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GMRS / FRS - Discussions related to GMRS (General Mobile Radio Service) and FRS (Family Radio Service) communications

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Old 03-19-2010, 12:33 AM
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Default Scrambling On MURS Legal?

I didn't see a MURS Forum so I posted here, Can be moved if necessary. I have read on the FCC site and have found nothing about the answer I'm looking for. So I thought I'd ask about it to somebody who might know more about it.. Can anyone tell me if it is illegal to use voice inversion scrambling (Not Very Secure I Know, Just Curious) on murs. My PS radio has the scramble capability if you enable it. I have no use for it but I wondered if I ever got a murs radio in the other car or something if it would be illegal to use the inversion scramble. It's kinda neat to use so I just wonderd before I used it, If I do.. Does anyone know if its illegal to use it? Thanks,
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Old 03-19-2010, 12:51 AM
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Quote:
Originally Posted by btritch View Post
I didn't see a MURS Forum so I posted here, Can be moved if necessary. I have read on the FCC site and have found nothing about the answer I'm looking for. So I thought I'd ask about it to somebody who might know more about it.. Can anyone tell me if it is illegal to use voice inversion scrambling (Not Very Secure I Know, Just Curious) on murs. My PS radio has the scramble capability if you enable it. I have no use for it but I wondered if I ever got a murs radio in the other car or something if it would be illegal to use the inversion scramble. It's kinda neat to use so I just wonderd before I used it, If I do.. Does anyone know if its illegal to use it? Thanks,
btritch
Yes encrypted communications is legal on MURS. On GMRS and CB it is not legal.
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Old 03-19-2010, 12:42 PM
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Originally Posted by kilowa22 View Post
Yes encrypted communications is legal on MURS. On GMRS and CB it is not legal.
Only in FM?
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Old 03-19-2010, 2:05 PM
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MURS Emissions:

(j) A MURS transmitter must transmit only emission types A1D, A2B, A2D, A3E, F2B, F1D, F2D, F3E, G3E. Emission types A3E, F3E and G3E include selective calling or tone-operated squelch tones to establish or continue voice communications. MURS transmitters are prohibited from transmitting in the continuous carrier mode.

APCO 25 is F1E, not authorized.
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Old 03-20-2010, 6:49 PM
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ok that's what I was wondering, I wasn't sure of the emissions type to look it up and see but I found a while page on the different ones now and have figured out what emissions type that is, I didn't know if it would be legal on murs or not. I have that capability in my radio but I don't use it, I just wonderd if I had decided to use it if it was legal or not to use. I don't plan on using it anytime soon, Just had me curious. Thanks For The Answer On That.. I Appreciate it once again...
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Old 04-19-2010, 7:49 AM
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What about DES?
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Old 04-21-2010, 2:16 PM
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Did a little checking DES is in the F1D family, so you can use it. It probably would work better on the wide band channels
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Old 04-21-2010, 6:34 PM
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I have heard DES transmissions on MURS many many times in a nearby city. Not sure who is using it, but its distinctly DES, after a while you start to recognize each form by ear.
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Old 04-21-2010, 6:40 PM
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Originally Posted by radioman2001 View Post
What about DES?
That DES would have to be coming from an Analog Saber - IE it would have to be encrypted *analog* voice - which no modern P25 radio will do.
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Last edited by bezking; 04-21-2010 at 6:51 PM..
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Old 04-22-2010, 9:50 AM
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Originally Posted by bezking View Post
That DES would have to be coming from an Analog Saber - IE it would have to be encrypted *analog* voice - which no modern P25 radio will do.
Yep, exactly... That's what i'm betting the user i hear has, Saber's with a DES module in them.
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Old 04-22-2010, 11:06 AM
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CVSD emission type on analog Sabers with Securenet is 20K0F1E. This is not an approved emission type for MURS under Part 95.

Although these radios don't transmit P25, they do transmit a digital emission when switched to .

Even public safety agencies are supposed to have their licenses granted with this emission if they use it.

I believe it is in within "the spirit" of the law to use analog scrambling techniques on MURS. This would include inversion, VSB, hopping inversion, and possibly FFT spectral dispersion such as Midian VS-1200 and Transcrypt's DES "analog" boards. The latter scramblers utilize DSP technology to randomly mix the voice spectral components over the audio pass band and be transmitted and received over analog repeaters. The emission type is still F3E or G3E, but the voice components are effective mangled beyond recognition to casual and to some extent determined eavesdroppers.

