Cross over from 650 to 6375 & 6625 ...??

[Photoman5k]

Not sure if it's the radio settings or something else but I often pick up transmissions from 650(channel 19) on 6375(channel 4) as well. It's not the greatest audio on 6375 but good enough to know it's the same traffic. Occasionally it bleeds over to 6625 (channel 5) too, though usually only when it's the local repeater on 650 sending out it's auto ID at the top of the hour. Happens regardless of the radio (kg905g, GMRS v2, GMRS v1, UV5R) or antenna(factory rubber ducks, Abbree 18.5in, na701g, na771g). Is this something I havent set up properly in the radios or is this something else outside my control? The crossover to 6375 & 6625 is only from the local repeater when it sends out it's auto id. But the simplex traffic on 650 from Chic-Fil-A which is like 4 blocks away can occasionally be heard on 6375 as well, again not clear but clear enough to know it's the same traffic. Anyone got any ideas? 

[KAF6045]

4 hours ago, Photoman5k said:

Not sure if it's the radio settings or something else but I often pick up transmissions from 650(channel 19) on 6375(channel 4) as well. It's not the greatest audio on 6375 but good enough to know it's the same traffic. Occasionally it bleeds over to 6625 (channel 5) too, though usually only when it's the local repeater on 650 sending out it's auto ID at the top of the hour. Happens regardless of the radio (kg905g, GMRS v2, GMRS v1, UV5R) or antenna(factory rubber ducks, Abbree 18.5in, na701g, na771g). Is this something I havent set up properly in the radios or is this something else outside my control? The crossover to 6375 & 6625 is only from the local repeater when it sends out it's auto id. But the simplex traffic on 650 from Chic-Fil-A which is like 4 blocks away can occasionally be heard on 6375 as well, again not clear but clear enough to know it's the same traffic. Anyone got any ideas? 

Channels 1-7 are referred to as "interstitial" channels. They OVERLAP the edges of "main" channels 15-22. 1-7 are low power (5W max) channels. 15-22 are allowed up to 50W max. If you are near such a transmission, it is quite possible that the interstitial is locking onto the edge of the main signal. (If close enough, it is equally possible for the interstitial to "leak" into a main channel).

GMRS is authorized a 20kHz bandwidth. (Though few of the common radios here implement it -- they use a 25kHz bandwidth for signal input)

.650 +/- 10kHz means the channel is .640-.660; .6375 +/- 10kHz spans .6275-.6475.; .6625 +/- 10kHz spans .6525-.6725. Note the overlaps -- add/subtract another 2.5kHz if allowing for a 25kHz filter. FM has what is known as "capture effect" -- the receiver will lock onto the strongest FM signal and follow its deviation.

The (formerly) FRS (only) 8-14 are also interstitial frequencies, but they are interstitial to repeater inputs, and by regulation are narrow FM and 0.5W ERP to avoid leaking into repeaters.

[Photoman5k]

Thanks for the answer. Makes sense that it happens from the repeater. Kind of surprised that it would happen from the bubble pack radios chick-fil-a uses. Just nice to know it's something out of my control lol. I'm actually surprised they use the 650 freq though since they have bot to be hearing that repeater ID over their radios every hour. I've scanned the ctss/dcs tones when they are on and they dont appear to be using any. Can only imagine what it would be like for them if that repeater had a good bit of traffic as is it crickets on that thing except when it IDs.

[WRQX963]

11F3 channels should never have been sandwiched between 20F3 channels.
The primary 20F3 GMRS users are protected but the secondary 11F3 FRS users are not.
I suggest that whenever possible, you use channels 8-14; I do and never hear QRM.

 

[KAF6045]

4 hours ago, WRQX963 said:

11F3 channels should never have been sandwiched between 20F3 channels.
The primary 20F3 GMRS users are protected but the secondary 11F3 FRS users are not.
I suggest that whenever possible, you use channels 8-14; I do and never hear QRM.

FRS wasn't involved there...

The original GMRS interstitials are 20kHz bandwidth, and overlap with the GMRS main channels on 462MHz. "8-14" are 0.5W ERP ONLY, and are interstitial on the 467MHz (repeater inputs). (emphasis mine)

Quote

§ 95.1773 GMRS authorized bandwidths.

Each GMRS transmitter type must be designed such that the occupied bandwidth does not exceed the authorized bandwidth for the channels used. Operation of GMRS stations must also be in compliance with these requirements.

