coryb27
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Posts posted by coryb27
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Sounds like TRBO or P25 to me.....
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height is you friend.
that being said I would look into a better cable for the 90 footer. 3.3dB loss to me not acceptable. I would at least entertain the idea of LMR400 at a minimum cable w/2.5 dB loss/100'.
as to the above post on the antenna propagation site it's close enough if you have the right numbers to plug in.
just my thoughts, JE
You can get 1/2" or 7/8" hard line New for $2 a foot...
Corey
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its the best wide band meter for the buck and like I said, side by side with a calibrated BIRD both of mine are close enough that it would not make a difference.
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You should be able to hear it until the curve of the earth gets in your way or you get above the radiation dome of the antenna. Scanner well flying is always a good time!
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http://www.theantennafarm.com/catalog/daiwa-cn-103l-1198.html
100 bucks, does power and SWR. I own 2 of these i leave inline in my UHF and VHF base radios. No issues at all. I have compared them to my calibrated BIRD meter and they are extremely close in accuracy.
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i have several TPL amps and stand behind them 100% if used per the manufacture directions and engineering limits. From experience I have found if you under drive most TPL amps it can cause issues with adjacent channel interference, possible cycling of the amp or high swr to the TX radio.
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The LMR 400 is fine for that, just stay away from it as a feed line as it preforms poorly in full duplex operation.
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when is the last time that duplexer was put on a spectrum analyzer? It is way off freq.
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I was concerned about this "the unit stays locked in decode all the way down to 0.25 uV" I have 16 year old MTR2000's that will hear down to .20uV and my XPR8400's still hear down to .18uV. Maybe that's just the spec on that repeater duplexer combo. Sounds a little def to me but again, that could be the best the receiver has to offer.
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It is out of tune unless filled with water or hit by lightning
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yea that's a bad duplexer, did you try reversing the tx and rx leads into the duplexer? I have seen people tun them backwards before.....
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This is the reason I run all Motorola gear
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You could go out and invest $4k bucks on a repeater and put it on a well placed site with a 200' high antenna and the guy down the block could grab 2 mobiles and stick a repeater in his back yard on the same channel and there is nothing you can do. You can try to work it out but if you cant nobody can help you.
Operating simplex on a repeater output would be the proper way to use simplex on GMRS, this results to what is known as talk around.
Several repeaters can co exist on the same channel as long as everybody is using a different pl/dpl the only time its going to be an issue is when both are transmitting at the same time, the better repeater most always wins.
GMRS Operators tend to work together and solve most interference issues unless one is a total jerk.
Corey
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i am shocked a company that markets repeaters with duplexes has to order one....
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So this was tested without a duplexer? If so it sounds like you are hearing ok. What kind of duplexer are you using?
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I would check the SWR between the transmitter and the duplexer and see what you get. I am leaning toward duplexer due to the vanishing audio. When is the last time it was tuned? Also, you did not mention the the type of repeater.
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That is rather unfortunate somebody had created a zello radio station, have you reached out to the repeater owner to see you you can come to an agreement?
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I would verify the repeater and radios did not somehow get programed to narrow band. Not a fan of comet antennas in full duplex operation, that's one place to look as well. Also did somebody swap the cables or tun the duplexer backwards? Let us know what you find.
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Sites can be hard to find, you have to knock on a lot of doors!
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Yea something is not right, I would try a different antenna before I blame the repeater if it was just built and tested.
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Maybe I can plan a ride down, your not that far away. I have all the ends, tools etc to work with that cable. In fact I think I have a few 100 feet in the garage.
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The duplexer is one that Bridgecom installed when building out my repeater. It is a Cellwave mobile duplexer with BNC connectors.
Ron Kochanowicz (owner/engineer) replied this morning that "...when I tested your box with a service monitor, I was getting solid decode down to less than 0.25 uV with duplexer installed." He further clarified that this was an iso-T test. Nonetheless, even he suspects a duplexer desense problem.
Not seen in the photos is this one showing about 10' of excess heliax. I can easily re-route the heliax through the lower sash of the window and connect it directly to the repeater to eliminate the lighting protector and the 6' RG213 jumper:
http://puu.sh/orJSo.jpg
I wonder if your not creating a choke with that loop...... what is that about 4 large wraps of cable?
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Mystery solved.
I am guessing this is close since the 8' mark 1. is at the top of your door and windows. I would almost bet the top of your door is more like 6', if that is the case subtract 2' from each increment. Using the mast to do a rough calibration of 10' I was able to use photo shop to plot some rough measurements. I think your statement "the base of the 8' antenna is at 52' AGL" is way off. That would mean your single story ranch home has a roof peak of 42'.
I live in a 2 story condo with 10' ceilings downstairs,10' ceilings upstairs with 10' of attic space above it. Measuring from the peak of the roof to the ground with a tape measure I got 32'. I would guess if you re run your calculations using a 25' AGL to be realistic; you will see it is much closer to the results you are seeing in the field. It is easy to over estimate height from the ground.
The below image is a 35' tower next to a typical single story house to compare.
My coverage results using 25' AGL, 6dB gain, 30W of power with an 70% reliability factor. I used 2dB of TX-RX loss to factor in the coax and duplexer. for the other end I used 6' antenna height and 2dB of gain to simulate the average car. When using 5' and 0dB of gain (HT) I got less then 3 miles. Interactive Coverage Map I have 2 commercial sites and have used this program for FCC coordination and coverage, the results have always been real close to reality as long as you input the best possible data. The difference in 25' to 35' is huge so you have to be as close as possible.
Base Station Antenna Locations
in Technical Discussion
Posted
Tessco has great deals on cable.
CommScope FXL-780 is a 7/8 smooth-wall aluminum shield and copper center conductor. I use this and swear by it, I have 2 sites that have 155' runs in service. Loss 100 ft @ 450 MHz 0.775 dB $1.99 per foot
CommScope LDF4-50A 1/2 Foam Heliax Cable Loss 100 ft @ 450 MHz 1.45 dB $1.98 per foot