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Why aren't scanners continuous?

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Airdorn

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#1
I know why the cell bands are omitted, but why do scanners omit other frequency ranges?

I have this one scanner, a BCT-8... it jumps from 174mhz to 400mzh... completely snubbing the military air band. That's just 1 example.. there's other gaps.

My BCD996T has much better coverage, but there's some gaps with that one too.. a bunch of the 700mhz range is inaccessible -- it jumps from the 900's right to 1240Mhz.. etc.

Is there a technical reason for it, or is it legal issues, or the fact that there's nothing in some of those areas to scan, or a combination?

Thanks for any insight!
 

Jay911

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#2
Mainly nothing to listen to there, and costs less to produce without those bands.

Kind of like how your outdoor thermometer doesn't go all the way down to absolute zero (-459.67°F or -273.15°C). Even if it was possible for the temperature to go down that far, very very very few people would be able to make use of a thermometer that goes that low - so few that it's not cost-effective to build them. ;)
 

Airdorn

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#3
Ok.

But then, why would they leave out the military band? That's prime listening right there.
 

SAR923

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#4
The BCT-8 is an entry level scanner primarily for mobile use. Most buyers of that radio want trunk tracking and conventional vhf/uhf frequencies. The military air band adds cost to a scanner so it's primarily found in more expensive scanners like the 996. Even that is subject to weird variations, like the RS Pro-96 not having Mil Air and the less expensive Pro-97 having Mil Air. 700 Mhz hasn't had any activity of note until the newer 700 Mhz trunk systems started coming on-line as a result of the spectrum reallocations so I'm not surprised any scanner older than a few years won't cover that part of the spectrum. Again, there's virtually no voice communication above 980 Mhz until you get to the 70 cm ham band, and that's pretty darned quiet.

Manufacturers tend to make receivers as cheaply as possible to appeal to the majority of users. Consequently, portions of the spectrum get left out depending on the cost to add them and what the manufacturer thinks it will add to the sales appeal of the receiver.
 
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#5
There HAVE been scanners that had fairly continuous coverage. Many years ago I had an MX7000 that covered from 25 MHz to 1300 MHz. There are huge chucks of spectrum that have nothing worthwhile to listen to. It was nice to have a single receiver that could listen to public safety and aircraft, as well as FM broadcast and TV audio. Now, cellular is off limits and digital, TV is going digital, and listening to aircraft transponders has ALWAYS been a bore. There really isn't any reason to listen outside the bands commonly made available in scanners. Don't sweat about those gaps. You're either already watching or listening to it, or there simply isn't anything to hear.

By the way, those super wide band receivers that go up to 3 GHz...? You're wasting your money. What few analog services still exist there are not generally voice modes. You may occasionally find weak signal amateur stuff on a few selected frequencies, but even that's doubtful. The performance of those receivers just isn't good enough to be useful.
 

Airdorn

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#6
Oh I ain't sweating it. I got this 996T here, and it has a great coverage.

I was just reading something about the mil band and how some fairly recent scanners don't cover it, and that got me wondering WHY it would be omitted in the first place.

Thanks.
 

W4KRR

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#7
Airdorn said:
Ok.

But then, why would they leave out the military band? That's prime listening right there.
There's a lot of people out there that care nothing about the mil-air band. And if you can get a scanner that doesn't cover that band, and it's cheaper, then many people opt for that choice.
 

Airdorn

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#8
OK..

Thanks for the info! I guess it's not as simple as just counting up from 0 to 1300mhz and that's it. :)
 
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#9
like the RS Pro-96 not having Mil Air
Yes, to most people the 96 cant recieve the military band, unless you have Win96 program and have the extended frequencies box checked. It opens up more than just that, but its one thing it does let you listen to.
 

kb2vxa

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#10
"Thanks for the info! I guess it's not as simple as just counting up from 0 to 1300mhz and that's it."

If it were that simple you wouldn't BELIEVE the intermod and crap the cat dragged in! Now do you want to open the door just a crack and let in only the cat or open so wide he brings in a herd of elephants, a troupe of monkeys, a few crocodiles and a couple of pythons?

Maybe that's the reason we tend to frown upon those ultra wide band DC to light preamplifiers?
 
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#11
If they put everything into one scanner, they couldn't get more money out of you! Scanner #1 gets A & B. Scanner #2 Gets B & C. If you want to listen to A, B, and C, you have to buy both!!!! ;op

Roger
 
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#12
kb2vxa said:
If it were that simple you wouldn't BELIEVE the intermod and crap the cat dragged in! Now do you want to open the door just a crack and let in only the cat or open so wide he brings in a herd of elephants, a troupe of monkeys, a few crocodiles and a couple of pythons?

