Other Modes on GMRS?

[Lscott]

Looking over the rules the FCC allows several types of emissions, modes, on GMRS:

 

95.1771 - GMRS emission types.
95.1787 - GMRS additional requirements.

 

https://en.wikipedia.org/wiki/Types_of_radio_emissions

https://www.law.cornell.edu/cfr/text/47/95.1771
 

A1D:
Double-sideband amplitude modulation
One channel containing digital information, no subcarrier
Data transmission, telemetry or telecommand (remote control)

F1D:
Frequency modulation
One channel containing digital information, no subcarrier
Data transmission, telemetry or telecommand (remote control)

H1D:
Single-sideband with full carrier
One channel containing digital information, no subcarrier
Data transmission, telemetry or telecommand (remote control)

J1D:
Single-sideband with suppressed carrier
One channel containing digital information, no subcarrier
Data transmission, telemetry or telecommand (remote control)

R1D:
Single-sideband with reduced or variable carrier
One channel containing digital information, no subcarrier
Data transmission, telemetry or telecommand (remote control)

F3E:
Frequency modulation
One channel containing analog information
Telephony (voice intended to be listened to by a human)

G3E:
Phase modulation
One channel containing analog information
Telephony (voice intended to be listened to by a human)

H3E:
Single-sideband with full carrier
One channel containing analog information
Telephony (voice intended to be listened to by a human)

J3E:
Single-sideband with suppressed carrier
One channel containing analog information
Telephony (voice intended to be listened to by a human)

R3E:
Single-sideband with reduced or variable carrier
One channel containing analog information
Telephony (voice intended to be listened to by a human)

F2D:
frequency modulation
One channel containing digital information, using a subcarrier
Data transmission, telemetry or telecommand (remote control)

G2D:
Phase modulation
One channel containing digital information, using a subcarrier
Data transmission, telemetry or telecommand (remote control)

 

The interesting one is running SSB. Has anybody run across a Part 90 certified radio that can do SSB on the GMRS frequencies?

 

If the FCC seems to be "OK" with Part 90 LMR radios on GMRS would they have a problem with one doing SSB? At least the emission mode is allowed, J3E.
 

[kidphc]

Wouldn't going ssb bleed into adjacent frequencies since the FCC attempted to make the service channel based?

 

I know that no one has been able to free band the ft991a on UHF/VHF.

 

Sent from my SM-G975U using Tapatalk

[berkinet]

...If the FCC seems to be "OK" with Part 90 LMR radios on GMRS ...

 

Yes, if the FCC seemed to be ok with that. But, there is no evidence they are. Failure to cite people for use of Part90 equipment is not the same as being OK with the use of such equipment. 

 

On the other hand, since they clearly are not actively opposing use of such equipment, I don't see any difference in using a Part95 radio for FM or SSB.  

 

Of course, as @kidphc points out, there may be other reasons to not use SSB.  But, other than for experimentation's sake, and maybe a slight increase in simplex range, why bother?  Isn't that what amateur radio is for?

[kidphc]

Yup, that is what amateur radio is about. I figured SSB on 70cm isn't all that popular due to range, unless you get lucky with tropo. So much I have dropped 70cm SSB from my plans. Even 2m SSB maybe dropped.

 

Sent from my SM-G975U using Tapatalk

[Lscott]

Wouldn't going ssb bleed into adjacent frequencies since the FCC attempted to make the service channel based?

 

I know that no one has been able to free band the ft991a on UHF/VHF.

 

Sent from my SM-G975U using Tapatalk

No, that shouldn't happen. On SSB the bandwidth can be rather narrow. On my old ICOM IC706MKIIG I had a optional narrow SSB filter installed. Many Hams run a 2.2 KHz to 2.4 KHz bandwidth, or a bit more. SSB is more spectrum efficient than FM, at lest for the typical bandwidths being used.

 

https://www.dxengineering.com/parts/ico-fl-223

 

The above radio opens up a lot.

 

http://www.catlog.net/_Descarregas/Manuals/01-Icom/Icom%20706MKIIG%20OBM.pdf

 

Yes the FT991A you can only open up the HF section.

 

http://blog.pauls.li/wp-content/uploads/2015/01/FT-991_MARS_Mod.pdf

 

So far nobody has found a general way to open the VHF and UHF bands. There is a way to do it on a per frequency basis however using a test mode from what I've found.

 

https://forums.qrz.com/index.php?threads/ft-991a-expanded-tx-on-vhf-uhf.623521/

[kidphc]

 

So far nobody has found a general way to open the VHF and UHF bands. There is a way to do it on a per frequency basis however using a test mode from what I've found.

