how-to block ads
|
AZ_OGM
join:2007-01-12
Phoenix, AZ
|  What about hospital equipment disrupting TV channels?
A long time ago (late 80s-early 90s), I used to live about a block away from a hospital and their paging/intercom system would disrupt the cable TV signal every time they would use it. Thankfully it only seemed to affect cable channel 19 which was an out of market network station that was blacked out about 2/3 of the time.
I never understood how they were allowed to bleed over TV signals like that but god forbid you have a cell phone turned on within the premises. | |
TamaraB
Question The Current Paradigm
Premium
join:2000-11-08
Brooklyn NYC
 ·Verizon Online DSL
| said by AZ_OGM  :I never understood how they were allowed to bleed over TV signals like that ... They are NOT allowed. If you were to have called the FCC, they would have been forced to fix it, and get fined.
Bob
--
Motor Vessel - Tamara B.
43' Long-Range Trawler
Cape Elizebeth ME.
See her Here. | |
dishrich
join:2006-05-12
Springfield, IL
4 edits | reply to AZ_OGM
said by AZ_OGM :I never understood how they were allowed to bleed over TV signals like that but god forbid you have a cell phone turned on within the premises. said by TamaraB :They are NOT allowed. If you were to have called the FCC, they would have been forced to fix it, and get fined. FALSE, because they ARE allowed, as cable ch 19 thru 21 are commonly used for over the air paging services, which is where they ARE legally assigned spectrum. The problem was, your cable system was most likely suffering from signal ingress/egress, which was allowing those signals to bleed into your cable. (& most likely was leaking it's own signals OUT) Cable ch 16 was/is commonly used for air traffic control transmissions, which is one of the primary reasons why the FCC started cracking down on "leaky" cable systems in general. There are many OTA services that share the SAME spectrum that a cable system uses, many of which commonly reside in the CATV "midband" range of 14-22.
Do you also realize that CATV ch's 95-97 ARE across the entire FM band freqency? And obviously, CATV ch's 2-13 ARE the same at the OTA broadcasts, which in cities that DO have these same OTA channels, it causes reception problems on the cable system - in many cases, the cable system may not even choose to use those channels, due to high-powered TV stations. (we don't have that problem, since our closest VHF station is over 60+ miles away) But because a cable system is considered a "closed" transmission system, THAT is why this is allowed - it's up to the cable system to make sure they are compliant with leakage standards, both ingress/egress. 
We had the very same problems all over Springfield back in those days as well. All these channels throughout Springfield would range from pretty clean, to totally TRASHED, depending on where you were, quality of the hookups, etc. Our system leaked SO bad, that they could NOT even use Ch 16 for awhile, until they fixed their leaks.
But after 2 system rebuilds, the majority of locations I've seen have everything clean - but again, if a particular residence has bad cabling, splitters, connectors, poor shielded TV tuners, etc, the very same problem WILL come back. It only takes ONE bad connector for these problems to surface. But unfortunately, if you are like next door to one of these particular transmitters, sometimes it is just not possible to 100% shield the system from these transmissions. | |
TamaraB
Question The Current Paradigm
Premium
join:2000-11-08
Brooklyn NYC
·Verizon Online DSL
1 edit | said by dishrich :FALSE, because they ARE allowed, as cable ch 19 thru 21 are commonly used for over the air paging services, which is where they ARE legally assigned spectrum. Wait a Sec! As a former amateur radio operator, I know that the FCC regulates the frequency spectrum. If "ch 19 thru 21 are commonly used ... [for] paging services" then they must comply with FCC regs mandating they not interfere with licensed services on those same frequencies. Their use of that spectrum is limited to "in-house" use, and they may not radiate it outside their premises.
If the Hospital's paging system interferes with licensed spectrum outside the hospital itself, it violates FCC regulations.
Are you saying this is a "FALSE"statement?
Bob
--
Motor Vessel - Tamara B.
43' Long-Range Trawler
Cape Elizebeth ME.
See her Here. | |
dishrich
join:2006-05-12
Springfield, IL
4 edits | said by TamaraB :Wait a Sec! As a former amateur radio operator, I know that the FCC regulates the frequency spectrum. If "ch 19 thru 21 are commonly used ... [for] paging services" then they must comply with FCC regs mandating they not interfere with licensed services on those same frequencies. Their use of that spectrum is limited to "in-house" use, and they may not radiate it outside their premises. If the Hospital's paging system interferes with licensed spectrum outside the hospital itself, it violates FCC regulations. Are you saying this is a "FALSE"statement? Yes, because "the FCC regulates the frequency spectrum" ONLY for OTA signal transmissions - NOT for what a CATV system "chooses" to use within their OWN closed system.
It all depends - IF the hospital's particular paging system spectrum was ONLY for use WITHIN the hospital confines, & is exeeding their authorized power level, &/or it is NOT staying within it's assigned freqs, only then is it violating FCC regs. But, you DO realize there IS spectrum that is used for high-powered pocket pagers, police radios, airline traffic, etc. & unfortunately, those freqs ARE in the CATV midband. As I also told you, there are 3 CATV channels that share the FM band space - unfortunately, there are instances where strong FM transmitters can trash those freqs on a CATV system, making them unusable, that NO amount of shielding can fix.
And as far as the CATV system goes, they do NOT have to get a license to use those same freqs, since as I already mentioned, a CATV is considered a "closed-loop" system, & therefore is NOT "broadcasting" on those freqs. Because of this, there (in theory) is NO co-mingling of transmissions between the CATV system & those OTA devices. A CATV system does NOT have to get FCC permission on which freqs they use - only that they do NOT radiate their signal over a certain threshold. And this is one problem where CATV companies get into with customers who do their own wiring, & DON'T know what the hell they are doing! I run into this constantly with clients, who (incorrectly) blame the cable system for their crappy reception, which they actually brought onto themselves with their do-it-themselves TV hookups.  (ask fiberguy & cabletool & they'll tell you the same thing )
The bottom line - almost EVERY CATV system IS sharing many of the same freqs as many OTA devices & services. Again, the FCC gives the priority to the OTA devices, as long as they are within defined limits. It is up to the CATV system to ensure the proper shielding of their system/equipment. Again, it is NO different than a CATV system attempting to use ch 2-13 in markets WITH strong 2-13 OTA stations.
When I was going down to school@SIU-Carbondale a few decades ago,  the local VHF stations (3, 6, 8, 10 & 12) would sometimes have "co-channel" interfearance in them, since the cable system used all those same channels for TV service. In the case of ch 10, it was also an OTA translator for the local NBC station on 6, which you could see superimposed on top of WGN, which was on CATV ch 10. The rest of the stations were broadcast on the CATV system on the same channels, which sometimes caused multiple ghosting, sync bars drifting, etc. If you didn't have EVERY connector tight, it only got worse. Finally after they rebuilt the system, the reception improved drastically, but again, you had to have a TIGHT system to keep it like that. | |
|
