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CAP Talk  |  Operations  |  Tools of the trade  |  Topic: DSL Causing Harmful Interference on CAP Frequencies
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Author Topic: DSL Causing Harmful Interference on CAP Frequencies  (Read 2296 times)
wuzafuzz
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Posts: 1,160

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« on: December 20, 2016, 07:31:23 AM »

After putting up with killer noise on some CAP HF channels I finally made time to diagnose sources.  After turning off all the circuit breakers and running an HF receiver on battery power, I slowly turned everything back on while a friend (also a CAP member) monitored the radio.

We found a few noise sources. 

First was a battery charger for a portable ham radio (Tytera MD-380).  That was good for one S unit.
Second, a Motorola XPR5550 made a continuous low growl on HF.  Not worth an S unit, but annoying.
Finally, booting the DSL modem caused massive mayhem.

The modem was silent at initial power up.  So the wall wart power supply got a clean bill of health, as did the Ethernet portions of the modem/router/switch. Then all hell broke loose when the DSL negotiations started a minute or two later. My receiver went from S3 to 20 over S9!  The negotiation noises were awful and perfectly readable on my receiver and CAP Micom 2. Once the modem settled in the noise changed to constant hash, but still 20 over S9.

I can't tell whether the problem is the modem itself or DSL as a whole.  Since I can't separate the two it's hard to tell. The phone company offered to sell me a new modem to resolve the harmful interference caused by their equipment. Sorry nice call center lady, I'm not spending a bunch of cash only to discover the modem wasn't the problem.  So I'm switching to a cable provider another CAP HF guy is using without issues.  In this case the ActionTec Q1000 modem on CenturyLink DSL is the culprit.

Why post about this on CAP Talk?  I know a lot of people who try CAP HF and can't get past the noise floor caused by other electronics. Perhaps some of you will benefit from lessons learned by others.
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arajca
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« Reply #1 on: December 20, 2016, 12:16:32 PM »

Isn't there something about consumer electronics not causing harmful interference?
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NIN
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« Reply #2 on: December 20, 2016, 01:11:27 PM »

Isn't there something about consumer electronics not causing harmful interference?
I should know/remember this as a ham,  but my operations practice is wayy out of date.


IIRC, consumer devices are supposed to *reject* harmful interference.

Our gear isn't consumer

Sent from my SM-G920V using Tapatalk

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Darin Ninness, Lt Col, CAP
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The contents of this post are Copyright © 2017 by NIN. All rights are reserved. Specific permission is given to quote this post here on CAP-Talk only.
SarDragon
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« Reply #3 on: December 20, 2016, 03:32:07 PM »

Isn't there something about consumer electronics not causing harmful interference?
I should know/remember this as a ham,  but my operations practice is wayy out of date.


IIRC, consumer devices are supposed to *reject* harmful interference.

Our gear isn't consumer

Sent from my SM-G920V using Tapatalk

Nope, got it backwards. The applicable bit is Part 15, and here's what it sez (emphasis mine):

Quote from: CFR 2015 Title 47
§ 15.5 General conditions of operation.

(b) Operation of an intentional, unintentional,
or incidental radiator is subject
to the conditions that no harmful
interference is caused
and that interference
must be accepted that may be
caused by the operation
of an authorized
radio station, by another intentional
or unintentional radiator, by industrial,
scientific and medical (ISM)
equipment, or by an incidental radiator.

