I know everyone has there own opinion on the matter and the topic can get way out of control but i was interested in know why someone would be using a Omni Fiberglass over a DB404 or DB408?
I cant tell the exact model but im pretty sure it is a Sinclair 450-470 being used for the fiberglass.
https://www.tessco.com/products/displayProductInfo.do?sku=591824
Just trying to understand the reasoning for picking this over the DB's they have access to.
Thanks!
The antenna selection can depend on a number of issues. The first is just where the antenna will be mounted. Is this going to be on top of a mountain or down on the flat land? Next comes the question of what kind of ice conditions will the antenna be subjected to? What kind of winds will the antenna be subjected to? How bad is the lightning at the location the antenna will be mounted? What kind of range are you expecting from this antenna? Are birds roosting on the tower and antennas? How well built is the tower ground system. If your on sandy soil, a single, 8 foot ground rod will not cut the mustard. If your on the top of a rock mountain, grounding the tower can be a major problem.
This might seem like a long list of questions, but you need to consider all the information that they bring to the table. Wind is a death sentence to some antennas and the way they are constructed. You have to be concerned about the constant flexing the different components of the antenna make in order to survive the mounting location. The stick type antennas flex a considerable amount and cause metal fatigue at some of their internal component connections. This is why you will find standard and heavy duty versions of some of the pole type antennas.
If your in an ice prone area, the ice forming on the antenna will drastically effect the function and SWR of that antenna. The folded dipole type construction is very prone to the ice build up on the dipoles. Yes some companies have come out with a black Teflon type coating on the dipoles to attempt to combat the ice problem.
Lightning damage to the stick antennas is well documented and there are a number of photos around showing a banana pealing look of the antenna that has taken a direct strike. Fiberglass tubes just don't seem to do well being struck by a lightning bolt.
With all that said, where and how you mount an antenna on a tower will have much to do with the performance and survival on the tower. Never, never mount your antenna at the very top of the tower if you want long term survival. Always make sure there is something metallic that is taller than your antenna.
If your planning on using a fiberglass stick on a tower in a high wind region, it is best to use a top brace on it to keep the flexing down to a minimum. There are support arms with an insulating section on the end that slides down over the pole to keep the flexing to a minimum. Even the 700/800 trunking antennas use this top brace. Just make sure that the support arm will not wear through the fiberglass pole where it connects to the pole.
Have I provided a true choice between the 2 types of antennas? No, because the choice has too many variables that are site dependent. You have to look at the pro's and con's to come up with the correct answer.
A couple of comment about the antennas. The fiberglass sticks tend to loose their coating over time and the fiberglass itself becomes rough and the strands start showing up. Once this starts to happen over time, water will be able to penetrate the tube and cause all sorts of problems. The metal dipole antennas will have water that gets into the phasing harness after a number of years. But the metal dipole antennas hold up better to lightning strikes.
With the sale and resale of the different companies that have made the folded dipole type of antenna, the position now is they no longer will sell you just the harness. If the harness goes bad, your now forced to buy a whole new antenna. This has not set well with the radio users and has caused a major thinking on just which antenna to purchase. Many of the radio shops got a hair across their butt when this change took place.
So now your forced to throw away a perfectly good metal dipole antenna because the vendor refuses to sell a replacement phasing harnesses. Not a good marketing move in many peoples eyes. But it makes more money in the eyes of the company that sells the antenna. But how has this effected the bottom line on how many antennas they sell in the long run? If it was me, I would take my business to a different company.
So now you have some feedback on the different antennas. Good luck on your choice.
