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Old 11-11-2009, 09:23 PM
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Using an analog transmitter at home.

What is the highest output power at the antenna that is still legal in the U.S. for vhf/uhf? I want to either assemble a small set-up for my portables or buy a preassembled one 'from the far-east' on eBastid.

But I do not want to piss off the authorities and have them take my shit away either. Last I heard, the fcc was calling on state and local officials to watch out for pirate activity on analog tv.....because it's "for first responders now"

Thoughts?
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Old 11-11-2009, 10:54 PM
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http://www.fcc.gov/oet/info/rules/pa...5_07-10-08.pdf

Lots of considerations in Part 15 for the various frequency bands/spectra.

Oh, and you'll be an " intentional radiator "


Cheers,
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Old 11-11-2009, 11:10 PM
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Findm-Keepm Findm-Keepm is offline
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UPDATED in February to include the Digital Transistion - you'll need to check out 47 CFR, FCC Part 15.701:

This subpart sets out the regulations for Television Band Devices (TVBDs) which are unlicensed intentional radiators operating on available channels in the broadcast television frequency bands at 54–60 MHz, 76–88 MHz, 174–216 MHz, 470–608 MHz and 614–698 MHz bands.


(a) Power limits for TVBDs are as follows: (1) For fixed TVBDs, the maximum conducted output power over the TV channel of operation shall not exceed one watt. Transmitter power will be measured at the antenna input to account for any cable losses between the transmitter and the antenna. If transmitting antennas of directional gain greater than 6 dBi are used, the maximum conducted output power shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi.

(2) For personal/portable TVBDs, the maximum conducted output power over the TV channel of operation shall not exceed 100 milliwatts; except that for personal/portable TVBDs that do not meet the adjacent channel separation requirements in §15.712(a), the maximum conducted output power shall not exceed 40 milliwatts. If transmitting antennas of directional gain greater than 0 dBi are used, the maximum conducted output power shall be reduced by the amount in dB that the directional gain of the antenna exceeds 0 dBi.

(3) TVBDs shall incorporate transmit power control to limit their operating power to the minimum necessary for successful communication. Applicants for certification shall include a description of a device's transmit power control feature mechanism.

(4) Maximum conducted output power is the total transmit power in the entire emission bandwidth delivered to all antennas and antenna elements averaged across all symbols in the signaling alphabet when the transmitter is operating at its maximum power control level. Power must be summed across all antennas and antenna elements. The average must not include any time intervals during which the transmitter is off or is transmitting at a reduced power level. If multiple modes of operation are possible ( e.g. , alternative modulation methods), the maximum conducted output power is the highest total transmit power occurring in any mode.

(b) Antenna requirements . (1) For personal/portable TVBDs, the antenna shall be permanently attached.

Cheers,
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Old 11-12-2009, 08:35 AM
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electroking electroking is offline
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If you want to use significant power, you have to become a ham! I don't remember
the details, but one of the CATV channels falls into the UHF ham band and can be
received using any old VCR connected to a TV set.
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Old 11-12-2009, 04:05 PM
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I'm using a Blonder-Tongue agile modulator to broadcast TV in my house, so I'm curious about this, too.

1. How would you know whether "first responders" or anyone else is using a particular frequency in your area?

2. How am I to know whether this modulator exceeds the 100 miliwatt maximum? I just tried walking out into the yard with a handheld Panasonic Travelvision in my hand. The signal starts to fade maybe 100 feet from the house. At about 200, it's snowy but still watchable. Which tells me I might interfere with someone camped in my yard, but probably not the neighbor across the road.

I also have an old TV field strength meter that I bought for fun years ago. Who knows how accurate it is, but it does register the signal and move the needle when you turn the antenna, etc. Its scale says my signal is around .7 microvolts inside the house, whatever that means.

Phil
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Old 11-12-2009, 06:32 PM
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Electro,

Cable channel 59 is the culprit. I have a matchbox sized xmtr around here on that freq that will shoot for a mile over clear terrain but hams might howl. It needs a ground plane antenna at both ends and is video only so it is not of much use for our needs.
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Last edited by Dave A; 11-12-2009 at 06:36 PM. Reason: spelling
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Old 11-13-2009, 12:20 PM
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zenith2134 zenith2134 is offline
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Thanks for the info, FindmKeepm! Helpful as usual....i think a d.i.y. xmitter would be a fun project. Shame to see all my portables tethered down to cable or converter boxes. And, I have access to a 4th story (rooftop really) room here which would be the perfect spot to set this up.

re: becoming a ham, I have thought about it but to be honest I need to wait until I can afford some real equipment first.
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