Migration away from VHF Low

[k2hz]

Guess you have never priced out a radio system for coverage. It takes towers much closer at the higher bands. That means more towers for the same coverage area over what low band was providing. More towers means more up front costs, more maintenance costs, more backbone costs to link the sites together. problems, depending on how strong the signals are. At least on low band you can work with the problems.

jim202 - Thank you for clearly stating what everyone involved in radio system planning should know.

I have been involved with mobile radio for almost 50 years, mostly on conventional land mobile but also with IMTS, paging and early implementation of cellular and you summed up what I have always preached but was often drowned out by the BS from salesmen.

One specific case was a low band utility system covering 3 large southern tier counties. It originally had 2 primary base sites and had coverage issues that I fixed with a third site and antenna improvements. Field crews were happy with the coverage but management was listening to salesmen that Low Band was "obsolete technology". I had to sit through a sales presentation that we should go 800 trunked. When I raised the infrastructure cost of additional towers, the salesmen said I did not know what I was talking about because "everybody knows the higher the frequency the greater the range". There was also the issue of the radio vendor discontinuing Low Band and telling management Low Band could no longer be used because "the FCC requires conversion to narrow band and since Low Band is not being narrow banded it can no longer be used". We solved that by going with a different vendor who also had nice dual band mobiles that fit our mix of VHF and UHF in the city and Low Band in the rural areas.

I did a design for 800Mhz to cover the area and found it would need 16 towers to equal what we had with 3 Low Band towers. This was before cellular was built out so there were no existing towers or even road access or power at several of the hilltop sites that would be needed. I pointed out to management that the 16 towers for a system that only had about 12 mobiles in the area was absurd but I had to keep fighting off the "obsolete technology" arguement.

Having said that, the one problem with Low Band for the Fire service is poor portable performance meaning fireground comms are best handled on VHF or higher. VHF high is a good alternative in hilly rural areas. I greatly enhanced some VHF systems with just the addition of voting receivers although multisite simulcast is sometimes needed for in building portable coverage.

If you have the money to build out and maintain an elaborate trunked system is has some advantages but what is the cost benefit ratio? Also, for critical applications, consider the survivability of a simple Low or High Band system vs a complex trunked system in a widespread disaster situation like a hurricane or ice storm.

We need more input like jim202's comments to the planning process.

 

[902]

In the 3 rpc plans you mention, those 700 general use channels are packed on a county basis in terms of geography, but are available to eligible entities below the county level.



I think most in the field who are working on the public safety broadband planning expect that the devices will be public safety hardened (while they may have the guts of a consumer device, the form will be different) and direct mode is being worked on.
One idea is a lte device and a p25 radio in one.

So, what do you do with the orphaned channels in the RPC packing? Does the plan allow for reassignment by the RPC, or is it pretty much monolithic? You're right, it could be used by any agency within the allotted area, but realistically, what happens when the first-come has been served? Back to pretty much no available spectrum, while something may be free and clear from another part of the state, but is being held in abeyance for a time that may never come (some places have no interest in 700 at all). BTW, I used to be an RPC chair.

I was out at IWCE a year or two ago at the FCC's presentation where Stagg Newman insisted that these devices should be Band Class 14 chipsets so that they could be cross-compatible with other carriers and that there would not be the expense of having to manufacture proprietary hardware. Would you know, then, whether this chipset has the capability for P25 in the narrowband portion (and into the 800 band, after all, it was supposed to be a contiguous band)? If it can do P25, AND if the vocoded noise situation is resolved, AND if this could function off-network in simplex mode, maybe it IS useful.

 

[62Truck]

Anything to make a buck, that's what they will do while ago our vendor told us we would have to switch to a digital radio system to meet the requirements for narrow banding, and we are currently on that vendors 800 trunking system that is not effected by NBFM.... :roll:

jim202 - Thank you for clearly stating what everyone involved in radio system planning should know.

I have been involved with mobile radio for almost 50 years, mostly on conventional land mobile but also with IMTS, paging and early implementation of cellular and you summed up what I have always preached but was often drowned out by the BS from salesmen.

