Sporatic broadband interference VHF high band

Status
Not open for further replies.

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
This just started a couple of weeks ago. I don't know what to make out of it. The frequencies I listen to have been long time standard for myself, so I know what I have a problem with and what I don't for the past almost FIFTY years. This is new.

Take note of the Details:
1. Between 156 & 162 MHz, usually the most important ones (to me), varies during the period of occurrence, (Railroad & Marine channels affected)
2. Two different radios (scanners) Realistic Pro2004 & a Regency HX-1000 (which I have yet to find a radio that comes anywhere close to the performance, interference (image) rejection specifically to this,
3. Early morning that seems to decrease mid morning (from around 7-8am to around 10-11am) then disappears completely.
4. No set days, example; happened a Sunday morning, but not the next Monday,
6. Comes across as broadband noise, rapid fluttering as someone has a button stuck in a fast moving vehicle. It remains fairly constant level (for the most part)
5. Breaks squelch, not strong, sometimes unable to 'squelch' out on the Regency due to a excellent squelch circuit.,
6. Both radios connected roof mount discones,
7. Same channels programed on both radios,
8. Usually on both radios the affected channels are the same, or close in frequency,
9. I have a FM trap and a custom notch trap for UHF on the 2004, nothing needed on the 1000).

My only guess based on the behavior is distant reception due to weather (short range skip or similar). As far as what is causing it, I have no guess, thanks to the FCC, there is so much CRAP out there, though one would think (hope) the high band would be least affected. :mad:

Ok, any guesses out there?? :confused:
 
Last edited:

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
I don't know what type of appliance would ever create this. :confused:
This isn't impulse noise or from noisy motor brushes.
 

pro92b

Mutated Member
Premium Subscriber
Joined
Jun 27, 2002
Messages
1,908
If the interference covered a wide area it would disrupt communications for a number of agencies. Since you didn't mention hearing on-air complaints from anyone you monitor, the noise is probably low powered and local to you.


When the noise is present, use the HX-1000 on batteries to monitor it. Turn off the main breaker to your house and see if the noise changes at all.


If not, try to monitor the noise on the HX-1000 with a portable antenna, rubber duck or telescoping whip about 18" long. Take a walk around your immediate neighborhood to see if you can localize the source of the noise. If you figure out the source of the noise then you can determine if anything can be done about it.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
8,944
Location
Stockholm, Sweden
If you don't have a $25 SDR dongle then get one and look at the spectrum.
Do you have a scanner that can do small steps 5KHz or less? Seek around the frequencies with the squelch open and see if the signal drift so that it is exact on your frequencies just part of the day and other times it is so offset from it that it isn't noticed.

I got something similar from a neighbours climat control that generates spikes at a even 200KHz intervals from 140MHz to 170Mhz that drift slightly and varies in strenght depending of the time of day and weather. It only reaches 50 meters from the house and its not much I can do about it.

I have heard that lawn mower robots uses a buried signal cable for area control that migh use constant pulses from a badly design generator that interfere with multiple overtones on all kind of frequencies.

/Ubbe
 

bob550

Member
Premium Subscriber
Joined
Apr 5, 2005
Messages
2,070
Location
Albany County, NY
Can you post an audio clip of this interference? If you do pick up an SDR dongle, you could also post a screen shot for us to analyze. Although this is not a solution to eliminating the interference, a newer scanner with CTCSS, or tone-encoded squelch, would stop the scanner from breaking squelch on the interference.
 

jim202

Member
Joined
Mar 7, 2002
Messages
2,729
Location
New Orleans region
With the limited info you have provided, it is anyone's guess as to the source.

You could have a computer with the LAN connection causing all sorts of RF radiation. It could be coming from a TV or a plasma video display. The possible sources need to be narrowed down.

Like one poster already stated, kill the main breaker to your house and see if you still hear the problem. Instead of walking the street, I would take to driving around. It is faster and much lighter on the knees when trying to walk.

Give the group some feedback. There are many of us here that have had to track down noise problems over the years. One I found was from a fish tank heater. It would not be uncommon to have a leaky power line insulator arcing and causing wide band noise.

Also pay attention to the weather. Do you get it more when it's dry or damp outside like when it's raining?

