license free 900 mhz system questions

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kc8gpd
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license free 900 mhz system questions

Post by kc8gpd » Tue Dec 23, 2014 5:59 pm

I have a pair of 900 mhz 300mW IP link Radios.

problem i am having is the path is not Line Of Site and i want to send streaming audio over them.

streaming audio is not stable and from what i am thinking is due to cancellations and reflections of the buildings. i do get a path but it isn't stable.

if i bought or made a dual antenna phasing harness and put one antenna horizontal and one vertical on both the sides of the link you think it will solve the issue i am having?

these are not diversity capable and are made by avalan.

i wondering if my quick and dirty approach to diversity will work?

i'm trying to get internet and/or streaming audio to a site about 1000ft away in another apartment.

i am on the ground floor and the other site is on the 3rd floor on opposite site of building.

as i said i do get a good link path it is just not entirely stable. also keep in mind that these are IP radios and as such are TX/RX in the same unit using some sort of digital modulation scheme.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

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Xenirad
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Re: license free 900 mhz system questions

Post by Xenirad » Wed Jan 28, 2015 10:05 pm

Are your license free radios anywhere near an STL transmitter? If they are the STL will cause you problems because the front end in the license free radios is very wide banded. If you are near an STL you will need a notch filter to remove the STL frequency. Otherwise I would suggest installing an amplifier to boost the radio output and receive signals you will need one on each end.

http://www.l-com.com/wireless-booster-9 ... oCYvrw_wcB
Fred Francis, Owner Xenirad Broadcast Engineering http://www.xenirad.com

kc8gpd
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Re: license free 900 mhz system questions

Post by kc8gpd » Thu Jan 29, 2015 4:38 pm

i didn't even think of that. your right. i'm across the street from a youth correctional facility with 800/900 mhz trs stuff and down the street from k-love studios who does have an stl setup there and also within a 1/2 mile of 2 x-band AM stations who may or may not have stl's. i will try the bandpass filters. don't really want to tinker with amps not sure what that would do to their part 15 certification if i added amplifiers.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

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Xenirad
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Re: license free 900 mhz system questions

Post by Xenirad » Thu Jan 29, 2015 5:58 pm

You could use one of these, http://www.microwavefilter.com/ISM%28900MHz%29.htm or one of these http://www.l-com.com/bandpass-filter-rf ... -full-band

You might also get by with a quarter wave shorting stub or a quarter wave open filter I would try one of these first as they are cheap to make.
Fred Francis, Owner Xenirad Broadcast Engineering http://www.xenirad.com

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Re: license free 900 mhz system questions

Post by radio_guru » Sat Jan 31, 2015 10:32 am

Or get a new set of Nano series 900 radios for less than $250.

RG

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Jim Sofonia
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Re: license free 900 mhz system questions

Post by Jim Sofonia » Wed Feb 11, 2015 12:37 pm

If you suspect a nearby 900 link, just ask them to shut it off briefly and see if it clears up, then go buy your filters.

kc8gpd
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Re: license free 900 mhz system questions

Post by kc8gpd » Wed Feb 11, 2015 12:58 pm

my suspicion is because i don't have LOS it is bouncing off of buildings and causing signal cancellation. i will (when money permits) invest in the ubiquiti 900 series radios and that will likely clear up the problem.
kc8gpd

"The scientists of today think deeply instead of clearly. One must be sane to think clearly, but one can think deeply and be quite insane."

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