One specific case was a low band utility system covering 3 large southern tier counties. It originally had 2 primary base sites and had coverage issues that I fixed with a third site and antenna improvements. Field crews were happy with the coverage but management was listening to salesmen that Low Band was "obsolete technology". I had to sit through a sales presentation that we should go 800 trunked. When I raised the infrastructure cost of additional towers, the salesmen said I did not know what I was talking about because "everybody knows the higher the frequency the greater the range". There was also the issue of the radio vendor discontinuing Low Band and telling management Low Band could no longer be used because "the FCC requires conversion to narrow band and since Low Band is not being narrow banded it can no longer be used". We solved that by going with a different vendor who also had nice dual band mobiles that fit our mix of VHF and UHF in the city and Low Band in the rural areas.

I did a design for 800Mhz to cover the area and found it would need 16 towers to equal what we had with 3 Low Band towers. This was before cellular was built out so there were no existing towers or even road access or power at several of the hilltop sites that would be needed. I pointed out to management that the 16 towers for a system that only had about 12 mobiles in the area was absurd but I had to keep fighting off the "obsolete technology" arguement.

Having said that, the one problem with Low Band for the Fire service is poor portable performance meaning fireground comms are best handled on VHF or higher. VHF high is a good alternative in hilly rural areas. I greatly enhanced some VHF systems with just the addition of voting receivers although multisite simulcast is sometimes needed for in building portable coverage.

If you have the money to build out and maintain an elaborate trunked system is has some advantages but what is the cost benefit ratio? Also, for critical applications, consider the survivability of a simple Low or High Band system vs a complex trunked system in a widespread disaster situation like a hurricane or ice storm.

We need more input like jim202's comments to the planning process.

 

[902]

while ago our vendor told us we would have to switch to a digital radio system to meet the requirements for narrow banding, and we are currently on that vendors 800 trunking system that is not effected by NBFM.... :roll:

If you ever get a chance, take a look at some of the low band applications that come through - a few of those have changed their emissions from 20K0 down to 11K2. Seems like someone's been pushing for that and maybe collecting a few dollars to "help" along the way. I always think these wonderfully helpful folks are like the doctor in Johnny Dangerously.

Hi Dr. Magnus. How's my mother?
It's her thyroid, Johnny.
What's wrong with it?
We can't find it. Gonna have to do a thyroid search.
How much is that gonna cost?
You're in luck. This week a special. $999 dollars.

Best thing any agency can do is stay informed and know what they want before someone tries to bamboozle them into something they don't need.

On 800 trunked, I love (not) the premature sunset of analog systems and the "we won't support them anymore"s from a handful of the manufacturers. That's why I said that if I ever had to put something together, I'd rather put LTR panels on it than anything proprietary or use a format that drives up the price of subscriber units.

 

[GTR8000]

If you ever get a chance, take a look at some of the low band applications that come through - a few of those have changed their emissions from 20K0 down to 11K2. Seems like someone's been pushing for that and maybe collecting a few dollars to "help" along the way.

Are those applications comprised solely of LB frequencies? Or are they some mix of LB, VHF and UHF? I've seen applications where, while in the process of correctly changing the VHF/UHF emissions to narrowband, they also did the same to the LB on the same license. Basically, just a clean sweep change of everything on the license to 11K_.

Unless you've seen a pattern with a certain outfit converting pure LB licenses to narrowband, I'd say your post is pure speculation that some conspiracy is afoot here. :wink:

 

[radioman2001]

Yea, the snake oil salesmen are coming out of the woodwork. Even the co-ordinators are doing it to the customers. I work for a P.S. agency, and the AAR charged us for changing our emission designators, when the FCC would have done it for free.

 

[GTR8000]

Yea, the snake oil salesmen are coming out of the woodwork. Even the co-ordinators are doing it to the customers. I work for a P.S. agency, and the AAR charged us for changing our emission designators, when the FCC would have done it for free.

