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Author Topic: FCC Approved Users for Cellular Monitoring Equipme  (Read 2486 times)
NIMA
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Posts: 7




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« on: March 09, 2001, 05:26:41 PM »

As everyone knows, all receiving and scanning equipment sold in the US is cellular blocked.  However, in advertisements, you'll see "Unblocked versions available to FCC approved users."  What constitutes an FCC approved user?
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K9STH
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Posts: 11




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« Reply #1 on: March 11, 2001, 11:38:54 AM »

As far as I can surmise, this would be someone engaged in the ACTUAL repair of cellular equipment, engineering personnel doing performance measurements on the cell sites, and the like.  However, the VAST majority (and I mean VAST majority, if not all) of those persons would have the proper test equipment to perform the tasks and not have to resort to things like scanners.

The holding of a General Radio Telephone Operator's licens granted by the FCC (replaced old "first phone" and "second phone") would be prima-facie evidence of a person authorized to do repair on cellular telephones (although you no longer have to have such license to work on this equipment except under certain circumstances).

I have held a commercial operator's license since September, 1962, have been (over the years) engaged in the repair business (worked my way through Georgia Tech as a two-way radio tech for Motorola), etc.  However, I don't have a scanner "modified" for the cellular frequencies.  Frankly, if I really wanted to listen in, I have service monitors, etc., that work very well.  However, I dislike scanners (they never "shut up") and am not interested in listening in on personnal conversations.

Frankly, the statement is just a "ploy" to put the burden of owning a scanner modified for cellular on the purchaser and not on the person doing the modification.  The person who modified the receiver can always point out that fact was "advertised" and that he/she did nothing wrong my modifying the scanner.  The person who "bought" the scanner was being "deceptive", not the person who modified it.
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N7JAU
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Posts: 90




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« Reply #2 on: March 11, 2001, 12:50:12 PM »

K9STH, I thought your answer was VERY good.  However, lugging a big, heavy monitor around all the time is not always fun.   Before I was injured, I did some work in this regard, and found that (at that time) my little Yaesu FT50 was VERY useful for all kinds of stuff.  One, for example, was a multisite paging system we set up with 900 mhz links.  Pretty nice, to be able to monitor the link from the truck, a mobile antenna, and an FT-50 (or any other portable receiver.)

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NIMA
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Posts: 7




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« Reply #3 on: March 11, 2001, 01:53:22 PM »

Hey guys,

Thanks for the great answers.  Just one new question... what exactly is a service monitor?

-Nima
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K9STH
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Posts: 11




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« Reply #4 on: March 11, 2001, 03:38:22 PM »

Actually, his question was on the subject of cellular monitoring.  For other services, it can be handy to use some type of monitor receiver including scanners.  When I was in the service business, I used to have quite a number of my customers' repeater frequencies in my mobile (including the proper CTCSS tone).  That way I could communicate directly with them if necessary.  Also, it was easy to check the repeater.

Service monitors have gotten a "bit" smaller these days.  However, all three that I have around the shack don't exactly qualify as being "smaller".  Of course, when I was in college, the frequency meter weighed about 50 pounds, the signal generator weighed about 35 pounds, the modulation meter weighed about 15 pounds, and the wattmeter (including spare "slugs") weighed about 5 pounds!  That, plus a tube caddy, tool box, etc. was "real" fun to take up a tower to do repair work on a customer's repeater /  base station!
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K9STH
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Posts: 11




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« Reply #5 on: March 11, 2001, 03:47:22 PM »

A service monitor is a combination piece of test equipment that normally includes a signal generator (digital model), a frequency measuring device (usually, but not necessarily, digital, can be a counter), modulation meter (or oscilloscope, or both), often a built-in wattmeter / dummy load, and usually a tone generator.

Usually the frequency coverage is up to either 512 MHz, or, more common, 1 GHz.  The most popular manufacturers of these include IFR, Cushman, Motorola, and Singer-Gertsch.  Prices new for these manufacturers start at around $10,000 and go up from there.  There have been a few lower priced units, especially those using a frequency counter instead of digital "dial up" that have started at around $3000.  In the two-way radio business these days, it is MUCH easier to use a service monitor than try to use all of the individual test equipment items that they replace.