That's what the stickers on Part 15 gear tell us. Full text here.
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Dave Bowles
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DakRadz
Salty & Seasoned Contributor

Posts: 1,351

« Reply #4 on: December 20, 2016, 03:47:15 PM »

So Dave, for the untrained layman... I really can't quite follow that quote. I don't have the background without more information. Does that mean our devices MUST accept the interference?
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Toad1168
Forum Regular

Posts: 131
Unit: NCR-MO-110

« Reply #5 on: December 20, 2016, 04:08:24 PM »

CenturyLink is terrible.  I think smoke signals are better than their service.
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Mike Toedebusch
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« Reply #6 on: December 20, 2016, 04:32:22 PM »

I always get that confused.  Thanks Dave!
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Darin Ninness, Lt Col, CAP
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The contents of this post are Copyright © 2017 by NIN. All rights are reserved. Specific permission is given to quote this post here on CAP-Talk only.
sardak
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Posts: 1,144

« Reply #7 on: December 20, 2016, 05:05:45 PM »

Quote
So Dave, for the untrained layman... I really can't quite follow that quote. I don't have the background without more information. Does that mean our devices MUST accept the interference?
Yes, as long it's not harmful interference. The section has two parts:

1)Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused

2)and that interference must be accepted that may be caused by the operation.

If it can be shown that the interference is harmful, it's not acceptable. So what's harmful interference?

§ 15.3 (m) Harmful interference. Any emission, radiation or induction that endangers the functioning of a radio navigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunications service operating in accordance with this Chapter.

The American Radio Relay League (ARRL, the national association for ham radio) uses this example to explain the concept:
There are a lot of urban myths about Part 15 rules and devices. The first is that their signal levels are very small and it is not likely that they will cause harmful interference.
Although this is true in most cases, the radiated emissions levels in Part 15 were designed to protect one neighbor's television reception from another neighbor's video game, as an example.
The permitted radiation levels are not enough to always protect sensitive amateur reception. As one example, intentional radiators and carrier-current devices are permitted a field strength of 30 microvolts/meter at 30 meters distance from the source. On HF, this legal signal, if heard on an 80 meter half-wave dipole, would result in a received signal of S9+15 dB on most receiver S meters! This clearly would be harmful interference in the Amateur Radio Service.
[In the OP, the value was S9 +20 dB, even worse than this example.]

While this example uses the Amateur (ham) Radio Service, it is just as applicable to other designated radio services.

Here's the next kicker. If the interference is deemed to be harmful, then the user of the offending device must resolve the problem. So in the OP's case, it really is up to Eric, not the phone company, to eliminate the interference.

Here's the ARRL page on interference. http://www.arrl.org/part-15-radio-frequency-devices  and note all the specific topics in the left margin.

Mike
« Last Edit: December 20, 2016, 05:11:52 PM by sardak » Logged
Mordecai
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« Reply #8 on: December 20, 2016, 06:28:10 PM »

Give this a shot: http://www.instructables.com/id/Shield-Your-Wireless-RouterModem-From-RF-Energy/?ALLSTEPS
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chief2
Recruit

Posts: 28

« Reply #9 on: December 20, 2016, 09:14:31 PM »

I have century link with the Actiontec modem that I purchased, due not have any interference with any radio equip,
that includes 6 hf and 2 vhf radios
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PHall
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Posts: 5,877

« Reply #10 on: December 20, 2016, 09:16:40 PM »

Okay wuzafuzz, lets do some trouble shooting.
Is your phone line fed by an Aerial drop from the pole or do you have buried service?

If it's Buried, is the shield on the drop bonded and grounded at the protector?
 
Is the protector grounded? Per the National Electric Code, the protector shall be grounded and a buried drop shall be grounded/bonded.

Is the DSL Modem Power Supply plugged in to a Grounded Outlet?

Is the ground for your radio a "good" ground? Is the antenna ground a "good" ground too?
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Eclipse
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« Reply #11 on: December 20, 2016, 09:20:33 PM »

DSL?  It's 2016.
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The contents of this post are Copyright © 2017 by eclipse. All rights are reserved. Specific permission is given to quote this post here on CAP-Talk only.

wuzafuzz
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Posts: 1,160

TVCS Website
« Reply #12 on: December 20, 2016, 10:14:59 PM »

DSL?  It's 2016.
Comcast was my other choice, and they used to block VPN which I needed for work.  CenturyLink didn't block it and gave me acceptable speeds for less money.  Non-issue until I discovered the RFI.

