How do FSR sub-channels work?

[Pat_in_Utah]

Just got 2 Cobras ($30 Staples) and only had 2 minutes to play with them. I never had ones with sub-channels before and they work kinda "weird"?



Does the sub-channels allow you to hear only on one sub-channel, while you talk over the entire channel's sub-channels? So, if I talk on channel 14, I transmit on every sub-channel within channel 14, but people can only hear the sub-channel we are on?



Or was I day-dreaming they worked different than non-sub-channeled radios?



Takin' 'em up to Henry's Lake in Idaho this weekend.



Thanks,

Pat

 

[jthorpe]

Sub channels are really a marketing farce. Basically, FRS has 14 "channels". Those are actual frequencies in the 462mhz range. For instance, FRS channel 1 is 462. 5625mhz. This does not change. What they market as a sub channel really is a code called CTCSS. It stands for Continuous Tone Coded Squelch System. What it does is allow you to transmit a sub-audible tone over the air when you're talking. It's only purpose in life is to prevent you from hearing people on the same channel. So lets say you're using 103. 5hz as your CTCSS code. If someone is transmitting on 107. 2hz, you would not be able to hear them, even though you're both on the same frequency. It does not prevent them from hearing you though. If you're talking, and ther other radio is using carrier squelch, then they will hear you no matter what tone you're using. In order for you to hear them, they would have to be using 103. 5hz CTCSS to open up the audio on your radio speaker.



In a nutshell, the CTCSS or "sub channel" system is only there so you won't hear a bunch of people talking on the same channel except for those who are on your code. In busy environments such as fairs and stuff, many people might be on your CTCSS code which would make it useless at that point.



If two people are talking on the same channel at the same time, no matter what sub channel they're using, the audio will sound like jibberish and cancel each other out. So basically, there really is no such thing as a sub channel.



I know this explanation isn't very good, but that's the technical gist of it.



Jack

 

[Ethdee]

I disagree with you, Jack.



That was a great explanation.



Jim

 

[Jammar9082]

Hear! Hear! A very good explanation.



I am looking for some radios and have been confused by all of the hype. It is impossible to evaluate the many different brands on the market. it seems that there are good and bad reports on the same models. I sometimes wonder if the quality control in the manufacturing process is approaching zero. Does anyone have a recommendation based on hard evidence or tests?

 

[jthorpe]

Guys,



For about as much info as you could ever handle on this stuff, go to http://www.gmrsweb.com



They also have a forum area and lots of q&a stuff.



Jack

 

[BK]

jthorpe did a good job of describing it.



the only thing I would add is that you transmitte on a carrier frequency... . such as the channels 1-14. . and you add the CTCSS or tone squelch on to your signal when it's selected. . your not transmitting "on" a tone squelch freq. . it's just added to the carrier frequency such as your voice is.

(CTCSS - privacy code - tone squelch. . or any other name for the low frequency audio tone )



The only other thing to keep in mind since the tone squelch is there to only break the squelch of those radios set to the same tone... once you receive a signal with the tone to "open" up your receiver... . you will hear any and all carriers transmitting on the same carrier frequency.



So if your in a local mall or amusement park with lots of other folks close by on the same channel, but using different tones. . once your receiver is opened by a member of your group transmitting, you can hear another person that's closer even though they are using a different tone squelch. Or as jthorpe pointed out. . if the rf levels are close to the same you wind up with garbage.



BTW I have 4 cobras for the family and for the money I don't think you can beat them. Battery life is great, the tones and channels are very tight.

 

[jthorpe]

That's a good point to make. It's just a tone riding the carrier. I went GMRS about a year ago for the family. We put a repeater up and we're getting about a 25 mile radius around it with handhelds, and about 50-60 with mobiles. We're using a CSI TP3200 tone panel so we can run multiple tones through the same repeater. We have 4 families using it right now with a total of about 40 radios or so. Works GREAT! We're lucky because we had tower space available, but that is definately the way to go! Our repeater is about 360 ft AGL, 650 MSL I believe.



My personal radios are:



Motorola Syntor X9000 vhf (ham rig)

Motorola GM300 (uhf gmrs and ham)

Maxon 16 channel (wifes GMRS car)

2 motorola GP300's (portable UHF)

1 Motorola JT1000 UHF

1 Motorola MT1000 UHF

1 Motorola HT600 UHF





Can you tell that I like Motorola? I'd say you can't go wrong with their gear. I have never owned one of their FRS radios, but their commercial stuff is awesome. I'm going to be replacing the GM300 with a 128 mode Spectra here pretty soon for my truck. I can't wait!



Have fun



Jack - WA0ERX / WPQT431

 

[Pat_in_Utah]

Thanks

Great info - thanks. Starting to go WAY over my head tho - but that's ok, I'm wearing protection!!



The Cobras were of great value. My friend bought the basic 14 channel Cobra for $60/pair 2-3 years ago. The same units sold at Staples for $20/pair with a rebate. I got the $30/pair ones with the sub channels.



I too was very surprised with the battery life. Left one on all night and it still ran for 3 full days total! These are Energizer batteries.



Great for traveling and fishing. We let our young boys sleep in while we went fishing and they called us when they were ready!



Pat

 

[BK]

jthorpe , I totally agree regarding Mot commercial stuff.

The only problem with their frs radios is that they use a special compander. Two mots of the same family work excellent together. The compander has been shown to extend the range in several tests. BUT, when used with other brands, which of course do not have a compander... . the mots sound terrible when being hear on another brand with basic FM modulation.



Thats great you've been able to get a repeater up... I'd love to.



I have my ham ticket and have a GMRS ticket too. But around here we don't have the space, it's saturated with GMRS by businesses. CT is 7 miles across the LI sound... we even get hit with their GMRS repeaters.



Went GMRS and FRS cause my wife doesn't want to try and get her ham ticket.....



I haven't used GMRS lately. . forgot my calls... WPOOO something. .

oh found my ticket. . WPUH685

Ham is N2PZN.



I let my kids and the kids of other families run around with them when camping. . at the price IF they break one... . it's just part of the cost of the trip. I've had really good luck with them