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General Scanning Discussion - For general questions not specific to a model of scanner or general discussion of use of a scanner. Manufacturer specific posts should be directed to the appropriate forums below and location specific posts should go in the appropriate regional forum..

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Old 08-12-2017, 8:23 AM
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Default Why Won't My Counters Pick Up Signals?

Hi folks. Can anyone comment on why my two frequency counters don't pick up a digital transmission when I'm practically on top of the source? One is a traditional Cub and the other is a less expensive but newer technology model. Shouldn't they pick up any strong signal source in the frequency range regardless of the modulation format? Thanks, all.
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Old 08-12-2017, 9:52 AM
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They need to be marked digital to be able to pick up mobile/portable digital signalling if the system use TDMA, time slots.

Basestations, analog and digital, shouldn't be any problem if there are not any other transmitters nearby that also transmit at the same time and interfere.

/Ubbe
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Old 08-12-2017, 10:41 AM
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Many digital formats use TDMA (Time Division Multiple Access) schemes in which the carrier turns on and off multiple times per second. The intermittent nature of the carrier fools the counter into rejecting the signal as a spurious transient rather than a valid signal. It has to be designed to recognize the format properly before it can properly interpret it.
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Old 08-12-2017, 3:37 PM
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Quote:
Originally Posted by jonwienke View Post
Many digital formats use TDMA (Time Division Multiple Access) schemes in which the carrier turns on and off multiple times per second.
No. It splits the carrier in different time slots but the carrier are always continuos from the basestations.

/Ubbe
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Old 08-12-2017, 3:47 PM
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I was referring to simplex, which does turn on and off. Not all digital formats go through a repeater.
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Old 08-12-2017, 7:38 PM
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Thanks folks. So does this mean that I can't expect to pick up a near field digital signal with either counter?
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Old 08-12-2017, 8:58 PM
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Default i don't know if this helps

take the antenna off the radio.
set it to scan the suspected band.
this works great to find repeater outputs.
about 1 mile from my house there are two towers.
i had only noticed one of them and thought the county used that one.
i went by and got nothing from the radio.
then i crossed the highway. and there was the second tower.
sure it was at a firehouse and it was the county system.
good signal from the data channel.
and you have to be about 200 feet away to get it.
todd
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Old 08-13-2017, 3:44 AM
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Quote:
Originally Posted by Jimbo695 View Post
Thanks folks. So does this mean that I can't expect to pick up a near field digital signal with either counter?
If it's a TDMA system you will not catch anything from mobiles/portables.
If its another type of digital system, like a P25 phase1, you should be able to catch the frequency from a mobile/portable.

All types av basestations, regardless of digital format, should be possible to show on a frequency counter if the signal are not interfered from other basestations at the same location.

A $200 digital frequency counter will catch everything if the signal is more or less isolated, even your own cellphone.

Aceco SC-1PLUS hand-held radio frequency counter

/Ubbe
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Old 08-13-2017, 6:20 AM
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Also have to take into account the sensitivity of your meter, perhaps the signal strength of the source is too low to be detected.
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Old 08-18-2017, 10:29 PM
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Originally Posted by spongella View Post
Also have to take into account the sensitivity of your meter, perhaps the signal strength of the source is too low to be detected.
This was my thought. I have a Tenma handheld counter. With a UHF stubby antenna on the counter's input, I still have to be within a couple of feet for it to read a 5 watt handheld's freq.
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Old 08-19-2017, 4:15 AM
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If it's a Tenma then it is not supposed to work with noisy unstable radiosignals. It needs a clean steady signal like when you saturate the input with that 5watt handheld.

You'll need a counter that's made for radiosignals to get any kind of range with it.

/Ubbe
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Old 08-19-2017, 5:13 AM
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No rule that you have to use the stubby, try using a telescoping antenna.
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Old 08-19-2017, 11:32 AM
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Most frequency counters are far less sensitive than the receiver of any radio. This is deliberate,
so the counter only works with a signal that is strong enough that it is unquestionably the signal of interest.

If you want to use a frequency counter for more distant signals then you'll probably have to invest in a good spectrum analyzer and a decent antenna. And learn how to use it.
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