Now that I don't need VPN like I did a few years ago, I can move around.   8)
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wuzafuzz
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TVCS Website
« Reply #13 on: December 20, 2016, 10:21:54 PM »

Okay wuzafuzz, lets do some trouble shooting.
Is your phone line fed by an Aerial drop from the pole or do you have buried service?

If it's Buried, is the shield on the drop bonded and grounded at the protector?
 
Is the protector grounded? Per the National Electric Code, the protector shall be grounded and a buried drop shall be grounded/bonded.

Is the DSL Modem Power Supply plugged in to a Grounded Outlet?

Is the ground for your radio a "good" ground? Is the antenna ground a "good" ground too?
  • Buried service.
  • No idea about the shield at the protector.  It's all outside under snow.
  • Same answer re: protector.
  • Modem power supply is connected to a grounded outlet.
  • Radio electrical ground is an 8' ground rod about 10 feet from the radio.  RF ground is a 40' counterpoise wire.  Not ideal but with an HOA...  Chokes on the coax, and the ingress connectors are grounded.
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Eclipse
Too Much Free Time Award
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« Reply #14 on: December 20, 2016, 10:25:28 PM »

DSL?  It's 2016.
Comcast was my other choice, and they used to block VPN which I needed for work.  CenturyLink didn't block it and gave me acceptable speeds for less money.  Non-issue until I discovered the RFI.

Now that I don't need VPN like I did a few years ago, I can move around.   

Interesting, I've never known Comcast to block anything but good customer service and friendly attitudes.
They all make like Hoover, but at least when it works Comcast is the fastest on the block (unless you can get fiber, which would also solve your RFI issues).

This is your modem, right, not an AP?  Can't you just stick in a tinfoil-lined box or otherwise move it away from the radio / antenna?
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The contents of this post are Copyright © 2017 by eclipse. All rights are reserved. Specific permission is given to quote this post here on CAP-Talk only.

wuzafuzz
Salty & Seasoned Contributor

Posts: 1,160

TVCS Website
« Reply #15 on: December 20, 2016, 10:31:56 PM »



The American Radio Relay League (ARRL, the national association for ham radio) uses this example to explain the concept:
There are a lot of urban myths about Part 15 rules and devices. The first is that their signal levels are very small and it is not likely that they will cause harmful interference.
Although this is true in most cases, the radiated emissions levels in Part 15 were designed to protect one neighbor's television reception from another neighbor's video game, as an example.
The permitted radiation levels are not enough to always protect sensitive amateur reception. As one example, intentional radiators and carrier-current devices are permitted a field strength of 30 microvolts/meter at 30 meters distance from the source. On HF, this legal signal, if heard on an 80 meter half-wave dipole, would result in a received signal of S9+15 dB on most receiver S meters! This clearly would be harmful interference in the Amateur Radio Service.
[In the OP, the value was S9 +20 dB, even worse than this example.]

While this example uses the Amateur (ham) Radio Service, it is just as applicable to other designated radio services.

Here's the next kicker. If the interference is deemed to be harmful, then the user of the offending device must resolve the problem. So in the OP's case, it really is up to Eric, not the phone company, to eliminate the interference.


Mike
Excellent research, as usual, Mike!  I'm stunned at the permissible signal levels before we approach "harmful" interference.  Pretty much everything with electricity in it is going to generate RF somewhere, but wow. 

I ran into similar problems years ago with an Ethernet switch causing mayhem on CAP VHF and a swath of amateur 2 meter frequencies.  In that instance nothing worked to resolve the problem, except replacing with a different switch.  (The offending switch was destroyed with extreme prejudice, never to radiate again.)  Similar measures may be taken in this instance.

Thanks for the scoop!
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wuzafuzz
Salty & Seasoned Contributor

Posts: 1,160

TVCS Website
« Reply #16 on: December 20, 2016, 10:42:05 PM »

DSL?  It's 2016.
Comcast was my other choice, and they used to block VPN which I needed for work.  CenturyLink didn't block it and gave me acceptable speeds for less money.  Non-issue until I discovered the RFI.

