Hey everyone,
I'm attempting to get the maximum range out of an UHF repeter antenna we have and I was considering using three panel antennas, much like cellular type antenna configurations. My only question would be whether or not this would be a good idea / fesable. Would I simply connect the three together in parallel type fashion, or would I need some sort of intermediary device. Thanks in advance!
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Three Antennas, one transmitter
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Re: Three Antennas, one transmitter
Well, if you expect to maintain an impedance match to the feedline that you're using, you generally can't just connect three of any type of antenna in parallel. If each antenna presents an impedance of 50+j0 ohms at the operating frequency, three in parallel would present (50/3) ohms or about 16 ohms. That's not a very good match to a 50 ohm transmission line. You can use a resistive type power divider(1 X 3) but expect to see about 4 dB of loss from the input to each output(and from each output to the transmission line port on receive).
Panel antennas are usually an array of antennas built onto a substrate, and are directional. Unless this a very special application, why would you want a directional antenna system on a repeater? If general range improvement is your only reason, and this is not a specialized application, you probably would be better advised to choose a better omnidirectional single antenna(better, that is, based on your geography, terrain, obstructions, antenna height above ground).
Panel antennas are usually an array of antennas built onto a substrate, and are directional. Unless this a very special application, why would you want a directional antenna system on a repeater? If general range improvement is your only reason, and this is not a specialized application, you probably would be better advised to choose a better omnidirectional single antenna(better, that is, based on your geography, terrain, obstructions, antenna height above ground).
Re: Three Antennas, one transmitter
You will need a phasing harness to connect those antennas. The harness will have to have a power divider that will feed all the antennas. The divider is a section of cable that has an impedance very much NOT 50+0j ohms, which is cut such that at the operating frequency of the repeater, it will transform the 50 ohm line impedance into the 50|50|50 impedance of the three panels.
IF you have access to a vector network analyzer you could make the power divider yourself, but you could be better off ordering it from a company with experience making them.
IF you have access to a vector network analyzer you could make the power divider yourself, but you could be better off ordering it from a company with experience making them.
This is my opinion, not Aeroflex's.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
I WILL NOT give you proprietary information. I make too much money to jeopardize my job.
I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.
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Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
Re: Three Antennas, one transmitter
You haven't indicated the present height (Height Above Average Terrain) of the antenna and manufacture model number that you're using above ground level, the type of RF coaxial cable, i.e. RG-U, LMR-400, 1/2" or 7/8" Andrews Heliax, the RF Power Output and receiver's sensitivity. Generally most repeater transmitters emit enough RF to out perform the repeater's receiving capability. In other words, the said repeater is having Path Losses from in-bound RF signals from the Subscriber units. Which brings up another question, Are you experiencing problems from Subscriber Mobiles or Portable Handhelds and/or both?
In most cases when adding or replacing Base Station Antennas to increase the dB gain and range, you would want to ADD: 2 for +3 dB or 4 for +6 dB Omni directional Gain with a commercially manufactured, Frequency Dependent 50-Ohm RF Power Divider. If this happens to be single user repeater system, the use of a Voting Comparator and Remote Satellite Receiver(s) placed out in the 70% RF Coverage Area will accomplish this task.
I would suggest providing more detailed system information and RF coverage problems to allow all of us on the Batboard, to recommend intelligent alternative solutions to your coverage problems.
Dan
In most cases when adding or replacing Base Station Antennas to increase the dB gain and range, you would want to ADD: 2 for +3 dB or 4 for +6 dB Omni directional Gain with a commercially manufactured, Frequency Dependent 50-Ohm RF Power Divider. If this happens to be single user repeater system, the use of a Voting Comparator and Remote Satellite Receiver(s) placed out in the 70% RF Coverage Area will accomplish this task.
I would suggest providing more detailed system information and RF coverage problems to allow all of us on the Batboard, to recommend intelligent alternative solutions to your coverage problems.
Dan