 alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2
 ·Socket Internet ..
 ·Mediacom
| Power divider? OK, guys, the folks here are on me to find a solution to this problem. Our new repeater is in place and operating great... with one exception:
In the maintenance shop/boiler room, are our CATV distribution splitters, and they put out a lot of gunge, as there are a LOT of RG59 cables running up from there to the apartments. One such spike of noise lands right on our repeater output... I've PL'ed the output frequency (which of course only silences the radios, not solves the interference...). The issue is the HT's are overloaded by that noise and can't hear the repeater well in that room.
I was thinking about a power divider to send 95% of our power to our main TX antenna, and 5% to a little 1/4 wave in the shop. My issue is I can't find any circuits that do this...all I can find are 50/50 dividers.
Has anyone ever done something like this before?
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 DrStrangeTechnically feasiblePremium
join:2001-07-23
West Hartford, CT
kudos:1
2 edits | How about passive coax running from a low-power transmitter on the same frequency as the main repeater, operating in tandem with it?
Another alternative is a 'cylinder' notch filter for your repeater output before the main distribution amp. |
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 burner50Helping Darwin WINPremium,VIP
join:2002-06-05
Cowtown
kudos:1
 ·inmotionhosting
| reply to alphapointe
said by alphapointe:OK, guys, the folks here are on me to find a solution to this problem. Our new repeater is in place and operating great... with one exception:
In the maintenance shop/boiler room, are our CATV distribution splitters, and they put out a lot of gunge, as there are a LOT of RG59 cables running up from there to the apartments. One such spike of noise lands right on our repeater output... I've PL'ed the output frequency (which of course only silences the radios, not solves the interference...). The issue is the HT's are overloaded by that noise and can't hear the repeater well in that room.
I was thinking about a power divider to send 95% of our power to our main TX antenna, and 5% to a little 1/4 wave in the shop. My issue is I can't find any circuits that do this...all I can find are 50/50 dividers.
Has anyone ever done something like this before?
how about fixing the problem instead of finding a workaround?
Seriously... if the CATV gear is leaking THAT bad, you could be facing other problems.
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alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2 Reviews:
·Socket Internet ..
·Mediacom
| I know we have cable leakage in that room, but at this time we can't do anything about it (management isn't going to spend $50k to rewire the building with RG6QS because we have a spur on our repeater output...  ) Input on the cable system is +40dbm, and leaks out of the RG59 a bit (it's actually not that bad (I can't see it on the spectrum analyzer at 10 feet) but when a BPR40 with a shitty receiver is 3 feet away from it, it screws up)
We don't have a duplexer, we have separate TX and RX antennas. The RX antenna is on the 4th floor, and the TX antenna is on the 3rd floor. As I said, this works really well, except in the shop. I was thinking of trying the "passive repeater" trick of two antennas connected back to back (one on 3 next to the transmitter, and one in the shop), but I was hoping for something a little more refined...
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burner50Helping Darwin WINPremium,VIP
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Cowtown
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·inmotionhosting
| said by alphapointe:I know we have cable leakage in that room, but at this time we can't do anything about it (management isn't going to spend $50k to rewire the building with RG6QS because we have a spur on our repeater output... ) Input on the cable system is +40dbm, and leaks out of the RG59 a bit (it's actually not that bad (I can't see it on the spectrum analyzer at 10 feet) but when a BPR40 with a shitty receiver is 3 feet away from it, it screws up)
We don't have a duplexer, we have separate TX and RX antennas. The RX antenna is on the 4th floor, and the TX antenna is on the 3rd floor. As I said, this works really well, except in the shop. I was thinking of trying the "passive repeater" trick of two antennas connected back to back (one on 3 next to the transmitter, and one in the shop), but I was hoping for something a little more refined...
I'm not sure what kind of setup there is down there, but I'd look more at the passive devices being the cause of the leak. If they're as old as the coax, i'd bet its time for them to be replaced anyway.
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 drjimPremium,MVM
join:2000-06-13
Long Beach, CA
kudos:3 | reply to alphapointe
+40dBm??
That's TEN WATTS! |
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burner50Helping Darwin WINPremium,VIP
join:2002-06-05
Cowtown
kudos:1 Reviews:
·inmotionhosting
1 edit | said by drjim:+40dBm??
That's TEN WATTS!
40dBmV
And that sounds a little weak for a hospital... the hospital in the town where I grew up had almost 600 cable outlets when you count all of the break rooms, doctors lounges, offices, cafeteria, etc.
