Does Ham radios effect FM reception or TV if you are right by someone who is broadcasting out? I always wondered that. I know there was a place I saw someone who had a 2m antenna up, and someone next door had a outdoor TV antenna up. The person that had the 2m ham antenna also had a tv & a fm antenna up in the air also.
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Does Ham effect Tv/fm?
- Thread starter jras20
- Start date
J
JasonW
Guest
jras20 said:
It depends on the ham transmitter's frequency, output power, harmonic suppression, and proximity to the TV or FM receiver (or its outdoor receiving antenna).
QRP (low power--usually 5 watts or less) ham transmitters seldom interfere with TV or FM reception, especially on the HF or MF bands. QRO (high power--up to 1500 watts) transmitters can be a different story. In Miami, I once heard my ham neighbor two houses down the block talking on TV Channel 3 while changing channels on my old manually-tuned (with no remote control) television set.
The reverse also sometimes happens, as TV sets and computers can also interfere with ham receivers located near them due to internally-generated RF (radio frequency) noise.
-- Jason
jras20 said:
Depends on what frequency and power output the ham rig is running on, as well as the channel/frequency of the receiver in question and how far they are apart. Hams operating on 30 meters and below probably won't be a TVI problem, but 20 and up could be.
20 Meters (14.0-14.35 MHz)
4th harmonic: Channel 2
5th harmonic: Channel 4
6th harmonic: Channel 6
17 Meters (18.068-18.168 MHz)
3rd harmonic: Channel 2
5th harmonic: 90.3, 90.5, 90.7 FM
15 Meters (21.0-21.45 MHz)
3rd harmonic: Channel 3
4th harmonic: Channel 6
5th harmonic: 105.1-107.1 FM
12 Meters (24.89-24.99 MHz)
4th harmonic: 99.5, 99.7, 99.9 FM
10 Meters (28.0-29.7 MHz)
2nd harmonic: Channel 2
3rd harmonic: Channel 6 & 88.1-89.1 FM
6 Meters (50-54 MHz)
Fundamental: Could overload a TV turned to Channel 2
2nd harmonic: Top half of FM band
4th harmonic: Channels 11-13
These days it's relatively rare for ham stations to interfere with consumer electronic equipment. Unfortunately it's quite common for consumer electronic equipment to act as ham receivers and pick up transmissions on the amateur frequencies.
Back in the 1950s and 1960s, harmonic interference was a pretty big problem. All radio transmitters radiate *some* signal on multiples of the desired frequency - if you're transmitting on 28.1MHz, you have some signal on 56.2, 84.3, 112.4, etc... Before WWII, all ham frequencies were harmonically related - if your transmitter did have strong harmonics, they'd only interfere with other hams. Hams didn't have to take much care to shield or filter their transmitters.
Of course, after the war TV came along. Now, millions of hams' neighbors were trying to pick up TV stations on the frequencies into which the hams' harmonics fell. You can guess that interference was endemic. (it probably didn't help that early TV stations were often running relatively low power, and the 1948-1953 freeze on new TV licenses left many viewers forced to "DX" distant TV stations if they wanted any reception at all; it took a lot less of an interfering signal to wipe a DX signal off the dial) The postwar TV interference problem badly damaged ham radio.
Hams adapted by learning how to shield their transmitters; how to install low-pass filters and modify their transmitters' operating parameters to limit harmonics. TV stations increased power, to the point where, today, virtually all VHF TV stations are running the maximum power allowed by FCC regulation. More TV stations were built, ensuring most viewers weren't *forced* to be DXers, and in many places where new main stations weren't possible, the construction of TV translators or early cable systems took care of the "DX" problem.
Today, the widespread use of cable and satellite TV has nearly eliminated interference from spurious emissions of ham transmitters as a problem.
Unfortunately, as hams *added* filters and shielding to their transmitters, consumer electronic manufacturers *removed* it. A lot of electronic gear picks up signals on frequencies it's not supposed to pick up, often including ham frequencies. (now, to make it worse, a lot of this gear is actually *transmitting* signals and *causing* interference! - I would suggest that computers and other noisy consumer electronic gear are a major component of the reason AM radio is having so much trouble...)
Back in the 1950s and 1960s, harmonic interference was a pretty big problem. All radio transmitters radiate *some* signal on multiples of the desired frequency - if you're transmitting on 28.1MHz, you have some signal on 56.2, 84.3, 112.4, etc... Before WWII, all ham frequencies were harmonically related - if your transmitter did have strong harmonics, they'd only interfere with other hams. Hams didn't have to take much care to shield or filter their transmitters.
Of course, after the war TV came along. Now, millions of hams' neighbors were trying to pick up TV stations on the frequencies into which the hams' harmonics fell. You can guess that interference was endemic. (it probably didn't help that early TV stations were often running relatively low power, and the 1948-1953 freeze on new TV licenses left many viewers forced to "DX" distant TV stations if they wanted any reception at all; it took a lot less of an interfering signal to wipe a DX signal off the dial) The postwar TV interference problem badly damaged ham radio.
