Wbob-tv is on the air!

[ohohyodafarted]

Well, I finally got around to putting it all together, and it works great. AThe shut down of analog NTSC is not going to silence my tv's

WBOB is transmitting on VHF chanels 3,6,8,10, and 12. The front end is 4 Magnovox Digital to Analog converters and one DVD player. They feed 5 Holland modulators which feed into a 12 input Holland combiner. Output is sent via wire to my sets. Signal is strong and clear.

I still need to put up an antenna to feed the D to A converter boxes, but at least it is functioning and most of the hard work is already done.

I welded up a small equipment rack frame and designed the whole mess to mount with a couple of lag screws to the wall.

When completely finished, each converterwill be tuned to a local chanel and I will be able to use the tuners in my tv's to switch from chanel to chanel and even select the dvd player, which will be transmitting on chanel 8 (DVD player is not shown in photos)

What sort of work arounds have other AK members dreamed up to keep their old sets fed with signals?

Bob

[newhallone]

My plan is to get one of these media players with a terabyte or more and shoot the signal throughout the house. I have not checked into it but it would be great if the remote for the thing was RF. We used to have a satellite dish receiver that had a rf remote and you could use it anywhere in the house. Here is a link to one.

http://www.popcornhour.com/onlinestore/

[zenithfan1]

Looks great Bob! I remember when we had a lengthy conversation on this subject, now I need to build mine too! Great work!!

[AUdubon5425]

Nice!

I would like to set up something similar for testing and just for kicks - one channel would be fine for me. Looks like I'll have another project on the list for this year.

[old_tv_nut]

Nice!

[Phil Nelson]

I see a new cottage industry in your future -- building these units for other TV collectors

Phil Nelson

[Hemingray]

Mine is two dish boxes, and a DTV convertor, however I'm on channels 3, 31, 54 and 60.

[ohohyodafarted]

I kept to the vhf spectrum because most of the old sets I collect do not have a UHF tuner.

[jhalphen]

Hi Guys!

My solution to End-of-Analog, scheduled for 2011 OTA SECAM L norm is personal transmitters.

I currently run:
- 2 x NTSC, VHF, Ch-3 & Ch-12
- 1 x PAL B/G, VHF, Channel E-12

& occasionally
- SECAM L France, VHF
- UK, PAL/I, UHF, Ch-30 something.

All are home-built, 100 mW into the antenna.

If the government sells off the frequencies i will either:
- Move all to VHF Band I (35-60 MHz) abandonned here
or
- Pump Watts into the PA's!

Have stocked up on wideband +30dBm/1 Watt RF power modules, "just in case".

Advantages:
- No coax all over the place to feed numerous TVs
- Use TVs with "Rabbit Ears" (easy)
- Non-broadcast modulators are DSB (Double SideBand) NOT Vestigial SideBand like Broadcast transmitters, therefore channels must be spaced wide apart and there is always a risk of interference because of harmonics.

US Solution: When NTSC goes dead, cable networks will offload Pro-Modulators by the truckload, so there will be good deals to be made.

Just FYI, over here we currently receive 18 free OTA channels encoded in MPEG-2/625/50/i it's called TNT! not meaning dynamite but "Television Numerique Terrestre" (Terrestrial Digital Television)

5 additional channels are encrypted and require a subscription + smartCard.

HD terrestrial started Oct 1st. It is encoded in MPEG-4 which allows transmitting an HD channel using the same bandwith as MPEG-2/625. The standard adopted is 1080i/50. So far, 4 channels are broadcasting Free to Air.

TNT tuners are available from 30 Euros (35 Bucks) to 300 Euros.
30 Euros gets you a basic tuner. All have composite video out + RGB which we use with the 21 pin SCART plug, a requirement since 1980.

For 60 Euros, you get 2 tuners, watch one channel, record another.

For 130 Euros, the same + a Hard Disk for recording, also a slot for memory card recording.

For 200 Euros, you get an HD Tuner + 625 tuner.

For 300 Euros, the same + HDD/SmartCard recording.

My experience: i have 5 TNT tuners, first of which in service May 2005 when experimental programs started. All have the sensitivity of a crystal set "Hello! where have all the good RF Engineers gone".

I'm slap-bang in the heart of metro Paris with the Eiffel Tower transmitter 5 miles away and on certain Multiplex frequencies (8 channels together) reception is touchy. No DX-TV for sure with these tuners...

Such is the status of the market in France as of Jan 2009.

Best Regards

jhalphen
Paris/France

[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