Can side by side scanners interfere with each other?

Status
Not open for further replies.

kma371

QRT
Joined
Feb 20, 2001
Messages
6,204
If 2 scanners are turned on side by side both with interior , can they interfere with each others receptions?

No, since they are receiving, they have no emissions. If anything, electrical only, but not likely.
 

KB0VWG

Member
Joined
Apr 9, 2006
Messages
535
Location
Lyford, Texas
Maybe sometimes I had an old scanner that would stop on one frequency and it would cause another scanner to stop scanning. But that was on a old analog regency scanner back then like 10 years ago but so far now on my newer scanner don't or haven't noticed.
kb0vwg
wqoi992
 

Voyager

Member
Joined
Nov 12, 2002
Messages
12,060
Not true. Scanners use internal frequency oscillators, and they CAN interfere with one another. I've experienced this many times. For example, if you try to monitor a frequency of X where X is the frequency of another scanner plus or minus the IF frequency (depending if it's high or low injection), you will hear a dead carrier because that is the frequency generated in the second scanner.

I used to use that method to determine what others were scanning when I knew the model number of the scanner they were using. These signals can be heard for up to a mile or more. That was using crystal scanners, and scanners have since become much more RF emission friendly, but the same issue still exists.

Similarly, a few years ago I was mobile and had two GPSs next to each other. Neither was working. I suspected similar interference, and I separated them. They both started working fine. They required 3 feet of separation to eliminate the mutual interference.

Of course, now that you have trunked systems, CTCSS, CDCSS, and NAC, those mask the issues making them less noticeable compared to scanner carrier-only. Note that I said MASK. They do nothing to eliminate the interference. They simply hide it. If you tried to monitor "frequency X" as above, you would still have a competing signal to the one you want to receive.
 

R8000

Low Battery
Premium Subscriber
Joined
Dec 19, 2002
Messages
1,009
Not true. Scanners use internal frequency oscillators, and they CAN interfere with one another.

Same here, they can interfere . There is a lot of variables here, but yes they can.
 

HM1529

Pennsylvania DB Admin
Database Admin
Joined
Jul 16, 2003
Messages
3,087
Location
West of the Atlantic Ocean
A for instance to support the fact of interference...if I set my BCD436 within 4-5 inches of my PSR800, the 800 begins getting interference in 364.2. If I keep them farther apart, no problems.
 

K5MPH

Member
Joined
Jul 16, 2003
Messages
1,622
Location
Brownsville Texas,On The Border By The Sea.
Not true. Scanners use internal frequency oscillators, and they CAN interfere with one another. I've experienced this many times. For example, if you try to monitor a frequency of X where X is the frequency of another scanner plus or minus the IF frequency (depending if it's high or low injection), you will hear a dead carrier because that is the frequency generated in the second scanner.

I used to use that method to determine what others were scanning when I knew the model number of the scanner they were using. These signals can be heard for up to a mile or more. That was using crystal scanners, and scanners have since become much more RF emission friendly, but the same issue still exists.

Similarly, a few years ago I was mobile and had two GPSs next to each other. Neither was working. I suspected similar interference, and I separated them. They both started working fine. They required 3 feet of separation to eliminate the mutual interference.

Of course, now that you have trunked systems, CTCSS, CDCSS, and NAC, those mask the issues making them less noticeable compared to scanner carrier-only. Note that I said MASK. They do nothing to eliminate the interference. They simply hide it. If you tried to monitor "frequency X" as above, you would still have a competing signal to the one you want to receive.
It is possible for the Oscillator to create a 1st,2nd 3rd and 4th Harmonic that could interfere with another scanner.........
 

popnokick

Member
Premium Subscriber
Joined
Mar 21, 2004
Messages
2,837
Location
Northeast PA
A mobile scanner can also interact with the FM radio in your car. And by that I mean the scanner may cause a signal to appear on the FM broadcast band.... or worse, tuning a certain FM station at the right frequency relationship (often harmonically related to the IF frequency and offset of the scanner)... and the scanner stops scanning with a strong but quiet carrier on the channel that is related to the frequency to which the FM radio is tuned.
 

Voyager

Member
Joined
Nov 12, 2002
Messages
12,060
It is possible for the Oscillator to create a 1st,2nd 3rd and 4th Harmonic that could interfere with another scanner.........

Absolutely. It's just like any other signal. Of course, we are talking about relatively weak signals to start with, so it's won't be as prominent as say a 100W transmitter's harmonics.
 

bharvey2

Member
Joined
Mar 12, 2014
Messages
1,842
They certainly can interfere with each other. The IF stages produce RF and and can cause interference. I believe they can even interfere with themselves causing "birdies".
 

Voyager

Member
Joined
Nov 12, 2002
Messages
12,060
True on the birdies, but recent designs have pretty much eliminated those. I remember a 'birdie list' in the manuals on older models.
 

majoco

Stirrer
Joined
Dec 25, 2008
Messages
4,278
Location
New Zealand
Certainly, and not just scanner to scanner - my JRC NRD515 HF comms receiver puts out a nice clean signal on 119.5MHz!
 

mitbr

Active Member
Joined
Jun 22, 2007
Messages
1,347
Location
Tampa Bay Florida
Interesting topic.....so I am sitting here listening to my 436 and hp1.
Hp1 and 436 are right next to each other.Hp1 on adapter power 436 on usb power and 800mhz RS rubber duck ant. Signal on local p25 system breaking up occasionally on 436, move the hp1 a foot away break up stops. Move it back 436 starts to break up occasionally. The hp1 must be producing some decent interference to cause this.
Did this test numerous times with same result.
Tim
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
23,618
Location
Hiding in a coffee shop.
There's often (usually, always, if you look) a brief paragraph somewhere in the owners manual on these sorts of consumer electronics that directly mentions this effect. Standard FCC boiler plate Part 15 wording.

Some useful stuff to read:
Part 15 - Radio Frequency Devices

Many user manuals will have something that looks an awful lot like this:
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

—Reorient or relocate the receiving antenna.
—Increase the separation between the equipment and receiver.
—Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
—Consult the dealer or an experienced radio/TV technician for help.
 

rcool101

Member
Feed Provider
Joined
May 31, 2002
Messages
964
Location
Eastern Ohio
Interesting topic.....so I am sitting here listening to my 436 and hp1.
Hp1 and 436 are right next to each other.Hp1 on adapter power 436 on usb power and 800mhz RS rubber duck ant. Signal on local p25 system breaking up occasionally on 436, move the hp1 a foot away break up stops. Move it back 436 starts to break up occasionally. The hp1 must be producing some decent interference to cause this.
Did this test numerous times with same result.
Tim
Turn the HP1 off when they're close. See if the 436 still does it

Sent from my XT1080 using Tapatalk
 

bharvey2

Member
Joined
Mar 12, 2014
Messages
1,842
In the situation you described, don't discount interference from the power supply. A cheap switching supply can cause havoc as well.
 
Status
Not open for further replies.
Top