bb@trsvax.UUCP (05/31/89)
I am interested in transmitting a TV RF signal over a distance of at least 2000 feet. I realize I will probably need some kind of FCC license. Does the FCC grant licenses to send a TV signal of that strength? What is the size, cost, weight, and wattage that I am looking at to send 2000 feet? Has anybody out there (such as robotics types) tackled the same problem? Any replys would be appreciated.
flloyd%crank@Sun.COM (Fred Lloyd) (06/02/89)
In article <190700040@trsvax> bb@trsvax.UUCP writes: > >I am interested in transmitting a TV RF signal over a distance of at least >2000 feet. I realize I will probably need some kind of FCC license. Does >the FCC grant licenses to send a TV signal of that strength? What is the >size, cost, weight, and wattage that I am looking at to send 2000 feet? > >Has anybody out there (such as robotics types) tackled the same problem? > >Any replys would be appreciated. If you're up to experimenting then here's some fuel for thought: Take an ordinary VCR and attach it's output cable to a regular TV antenna. For best results, get an antenna which is specifically tuned to either channel 3 or 4, depending on the output of your VCR. Avoid those multi-channel "color" antennas with dozens of odd-sized elements. Stick with the single-channel multielement Yagi design. You should be able to pick up this retransmitted signal for some distance, depending on conditions and quality of construction. If necessary, an MATV distribution amplifier could be used to boost the output power on the sending antenna. The receiving antenna should be in-line with the sending unit (sorry, no around-the-corner operation :-). Don't forget to be sure that the polarization of the two antennae are the same (both vertical or both horizontal). Whatever the VCR is tuned to, or what ever is playing on the tape, will be received on channel 3 (4) on the other end. Of course this is illegal... and the signal won't be extremely strong, but anyway, you asked for "any" replies :-). And now for the real DISCLAIMER: I've never done this myself and probably would look for an alternative (read legal) method if I wanted to extend my tv signal. Several devices are due to come out on the market shortly which perform this exact function (but not on broadcast frequencies), and which it may be possible to string multiple units together for more range. Don't however, look for them in Radio Shark anytime this year... -fred -------------------------------------------------------------------- | Fred Lloyd KJ6RK PP-SEL flloyd@sun.com | | Sun Microsystems, Inc. ...sun!flloyd | | Mountian View, CA | | (415) 336-6322 | | Disclaimer: If it ain't broke, don't fix it! | --------------------------------------------------------------------
mbutts@mntgfx.mentor.com (Mike Butts) (06/03/89)
From article <190700040@trsvax>, by bb@trsvax.UUCP: > > I am interested in transmitting a TV RF signal over a distance of at least > 2000 feet. I realize I will probably need some kind of FCC license. Does > the FCC grant licenses to send a TV signal of that strength? What is the > size, cost, weight, and wattage that I am looking at to send 2000 feet? > > Has anybody out there (such as robotics types) tackled the same problem? > 1) With a technician-class ham license, you can transmit standard color video over a distance of dozens of miles. See, for example, any recent edition of the ARRL Radio Amateur's Handbook, which you can find in most libraries and tech book stores. Ham TV equipment is available commercially. For example, there are several small TV transceivers available with a few watts of power which are said to work for a mile or so. Hams use them at amateur sporting events, disaster relief, festivals, etc. They cost around $300, plus camera. See ads in QST, 73, or Ham Radio magazines. In some cities there are ham TV repeaters. The only restrictions are that ham TV must be strictly non-commercial (re-transmitting commercial TV is out) and hams aren't allowed to transmit music, for similar reasons. A tech license is not that hard to get - multiple choice technical exam, very easy code test. I got my tech when I was 13. 2) You can get an experimental license from FCC if you qualify. I believe John Nagle at Stanford, who is often on the net, (jbn@glacier.UUCP) has one for his robotics work. -- Michael Butts, Research Engineer KC7IT 503-626-1302 Mentor Graphics Corp., 8500 SW Creekside Place, Beaverton, OR 97005 ...!{sequent,tessi,apollo}!mntgfx!mbutts OR mbutts@pdx.MENTOR.COM Opinions are my own, not necessarily those of Mentor Graphics Corp.