Hams adapted by learning how to shield their transmitters; how to install low-pass filters and modify their transmitters' operating parameters to limit harmonics. TV stations increased power, to the point where, today, virtually all VHF TV stations are running the maximum power allowed by FCC regulation. More TV stations were built, ensuring most viewers weren't *forced* to be DXers, and in many places where new main stations weren't possible, the construction of TV translators or early cable systems took care of the "DX" problem.
Today, the widespread use of cable and satellite TV has nearly eliminated interference from spurious emissions of ham transmitters as a problem.
Unfortunately, as hams *added* filters and shielding to their transmitters, consumer electronic manufacturers *removed* it. A lot of electronic gear picks up signals on frequencies it's not supposed to pick up, often including ham frequencies. (now, to make it worse, a lot of this gear is actually *transmitting* signals and *causing* interference! - I would suggest that computers and other noisy consumer electronic gear are a major component of the reason AM radio is having so much trouble...)
The Dude said:
Harmonics of 11-meter frequencies (26.96-27.41 MHz) would be just below those of 10 meters. The 2nd harmonic would be at the very high end of the 6 meter ham band and the low end of Channel 2, while the 3rd harmonic would be at the upper end of Channel 5 and the very low end of Channel 6.
(Y didnt I think of that??)Ham transmissions can definitely affect TV. I've heard a couple of local guys (one of whom is a co-worker) over CNN on cable channel 17 a few times in the past.
Also, last week, I caught what was apparently a ham or CB while waiting for Eskip on channel 2 with the antenna hooked up. I would guess that was a second harmonic from the 10-meter band per the chart above.
Also, last week, I caught what was apparently a ham or CB while waiting for Eskip on channel 2 with the antenna hooked up. I would guess that was a second harmonic from the 10-meter band per the chart above.
clichemoth said:
Cable Channel 17 is 138-144 MHz. Channel 18 is 144-150. You sure you weren't watching 18?
Cable channels that are on the same frequencies as over-the-air services:
Ham: 18 (144-150 MHz), 24 (222-228 MHz), 57-61 (420-450 MHz)
FM Broadcast: 95-97 (90-108 MHz)
Aircraft: 98-99 (108-120 MHz), 14-16 (120-138 MHz)
Public Safety: 19-22 (150-174 MHz), 62-64 (450-468 MHz)
Other channels also use frequencies assigned to licensed services or the military, but interference generally isn't as much of a problem. In all cases, it's the cable company's fault if signals from these services leak into the cable system or their broadcasts interfere with over-the-air radio services.
BTW, if you have a cable-ready TV, set the tuner to cable and hook a UHF antenna to it. If there's amateur television in your area you might pick it up on Chs. 57-61.
Link: Cable & Broadcast TV frequency allocations
KeithE4 said:
Cable Channel 17 is 138-144 MHz. Channel 18 is 144-150. You sure you weren't watching 18?
They were on 142.something (I think 142.385). They mentioned the frequency on-air. Never heard it on 18, but I don't watch the National Geographic Channel much.
I've seen the Huntsville hamTV that operates on 58 once. That's the only one near me that I know of. Is anyone in Birmingham or East Alabama doing something similar?
clichemoth said:
The 2 meter ham band is 144-148 MHz. 142.385 MHz is indeed inside cable channel 17, but whoever was using that frequency wasn't operating under an Amateur Radio license. MARS or other military, maybe? The 138-144 MHz band is allocated to U.S. Gummint fixed and mobile services.
KeithE4 said:
I personally know both people I heard. They gave their calls, which match their license plates. It was a personal convo about equipment. I'm guessing they were just operating off the band for whatever reason. Not a bright idea around here with the Anniston Army Depot and Ft. McClellan close by...
C
CW
Guest
clichemoth said:
Cable TV channel 57 is 421.25 MHz...which is often used as repeater output frequency in the 70cm ham band (420-450) where possible; sometimes 426.25 (not dead on channel wise) and 427.25 (CATV channel 58) are used due to frequency issues (or because the ATV group does not want to install a filter on the transmitter to make it VSB capable which it would need to be legal on 421.25) but the use of 427.25 as a repeater frequency is questionable as it puts the audio 4.5 MHz higher within the 431-433MHz range which repeaters are prohibited from using (and FCC rules require ALL emissions from any amateur station fall within the required band or subband...thus the audio carrier of an ATV repeater cannot fall into an area where repeaters are not allowed!)....Channel 60 is sometimes used as the input (which is 439.25) but this has become less and less in metro areas due to FM interference from hams on voice repeaters in the 440-450 range.
Simplex operation still occurs (legally) on 427.25 and also 439.25 even though they may get interferred with by the FM voice carriers...most ATV repeaters nowdays have gone crossband 900 or 1200 FM in and 421.25 AM out...FMTV is SOOO much easier for the USER to transmit and the AM repeater output is easier for the USER to decode....FM receivers are a little more technical and thus, better for the repeater INPUT.
73
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