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#95793 - 06/07/09 09:45 AM
CFR47 Part15.247 900 MHz GMRS Link
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kc8gpd
Radio-active Reader
Registered: 04/17/07
Posts: 208
Loc: Glen Gardner, NJ 08826
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anyone ever try to use 900 MHz FHSS Radios under part 15 as a voter link for remote receive sites or linking 2 repeaters?
GMRS has one downfall that i can tell and that is portable coverage in mountainous area's can be terrible.
part 90 and 97 users solve this with remote receive sites and voters.
GMRS has regulatory issues regarding remote control and interconnection to PSTN.
anyone see any regulatory issues in using 900 MHz license free (under part 15, Not Part 95 or 97) P2P links for remote receive sites to improve portable coverage?
just something i dreamed up in my sleep.
ideally you could centrally locate a TX Site and set some small voter sites throughout the Tx's coverage area to improve the portables ability to get into the repeater.
i'm sure there is off the shelf transceiver or transmitter units for 900 mhz and this can be tied to a off the shelf voter and you can use something like maxtrac's as remote receivers with 2 bay folded dipoles.
the main tx site could have a MSF5k standard Repeater/voter with a DB-420.
the 900mhz links could be horizontal polarization using dishes or corner reflectors for antenna's to keep interference from others user of the band to minimum.
any input?
_________________________
Thank You, Rev. Robert P. Chrysafis Universal Life Ministries http://www.ulc.orgModerator: Hunterdonfree Owner & Moderator: freestuffwarrennj
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#95798 - 06/07/09 12:57 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: kc8gpd]
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rdunajewski
The Copy-n-Paste King
Forum Big Guy
Registered: 03/05/06
Posts: 1229
Loc: Edison, NJ
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The main issue is that unlicensed 900 MHz users have the potential of matching your FHSS pattern and can inadvertently (or intentionally) key up your GMRS system, a licensed service. That was always the problem with using MURS as a link frequency. Granted, FHSS is infinitely more secure than a MURS channel, but it's still an unlicensed service.
A Ham up here was telling me that there are, or used to be, 900 MHz channels which could be licensed for linking purposes. I'm assuming they would be Part 90 channels, and as long as you meet eligibility for Part 90, you could license a channel and use it as a private link channel. I haven't looked into how true this is, but it's an idea. Who knows, those frequencies could have been reassigned years ago.
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#95799 - 06/07/09 01:10 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: rdunajewski]
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kc8gpd
Radio-active Reader
Registered: 04/17/07
Posts: 208
Loc: Glen Gardner, NJ 08826
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a station my friend engineers for uses license free 900 mhz stl equipment and the equipment has security in place to prevent unlicensed users from taking over the link and the 50kw fm.
_________________________
Thank You, Rev. Robert P. Chrysafis Universal Life Ministries http://www.ulc.orgModerator: Hunterdonfree Owner & Moderator: freestuffwarrennj
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#95840 - 06/13/09 04:21 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: kc8gpd]
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jwilkers
Moderator
Forum Big Guy
Registered: 04/09/99
Posts: 1203
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Are RF links legal in any case though? (on GMRS)
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#95842 - 06/13/09 06:14 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: jwilkers]
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rdunajewski
The Copy-n-Paste King
Forum Big Guy
Registered: 03/05/06
Posts: 1229
Loc: Edison, NJ
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Are RF links legal in any case though? (on GMRS)
They're not banned outright by the rules, but good luck finding a viable RF link solution that doesn't violate any other GMRS rule. Like I was saying about using an unlicensed service to carry a GMRS link.. someone can legally transmit on the link frequency without a license and come out on a licensed service. Big no-no. WiFi is a possibility, but you would then run it like an Internet VoIP link (say, in an area with no Internet service).
At that rate, using VoIP over the Internet is permissible. Access control and station control still apply though, so a proper method has to be developed that takes this all into account. Using Echolink, IRLP, and eQSO is a huge no-no as you're potentially opening up Ham and GMRS repeaters to use by unlicensed individuals. A custom VoIP system would be ideal, or even something like Skype where there's an inherent security layer in place to prevent casual people from stumbling onto your link.
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#95847 - 06/14/09 04:43 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: rdunajewski]
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Tower Rigger
New Reader
Registered: 11/11/04
Posts: 20
Loc: Elizabeth NJ
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I believe Echolink can be configured to allow only listed users and therefore no one else could access your setup. Saves having to develop your own VoIP method.
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#95848 - 06/14/09 06:09 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: Tower Rigger]
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rdunajewski
The Copy-n-Paste King
Forum Big Guy
Registered: 03/05/06
Posts: 1229
Loc: Edison, NJ
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You can only enter valid Ham callsigns into Echolink, so it's a bad idea. If you went the Echolink route, you're just begging for the FCC to bother you. It's not hard to write basic VoIP software using Visual Basic, for example. I should know!
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#95899 - 06/20/09 01:59 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: rdunajewski]
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Tower Rigger
New Reader
Registered: 11/11/04
Posts: 20
Loc: Elizabeth NJ
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"It's not hard to write basic VoIP software using Visual Basic, for example. I should know!"
Sounds cool. I know nothing about writing software. Maybe you could come up with something for us? You'd be the gmrs hero around here.
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#95904 - 06/21/09 07:44 AM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: Tower Rigger]
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Critter
Professional geek
Awesome Reader
Registered: 02/01/00
Posts: 5133
Loc: Schenectady NY USA
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Generally, I have thought of BASIC as being a tad short on processing power, so let me ask a stupid question: how do you do this in VB? (This isn't a challenge; rather I'm actually curious)
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#95907 - 06/21/09 03:44 PM
Re: CFR47 Part15.247 900 MHz GMRS Link
[Re: Critter]
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rdunajewski
The Copy-n-Paste King
Forum Big Guy
Registered: 03/05/06
Posts: 1229
Loc: Edison, NJ
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VB is based on, but totally different than, BASIC. The learning curve is much easier if you have experience in BASIC like I did, although I was never writing anything useful in BASIC. But knowing the basics of the language will be an immense help. VB is object-oriented, so you can create "controls" which are basically micro-programs or macros that can be added to a form (a Windows window) and be controlled via events such as clicking a button, etc. As far as I know, you'd never be able to pull a VoIP program out of BASIC -- for one, there's no networking support at least in QuickBASIC/GW BASIC.
BASIC, as I understand it, is run line-by-line and has to constantly be told what to do. If it shouldn't be doing anything, you have to set up a loop of some kind to keep the program busy (including the SLEEP command). With VB, the code doesn't run until the assigned event fires, such as your button being clicked. All the code is packed away into Subroutines which the events call upon.
Anyway, trying not to get off topic here. VB allows VoIP to be utilized because you can use DirectX for your audio and even the VoIP system if you choose to rely upon it. You also have easy access to the soundcard directly so you can capture the audio and do something useful with it. You're really only limited by your coding ability in what you can achieve. Since VB is events-driven, you can write a very powerful program that doesn't get bogged down because it's constantly trying to pause during loops or sleep cycles.
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