Ploni.Almoni@mailcom.FIDONET.ORG (Ploni Almoni) (06/03/89)
> don't however. look for them in Radio Shark
Ektually, RS DOES sell the gadget you need - it's called a "Rabbit" and
works on infra-red -- no license, no hassle (my cousin the FCC inspector
says that it solves a lot of problems).
Cousin Charlie also sez that those who use MATV amps, modulators, etc.
get caught quite readily, since all the neighbors ALSO pick up the
signal, and if you want to go 2000 feet, that's a real hefty signal!
They busted a well-known radio engineer in the South Bay for doing just
that (by "accident" of course) and the penalty was $2000 , installments
accepted but no credit cards.
And of course we (me and thee) assumed that the original inquiry was for
extending broadcast TV -- probably not so. If for hobby, ATV is ideal,
and if for business use, several manufacturers make neat 22 GHz systems
including camera etc. just for that purpose -- used for security, etc.
Several manufacturers of "modulators" have had their goods seized and
forfeited for "home use". Not a pleasant thought.
Peace. -=Ploni=-
--
Via apple!mailcom, Fido 1:204/444thomas@mvac23.UUCP (Thomas Lapp) (06/03/89)
> sending unit (sorry, no around-the-corner operation :-). Don't forget > to be sure that the polarization of the two antennae are the same (both > vertical or both horizontal). Whatever the VCR is tuned to, or what I'd tend to make the polorization vertical, since most regular (legal) signals are horizontally polorized. Same disclaimer below applies to this response: > And now for the real DISCLAIMER: > I've never done this myself and probably would look for an alternative > (read legal) method if I wanted to extend my tv signal. - tom ============================================================================== uucp: ...!udel!mvac23!thomas ! Internet: mvac23!thomas@udel.edu Location: Newark, DE, USA ! or mvac23%thomas@udel.edu ==============================================================================
nagle@well.UUCP (John Nagle) (06/04/89)
>In article <190700040@trsvax> bb@trsvax.UUCP writes: >> >>I am interested in transmitting a TV RF signal over a distance of at least >>2000 feet. I realize I will probably need some kind of FCC license. Does >>the FCC grant licenses to send a TV signal of that strength? What is the >>size, cost, weight, and wattage that I am looking at to send 2000 feet? >>Has anybody out there (such as robotics types) tackled the same problem? I have a setup on my bench doing exactly this. But it is nontrivial. I'm using an FM TV transmitter running on 1.245GHz, with a power of 50mW. The equipment is a Wood and Douglass 1240TVT modulator, and the receiver is a Wyman Research WR-FM4912R. The receiver is front-ended with a GaAs RF preamp. Antennas are drooped verticals. An external preemphasis unit is used at the transmitter. I also have a 5W linear amp from Wyman, but it has never worked. I'm licenced to operate this as an experimental station under Part 5, as KA2XXF. Such licences are straightforward to get for research purposes, and cost nothing, although the paperwork is something of a nusance and it takes several months for frequency coordination. At low power levels, though, the FCC will generally grant an experimental licence. See 47 CFR 5 for the regulations. Alternatively, a ham licence will allow this operation, and under fewer restrictions. Overall results are mixed. It's definitely good enough for manually driving a robot by remote control. But reflection nulls are frequent, so as the transmitter moves, the image wavers. What's needed is a pair of receivers and a diversity switch. It would also help to use a circularly polarized antenna. The Wyman gear suffers from poor linearity in the video section, and this translates into distortion of the grey scale in the video transmission. There is also cross-coupling from the audio section into the video in the receiver, but it's in the audio amp for the speaker in the receiver, so if you don't use the internal speaker, this problem can be avoided. The audio channel is good from about 100hZ to 20KHz (with significant attenuation above 10KHz), so it could be used for data. The audio subcarrier is FM, mixed with the video. The RF system is all FM, so noise isn't a a problem as long as you have enough signal strength for capture. The gear at the transmitting end is small. The modulator is about 1"x4"x6", the preemphasis unit is about 2"x3"x1", and the linear amp is about 3"x3"x3", including heat sink. Everything runs on 12v DC. John Nagle John Nagle