Well that's interesting, considering the AAR's own website clarifies that no coordination is required for a simple wideband to narrowband emission designator change (per FCC PN DA 11-1189). I really have to laugh at the ignorance of some of these agencies, allowing themselves to get hoodwinked like they apparently have. :roll:

 

[radioman2001]

It's not the co-ordination, just them handling the application for the change is what cost us. The FCC does it for free.

 

[GTR8000]

Why would you have to pay an application fee, when you can file via the ULS at no cost? I must be missing something.

 

[radioman2001]

Wasn't my call, and I suspect something else was going on, we have been waiting for our 6.25 channels for over a year. Now I am not saying they are related, but right after the existing licenses were updated, our 6.25 channels showed up.

 

[902]

Are those applications comprised solely of LB frequencies? Or are they some mix of LB, VHF and UHF? I've seen applications where, while in the process of correctly changing the VHF/UHF emissions to narrowband, they also did the same to the LB on the same license. Basically, just a clean sweep change of everything on the license to 11K_.

Unless you've seen a pattern with a certain outfit converting pure LB licenses to narrowband, I'd say your post is pure speculation that some conspiracy is afoot here. :wink:

There were only a few low band only ones. Now, to be fair, there's like one frequency on low band that is Limitation 27 (narrowband only) - 42.40. Nearly all those funky apps are mixed ones that the license preparers are sending through and the coordinators aren't questioning.

 

[902]

It's not the co-ordination, just them handling the application for the change is what cost us. The FCC does it for free.

Yeah, but the only catch is you must maintain the same emission type. So, you can go from 20K0F3E down to 11K2F3E through ULS, but you cannot go from 20K0F3E down to 7K60FXE (DMR) because you're going from an analog voice emission to a digital voice. Or you can't go from an E (voice) to/or add a D (data) without it getting returned. One of the four public safety coordinators has to submit those kinds of changes. You will sometimes see EWA and the other business/industrial coordinators submitting changes in bandwidth only (for a fee), but they can't do emission type changes. ULS will take these, but I'm not sure they've scripted an automatic passthrough without a manual review. I hear they're very backloged. If you send it through the coordinator, it gets "EBF'ed" (electronic batch filed) to the FCC and it's a more direct conduit. The other caveat is that you may be required to enter HAAT values and ERP now. Typically the ERP is assumed to be unity gain (output = ERP) and writing in a higher value might trigger a return and a letter requiring coordination. Canada also comes into play across Line A. Sometimes they spit out a HIA going from wider to narrower emission, everything else being the same.

If you're hands-on and are confident you can get into ULS without deleting your licenses, then that's a very good way to save some money. If you're hands-off or not very sure about numbers or forms, or you're good at what you do but it's not radio, then the coordinator routes are available for a fee. It's not a "have to" unless you're making changes.

 

[zerg901]

"But low band has 2 big oopsies - skip and big antennas. (Check out the Skip Forum here at Radio Ref)" - quoting myself

Would you believe 3 big oopsies?

1. Big antennas on portables

2. Skip at very strong levels - ( stronger than VHF or 800 - I dont know - maybe )

3. Very few states have any appreciable low band public safety ops now. Sorry guys, but that horse has long since left the gate. I suspect that if you studied the savings associated with using low band versus the costs of trying to maintain interops with yet another band in the public safety game, it wouldnt even be close. Just about all of Pennsylvania FD/EMS has moved from low band to VHF high and UHF now. New York FD/EMS is starting to finish the move from 46 Mhz to higher freqs. Massachusetts just has a few old band radios left. Connecticut FDs still have low band mobiles, but I think all their portables are at UHF. Ohio maybe still has some low band countys - but - ' wheres Ohio '? Even West Virginia has left low band. West of the Mississippi - I think that Calif Howie Patrol is the only "appreciable" agency on low band. There might be 1 FD in California on low band - ( ? Sierraville in Sierra County ? ) - but the only way to get to Sierraville is via Peruvian mule train.

