Noise when there is no traffic

[Fixitt]

Retired auto mechanic new to scanners still learning by mistake which is expensive. Would like someone more knowledgeable to verify my diagnosis. This has been an issue for months.

Picking up noise (hum and what sounds like a really attenuated NOAA broadcast) when there is no traffic. I’m not sure if it NOAA but it is constant muted unintelligible talking.

Setup includes 50 feet of RG8x (#1 suspect), a Tram discone antenna, and a Home Patrol II. The XYL doesn’t like the ‘chatter’ so I bought wired headphones.

The RG8x coax connects to an air gap arrestor grounded to an 8 foot ground rod. The other end of the arrestor has a 1 foot RG8x jumper through the wall. A 6 foot PL259 to SMA cable connects to the scanner. All connections are tight.

Once in a while the noise stops for 1-2 seconds. If I disconnect the coax from the scanner, the noise stops. If I touch just the coax nut to the scanner connector (not threading it on) I can hear the noise.

If I use the antenna that came with the scanner there is no noise. If I disconnect the cable from the antenna outside and connect the antenna that came with the scanner there is no noise.

I heard the noise with my PRO2096 scanner also.

Before this 66 year old man with arthritis climbs on the roof again to replace the coax with something better, is my diagnosis a possibility?

Could the coax be the cause of the noise? I read that RG8x has a lot of loss.

The closest power line is over 100 feet away. There is nothing nearby like a transmitter. I can hear the noise any time day or night.

 

[littona]

If it's weather radio, you should be hearing it on 162.55MHz. Might want to see if it is indeed the same.

NWR Transmitters

www.weather.gov

Check your grounding. For kicks, try disconnecting it to see if that changes anything. Not that I'd recommend running an outdoor antenna with no grounding, but we're doing trouble isolation here.

RG-8X is best suited for HF. I wouldn't think that 50 feet would be too horrible. Here's another read referencing this exact subject:

Recommended max length for RG8x cable?

I was looking at this - 100ft RG8x Coax UHF (PL259) Male to Male 50 ohm Antenna Cable - R-U100 for running a temp. jpole antenna. I didn't see any 75ft which would work for me however if it is not recommended to use 100ft I could use the 50ft and maybe add on an additional 10ft. I'd be running...

forums.radioreference.com

 

[a417]

How close is the nearest broadcast antenna? I am 2000 ft from a 25k watt country music station, and I pick it up on every electronic device in the house that contains a speaker, is powered off and grounded. I feel your pain.

 

[buddrousa]

AM Radio Towers are bad about things like this.
Have a 3000 watt AM Station gets in phones for a mile.

 

[Fixitt]

Ground temporarily removed with no change.

No radio transmitters I am aware of but I will check into that.

There is a cell tower about 1/2 mile away.

Lots of ideas. Thanks.

 

[WA0CBW]

Do you have the noise if you turn on the attenuator? The fact the hum went away with a less efficient antenna points to a strong signal overloading the scanner with the better antenna. Check again for nearby broadcast stations.
BB

 

[hamstang]

Maybe try coax to radio without the air gap arrestor.

 

[Fixitt]

The closest tower is over 2 miles away. The red X is my location.

I turned the attenuator on and the only thing I heard was the buzz. The muted station was gone.

Part of my diagnosis was eliminating the arrestor


My guardian angel was with me when I installed the antenna. Let’s see if I can keep from falling off the roof.

 

[WA0CBW]

What kind of arrestor are you using? You said "air" gap. The gap should be from the center conductor to ground. Easy to test with an ohm meter and taking it out of the line.

 

[wgbecks]

It appears that you're in close proximity to KMOX AM (50 KW) 1120 KHz who's transmitter located about five miles due west of Maryville that
is likely inducing a tremendous electrical field on your antenna and transmission line system.

One possible solution is to construct a common mode choke having enough reactance at 1120 KHz to diminish the RF current flowing through
your scanner's chassis, electronics and quite possibly to the A.C. mains. I might suggest that your first turn on an AM radio tuned to KMOX to
see if the voice heard in the scanner matches that on the radio.

The choke might be fabricated by winding multiple turns of the RG8x over several ferrite rods stacked together. It might also help to isolate the scanner's power supply with an appropriate line filter. You could test this by disconnecting the A.C. power source to the scanner and then powering it off a battery if your scanner is capable of being powered from 12 VDC such as would be done in a typical mobile installation.