 

https://forums.qrz.com/index.php?threads/ft-991a-expanded-tx-on-vhf-uhf.623521/

 

Done that. It is a test mode, locked to a frequency that you set before you power down to get into the test mode. 

 

So more of a kludge then a hack.

[tweiss3]

Yup, that is what amateur radio is about. I figured SSB on 70cm isn't all that popular due to range, unless you get lucky with tropo. So much I have dropped 70cm SSB from my plans. Even 2m SSB maybe dropped.

 

Sent from my SM-G975U using Tapatalk

Unless your plan was to get an IC7100 as and all band all mode, I don't see any reason to play on 2m or 70cm SSB, other than nobody else would pick up on your conversation (security through obscurity).

 

While it's an interesting proposal to do SSB on GMRS, good luck finding a rig that will do that portion of UHF SSB, let alone being cost effective and having part 95 certification.

[Lscott]

Yes, if the FCC seemed to be ok with that. But, there is no evidence they are. Failure to cite people for use of Part90 equipment is not the same as being OK with the use of such equipment. 

 

On the other hand, since they clearly are not actively opposing use of such equipment, I don't see any difference in using a Part95 radio for FM or SSB.  

 

Of course, as @kidphc points out, there may be other reasons to not use SSB.  But, other than for experimentation's sake, and maybe a slight increase in simplex range, why bother?  Isn't that what amateur radio is for?

My goal here was to find out if there is currently, or in the past any LMR/Part 90 radios that could in fact do SSB.

[tweiss3]

My goal here was to find out if there is currently, or in the past any LMR/Part 90 radios that could in fact do SSB.

A quick search on FCC EAS database, I saw zero matches for the UHF band that had H1D, J1D, J3E or H3E emissions. Quick Google didn't pull anything up at all.

[Lscott]

A quick search on FCC EAS database, I saw zero matches for the UHF band that had H1D, J1D, J3E or H3E emissions. Quick Google didn't pull anything up at all.

Thanks. I was sort of expecting that kind of result. Given the usual crystal reference frequency accuracy and temperature stability makes it difficult to stay on frequency. Being off frequency by 100 Hz or so SSB signals are petty much unreadable.

[Radioguy7268]

The only Part 90 radios that I'm aware of that used Sideband was some Aerotron stuff in the '80's that worked on certain odd narrowband splinter frequencies in the VHF band.  SEA (Datamarine) took that same tact and used ACSB for the 220 MHz band in the late 90's. I'm not aware of any manufacturer who tried any AM Sideband for UHF frequencies with Part 90 equipment.

 

I played around a little with the SEA stuff and thought it was decent for what it was. They used a pilot tone in the middle of each narrow channel to try to keep everything centered on frequency. I remember that certain voices (higher pitched young women) would drop out certain sounds - I specifically remember that "Six" and "Seven" would cause problems. Put a middle aged male with a raspy voice on the mic, and it came through loud and clear with every test count. Ran our techs around in circles until we figured out what was going on - the higher pitched voices were running right in the middle of the notch for the pilot tone!

[Lscott]

The only Part 90 radios that I'm aware of that used Sideband was some Aerotron stuff in the '80's that worked on certain odd narrowband splinter frequencies in the VHF band.  SEA (Datamarine) took that same tact and used ACSB for the 220 MHz band in the late 90's. I'm not aware of any manufacturer who tried any AM Sideband for UHF frequencies with Part 90 equipment.

 

I played around a little with the SEA stuff and thought it was decent for what it was. They used a pilot tone in the middle of each narrow channel to try to keep everything centered on frequency. I remember that certain voices (higher pitched young women) would drop out certain sounds - I specifically remember that "Six" and "Seven" would cause problems. Put a middle aged male with a raspy voice on the mic, and it came through loud and clear with every test count. Ran our techs around in circles until we figured out what was going on - the higher pitched voices were running right in the middle of the notch for the pilot tone!

Thanks for the info. I never heard of this radio before.

 

The description of the method to hold the frequency centered on the channels using a pilot tone brings up a question. I'm assuming they used the pilot tone in a PLL circuit to adjust the TX/RX frequency until the tone was exactly in the filter's pass band?  The pass band of that filter would need to be rather narrow too I assume.

 

[Lscott]

I did some snooping around and located some info on the Aerotron radio. Not much to see. Just had to check it out.

 

https://fccid.io/APC9RB60ACC25B

 

The interesting part is besides doing SSB it also had some sort of digital mode. Also the frequency tolerance is far better than the usual FM radio.

 

Part 74

https://ecfr.io/Title-47/pt47.4.74

 

Part 9

https://ecfr.io/Title-47/pt47.1.9