 

[radioman2001]

There was no change to digital on the existing frequencies, only to narrow band. The 6.25's digital were to be new ones for yard channels. My point is that everyone is taking advantage of this no win for anyone narrow banding. There won't be any more VHF's after the 12.5 conversion, all interference contour rules remain the same. UHF has been narrow since 1995, so if you didn't get interference then you won't after 2013.
Back to the original OP, I intend to apply for 6 Low Band channels duplex and trunk them with LTR as a test system. From Alpine Tower ,Mt beacon and Science Hill, should be a kick *** system.

 

[k2hz]

Back to the original OP, I intend to apply for 6 Low Band channels duplex and trunk them with LTR as a test system.

Wow! LTR should work fine on Low Band and it sounds like quite a system.

What do you plan for duplexers and combiners? Floor space at the site for the huge cavities has been a problem for the few Low Band repeaters I have seen. With the cans over 8 ft tall for a 37/39 system it was a challenge to fit a single channel in the available space with them needing to be horizontal because they were too tall to stand up. Fitting six channels in one building sounds like an interesting project!

 

[902]

Wow! LTR should work fine on Low Band and it sounds like quite a system.

What do you plan for duplexers and combiners? Floor space at the site for the huge cavities has been a problem for the few Low Band repeaters I have seen. With the cans over 8 ft tall for a 37/39 system it was a challenge to fit a single channel in the available space with them needing to be horizontal because they were too tall to stand up. Fitting six channels in one building sounds like an interesting project!

You'd probably need a whole building for the filtering. The Wyolink guys building VHF high band trunking were talking about the large and expensive filtering requirements there, so this would probably look like a roomful of boilers. And, one antenna wouldn't be resonant to transmit and receive for wide splits. So, this would probably be too lossy. I mean, 4.5 dB or more insertion loss will probably impact the link budget pretty significantly. So, split antennas and rejects or maybe horizontal and vertical separation would probably be the way to start. Maybe even split sites with voting receivers being fed back on microwave. I don't think anyone's planing anything, though. Us frustrated radiomen just digressed off the original post.

As far as high band narrowbanding, between certain agencies saying "No, we won't go!" under any circumstances to narrowbanding (need I say who?), others seeking waivers, and the Rothman bill, who knows what will happen. We're still treating 7.5 kHz adjacents like they are co-channel. I'd love to apply TSB-88.1-C rationale to those, but there isn't consensus between the coordinators on how to handle things (remember, you put all four in a room for a meeting and they wouldn't be able to decide on where to go for lunch together). So, co-channel's the rule of thumb and a 42.2 dBu derated Carey interference contour (f 50,10) is the rule of thumb evaluation for narrowbands proposed 15 kHz away from an incumbent wideband system. Not very efficient, but it's current consensus. There's a push to apply 90.187 definitions to conventional, but right now, it's two separate ballgames between conventional and trunked.

Peter, every frequency band has its unique propagation characteristics and phenomena. One only need look at south Jersey and their major issues with the DT station on Channel 20 ducting in from your neighborhood down the coastline. EVERYTHING is risks vs. benefits. For "oopsie" 1, lowband portable antennas are notoriously inefficient and the efficiency is further affected by proximity to materials that detune resonance, and the lack of an efffective groundplane in the portable. I hate these things, but PacRTs with higher frequency portables may be the way to go. 2, "skip" see above. Risks and benefits. 3, this is actually a benefit! A brownspace created by the mass migration upward. Gentrification strategy with responsible coordination (I may have defeated my own cause by using the "c" word) can make responsible use of resources. And, I had my looseleaf map of Pennsylvania with the different counties outlined and their primary frequencies in the 33 or 46 MHz bands noted. You could even go out I-70 into Ohio and still have 33 MHz coverage to some extent. Those were pretty nice times, and they weren't that long ago, either. That all started changing around 1996 or 1997. Anything would be better than keeping unmonitored low band to dump your 800 MHz trunked talkgroup output out over.

