs.

Is it possible that he made a mistake with that model? Sure, I guess so, I haven't made a model to confirm his data, but knowing the source, I highly doubt he made a mistake.

G = η • D | the (G) gain of any radiator @ any radiation angle is equal to the (η) radiation efficiency of the antenna multiplied by the (D) directivity of the radiator.

This formula is flat out wrong. I get all three of the numbers used in this formula in the 4nec2 modeling software, and I checked the math on several models. The numbers in this formula creates simply don't give the results that your formula predicts.

radiation efficiency (for end fed / base fed radiators) is equal to radiation resistance divided by radiation resistance + radiation loss

This formula is actually accurate, and not just for end fed and base fed antennas as freecell stated, but for all antennas. To bad it is near impossible to get the radiation resistance, and the "radiation loss" or more accurately the loss resistance for an antenna without resorting to heavy math. My modeling software doesn't even give me that data, but I bet I could reverse engineer it with the other data that I do get...

Something else in that post to be addressed...

unfortunately most end users and hobbyists have no way to determine the radiation efficiency of either commercial or home brew antennas.

There is free software that does this, and it its easy enough that many hobbyists can figure it out if they put in some effort. You may not be able to get the exact efficiency for an antenna mounted on your roof or wherever it happens to be, but you can get a very good idea...


The DB

 

[Marconi]

Thanks to Shockwave, this thread is about a very interesting subject. I wish I had tested this out more.

Db, as best I know --- Eznec does not report % of efficiency.

 

[Recon]

Made in Barcelona, Spain. The language instructions could use some help. Other than that, seems like a fairly common half wave design.

Gotta love that 8 dbi gain!

This is scarry!
Any under warranty expedition must be done to our factory in Barcelona - Spain, the only authorized to decide about the warranty application (an original proof of purchase sales receipt must be included)