40dBmV would feed a few... but not all... |
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drjimPremium,MVM
join:2000-06-13
Long Beach, CA
kudos:3 | Yeah, I wondered about it being in dBm...... |
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alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2 Reviews:
·Socket Internet ..
·Mediacom
| reply to burner50
Sorry, I thought I said dBmV... This isn't the hospital, this is my apartment building.
All passives have been replaced with new SVI splitters. Connectors have been replaced too.
Cable comes in from the node on 3 pieces of RG11. Each RG11 goes to a combiner (to add our in-house modulated channels), then to an 8-way, then to 8 more 8-ways, then to each apartment. By the time it gets through all of the splitters and cable, it's about +1 at the apartment port, which gives some headroom for the tenant to split it themselves.
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 mb
join:2000-07-23
Washington, NJ
·Verizon Online DSL
 ·Callcentric
| reply to alphapointe
said by alphapointe:I know we have cable leakage in that room, but at this time we can't do anything about it (management isn't going to spend $50k to rewire the building with RG6QS because we have a spur on our repeater output... )
Is management in violation of FCC requirements by allowing radiation of a signal on that frequency at such a level? If so, management may have to spend the money...
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burner50Helping Darwin WINPremium,VIP
join:2002-06-05
Cowtown
kudos:1 Reviews:
·inmotionhosting
| said by mb:said by alphapointe:I know we have cable leakage in that room, but at this time we can't do anything about it (management isn't going to spend $50k to rewire the building with RG6QS because we have a spur on our repeater output... )
Is management in violation of FCC requirements by allowing radiation of a signal on that frequency at such a level? If so, management may have to spend the money... Apartment management isn't in violation of any FCC Requirements. Cable systems leak. All of them.
The cable provider is tasked with controlling the amount of leakage, not the subscribers... However, the complex faces disconnection if they won't pony up the dough.
SVI splitters are good, If they went with a decent splitter, I would wager that they also used a good connector.
Without a field strength meter and a dipole, I couldn't suggest anything else, but if there is leakage that is overloading the front end of a decent receiver, you have some problems in there.
RG6QS would be overkill, everyone thinks that is the best of the best, but really that stuff is only to protect the system in High RF environments. A utility room doesn't qualify  . A good dual shield with 60% or higher braid will be just fine as long as everything is terminated properly and the coax isn't damaged (like being bent in too tight of a radius). RG6 isnt as fragile as hardline, but it is still fairly fragile and the shielding can be easily damaged.
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alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2 Reviews:
·Socket Internet ..
·Mediacom
| I used RG6QS as an extreme example.
I don't think excessive leakage is the issue here, as the noise doesn't even show up on the spectrum analyzer when I get more than 10 feet away from that wall.
The noise doesn't bother my Sabers, so I wonder how good the receiver in a BPR40 is... (it affects my scanner, but I expect that, as they usually have no front-end filtering at all)
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mb
join:2000-07-23
Washington, NJ | Mixing issue in the receivers of the cheap ham handhelds... You answered your own question when you said the noise doesn't bother your Sabres... |
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alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2 | A BPR40 isn't an amateur transceiver, it's a Motorola radio as well... (but low-end) |
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| reply to alphapointe
If I understand you correctly, you want to send a small fraction of the transmitter output to a second antenna while the main antenna gets most of the power. And this would be transmit only.
Look for a "directional coupler". A 10 dB coupler will send one-tenth of the incident power to the coupled port. When selecting, make sure the coupler can handle the full transmitter output power.
Mini circuits sells a selection of couplers but the power is limited to just a few watts. I'm sure some other companies have higher powered ones. |
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burner50Helping Darwin WINPremium,VIP
join:2002-06-05
Cowtown
kudos:1 Reviews:
·inmotionhosting
| reply to alphapointe
There is something else that you need to think about.
If there is a place for signals to leak out of CATV, there is a place for noise to get IN
If you manage to achieve something like this, you may wind up wiping out TV service in your building whenever your repeater keys up.
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I'm tired of killing stupid people just trying to do my job and go home! |
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alphapointeDon't Touch MePremium,MVM
join:2002-02-10
Columbia, MO
kudos:2 Reviews:
·Socket Internet ..
·Mediacom
| There's a point... I'll have to put one of the HT's on talkaround and see what happens when everyone is gone over Christmas break. We get no problems when the handhelds transmit on the repeater input in that room, though...
Still, I'll check it out. |
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