What is the function of beamwidth and the meaning of pattern ratios? I've heard the terms spoken around the #hamr breakfast tables while drinking a cup of coffee while endeavoring to improve my level of personal competency.
Furthermore, my review of the literature is on-going, as a point of inquiry into Micro dB Theory, and its relationship to improving one's RadioSport score, as a result of micro-iterations in and out of the shack.
In my previous post, we examined a theoretical comparison antenna known as an isotropic radiator; the benefit of a directional antenna and a radio energy trade off as a function of concentrated energy; and gain as a ratio commonly expressed as a decibel.
What is the functional expression of concentrated radio energy? Is there a quantifiable pattern because of this concentration of energy?
I opened my Extra Class License Manual Ninth Edition (2011) published by the American Radio Relay League authored by Ward Silver, N0AX for an answer to my questions.
Silver defined beamwidth as an angular distant between reference points on either side of the major lobe with a gain not a gain in power of three decibels below the maximum (2011). He further stated such measurement is occasionally referred to as "-3dB beamwidth" and it illustrated in Figure 9-4, page 9-4, in the Ninth Edition of the Extra Class Examination Manual (2011).
Silver explained if one's directional antenna has a beamwidth of 30 degrees, then rotate your antenna half of the optimal heading, that is either +/-15 degrees. The resultant reaction is a drop in signal strength by three decibels hence the function of "-3dB beamwidth" (2011). Additionally, the author further stated, that gain is not everything and in the game one arrives at the same conclusion.
What function of an antenna system can be more important than gain?
According to Silver, an antenna systems ability to reject signals from other than one's direction of listening and concentration of radio energy, is as important as the function of gain itself (2011). The ability of one's antenna to reject signals, keeping in mind the back and side of an antenna, is referenced as a pattern ratio. There are three types of ratios, front-to-back; front-to-rear; and front-to-side.
I recommend reading further on page 9-4 of the Extra Class Examination Manual (2011) in its Ninth Edition, because Silver is the subject matter expert and his explanation is superior to my journeyman level of competency.
I've often wondered why a DXpedition did not hear my signal? Perhaps, a better explanation maybe, that my signal concentration is outside that of the receiving station's beamwidth, and/or within a pattern ratio of signal rejection of the same system, for example front-to-side.
The rejection I'm experiencing is not a fault in my system or poor propagation or the other operator inside the cans rather it is an antenna design characteristic of the receiving station and the antenna is performing to design requirements.
Overall, when getting ready to deploy one's antenna system such as a vertical or dipole, think about major and minor lobes; antenna nulls; height; and soil permeability factoring in ground reflection; then concentrate radio energy toward your primary target. Why not experiment this RadioSport season and discover your antenna system sweet spot?
73 from inside shackadelic near the beach.