Wbob-tv is on the air!

[ohohyodafarted]

Hi Jerome,

Is there some sort of amplifier that I can feed with the output of my combiner, that would allow me to broadcast over the air, my chanels 3,6,8,10,and 12 so that I dont have to hard wire cable to each of my sets?

And what kind of amplifier would it be and what sort of antenna do I pump the amplifier into?

[old_tv_nut]

Originally Posted by ohohyodafarted

Hi Jerome,

Is there some sort of amplifier that I can feed with the output of my combiner, that would allow me to broadcast over the air, my chanels 3,6,8,10,and 12 so that I dont have to hard wire cable to each of my sets?

And what kind of amplifier would it be and what sort of antenna do I pump the amplifier into?

NOTE: Unlicensed broadcast is not legal in the TV band in the US. Low power AM and FM radio-band transmitters are legal and work for some short-range purposes, because the band width is smaller and a radio receiver can get by on lower signals. FM adapters for auxiliary devices in cars (cassette, satellite radio) work this way. Also, the 'Mister Microphone" toy, if you remember that.

http://en.wikipedia.org/wiki/Part_15_(FCC_rules)

[Phil Nelson]

Ramsey has been selling a low power VHF TV transmitter kit for years.

http://cgi.ebay.com/Ramsey-TV6C-VHF-...QQcmdZViewItem

Also available from amazon.com, etc.

I built one over 10 years ago and was not very impressed with its performance.

You can also buy a "video sender" which broadcasts on a different frequency. Only rub there is that you need to buy a receiver for each of your vintage TVs, or swap the receiver around as needed. I have one of those, as well, and again, was not impressed with the range or signal quality, although it was definitely better than the Ramsey kit.

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html

[jhalphen]

Hi Bob, Gentlemen,

Basically i am a lazy guy, i.e. i have never relished tuning RF PA input & output circuits to operate on one frequency. In the 1980s i discovered there were wonderful products: Class A linear wideband amplifiers which would amplify from DC to 500 Mhz, 1 GHz or more with no tuning, so i adopted a "black box" gain block approach. Been doing this ever since.

Now Bob, to come back to your question, since your modulators are in the VHF band, an amp with an upper limit of 250 to 300 MHz is all you need. The good news is that these models are also cheaper than the multi-GHz models.

Typical modulators put out a fairly powerful signal to feed a TV antenna input but not enough to efficiently drive an RF Power Amplifier (PA) so you are going to need several gain blocks.

If amplifying from a typical TV modulator (Broadcast quality) i will typically use a first amp with 15-20 dB gain, then another, then a final PA with +27dBm output (1/2 Watts RF) or +30 dBm (1 watt) into 50 Ohms normalized RF Load.

You can browse the E-Bay RF amp section to get an idea of the products available:

http://business.listings.ebay.com/Pa...istingItemList

And if you give me your E-Mail address by PM, i can send you my photo/pdf data sheet library of suitable elements i've built up over time.

i've used a lot of Mini-Circuits products:

http://www.minicircuits.com/

And also Avantek devices, now defunct but readily available in the Used Market, great products with often MIL specs characteristics.

To Phil (Hi Phil! & Best Wishes for 2009)

Ramsey products SUCK!
I built their Ch-6 TV transmitter kit and the performance is abysmally low - avoid at all cost, a total loss of money.

If you want to buy a ready-made GOOD product, try this Greek, yes Greek company. I discovered them 6 years ago, and their transmitters are indisguishable on-screen from regular TV transmissions, and yes the transmitter works in NTSC/3.58/525/60 VHF & UHF - 100 mW RF out

http://www.aspisys.com/tvpll.htm

* i have no ties to the Co.

I should know: I run 40+ 1 inch to 5 inch small-screen TVs (Sony-Panasonic-Sharp) on their whip antennas and the TVs look like they are receiving WABC from across the Atlantic.

Originally Posted by ohohyodafarted

NOTE: Unlicensed broadcast is not legal in the TV band in the US. Low power AM and FM radio-band transmitters are legal and work for some short-range purposes, because the band width is smaller and a radio receiver can get by on lower signals. FM adapters for auxiliary devices in cars (cassette, satellite radio) work this way. Also, the 'Mister Microphone" toy, if you remember that

OK, i will be blunt: just do it! 35 years of tinkering with AM, FM, TV & Wi-Fi transmissions have taught me that:

- If you don't pollute neighbors reception nor a legit transmitter, "they"
couldn't care less !

Anyway, the FCC is now a shadow of the power they had in the 60s-70s so fight back, feed your vintage TVs with a decent analog signal & Amen.

Best Regards

jhalphen
Paris/France

[John Pinckney]

Jerome,

TVDX does take on new meaning! Like, "Digital means being able to see the tramsmitting antenna from your receiving antenna , but not being able to decode the data!"

Yes, I've seen the TVDX pics on asssorted websites. But, whether it's packet collisions (Ruins VSB-8/ATSC) or pulse interference (Ruins COFDM which DVB-T uses), not to mention the pending switchover here in the U.S., I think we're all going to be saying, "It wasn't broke, was it???"

Also, Jerome, I don'y know about elsewhere in the world, but in the U.S., there are already universities which have scaled-back or completely dropped RF from their EE programs. So, as for your question about RF Engineers, I think we're literally dying off! Or, is it going to all-zeroes in this digital age?

Best...

John