Can a cell phone damage the front end on your scanner?

[E_Tek]

I sometimes use my cell phone while listening and never thought anything about it until now. Can using your cell phone in close proximity to your scanner damage or overload the front end in anyway? Lets say you are on a call and you hold your cell phone upto the display of your scanner or close to the antenna? I always thought transmit power of a cell phone was in the mW's but a quick search says a typical cell phone can transmit up to 3watts in power!

Thanks,

 

[mmckenna]

In the old days, the "mobile" phones ran about 3 watts.

Newer ones are in the 300mw range. Some FirstNet high end stuff will run a bit over one watt.

300mw is the maximum. Usually the power is throttled back to whatever is necessary to reach the cell site.
Unlikely it would hurt the scanner.

 

[KK4JUG]

Most won't even set off a frequency detector.

 

[dlwtrunked]

Most won't even set off a frequency detector.

That is only because many (and most older) frequency counters do not properly work on many digital signals--it is not due to power.

 

[MTS2000des]

You may get some RFI into the audio amp, but as most have pointed out, even at it's highest power step, most put out around 1.4 watts max, the lower frequency bands used may be more prone to overloading your front end than others, e,g. T-Mobile's band 12 annd band 71, or AT&T's band 14, but the microwave bands like AWS and the old 2500MHz clearwire specrrum T-Mo is putting 20x20 5G-NR on shouldn't bother your scanners.

 

[KK4JUG]

That is only because many (and most older) frequency counters do not properly work on many digital signals--it is not due to power.

You got me. I never thought about that.

 

[R8000]

The power output on your cell phone varies. It's based on signal strength. This is why your cell phone battery dies faster when you have very little signal. It's upping the power to get back to the cell site. When you have great signal, little power is needed.
So, that's a variable.
To answer your question, no. It won't hurt it.

 

[E_Tek]

Thanks for the replies guys It did cause some slight RFI heard through the scanners speaker when held close but no signal fade or anything like that. This puts my mind at ease as sometimes my phone is inches away from my radios on the same desk.

 

[dlwtrunked]

Thanks for the replies guys It did cause some slight RFI heard through the scanners speaker when held close but no signal fade or anything like that. This puts my mind at ease as sometimes my phone is inches away from my radios on the same desk.

That RFI *may* be due to other electronics in the phone (like display circuitry) rather than the transmitted RF communication.

 

[slicerwizard]

It did cause some slight RFI heard through the scanners speaker when held close

A TDMA transmitter will do that.

 

[KevinC]

A TDMA transmitter will do that.

Nextel, Nextel
What ya gonna do, what ya gonna do when it interferes with you (sung to the theme of Cops).

 

[btt]

.. It did cause some slight RFI heard through the scanners speaker when held close but no signal fade or anything like that. This puts my mind at ease as sometimes my phone is inches away from my radios on the same desk.

This is likely due to near-field coupling (magnetic).

I sometimes use my cell phone while listening and never thought anything about it until now. Can using your cell phone in close proximity to your scanner damage or overload the front end in anyway? Lets say you are on a call and you hold your cell phone upto the display of your scanner or close to the antenna? I always thought transmit power of a cell phone was in the mW's but a quick search says a typical cell phone can transmit up to 3watts in power!

Thanks,

A well-designed front-end will have protection before the LNA. Usually RF chokes (inductors to ground) and/or limiting diodes. I have seen designs where an ESD sensitive T/R switch was not protected on the front-end. These will eventually fail in various ways due to ESD. Pin diode switches are much more robust.

 

[nd5y]

The cellular, wifi and bluetooth radios inside your phone don't destroy eachother.
People carry radios and a phone within a foot or so of eachother and they don't destroy eachother.

 

[mmckenna]

The cellular, wifi and bluetooth radios inside your phone don't destroy eachother.
People carry radios and a phone within a foot or so of eachother and they don't destroy eachother.

Excellent point. I carry my cell phone right next to a 3 watt 800MHz radio or a 4 watt UHF radio, depending which site I'm at. Never had a problem with any of them. The 800MHz radio is on a trunking system, so it periodically transmits on its own to check in with the system. No damage to the cell phone, and the phone causes no damage to the radios.

 

[RRR]

Good grief, I, as well as many others, have used mobile radios in the 35 - 100 watt range over the years with the antenna for the mobile about 3 or 4 feet from the scanner antenna, and never had an issue. Not saying it can't happen, but I haven't ever experienced any issue

 

[KC2CQD]

I would imagine the only damage you would do is if you actually threw your phone AT the scanner....even then, you'd damage your phone more than the scanner...

 

[mmisk]

Here are some of the frequencies I have found my cellphone using.
So there would be considerable isolation except for the 700 and 800 frequencies.
Guess there would still be good isolation at 700 and 800 cell input frequencies also.
Plus the very low wattage as previously mentioned.
At the moment my cell is receiving on 742.5 mhz [edit] now on 1960.0 1322 hrs
They are amazing devices.

753.5
887.5
1960.0
2147.5
2630.0
2860.5
2630.0


CELL BAND NUMBERS:
20- 800MHZ
13- 753.5 742.5
8- 900
7- 2600
4- 2147.5
3- 1800
1- 2100

 

[mmisk]

Appears to be wide-band signals from
729.5 to 738.5
740.2 to 744.8
751.2 to 755.8

 

[mciupa]

Is your SDR intentionally set to AM mode for this test?

 

[mmisk]

Hello,
It set itself to AM, had not noticed that, but guess it won't make any difference to the spectrum display.

My cell is now on 887.5. Wide-band signal there also.

It is now on 2147.5 [time: 1330]