When building antennas commercially, compromises have to be made for many reasons, tapered elements being one such area. The thicker the elements, the better the bandwidth of your beam so why would we choose to have thin elements that get thinner towards the ends? Having a single piece element on a 14 Mhz beam with 2 inch diameter elements is just not practical and therefore, tapering is common place. The second reason for tapering and why even 50 Mhz and 70 Mhz antennas are tapered is to allow for easy postage, another commercial benefit. If the antenna when broken into component form is nice and compact, it can be posted easily and cheaply. This methodology however does not lend itself well to long-term, uncompromised performance.
Whilst I do allow for this method of construction in some of my designs, the 'ideal' models I present generally have minimal connections or one piece elements. This is for the same reason I chose to use isolated elements within my antennas as this method of construction (multiple connections, tapered elements, elements to etc.) provides the basis of an antenna that can be de-tuned by the least amount of third party factors. Allow me to explain more fully.
It has been common place over the years for Yagi antennas to be designed with elements electrically connected to the boom. Often a gamma match is used on this type of antenna in order to match the system in these cases. Consider how many electrical connections there are within such an antenna. Have you ever dismantled one and notice the corrosion within each of these joints? Each of these corroding joints can produce a resistance and with this comes de-tuning of the antenna. If we use single piece, isolated (from the boom) elements, there are no areas for resistance to occur and as such, less opportunity for the antenna to be de-tuned. Furthermore, it’s performance will be sustained with the highest level of efficiency remaining, without change.
This is one of the reasons stainless steel hardware is provided with good quality beams. It ensures minimal reistance occuring due to it's tendancy not to corrode and create high resistance. This said, even using stainless steel in the above examples does not exclude such an antenna from having any resistance at all. Can you imagine building your perfect beam, tailoring it to provide the best performance in the section of the band you favour only to find in a few months time, the antenna has shifted to another, less desirable section of the band. Now imagine an antenna that you have built that performs admirably on the whole band regardless of your favoured portion and one that does not shift in frequency or performance, no matter how long it is in the air.
G0KSC Mechanical Design Summary
- Where ever possible, my designs will have single piece elements to ensure NO resistance and as a result, no aging will occur along any element length
- Insulated elements increase the ability to ensure no resistance and therefore no de-tuning will occur due to age or weather
- Thick, high stand off insulators are used to ensure limited (if any) effect on element length is made by the boom
- Quality, thick wall components should be use to ensure durability and longevity of life in addition to 'no sag' elements
- No feed point tuning or matching mechanisum is required which ensures minimal losses and maximum radiation
- Highest power rating antennas are the result - the power rating of my antennas (in most cases) being limited to the feeding coax only
If you are looking for a no compromise antenna with great performance, look no further, you have come to the right place!