Job one is to first identify the source of the RFI, and in your case, this may well be simple rectification taking place in the scanner's electronics.

 

[Fixitt]

Good idea about the AM station. The hum is louder and is what really annoys me.

The HPII can be used on battery, and the noise is still there with the external power supply disconnected.

Priority is swapping the RG8x with RG58. Waiting for my wife to hold the step ladder.

Hopefully my next post will be from the couch and not a hospital bed.

 

[Fixitt]

The hum and noise are GONE! And I am on the sofa.
Many many thanks for the advice.
I am a retired ASE CMAT L1 MRRT mechanic (never did like when they changed the title to technician)
My specialty at the shop was computer diagnostics, check engine lights, no starts, stuff like that. If I can offer any of my knowledge please don’t hesitate to ask.

 

[Fixitt]

This is the air gap arrestor I bought. Not marked in or out nor is the tube.

 

[Fixitt]

This is the air gap arrestor I bought. Not marked in or out nor is the tube.

This looks like a no-name arrestor that I probably shouldn’t rely on.

A brand I have heard about is Polyphaser. Those seem to be overkill for a scanner.

Another is Array Solutions.

For those using a lightning arrestor with a scanner, what are you using?

 

[mmckenna]

This looks like a no-name arrestor that I probably shouldn’t rely on.

A brand I have heard about is Polyphaser. Those seem to be overkill for a scanner.

Another is Array Solutions.

For those using a lightning arrestor with a scanner, what are you using?

The concern is that the 'no-name' stuff is made in China with poor quality control. Relying on a safety device with no real pedigree from an unknown manufacturer would be a concern.
Polyphaser is a very common brand in the two way radio industry. I have them at all my sites and stock spares.

Not really overkill for a scanner, hobby or ham radio use. Since a direct, or even nearby, strike can do a lot of damage, you ideally want something you can rely on.

 

[W5lz]

Retired auto mechanic new to scanners still learning by mistake which is expensive. Would like someone more knowledgeable to verify my diagnosis. This has been an issue for months.

Picking up noise (hum and what sounds like a really attenuated NOAA broadcast) when there is no traffic. I’m not sure if it NOAA but it is constant muted unintelligible talking.

Setup includes 50 feet of RG8x (#1 suspect), a Tram discone antenna, and a Home Patrol II. The XYL doesn’t like the ‘chatter’ so I bought wired headphones.

The RG8x coax connects to an air gap arrestor grounded to an 8 foot ground rod. The other end of the arrestor has a 1 foot RG8x jumper through the wall. A 6 foot PL259 to SMA cable connects to the scanner. All connections are tight.

Once in a while the noise stops for 1-2 seconds. If I disconnect the coax from the scanner, the noise stops. If I touch just the coax nut to the scanner connector (not threading it on) I can hear the noise.

If I use the antenna that came with the scanner there is no noise. If I disconnect the cable from the antenna outside and connect the antenna that came with the scanner there is no noise.

I heard the noise with my PRO2096 scanner also.

Before this 66 year old man with arthritis climbs on the roof again to replace the coax with something better, is my diagnosis a possibility?

Could the coax be the cause of the noise? I read that RG8x has a lot of loss.

The closest power line is over 100 feet away. There is nothing nearby like a transmitter. I can hear the noise any time day or night.

Try eliminating one device at a time till the noise stops or is greatly reduced. If you find such a device problem solved (hold your breath?). Then it's a matter of eliminating stuff close, then further away till you're willing to put up with that @#$ noise. Simple? Not really. Have fun.

 

[Fixitt]

The cheap RG8x was acting as an antenna. Once it was replaced with RG6 the audio is quiet.

And I will get the Polyphaser.

 

[Fixitt]

The PolyPhaser IS-50UX-C0 arrestor arrived today. Before I install it, I have a few questions.

PolyPhaser states the frequency range of this arrestor is 1.5 to 700MHz. Is this for transmit and receive or does the spec only apply to transmit? If it is for both transmit and receive, what happens to the frequencies I want to receive that are above 700MHz? I found nothing about the frequency range for receive. I currently can listen to 900MHz with my no-name gas tube arrestor. The specs for my Tram 1410 claim it can receive 25MHz to 1300MHz. Should I get a different PolyPhaser and change all the coax and connectors to N downstream of the arrestor to listen above 700MHz?