Maybe that's the reason we tend to frown upon those ultra wide band DC to light preamplifiers?
Now, to be fair, it IS possible to make a 0-1300 MHz receiver that won't let the elephants and monkeys in, but it not only wouldn't be cheap, it probably wouldn't be even remotely affordable. Everyones favorite uncle has such toys, and if you could afford the $20,000 price class, maybe you could too. I've often thought about what it would take to build something...

An $80 transistor on the front end with a +45 ip3 and .5 db nf, high side injection with a 3 GHz first IF for image suppression, YIG local oscillator phase locked to a low noise synthesizer... Hmmm...

This could be done with ebay parts for under $1000. But there's still nothing to listen to on most of that spectrum. It's an interesting technical problem, but little more.
 

Michael-SATX

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#13
Is there still any need for 800Mhz Cell phone gaps ?

Is there still any need for 800Mhz Cell phone gaps ? Now that AMPS analog cell service
has been retired as of Feb 18, 2008. Anyone's thoughts to whether new scanners
to be released in the future will have RESTORED / full coverage in the 800Mhz Band ?
Anybody in the know on this question ? Do chime in :)
 
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#14
Michael-SATX said:
Is there still any need for 800Mhz Cell phone gaps ? Now that AMPS analog cell service
has been retired as of Feb 18, 2008. Anyone's thoughts to whether new scanners
to be released in the future will have RESTORED / full coverage in the 800Mhz Band ?
Anybody in the know on this question ? Do chime in :)
There's nothing there to listen to, so why bother? Why worry about it? Why pine over it? You're not likely to see receivers opened up there for two reasons: Congress is not going to repeal the Electronic Privacy Act, and because everything is digital and encrypted there, there's nothing to hear.
 

Airdorn

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#15
zz0468 said:
There's nothing there to listen to, so why bother? Why worry about it? Why pine over it? You're not likely to see receivers opened up there for two reasons: Congress is not going to repeal the Electronic Privacy Act, and because everything is digital and encrypted there, there's nothing to hear.
That seems pretty short sighted. There might not be anything there to listen to this week, but what about next week? Next decade?
 
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#16
Airdorn said:
That seems pretty short sighted. There might not be anything there to listen to this week, but what about next week? Next decade?
Politicians rarely think beyond the timeframe they get into the office up to lunch.

Scanner companies won't mind selling locked units. If something is there to listen to next decade (and it becomes legal) they will make a NEW! FULL 800MHZ COVERAGE INCLUDED! scanner.

Win-win for everyone but us. ;-)
 
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#17
Airdorn said:
That seems pretty short sighted. There might not be anything there to listen to this week, but what about next week? Next decade?
If anything was going to happen to that spectrum within the next decade, we'd be hearing about it now. But with the amount of cell traffic taking place, I would expect MORE spectrum to be allocated for service, not less. That 870-896 chunk of spectrum isn't going away anytime soon, so I wouldn't be wasting time and money on a receiver to catch something. It's simply not there to be caught, and it ain't gonna be.
 
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#18
I'll admit it has been many years since I actually read the ECPA, so I may be way off on this, but... didn't it merely say that they couldn't manufacture radios capable of monitoring cellular communications, rather than spelling out in black and white which exact frequencies those were? In other words, does the ECPA actually address those now-dead frequencies, or does it only address the communications that were on them at the time? If it is the latter, then there is no legal revision necessary for the manufacturers to resume putting those freqs into the scanners again.
 
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#19
I can't understand why people can't grasp the idea that just because the analog cell service in the 800 MHz spectrum may have been turned off in most areas, it's still active in some. That being said there is still digital service intermixed in the same frequency allocation. Cell service is still using those frequencies.
 
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#20
af5rn said:
I'll admit it has been many years since I actually read the ECPA, so I may be way off on this, but... didn't it merely say that they couldn't manufacture radios capable of monitoring cellular communications, rather than spelling out in black and white which exact frequencies those were? In other words, does the ECPA actually address those now-dead frequencies, or does it only address the communications that were on them at the time? If it is the latter, then there is no legal revision necessary for the manufacturers to resume putting those freqs into the scanners again.
FCC rule 15.121 (Code of Federal Regulations, title 47, chapter I, part 15, section 15.121) says, in relevant part:

(a) scanning receivers shall:
(1) Be incapable of operating (tuning), or readily being altered by the user to operate, within the frequency bands allocated to the Cellular Radiotelephone Service in part 22 of this chapter (cellular telephone bands). ... Scanning receivers, and frequency converters designed for use with scanning receivers, also shall be incapable of converting digital cellular communication transmissions to analog voice audio.

(b) Except as provided in paragraph (c) of this section, scanning receivers shall reject any signals from the Cellular Radiotelephone Service frequency bands that are 38 dB or lower based upon a 12 dB SINAD measurement, which is considered the threshold where a signal can be clearly discerned from any interference that may be present.

Both tuning to the frequencies and converting digital transmissions seem to be prohibited by current law.
 
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