4/14/2021 0 Comments Antenna Db Gain Vs Distance
I was hoping for more than 6 dBd gain but since it is only 4 elements and quess I will have to live with it.For a better experience, please enable JavaScript in your browser before proceeding.
For instance I want to build a 4 element J-Beam antenna and I should get about 6 dBd gain. I have a signal (wireless mike) that I can pick up about 12 mile away. My question is how much farther can I pick up the wireless mike based on 6 dBd of gain I am trying to decide if building the antenna would be a waste of time. It depends on your RF environment (what signals are hitting your radio), terrain, radio quality, coax quality, antenna match, etc, etc. For what its worth, discones often have somewhat high lobes and you very well may have better luck with a beam as its radiation pattern is usually more concentrated towards the horizon. No amount of preamps, high gain antennas, or good coax will compensate for no signal. A 5 watt handietalkie can talk to another 5 watt handietalkie 200 miles away. And that with pretty poor antenna, too Gain antennas can help with signals that are present, but weak. They can also sometimes help you find a reflection of the desired signal from something not in the expected direction, but up high. But your actual expected range is 95 or more purely due to height of the transmitting antenna, height of your antenna, and lack of hillstreesbuildings in between that block line of sight. Sometimes atmospheric conditions can cause signals to bend a bit (tropospheric ducting) and can cause VHF signals to travel hundreds of miles. In most city areas, youll get more help from adding an FM Broadcast trap to the antenna line than you will from changing to a gain antenna, and thus reducing the front end overload FM broadcasters tend to cause to scanners in any major city. Probably the only area of listening where a good gain antenna (of the proper circular polarization) is especially needed is monitoring military UHF satellites, as they are very weak signals, even though they ARE line of sight. Your wireless mike in particular, might benefit some from a gain antenna. However, the MOST you can expect is double the range, to 1 mile, for 6 db gain over current. Wireless mikes are intended for no more than 100 foot range, if operated legally. The discone is probably not very good for receiving it, though. Given the low height of the wireless mike antenna, most of your problem is probably buildings and trees between you and the mike, which will degrade the signal badly. Here is a link to one useful calculator: You can estimate the radio horizon, path loss and tell it how much transmit power you have and it will give you expected receive levels. ![]() At least you can input your known parameters and see if it agrees with what you already get. ![]() Good luck. prcguy. I think I will go ahead and build this 4 element J-Beam since I have some copper pipe and and the other misc parts on hand.
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