All the arrestors PolyPhaser sells with UHF connectors had the same 1.5 to 700MHz frequency range. Everything from the antenna up to a short jumper at the scanner is PL259. Lots of hams hate PL259/SO239 connectors. Since I am only receiving, are these sufficient?

How important is getting the ground wire straight from the arrestor to the ground rod? Some say if there is a 90 degree bend on the ground wire, the lightning wants to continue going straight and won’t make the bend. When GM invented HEI ignition, several instructors from parts stores told us not to pull a spark plug wire off with the engine running or it would blow a hole through your elbow. Is this the same kind of hooey or should I remove the 3 90 degree bends in the 10 gauge solid copper ground wire?

My electrical panel is grounded on the other side of the house. Should I connect both ground rods together? I read something that said they should be connected so the ground potential (?) is the same.

Remember my skill level is below novice.

 

[WA0CBW]

"My electrical panel is grounded on the other side of the house. Should I connect both ground rods together? I read something that said they should be connected so the ground potential (?) is the same"
YES, per NEC.

 

[mmckenna]

The PolyPhaser IS-50UX-C0 arrestor arrived today. Before I install it, I have a few questions.

PolyPhaser states the frequency range of this arrestor is 1.5 to 700MHz. Is this for transmit and receive or does the spec only apply to transmit? If it is for both transmit and receive, what happens to the frequencies I want to receive that are above 700MHz? I found nothing about the frequency range for receive. I currently can listen to 900MHz with my no-name gas tube arrestor. The specs for my Tram 1410 claim it can receive 25MHz to 1300MHz. Should I get a different PolyPhaser and change all the coax and connectors to N downstream of the arrestor to listen above 700MHz?

It'll receive just fine up at 900MHz. The concern is the ability to handle power at the transmit frequency. For scanner use, no problems.

As for coax connectors, use whatever matches the components.

All the arrestors PolyPhaser sells with UHF connectors had the same 1.5 to 700MHz frequency range. Everything from the antenna up to a short jumper at the scanner is PL259. Lots of hams hate PL259/SO239 connectors. Since I am only receiving, are these sufficient?

UHF connectors are essentially a shielded banana plug. Back when they were designed, "Ultra High Frequency" was stuff slightly above the current VHF band. Above the VHF band, the odd size of the center conductor and outer shield creates an impedance bump that becomes problematic at higher frequencies.
Again, for scanning use, it'll work just fine. You won't hear the difference.
If you were building a system from scratch and had the money and time to do it, running N connectors would be a good choice. But don't tear your stuff out and start replacing it thinking you'll see an improvement.

How important is getting the ground wire straight from the arrestor to the ground rod? Some say if there is a 90 degree bend on the ground wire, the lightning wants to continue going straight and won’t make the bend. When GM invented HEI ignition, several instructors from parts stores told us not to pull a spark plug wire off with the engine running or it would blow a hole through your elbow. Is this the same kind of hooey or should I remove the 3 90 degree bends in the 10 gauge solid copper ground wire?

If you took a direct lightning strike, you'd want everything to be set up in such a way to get that energy to ground in as short and straight a path possible. Lightning travels thousands of feet through the air (air is a good insulator) and it's not going to care that your antenna is in the way. That energy is going to go where ever the hell it wants.
If you look at a mountain top radio site, you'd see large ground conductors or straps going as straight as possible.

Since it's unlikely (I hope) that you'll ever take a direct strike, you want to do the best you can. Don't purposely make sharp 90º bends in your down lead to the ground rod. Ideally keep it straight. If you do have to change directions, gentle bends.
The bigger issue for hobbyists where a direct strike is unlikely, is dealing with the pulse of energy that will get induced onto near by conductors in the vicinity of the lightning strike. You want to give that energy a path to ground that doesn't involve going through your home, radio, you, etc.

My electrical panel is grounded on the other side of the house. Should I connect both ground rods together? I read something that said they should be connected so the ground potential (?) is the same.

Yes. National Electric Code requires it. Differential in ground potential can be an issue that you don't want to deal with.