Antenna Help Needed Big Time Please
Posted: Thu Mar 27, 2003 12:01 pm
I am asking the age-old question: what type of antenna setup should I have?
I am debating between three different 900 mhz antennas made by Antenex.
Here are their specs:
1) 0 dbd ... 75 vertical beamwidth
2) 3 dbd ... 33 vertical beamwidth
3) 6 dbd ... 17 vertical beamwidth
This antenna will be mounted on top of a 2-story house, so the height couldn't be any more then around 40 feet above the ground.
I am just wondering which antenna to use.
This is for a future 900 MHz ham repeater.
Yes, I know: get more height. I would love to, but the homeowner's association wouldn't let that happen.
I was thinking the 0dbd antenna would be best [low vertical beamwidth for the suburban/urban area]... but factor in coax loss [~ 3db] then duplexer loss [~ 1db] and I'm already way in the hole. I have pre-amps, so I might be able to save the Rx.. but, as for the Tx.. I have no massive power amps.. it's just 10 watts on the stock PA. I was kind of hoping for an ERP of 125 watts, but given the situation, that isn't going to happen [unless I acquire a bigger PA.]
I've read what broadcast engineer's have said about antennas. One source I read said that going with low gain, and high TPO is the way to go in an urban/suburban enviroment... to reduce the amount of multi-path and also direct the signal down low, to where the users will be [portables and in cars.]
But, broadcasters need to only worry about the Tx power, and they don't have to worry about picking up weak signals from mobile users. And broadcasters antennas are mounted on towers sometimes over 500 feet tall. This antenna will only be 40 feet of the ground, at best.
In sum, help.
I am debating between three different 900 mhz antennas made by Antenex.
Here are their specs:
1) 0 dbd ... 75 vertical beamwidth
2) 3 dbd ... 33 vertical beamwidth
3) 6 dbd ... 17 vertical beamwidth
This antenna will be mounted on top of a 2-story house, so the height couldn't be any more then around 40 feet above the ground.
I am just wondering which antenna to use.
This is for a future 900 MHz ham repeater.
Yes, I know: get more height. I would love to, but the homeowner's association wouldn't let that happen.
I was thinking the 0dbd antenna would be best [low vertical beamwidth for the suburban/urban area]... but factor in coax loss [~ 3db] then duplexer loss [~ 1db] and I'm already way in the hole. I have pre-amps, so I might be able to save the Rx.. but, as for the Tx.. I have no massive power amps.. it's just 10 watts on the stock PA. I was kind of hoping for an ERP of 125 watts, but given the situation, that isn't going to happen [unless I acquire a bigger PA.]
I've read what broadcast engineer's have said about antennas. One source I read said that going with low gain, and high TPO is the way to go in an urban/suburban enviroment... to reduce the amount of multi-path and also direct the signal down low, to where the users will be [portables and in cars.]
But, broadcasters need to only worry about the Tx power, and they don't have to worry about picking up weak signals from mobile users. And broadcasters antennas are mounted on towers sometimes over 500 feet tall. This antenna will only be 40 feet of the ground, at best.
In sum, help.