I was wondering would a dual band yagi be better for distance over a dual band copper J-Pole? Any thoughts or help would be appreciated.
I was wondering would a dual band yagi be better for distance over a dual band copper J-Pole? Any thoughts or help would be appreciated.
I like to listen to public safety, was thinking of hooking this up to my scanner of which I would be pointing it in one direction at a time to pull in frequencies in the public safety range and some HAM in the 2m and 70cm, also some GMRS which is local chatter. I plan on mounting this to a rotor so I can change the direction if needed.More information on what you are trying to do will be much more helpful to us to help you than posting a picture of an antenna.
What frequencies are you trying to receive? Do they all come from the same direction or from multiple directions?
here is a pic of the yagi I was looking at.
Thanks for that tip, also what is the difference between a Log-Periodic and Yagi? I googled them and they seem to look a lot alike in design is it just the bandwidth or frequency coverage that make them different? Sorry for all the questions I been experimenting with different types of antennas on my scanner but it gets expensive after a bit so I'm just trying to figure out what would be the best fit, and btw I live way out in the woods and mountains so there is a lot of stuff that can get in the way of incoming signals.Using that with a rotor would allow you to search around and receive weak signals that a J-pole may not hear.
J-poles have their place, but I've never been impressed with them. 1/2 wave antenna, no ground plane, so 0dB gain. They are easy to make on your own if you want to give one a try, but I'd not spend money on buying one.
For wider bandwidth, you may want to consider a Log-Periodic antenna. It's directional, like a Yagi, but will cover a much wider bandwidth.
And don't be like the guy that mounted that antenna. Running the coaxial cable straight down along the driven element isn't the way to do it. Run the cable out the back of the antenna along the boom.
And don't be like the guy that mounted that antenna. Running the coaxial cable straight down along the driven element isn't the way to do it.
Thanks for that tip, also what is the difference between a Log-Periodic and Yagi? I googled them and they seem to look a lot alike in design is it just the bandwidth or frequency coverage that make them different? Sorry for all the questions I been experimenting with different types of antennas on my scanner but it gets expensive after a bit so I'm just trying to figure out what would be the best fit, and btw I live way out in the woods and mountains so there is a lot of stuff that can get in the way of incoming signals.
Thanks for the info, I learn something new every day, of course that is what the hobby of radio is suppose to be about anyways, learning and experimenting along the way,thanks again for all the input I really appreciate it.No, that's a good question. In simple terms:
A Yagi antenna is a directional antenna that is usually cut for one specific frequency, although they will often cover several megahertz on either side just fine. They are considered a single band antenna. The dual band one you linked to is just two separate Yagi antennas on the same boom.
A single band Yagi will have a driven element cut for one specific frequency. All the other elements are parasitic.
A log periodic antenna has all the elements driven (connected to the coaxial cable). There will be many different length elements, longer ones for lower frequencies, shorter ones for higher frequencies. The antenna is still directional, like a Yagi, but won't have as much gain.
For single band use, a Yagi will outperform a log periodic in most cases. For wide band use, like scanner listening, a log periodic antenna will cover more than one band.
For your application, a log periodic antenna fed with the best coaxial cable you can afford and a rotor will give you a lot of options. In fact, our county radio shop has one mounted on top of a tower at their shop for listening in on various systems, as well as narrowing down interference.
Thanks for the info, I learn something new every day, of course that is what the hobby of radio is suppose to be about anyways, learning and experimenting along the way,thanks again for all the input I really appreciate it.
Check if that antenna has a balun where the coax connects. In the picture it looks as if the impedance matching are done by short elements in parallell with the dipole element. It will not work as a balun and the coax will be an antenna element to the yagi independent of how you route the coax.And don't be like the guy that mounted that antenna. Running the coaxial cable straight down along the driven element isn't the way to do it. Run the cable out the back of the antenna along the boom.
if i go with ferrite rings how many and what size?Check if that antenna has a balun where the coax connects. In the picture it looks as if the impedance matching are done by short elements in parallell with the dipole element. It will not work as a balun and the coax will be an antenna element to the yagi independent of how you route the coax.
You probably need to get a 1:1 balun or a choke balun which is lots of ferrite rings on the coax where it attach to the antenna. At least make 5 turns of the coax next to the antenna to get some isolation between antenna and coax.
/Ubbe
yeah I seen some similar to that on ebay, I just thought I needed to clarify on those before I actually buy any. Thanks for the help.There are different ferrite material for different frequency ranges. They are supposed to stop any radiosignals or interferencies riding on the outside of the coax. The maximum signal level will be at 1/4 wavelenghts so to be sure that the rings are effective you could use enough of them to cover a 1/4 wavelenght. You could also measure a 1/4 from the antenna and use only 4-5 ferrite rings at that position, the middle one on the 1/4 wavelenght.
The hole in the middle of the ring should fit snuggle enough on the coax to have the best effect but a little loose fit are probably what will be available. It could look something like this:
/Ubbe