This is a gray area in the rules. Part 90 business band licensees may utilize analog scramblers under the rules, although the definition of a analog scrambler is not provided. Part 95 on MURS is silent on analog scrambling, although it seems to be permitted on FRS, but not GMRS.

This is a clear case where technology has outrun the rules.


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Last edited by kv5e; 04-22-2010 at 11:46 AM.. Reason: added narrative about analog
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Old 04-27-2010, 2:35 PM
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NO. The emission is 15K0F2D, according to an old NYPD license that definitly had DES on it. The E is for voice only, DES is digital.
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Old 04-28-2010, 6:10 AM
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Quote:
Originally Posted by radioman2001 View Post
NO. The emission is 15K0F2D, according to an old NYPD license that definitly had DES on it. The E is for voice only, DES is digital.
Is it possible that the license covered more than one emission type (as most do) and maybe they did not license CVSD - Securenet although they may have used it?

Here's a guide to emission designators and there are many other references available.

http://www.comsearch.com/articles/emission.pdf

F2D utilizes a modulating subcarrier and is a data transmision - MDC1200/MODAT
F1E is digitized voice.

Respectfully,

Craig
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Old 04-28-2010, 7:33 AM
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It's possible that the original emission designator wasn't able to correctly identify the CVSD emission. The way I decode the emission is 15K0 or 16K0 (I have seen both) is the band width, roughly 4kc wide deviation.
Which DES is, modulation is set for 3.75kc to 4.25kc deviation. F is Frequency modulation, 3 is a single channel with analog information, which is how CVSD is described, and I don't know why, since is is digital. D is digital transmission, I see no designator for digitized voice so that may be why that designator.. Maybe it should have been an X for other. It could be as I said that DES,DVP or CVSD was in a gray area of emission types. I do know that all the agencies I was doing work for had those emission types or similar on their licenses. All in all the FCC could say that you were not transmitting analogue voice, so the rest may be academic. BTW Motorola was probably the ones who either licensed the systems or provided the information for the 465 form back then.
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Old 04-28-2010, 9:43 AM
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Deviation is 3.9k on CVSD nominally, pretty cool looking on the eye pattern displays.

Most agencies here in Texas file it as 20K0F1E.

FCC Callsign WZT820 Details


Vocoders for digital speech were pretty pricey in the 70's and 80's when CVSD was developed for radio systems.

Sample rate is 12K bit per second and has some filtering to band limit the signal.

CVSD does digitize voice with encipherment and there's no data riding along other than the voice in DES. There's sync patterns in DES-XL which help to keep the decoders in sync when BER or fast fades stop effective decoding so it has superior range over DES.

I think going forward that Part 95 may be amended to permit digital emission types, particularly those that meet the 4800 bps/6.25 kHz emission mask. These will all likely be type accepted with perhaps P25 grandfathered in, but the FCC is no big hurry.

CVSD will go the way of the dodo with narrowbanding in public service usage.

Craig
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Old 04-28-2010, 10:00 AM
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I thought 20K0F3E was voice only, maybe they didn't bother with the DES emission designator. Unfortunately I agree about CVSD going away, I have had DES repeaters for nearly 20 years, and they have served me well. Has anyone tried running DES on a narrow band channel yet to see if you can get a decent decode? Sounds like a project for me in my spare time. Yea right, what spare time. LOL. I see the analogue emission and I see either P25 digital voice and data or NXDN voice and data also on that call sign. Any idea what 5K76G1E is for?

Last edited by radioman2001; 04-28-2010 at 10:08 AM..
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Old 03-28-2018, 6:32 PM
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So it's a yes on MURS and Yes on GMRS. And No on CB and No on HAM. But what about FRS?
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Old 03-28-2018, 6:52 PM
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Quote:
Originally Posted by King85me View Post
So it's a yes on MURS and Yes on GMRS. And No on CB and No on HAM. But what about FRS?
Some older GMRS and FRS units had scrambling but any new models cannot be FCC certified if they have it. See 95.381 Voice obscuring features.

Digital voice is still not allowed on FRS. See 95.587 FRS additional requirements.
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Old 03-28-2018, 7:15 PM
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How I see it's saying yes and no. It's stating to go back and review the 95.359 (I may be wrong) and .359 says the channels are in use to Shared among others and noone can claim a channel as specifically to be there's alone. But 95.381 states that devices in the future are no longer being certified to have Voice obsuring features. And may need a grant if passed 12-27-17
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Old 03-29-2018, 10:40 AM
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The simple and correct answer to the original question is NO.

All of the armchair lawyering and low reading comprehension in the world will not change what the regs actually say.
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