No one seemed to respond to this thread but for the sake of keeping to the rules, I post my amateur question here.
My place’s legal frequency is 477Mhz. My radio reaches that frequency, but I want to enhance it by changing the Antenna to a Nagoya as per review. However , looking at the Nagoya NA-701, it states 430Mhz. Does that mean, that the antenna would make no difference if I want to tune in to 477.Mhz?
Thanks.
It means the antenna is not tuned to frequencies above 430MHz. What radio are you using?
When understanding antenna’s, you have to know the Q of the antenna.
Most commercial antenna’s, are center cut for one exact frequency.
Anything above or below that one frequency suffers greatly from excessive SWR.
But when operated at that one frequency, that antenna will operate quite well.
The old Ringo line of antenna’s were designed that way.
As a example, a 50 MHz antenna was about 9 feet long.
It had about a 32 inch ring around the bottom and a shorting bar.
When you moved the rod, you increased the length or decreased the length of the antenna without having to take it down and reposition it.
Any other frequency, the antenna was basically a dummy load.
You have to look at both the size of the driven element and the spacing of each director to determine center cut frequency.
Then there is the matching network.
If you have a Delta - you can move the connectors.
If you have a Gamma you can change the length.
If you have a Beta - you can research how to change it.
The bottom line is - anything you do to a antenna will move the center cut frequency, and CB / amateur antenna’s has to work on more then one frequency.
When you lower the Q - you decrease the efficiency, at the cost of more bandwidth. It might not have as much gain, but its end SWR will be lower over a much greater bandwidth.