Funny. I was just reviewing the Part 15 Regulations which clearly state that low power is NOT allowed on VHF TV frequencies, and I remember two years ago asking Ramsey about a VHF LP transmitter in an old catalog, and they told me it was discontinued because of the rules. That all made sense.
Now I have a freshly printed Ramsey Catalog and the VHF TV Transmitter is back (page 73) under part # TV6C AC125.
I’m going to do a Wiki search under the subject “reality.”
Blast from the Past
I have a 1995 Popular Electronics magazine that has complete details and PCB layout for that item. Looks simple enough to build.
Seems to be mostly common items except for the 4.5 mHz transformer for the audio carrier.
Ramsey Catalog – micro power tv
The reason the TV transmitter is back in the catalog is for “export only”. These devices are illegal to sell to folks who are going to, or have the potential to, operate them in the U.S. The rules for legal video transmission are very naroow and strictly enforced. Micro power TV transmissions, or any TV transmissions, requires a license in the U.S.
And then there’s the receiving
I might be a bit urban-centric here, but how many folks still get OTA TV? And the few that do are using the new digital broadcast standard so, well, gosh – it seems pretty unlikely anyone would tune in.
Die Harder
I had cable 30 years ago for about 4 years and went back to roof top and rabbit ears antennas. Couldn’t see paying all that money to watch local stations.
I have a 19″ and 32″ LCD digital TV and one analog CRT TV on a converter box. I looked at my neighbors brand new 42″ LCD digital TV on standard cable. Doesn’t hold a candle to my OTA reception. I hear if you have the digital cable box it gets better. Oh wait, my other neighbor has one and the digital artifacts are very clear.
True, I don’t get all the “premium” channels but I just don’t watch that much TV anyway.
As for good ole analog TV signals, we still have two low power UHF stations in the area so analog isn’t completely gone yet. And of course in the spirit of home broadcasting, my TV channel 3/4 modulator put’s me on air all over the house.
At One time The FCC allowed
At One time The FCC allowed Part 15 Television.
However that was ended because of inappropriate material being aired over it. i.e Porn
Wow
That’s interesting Part 15 history. I’m glad you told about it, I hadn’t heard.
TV on the 900 MHz Band
I have a unit somewhere in my junk box which is a part 15 device for TV transmission in the 900 MHz band. I think it is called a “Rabbit” and consists of two boxes, one a transmitter and the other a receiver (actually a down converter). I used to use it to transmit VCR video to a remote TV and it worked pretty well. It covered my home well.
Though this did not use the broadcast TV frequencies it was part 15 TV and I don’t know if it is still legal.
Neil
Part 15 for 900 mHz
These rules are dated 10-1-97, so I need to check for updates, but for starters:
15.243 890-940 mHz Restricted to material measuring devices;
15.245 902 – 928 mHz Limited to intentional radiators used in field disturbance sensors;
15.247 902 – 928 mHz Limited to frequency hopping & certain spread spectrum intentional radiators;
15.249 902-928 mHz The field strength of emissions from intentional radiators shall comply with fundamental power 50-millivolts/meter
No other sections seem to mention the 900 mHz band, so it appears the Rabbit was a 15.249 device.
Revised Yesterday
Here is the updated 15.249
http://www.hallikainen.com/FccRules/2010/15/249/
And the amazing thing is it was updated YESTERDAY.
But The power level and authorization look the same, so maybe you can find the revised part.
Rabbit VCR Multiplying System
I also have a Rabbit. Mine is from Radio Shack, but they were also available from several other sources. The transmitter works in the 902-928 MHz band. The output power is about 8 mW. Transmission between the transmitter and receiver is not by antenna, but via twin-lead; so, it is not really a “wireless” system. The output is a normal NTSC analog television signal.
The current Part 15 rules do not seem to permit transmitting a television signal in the 902 to 928 MHz band. The transmission line from the transmitter to the receiver is not shielded, and so the twin lead probably does not make the Rabbit system legal.
My Rabbit is not a Rabbit After All
Ermi’s post made me wonder so I retrieved my “Rabbit” from the junk pile and it is not a Rabbit. It is a Gemini Videocaster and both the transmitter and receiver use whip antennas and not twin lead. The transmitter accepts video and audio input via RCA phono jacks. The transmitter FCC ID is EUY-VC2000 (not in the FCC ID search database) and I realize that this alone does not make operation legal since the rules may have changed since it was manufactured and sold. I believe I purchased this in about 1996 from a regional General Store (The Anderson’s).
I measured the output frequency to be 910.464 MHz on one of the three provided channels so it does use the 900 MHz band.
Neil
If it is not a Rabbit, it is
If it is not a Rabbit, it is a relative. All of the Rabbits came from Gemini.
TV Genie
This thread reminded me of a neat little black box I cherish, with a little history, called the TV Genie, made perhaps in the 70s by Orion Industries Las Vegas, NV. As I recall it was heavily advertised at the time, but, as the story was told to me, the FCC didn’t approve of it and seized all unsold inventory.
I am aware that other threads have talked about this unit, but here is a good place for some nostalgia. It transmits on UHF TV Channel 14, which in about 1973 was re-assigned to land mobile. It transmits an amazingly sharp video image, but the audio did not have the pre-emphasis needed for clear sound.
I designed a pre-emphasis circuit and installed it, but as a proper Part 15 operator, it never gets used.
Whoever made it was a TV genius.