 

[radioman2001]

Separate TX and RX antenna's. That would be a total of 4 antenna's. As with most radio sites nowadays you can play baseball in them, so I doubt space is going to be a problem.
Interference contours? My coordinator, not TCCI for AAR channels has said time and time again, he will not change the existing interference contours with 12.5 spacing, ( an unofficial rule that all the other coordinators are going along with, don't know about lunch ) so this whole mess is for nothing. Originally the thought was to vacate everyone off the 150-162 spectrum and place them in the 136-144 mhz, so some order could be attained. Well that didn't come to be so we are stuck with another unfunded federal mandate that will not really do anything to relive channel congestion.
If you are trying to put multiple transmitters on a single antenna, the costs and floor space is enormous, you are better off with a separate common RX antenna, and combine a few TX's together. In the long run, the costs associated with the combining, loss, heat that's generated, costs of AC power, and air conditioning vs the extra rental costs (if you rent) for antenna's makes going with multiple antenna's in my opinion more cost effective. That's how I had my 5 channel 470 trunking system designed on the Alpine Tower for 15 years.
And I hope the push to take away the TV channels 14-21 and use them for the East Coast P.S. gains some traction, and gets passed. You wouldn't believe what broadcasters are doing trying to prevent this, in my area we watch a picture of a lake 24/7 365 days a year. Someone just stuck a camera outside and are broadcasting it. Really funny to watch it when it's dark, no picture. LOL

 

[Alarms50]

There is a pending FCC application by Putnam County, NY ULS Application - Public Safety Pool, Conventional - 0004912629 - PUTNAM, COUNTY OF - Frequency Summary to narrowband 44.84MHz. Looks like it is strictly Low Band, nothing else.

 

[902]

There is a pending FCC application by Putnam County, NY ULS Application - Public Safety Pool, Conventional - 0004912629 - PUTNAM, COUNTY OF - Frequency Summary to narrowband 44.84MHz. Looks like it is strictly Low Band, nothing else.

Obviously they didn't need to do this. The coordinator is EWA, which should've known better, but is not certified as a public safety coordinator. They are allowed to do narrowbanding-only applications, but cannot add frequencies or modify them to digital. And, NYCOMCO is the point of contact. So, .

@Radioman2001, There are a couple of different rules for contours. The easiest way is to just derate the interference contour, but there's disagreement about how that derating was derived. The contour is field strength based, so it won't change with modulation. A 100 Watt 20K0 base station is the same field strength as an 11K2 or a 7K60. But the deratings try to simplify the relationships between the different modulations. That 42.2 dBu derating is supposed to approximate the response to a wideband incumbent by a proposed narrowband (analog) 15 kHz away. It doesn't say anything about an 11K2 7.5 kHz away from another 11K2, or a 4K00 7.5 kHz next to an 11K2. You and I will have to pick that up off-line or on the phone one day. We're probably putting people to sleep with that.

I was kinda hoping for 174-180 (Channel 7) as greenspace with 3 MHz spacing so we could play minesweeper underneath it. 136 - 144 is chock full of low earth orbital stuff and discrete federal systems. The frequencies above 2 meters are, too. NPSTC has a T-Band petition petition awaiting FCC action, but those are still co-mingled with IG and it's still first to plant the flag gets the channel pair in the market. Too many talking heads are still pushing for the demise of LMR.

Do you remember the Stevens Institute of Technology HD experiments circa 1991? They had two channels in Hoboken broadcasting 3D video of commencements all day using LCD goggles to decode them (guess no one in engineering lab ever mentioned what a dummy load was). Alpine would've been excellent for both horizontal and vertical spacing. And, what a fitting tribute to Edwin Armstrong to have a 42.8 MHz system running from his tower some 70 years later.

 

[radioman2001]

While I missed it a few years ago, there was a tribute day (W2XMN) with the original frequency 42.8 being broadcast for the day. The transmitting equipment is actually beautifully made, and has been restored to a like new condition. The transmitter actually sits right across the room from our transmitters. Every time I go there for my monthly FCC checks I keep looking it over in amazement as how it was built. Considering how Low Band is being vacated, maybe the Armstrong Tower group should apply for a full license, instead of the STA they got for the day.