LTR is dead???

[902]

You used to have to file a waiver to operate 2-6.25/12.5 . The R&O you refer to was when the FCC formalized the process. License with the 4K & 8K emission on the same freq. is authorization for the pair. And yes they operate at +/- 3.125 from center. There is a proposal at the FCC now to permit a third repeater on center under special conditions on a 12.5 FB8. Most trunked very narrow NXDN systems operate on the 6.25 single channels between the 12.5's because they are easier to combine and are still virgin spectrum in most markets and readily available as FB8.

bart

I dunno, Bart. Most of the markets I see nationwide are congested. Maybe we can find virgin UHF spectrum in North Dakota south of Line A. Anywhere else? Not so much. At least not where there is an opportunity to deploy commercially and get an ROI.

My read of the R&O requires the center frequency to be licensed, and that may have an 8K30/4K00 on it, but then the +/- 3.125 from there also need to be enumerated on the 601. Unfortunately, the FCC took to calling them "non-standard pairs," which, to me, means not a 5 MHz or 3 MHz separation between input and output, but that's just me.

This is a rhetorical question. I'm not putting you on the spot (I suspect it's got a lot to do with manufacturer lobbying). Now, if DMR is just as wide and achieves an efficiency of 6.25 kHz (and so does two of these), why isn't that also required to be FB8?

 

[domes]

I dunno, Bart. Most of the markets I see nationwide are congested. Maybe we can find virgin UHF spectrum in North Dakota south of Line A. Anywhere else? Not so much. At least not where there is an opportunity to deploy commercially and get an ROI.

My read of the R&O requires the center frequency to be licensed, and that may have an 8K30/4K00 on it, but then the +/- 3.125 from there also need to be enumerated on the 601. Unfortunately, the FCC took to calling them "non-standard pairs," which, to me, means not a 5 MHz or 3 MHz separation between input and output, but that's just me.

This is a rhetorical question. I'm not putting you on the spot (I suspect it's got a lot to do with manufacturer lobbying). Now, if DMR is just as wide and achieves an efficiency of 6.25 kHz (and so does two of these), why isn't that also required to be FB8?

You can trunk in UHF with either FB6 or FB8 channels or a mix of both. The FCC has 2 classes of trunking; "Centralized" or control ch trunking and "Decentralized" non-control ch LTR type. The only thing you absolutely have to have an FB8 for is for the continuously transmitting control channel of the centralized system. The FB designations have nothing to do with the type RF (FM, NXDN, DMR) you use. It has to do with the trunking platform (logic) you use. The difference between FB6 & FB8 is that an FB8 is a clear, "Exclusive Use" channel with no other licensees in your area to interfere with. Since there are no other users to interfere with, you are permitted to Tx without monitoring and you can Tx continuously, 24/7. An FB6 is not for your exclusive use because there may be 1 or more licensee within range so you can not continuously TX and you may have some degree of interference to deal with. I'm not going to discuss the requirements for monitoring on FB6. Obviously you can provide a better grade of service on FB8's without interference and those are the preferred channels.

Have you considered the 6.25 single channels sandwiched between the NB channels? There are as many of these as there are NB channels and they are underutilized in most parts of the country.

 

[domes]

I dunno, Bart. Most of the markets I see nationwide are congested. Maybe we can find virgin UHF spectrum in North Dakota south of Line A. Anywhere else? Not so much. At least not where there is an opportunity to deploy commercially and get an ROI.

My read of the R&O requires the center frequency to be licensed, and that may have an 8K30/4K00 on it, but then the +/- 3.125 from there also need to be enumerated on the 601. Unfortunately, the FCC took to calling them "non-standard pairs," which, to me, means not a 5 MHz or 3 MHz separation between input and output, but that's just me.

This is a rhetorical question. I'm not putting you on the spot (I suspect it's got a lot to do with manufacturer lobbying). Now, if DMR is just as wide and achieves an efficiency of 6.25 kHz (and so does two of these), why isn't that also required to be FB8?

The R&O is for 3 NXDN repeaters on one 12.5 center. Very narrow modulation is only 2khz. It is actually capable of 4 ch per 12.5 on 3.125 steps. It fits in a 3.125 channel space. It has to - that is what it was developed for because that is the FCC's modulation requirement for the so called 6.25 single channels I mentioned above. It is capable of 4 in a 12.5 channel. However ,the part 90 rules limit it to 3 - two at the 12.5 center and one at each end, or to be more mathematically correct, half at each end for a some total of 3 in 12.5 channel

 

[Voyager]

he difference between FB6 & FB8 is that an FB8 is a clear, "Exclusive Use" channel with no other licensees in your area to interfere with.

I know of FB8s within 20 miles of other users. But, I guess it all comes down to the definition of "in your area".

 

[domes]

Your area is defined by your ERP - antenna height & power.

 

[INDY72]

Your area is defined by your ERP - antenna height & power.

Yes, your Effective Radiating Power levels and the "official" range of the mobiles operational area as defined on your licenses. that's where the difference between an good engineer and bad one come in. If your system engineer has a good working mind, they can set up an very nice system with excellent coverage for mobiles/ht's in an very tight footprint of coverage. On the other hand, poor engineering can lead to real headaches with overload outside of your footprint, or even very spotty coverage in the center of your intended coverage footprint!