Now that I don't need VPN like I did a few years ago, I can move around.   

Interesting, I've never known Comcast to block anything but good customer service and friendly attitudes.
They all make like Hoover, but at least when it works Comcast is the fastest on the block (unless you can get fiber, which would also solve your RFI issues).

This is your modem, right, not an AP?  Can't you just stick in a tinfoil-lined box or otherwise move it away from the radio / antenna?
I should clarify.  (Fuzzy memory after 3+ years.)  They didn't support VPN unless customers payed for business grade service.  When they started that policy my VPN on residential service suddenly got wiggy.  Interestingly enough, my co-workers in a different city didn't have the same problems with their Comcast service.  Co-workers who lived in the same town as me had the same trouble.

Yeah, this is the modem.  The embedded wireless AP is disabled since I preferred a different box and location for the AP.  Shielding the modem has no effect.  I suspect the phone line itself may be radiating.
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EMT-83
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Posts: 1,823

« Reply #17 on: December 20, 2016, 11:22:23 PM »

Radio electrical ground is an 8' ground rod about 10 feet from the radio.  RF ground is a 40' counterpoise wire.  Not ideal but with an HOA...  Chokes on the coax, and the ingress connectors are grounded.

Are all of your grounds bonded to the service ground?
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Spaceman3750
Salty & Seasoned Contributor

Posts: 2,620

« Reply #18 on: December 21, 2016, 01:31:55 AM »

DSL?  It's 2016.
Comcast was my other choice, and they used to block VPN which I needed for work.  CenturyLink didn't block it and gave me acceptable speeds for less money.  Non-issue until I discovered the RFI.

Now that I don't need VPN like I did a few years ago, I can move around.   

Interesting, I've never known Comcast to block anything but good customer service and friendly attitudes.
They all make like Hoover, but at least when it works Comcast is the fastest on the block (unless you can get fiber, which would also solve your RFI issues).

This is your modem, right, not an AP?  Can't you just stick in a tinfoil-lined box or otherwise move it away from the radio / antenna?
I should clarify.  (Fuzzy memory after 3+ years.)  They didn't support VPN unless customers payed for business grade service.  When they started that policy my VPN on residential service suddenly got wiggy.  Interestingly enough, my co-workers in a different city didn't have the same problems with their Comcast service.  Co-workers who lived in the same town as me had the same trouble.

Yeah, this is the modem.  The embedded wireless AP is disabled since I preferred a different box and location for the AP.  Shielding the modem has no effect.  I suspect the phone line itself may be radiating.

They probably muck with IPSEC. I have a coworker who is currently running an IPSEC client VPN server on what I assume is Comcast consumer with no issues, and I have had a couple clients in the last 3 years who have successfully used site to site IPSEC from their Comcast home, but YMMV. This is why the cool kids are switching to SSL/TLS client VPNs.
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dbaran
Member

Posts: 82
Unit: PCR-CA-110

« Reply #19 on: December 21, 2016, 09:37:53 PM »

On the DSL interference - it is probably coming off of your phone wiring .  If you can put the DSL modem and the telco wiring further away from your radio, that will help.  When I had DSL, I had my gateway in the garage where the line came in and ran Ethernet to it.  DSL can run up to 4 MHz and the harmonics will take it  higher.  Regular phone wiring is unshielded and can act as an antenna.  The FCC rules apply to the equipment, which probably isn't radiating - but the equipment mfg can't do much about your inside wiring radiating.  If you can't move the DSL modem, you could replace the phone line with shielded cable so long as the shield is grounded (to a real ground - not to one of the phone wires).

I feel very comfortable saying that Comcast does not block VPNs.  I had Comcast until I moved and had no trouble with any sort of VPNs.  If you use the standard Comcast-supplied modem, it should work fine. 



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