Ramsey VHF TV Transmitter

[jimbofish]

Came across this from a reference in AK to something else.

http://www.ramseyelectronics.com/Ram...&searchSize=12

As I understand it, it's supposed to re-broadcast a video and audio signal on VHF channels 2-6. This sounds like just what I need to take an old portable TV out to the garage. I'm assuming it's using analog channels, not digital.

Anyone use or know about these? For $20 + s&h it seems too good to be any good.

[old_tv_nut]

There's an old review on youtube showing poor results. I personally don't know anything about this unit.

[jr_tech]

Only one review on Amazon:
http://www.amazon.com/Ramsey-VHF-TV-...tv+transmitter
not affiliated,
jr

[old_tv_nut]

Radio Shack sells one for under $30, settable to channel 3 or 4, that works OK when wired directly to the TV, but I suspect it's not powerful enough to broadcast through your home.

http://www.radioshack.com/product/in...ductId=2103095

[Phil Nelson]

I built one of the Ramsey TV transmitters years ago. It was just awful. I couldn't recommend it to anyone.

A much better solution is a surplus agile modulator, described in this article:

http://antiqueradio.org/HomeTVTransmitter.htm

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

[W3XWT]

If it isn't running on three-phase 4160 VAC, it's only QRP!

[DavGoodlin]

Originally Posted by W3XWT

If it isn't running on three-phase 4160 VAC, it's only QRP!

Makes sense that a commercial TV transmitter would operate on that, because some of the UHF channels are close to 1 megawatt, like one locally. That is at least 138 amps needed on 4160v 3p for 1 MW.

[old_tv_nut]

Originally Posted by DavGoodlin

Makes sense that a commercial TV transmitter would operate on that, because some of the UHF channels are close to 1 megawatt, like one locally. That is at least 138 amps needed on 4160v 3p for 1 MW.

Well, not quite - 1 MW is the ERP including the antenna gain. Actual transmitter output is probably around ten times less, because the power needs to be projected to the horizon, and not straight up or down..

http://harrisbroadcast.com/products/...itters/powercd

[wa2ise]

Ramsey kits were never known for quality...

[W3XWT]

Originally Posted by DavGoodlin

Makes sense that a commercial TV transmitter would operate on that, because some of the UHF channels are close to 1 megawatt, like one locally. That is at least 138 amps needed on 4160v 3p for 1 MW.

I remember tangling with a Gates BT-220U that was nothing short of awesome. At 220KW of output power. it was like the closest I'll ever come to one of the legendary AM rigs of XER, XERA, etc., that Dr. John Brinkley (and the Mexican government) used for nose thumbing the FCC. That transmitter was almost like a living being with various pieces moving around and such. Some of the panels had gaps so wide you could see into critical areas of the thing. Yes, this was pre-OSHA.

Both NEC and RCA also produced 220KW rigs. Alas, either the Gates rig at WDCA-TV in D.C. and/or the RCA at WTAF-TV in Philly ended-up cooking the only engineer I'd ever know who could tame them: Elizabeth Bartch. God rest your soul, Liz. The smile in your eyes is still missed.

[jimbofish]

Originally Posted by Phil Nelson

I built one of the Ramsey TV transmitters years ago. It was just awful. I couldn't recommend it to anyone.

A much better solution is a surplus agile modulator, described in this article:

http://antiqueradio.org/HomeTVTransmitter.htm

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

Thanks to all. Sounds like it was a good idea to ask here first. I'll pass on the Ramsey stuff.

Am I correct in presuming that an RF output can be transmitted by connecting an antenna?

I have some RF modulators and an RF amplifier laying around. May be time for some experimenting.

[Phil Nelson]

You are correct. In the article that I mentioned earlier, it shows that you connect an antenna to the RF OUT terminal of the agile modulator.

Phil Nelson

[jimbofish]

Couple questions about the agile modulators...

What's the difference between the one mentioned in the article, Blonder-Tongue model AM60-550A, and this type, :Blonder Tongue CAMS-60 Channelized Agile Modulator?

Are the output 'channels' standard broadcast channels or CATV or something else? Want to be sure the TV I'd use can receive them.

[bandersen]

Product description for the CAMS-60 says in part:

"Works in Conjunction with High Performance Channelized Output Filter Modules (OFM)"

"This design configuration permits easy channel changes in the field by simply replacing the output filter module and setting the output converts dip switches to the new channel."

So it sounds to me like there's an extra filter module required that matches your broadcast channel.