(a) Main channels. The authorized bandwidth is 20 kHz for GMRS transmitters operating on any of the 462 MHz main channels (see § 95.1763(a)) or any of the 467 MHz main channels (see § 95.1763(c)).

(b) Interstitial channels. The authorized bandwidth is 20 kHz for GMRS transmitters operating on any of the 462 MHz interstitial channels (see § 95.1763(b)) and is 12.5 kHz for GMRS transmitters operating on any of the 467 MHz interstitial channels (see § 95.1763(d)).

(c) Digital data transmissions. Digital data transmissions are limited to the 462 MHz main channels and interstitial channels in the 462 MHz and 467 MHz bands.

The 462MHz interstitial channels predate FRS as a service.

[gortex2]

My guess is a quality radio may not see that issue either. Granted high power next to any radio can cause issues but a radio with little to no filtering on the recevier doesn't help things.

[Lscott]

On 10/27/2022 at 1:33 PM, WRQX963 said:

11F3 channels should never have been sandwiched between 20F3 channels.
The primary 20F3 GMRS users are protected but the secondary 11F3 FRS users are not.
I suggest that whenever possible, you use channels 8-14; I do and never hear QRM.

 

Interesting comment.

I think those channels could be put to better use IMHO. In another thread there is a suggestion to use those interstitial channels for the addition of digital voice mode. Using a narrow enough digital signal overlap with the "official" 20KHz adjacent GMRS main channels could be reduce to less than the current 11KHz narrow FRS FM, or eliminated. There are some digital voice modes that only use 4KHz bandwidth and would fit in without overlapping the GMRS main channels. Might even run at much higher power too, like at least 5 watts, the limit for hand held GMRS radios.

[WRQX963]

On 10/28/2022 at 8:25 AM, Lscott said:

Interesting comment.

I think those channels could be put to better use IMHO. In another thread there is a suggestion to use those interstitial channels for the addition of digital voice mode. Using a narrow enough digital signal overlap with the "official" 20KHz adjacent GMRS main channels could be reduce to less than the current 11KHz narrow FRS FM, or eliminated. There are some digital voice modes that only use 4KHz bandwidth and would fit in without overlapping the GMRS main channels. Might even run at much higher power too, like at least 5 watts, the limit for hand held GMRS radios.

I believe that the digital PMR allowance across the pond does it well. It is inevitable that eventually, every transmitted RF voice signal will be digital, but as an interim step, make all new GMRS radios with the option of transmitting 20F3 or 11F3 by simple programming, most already do, and announce that in X number of years, everyone will need to narrow their footprints.

[WRQX963]

On 10/27/2022 at 3:48 PM, MichaelLAX said:

Q-R-Mary: He's one of "those!" 

I bring half a century of experience to this table and comments such as yours have no place here.

[Lscott]

46 minutes ago, WRQX963 said:

I believe that the digital PMR allowance across the pond does it well. It is inevitable that eventually, every transmitted RF voice signal will be digital, but as an interim step, make all new GMRS radios with the option of transmitting 20F3 or 11F3 by simple programming, most already do, and announce that in X number of years, everyone will need to narrow their footprints.

Yes, they already have several modes in use under their license free PMR service. They have the narrow band FM, similar to our old FRS, the low power DMR and Digital PMR.

The issue is getting the FCC onboard with doing any kind of digital voice mode on GMRS. They have been very resistant to the idea.  

1021937093_PMR446WhitePaper.pdf

[MichaelLAX]

2 hours ago, WRQX963 said:

I bring half a century of experience to this table and comments such as yours have no place here.

I was first licensed as a Novice in 1961 and have continuously held my license up to Amateur Extra (back in the old Morse Code days) since then. 

My comment was intended for some “insiders” here and…

The sideways laughing emoticon tells the uninitiated that this is a joke!

So my comments have a little place here.

Very little! 

[WRQX963]

50 minutes ago, MichaelLAX said:

I was first licensed as a Novice in 1961 and have continuously held my license up to Amateur Extra (back in the old Morse Code days) since then. 

My comment was intended for some “insiders” here and…

The sideways laughing emoticon tells the uninitiated that this is a joke!

So my comments have a little place here.

Very little! 

OK, I did nor recognize your sarcasm...de Ai4i

[MichaelLAX]

2 hours ago, WRQX963 said:

11F3 channels should never have been sandwiched between 20F3 channels.
The primary 20F3 GMRS users are protected but the secondary 11F3 FRS users are not.
I suggest that whenever possible, you use channels 8-14; I do and never hear QRM.

 

Q-R-Mary: He's one of "those!"