There are service monitors available for other frequency ranges, but, they are a much more specialized piece of test equipment.
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NIMA
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Posts: 7




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« Reply #6 on: March 12, 2001, 01:25:51 AM »

Thanks again for all the info, I appreciate it.  I own an Opto Scount frequency counter... but have never heard of a Digitial "dial up"... (?)
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K9STH
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Posts: 11




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« Reply #7 on: March 12, 2001, 04:31:59 PM »

Basically, a "dial up" piece of test equipment uses switches (like on 2 meter FM rigs) to set the frequency.  Usually, there are switches to the nearest 100 Hz.  For example, to dial up 146.9400 MHz you would set the first switch to "1", the second to "4", the third to "6", the fourth to "9", the fifth to "4", and the sixth and seventh switches to "0".  The signal generated by the service monitor then would be within 100 Hz of 146.9400 MHz to align the receiver.  Also included is a calibrated attenuator going (usually) down below 0.05 microvolts.

The transmitter frequency difference from the "reference" frequency of 146.9400 MHz is normally displayed on some type of meter.  You adjust the transmit frequency standard to the proper frequency.  Modulation / deviation is normally read on either a meter or a built-in oscilloscope.

There are all sorts of other "nicesities" depending on the particular model of service monitor.

You can purchase signal generators, audio generators, and other pieces of individual test equipment with "dial up" capabilities.  Because of the much tighter frequency tolerances of this equipment it normally costs a bit more than the old "analog" type of equipment.

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NIMA
Member

Posts: 7




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« Reply #8 on: March 13, 2001, 09:32:03 PM »

John,

Your input is greatly appreciated (not to mention addictive).  Speaking of Frequency Counters, when I begin using a transmitting device and hold it up to the Opto Scout, one of two things will happen.  Depending on the transmitting device, the Scout will either get a lock on the frequency or it will get a full signal strength of up to 16 out of 16, but cannot lock on to the frequency.  Is it simply that the device is transmitting outside of the Scout's frequency coverage range? (10MHz-1.4GHz ).

Examples of devices that cause this untraceable frequency effect include a remote control I use for turning on and off my room lights, along with the San Francisco Bay Area's new "FasTrak" electronic Toll Tag system that pays your toll automatically on all bay area bridges.  Oh, and my Microwave Oven (I just _had_ to try this... not that I was actually expecting a real frequency response, hi hi).

Thanks,

Nima

P.S.  If by chance you're wondering why I haven't been using my callsign, it's because I'm a new ham and I've been waiting for the FCC to assign me one for the past 3 & 1/2 weeks.  It's killer staring at my rig and not being able to push the PTT!
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K9STH
Member

Posts: 11




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« Reply #9 on: March 14, 2001, 02:02:15 PM »

The "toll tags" on your car for things like the bridge are "passive" devices.  That is, they don't have a built-in transmitter.  They are activated by a short-range transmitter that is contained at the toll station.  The "toll tag" acts as a transponder which "bounces" the signal back to the toll station with the billing information attached.  I have one on each of my cars for the toll roads in the Dallas, Texas, area.

Your microwave oven is probably operating at a frequency around 2.4 GHz which is outside of the range of your counter.  Also, it is supposed to be shielded which would keep the r.f. level below that which would "trigger" the counter.  If you could read the frequency, you would probably be getting a pretty high "dose" of r.f.

Counters can be a bit "tricky" to use.  If the signal level is too little, or too great, they can give false readings as well as no readings.  I have a couple of counters and they can be very useful devices.  However, you must know how to use them and their limitations.  They are very useful if you don't know the frequency that the piece of equipment is putting out.  Also, since they are much less expensive than service monitors, they are a good item to use to determine just what frequency the device is putting out.

Service monitors are most useful when the desired frequency is known and needs only to be adjusted to "exact".  Frankly, there are many more counters out there than service monitors.  You can get a pretty good counter for under $100 these days.

One thing to remember is that no frequency determining device is "absolute".  They have to be periodically adjusted to a frequency standard (like WWV).  Too many amateurs with "digital" readout transceivers (etc.) seem to think that "they" are on the "correct" frequency when they can be several KHz off (in the worst case) because the frequency standard inside their equipment has drifted and needs to be recalibrated.
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