I've got a customer with a coverage problem in a concrete tunnel.
We're thinking of a solution using a high gain yagi connected to a length of Radiax in the tunnel. If that doesn't work, the BDA route is next.
I've been searching for a yagi with better than 15dB gain. The best I've come up with is the Sinclair SY3074 series.
Any other suggestions out there? I'm looking for max dB. The donor repeater antenna is nearly line of sight, so a narrow bandwidth isn't a problem.
Looking for high gain UHF yagi antenna suggestions.
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Looking for high gain UHF yagi antenna suggestions.
"We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm. "
Re: Looking for high gain UHF yagi antenna suggestions.
You will probably not find the yagi / radiax solution will
work very well for you. This only works if you have a
very strong signal coming into the doner antenna. The
losses using this type of pasive repeater system don't
work well in most cases.
You would be better off going with a BDA right off. It will
still need the yagi and radiax cable to work. You probably
won't need the high gain antenna your currently looking
for though. Just make sure there is enough isolation
between the doner antenna and the radiax. Otherwise
it will jam itself.
Jim
work very well for you. This only works if you have a
very strong signal coming into the doner antenna. The
losses using this type of pasive repeater system don't
work well in most cases.
You would be better off going with a BDA right off. It will
still need the yagi and radiax cable to work. You probably
won't need the high gain antenna your currently looking
for though. Just make sure there is enough isolation
between the doner antenna and the radiax. Otherwise
it will jam itself.
Jim
motor59 wrote:I've got a customer with a coverage problem in a concrete tunnel.
We're thinking of a solution using a high gain yagi connected to a length of Radiax in the tunnel. If that doesn't work, the BDA route is next.
I've been searching for a yagi with better than 15dB gain. The best I've come up with is the Sinclair SY3074 series.
Any other suggestions out there? I'm looking for max dB. The donor repeater antenna is nearly line of sight, so a narrow bandwidth isn't a problem.
You may be right, but in this case I think I can get away with it.
The yagi will be line-of-sight to the repeater antenna - about 300 yds away. The repeater is putting out a measured 55 watts at the antenna. The tunnel is about 110 feet long, and we get penetration coverage about 40 feet in from the near side and 20 feet in on the far side. I'm just trying to extend the signal to that middle 50 feet.
If the passive repeater doesn't cut it, we'll add the BDA to the mix, but if I can do this on the cheap, then I'm the hero.
The yagi will be line-of-sight to the repeater antenna - about 300 yds away. The repeater is putting out a measured 55 watts at the antenna. The tunnel is about 110 feet long, and we get penetration coverage about 40 feet in from the near side and 20 feet in on the far side. I'm just trying to extend the signal to that middle 50 feet.
If the passive repeater doesn't cut it, we'll add the BDA to the mix, but if I can do this on the cheap, then I'm the hero.
"We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm. "
cave radio
http://batboard.batlabs.com/viewtopic.p ... cave+radio
check out this link it might have some useful info you can use Jhook
check out this link it might have some useful info you can use Jhook
BAT9228
If you are only 300 yards from the base, why not couple some signal from it (say 1 watt) and use a length of coax (heliax) to the tunnel?
Losses will be less than with the yagi (depends on the coax size, what losses you can tolerate and how much you're willing to pay) and no BDA required.
UHF path loss at 300 yards is over 60 dB, so if you used a 15 dB gain antenna, that brings it near to 45 dB. You can certainly get better results even with poor coax and a coupler. 1/2-inch heliax would be around 15-20 dB for same distance.
A 0-dBm signal into radiating cable at UHF should be very usable.
Losses will be less than with the yagi (depends on the coax size, what losses you can tolerate and how much you're willing to pay) and no BDA required.
UHF path loss at 300 yards is over 60 dB, so if you used a 15 dB gain antenna, that brings it near to 45 dB. You can certainly get better results even with poor coax and a coupler. 1/2-inch heliax would be around 15-20 dB for same distance.
A 0-dBm signal into radiating cable at UHF should be very usable.
-
Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
Motor59,
Is it possible that the repeater antenna has too much over-the-horizon gain for the local Building coverage? I haven't seen any information as to what model number antenna is installed above the repeater, how high above ground level ... average height, type of feedline and duplexers used. BTW, what's the measured RF receiver sensitivity through the duplexers? If you're using a +8~9 dB Gain antenna on the repeater, then this is where the RF signal problem originates from.
Most if not all high Gain single commercial Yagi antennas are spec'd at +9~10 dB Forward Gain and F/B +25 dB Gain. To increase the Forward Gain is accomplished by Stacking 2 or 4 Yagi antennas in a H Frame design with either a 2 or 4 Port RF Power Divider and using a minimum of 1/2" Heliax Cable. If you add 2 +9 dB Yagi antennas, you'll end up with +12 dB Gain and adding another pair of the same antennas, the Gain will increase by +3 dB ending up with +15 dB Forward Gain.
Typically in a system like yours, the Subscriber Portables can hear the repeater's transmit signal but can not over come the path losses in the reinforced concrete tunnel walls to talk back to the repeater. Using a good designed Yagi antenna array above ground, pointed up at the repeater antenna, 1/2" Heliax Cable and a 1/4 wave vertically mounted mobile antenna centrally located in that tunnel should provide better RF signal coupling so the Subscriber units are heard by the repeater's receiver. Using Radiax is normally a good idea if you can connect the cable directly to the repeater duplexers output through a 2-Port RF Power Divider but in your situation there will be too much signal loss without a BDA.
Is it possible that the repeater antenna has too much over-the-horizon gain for the local Building coverage? I haven't seen any information as to what model number antenna is installed above the repeater, how high above ground level ... average height, type of feedline and duplexers used. BTW, what's the measured RF receiver sensitivity through the duplexers? If you're using a +8~9 dB Gain antenna on the repeater, then this is where the RF signal problem originates from.
Most if not all high Gain single commercial Yagi antennas are spec'd at +9~10 dB Forward Gain and F/B +25 dB Gain. To increase the Forward Gain is accomplished by Stacking 2 or 4 Yagi antennas in a H Frame design with either a 2 or 4 Port RF Power Divider and using a minimum of 1/2" Heliax Cable. If you add 2 +9 dB Yagi antennas, you'll end up with +12 dB Gain and adding another pair of the same antennas, the Gain will increase by +3 dB ending up with +15 dB Forward Gain.
Typically in a system like yours, the Subscriber Portables can hear the repeater's transmit signal but can not over come the path losses in the reinforced concrete tunnel walls to talk back to the repeater. Using a good designed Yagi antenna array above ground, pointed up at the repeater antenna, 1/2" Heliax Cable and a 1/4 wave vertically mounted mobile antenna centrally located in that tunnel should provide better RF signal coupling so the Subscriber units are heard by the repeater's receiver. Using Radiax is normally a good idea if you can connect the cable directly to the repeater duplexers output through a 2-Port RF Power Divider but in your situation there will be too much signal loss without a BDA.