[RFI] RFI in the news

Roger (K8RI) k8ri at rogerhalstead.com
Sat Dec 7 20:51:02 EST 2013

On 12/7/2013 8:13 AM, Alan NV8A wrote:
> Especially when people have messed with (extended, rerouted, spliced)
> the coax in their homes and left everything leaking like a sieve,

There are many cases of TV antennas hard wired to the TV set along with 
the cable, making the TV antenna a strong radiator of these signals,

In many cases there is a preamp, no longer powered in the circuit that 
will rectify ham signals that the antenna re radiates as well as feeding 
them into the cable system.

Several decades ago I lived in a town where most of the system suffered 
from both ingress and egress.  Fortunately I was able to demonstrate at 
the office, which was also the location for the head end amplifier. 
With a 5W HT, I could shut the cable system for the entire town, down.

As we were about 20 miles from the repeater, most mobiles ran 25 to 50 
watts. I demonstrated that could shut the system down from over a block 

The next evening, after work, most of the town was cleaned up, the next 
evening I could find no leakage.


Roger (K8RI)
> 73
> Alan NV8A
> On 12/06/13 07:14 pm, W5JR.Mike wrote:
>> This is the great "TV White Spaces" project. Once the channels above
>> 21 are repurposed for more wireless broadband (known as "600 MHz"
>> despite including a large chunk of 500 MHz) save for channel 37
>> (astronomical use) and channels in the "duplex gap", and the remaining
>> UHF TV is "repacked" into channels 14-21 (and some upper VHF, 7-13),
>> there likely won't be much, if any, "White Space" left.
>> And again, the traditional cable TV plant, while using DTV like
>> signaling, still utilizes the same channel assignments as over the air
>> broadcasts. So, more interaction between a wireless phone/tablet and a
>> cable system is on the horizon.
>> tnx
>> Mike / W5JR
>>> On Dec 6, 2013, at 4:26 PM, "EDWARDS, EDDIE J"<eedwards at oppd.com>
>>> wrote:
>>> Speaking of cable TV systems, which is one of our main power line
>>> interference customers in town...
>>> I attended an IEEE meeting this week with a presentation on
>>> "Multicasting in Cognitive Radio Networks" by a PHD college professor
>>> from Iowa.  It was very good and pretty technical, and nearly over my
>>> head, but the presenter was basically describing a very efficient
>>> wireless mesh type data network system that would use the unused
>>> portions of the TV spectrum (since it would probably be unlicensed
>>> operation).
>>> When I asked if RF Interference issues were analyzed since there
>>> would be possible RFI to and/or from power lines and cable TV
>>> systems.  He gave me a deer-in-the-headlights look and said no such
>>> analysis had been done.  After the presentation, he approached me
>>> with some questions about possible RF interference, and he seemed
>>> amazed there could be such interference.  It clearly had not occurred
>>> to him.
>>> 73, de ed -K0iL
>>> -----Original Message-----
>>> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of W5JR.Mike
>>> Sent: Thursday, December 05, 2013 10:09 PM
>>> To: Anthony (N2KI)
>>> Cc: rfi at contesting.com
>>> Subject: Re: [RFI] RFI in the news
>>> Traditional cable TV systems use the same spectrum above 470 MHz that
>>> over the air broadcast uses. And they are still using the spectrum
>>> between channels 52 and 69 that has been repurposed for Land Mobile,
>>> Public Safety and cellular. And the issue goes both ways. Leakage
>>> from cable plants are heard by 700 and 800 MHz base stations.
>>> tnx
>>> Mike / W5JR
>>>> On Dec 5, 2013, at 1:05 PM, "Anthony (N2KI)"<n2ki.ham at gmail.com>
>>>> wrote:
>>>> This also happens with Direct TV C31-700 box.  FYI
>>>> Regards,
>>>> Anthony (N2KI)
>>>> On Thu, Dec 5, 2013 at 12:48 PM, Charles
>>>> Coldwell<coldwell at gmail.com>wrote:
>>>>> http://arstechnica.com/information-technology/2013/12/time-warner-cable-tv-goes-blurry-in-presence-of-verizon-lte-phones/
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