The more feedback you can provide, the faster your going to locate your problem.
 

scrotumola

Member
Joined
Jan 19, 2001
Messages
325
Location
So. Texas
I suspect he is picking up distant railroad NXDN or other digital noise not previously heard due to tropospheric ducting.

The times are right... although I suspect there could be times in the evening where ducting conditions are possible, as well.
 

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
The interference like I stated is sporadic. It's only reared its ugly head twice since I posted this thread. Both times it was short lived.

I don't have a manually tunable receiver, there are no single channels it shows up on other than within that bandpass I stated. Sometimes it's the same frequencies on both scanners, but not always.

I do have a SA which I did a initial sweep, but it didn't turn up anything. I tried the 1000 with a portable whip, but as I expected, it ndidn't receive anything thou it was only the 2004 that had the interference this time which not the usual case.

I made recordings of this, but they are too large to attach (by far with the 195k limit).
 
Last edited:

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
Do you have a scanner that can do small steps 5KHz or less? Seek around the frequencies with the squelch open and see if the signal drift so that it is exact on your frequencies just part of the day and other times it is so offset from it that it isn't noticed.
Yes, it does vary (drift) in frequency during the period that it is present.

The more feedback you can provide, the faster your going to locate your problem.
I fully understand, when I discover more I will post back.
 
Last edited:

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
It appears to be coming form the neighbors house.
I don't know the tenant, but I do known the landlord (owner occupied thank goodness). It is doing it now, but to a much lessor degree, but enough to tell. I had him kill his breaker on the lower and the interference continued.
I took a closer listen to this, and it pretty much seems digital as in a sputtering, spread spectrum type of signal as opposed to being a constant carrier on one frequency.

Question;
Can signals in the 2.5 GHz band (Wi-Fi & Bluetooth) have sub harmonics that would/ could go down to the VHF high band (160megs)?? I don't see how due to it being a lower frequency and well over 2G's away. :confused:
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
8,944
Location
Stockholm, Sweden
Not the signal itself but the devices electronic can spew out in the VHF band, especially from network and usb cables.

/Ubbe
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
6,859
Outdoor LED lamps on photocells? I have noticed with some of my LED exterior lamps, that enough current leaks through the photocells that the lamps emit some light during the day. I have not checked for noise, but most LED lamps emit RF noise,

If you have a scanner that receives the AM aero band, try walking around with it looking for noise sources. If it will tune AM in VHF hi band, all the better.




Sent from my SM-T350 using Tapatalk
 

TampaTyron

Beep Boop, Beep Boop
Premium Subscriber
Joined
Feb 1, 2010
Messages
1,091
Location
Phoenix, AZ
Switch mode power supplies, plasma TVs, compact flourescent ballasts, cheap USB cell phone chargers...... Anything. Time to get a SDR and a directional antenna or a loop at least. TT
 

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
I suspect he is picking up distant railroad NXDN or other digital noise not previously heard due to tropospheric ducting.
None of this falls exactly 'on frequency', usually noticeably off above or below.

Not the signal itself but the devices electronic can spew out in the VHF band, especially from network and usb cables.
PC 'Towers' are the worst, especially these post teenager 'gamers' that have a view window on one side lighting up the interior with LED lighting. :evil:

Outdoor LED lamps on photocells? I have noticed with some of my LED exterior lamps, that enough current leaks through the photocells that the lamps emit some light during the day.
I'm the only one with outdoor LED lighting (actually the only one with any outdoor lighting either side of me). I've had them for some time now, but that isn't the source, I did a walk thru with the portable radio directly underneath both fixtures..

Switch mode power supplies, plasma TVs, compact flourescent ballasts, cheap USB cell phone chargers
And the list goes on...........

I'm not 100% convinced it isn't the neighbor downstairs since when the initial test was done, the interference was not as strong as it gets and it was only affecting one channel. Usually it's 2 or 3.
I don't know how to approach the tenant upstairs since I don't know them at all. Also, the homeowner is going in for knee surgery today and will be away from a couple of weeks for PT afterwards.
That seems to place any further investigation on hold. :mad:
 

videobruce

Member
Premium Subscriber
Joined
Jan 5, 2004
Messages
396
Location
Buffalo NY
Making this deal worse, there is little pattern. As I type this at 9am there is no interference when it usually happens. :roll:
 
Status
Not open for further replies.
Top