Thought about this (for those with lots of sets)

[jpdylon]

I always hate having to connect each set up that I want to watch in and out of rotation. I saw this cool VHF transmitter kit, and thought "why the hell not?"

Anybody else think of doing something like this?

[roundscreen]

Jpdylon.
Yes I am and thanks for the tip. This will be a great thing to have when they turn off ntsc in 2009. I am about an hour away and have a good friend in rochester that knows the roads in victor. The other stuff thay have looks interesting too.

ED

[kx250rider]

Thanks for mentioning this... We all will need some way of using the old sets, and I personally don't want some kind of high-tech digital decoder stuffed between the legs of my Zenith roundie with all kinds of LEDs shining. With a whole-house transmitter, maybe even 2 or 3 of them set up to repeat local channels, it would be like nothing ever changed

Charles

[Adam]

"maybe even 2 or 3 of them set up to repeat local channels, it would be like nothing ever changed"

I like that idea, with that I could still use the remote on my remote sets for something other than just watching the dial turn.

[tgunner]

Looks easy enought to build one yourself. Anyone try finding just the circuit diagram for a VHF transmitter?

[Eric H]

Can you add an amp and broadcast to the entire nieghborhood?
Seriously though is this thing going to get you in trouble with the F.C.C. or is it below the level where it would be a problem.

[jpdylon]

with a range of 300 feet, i would assume its only a couple hundred mw or so. Thought it would be fun to broadcast, but I really don't want to pay the rediculous liscense fees, nor put up with being arrested for hosting a priate TV station.

would definitely be fun though.

[oldtvman]

with the new video compression technology, there is no reason why they can't run both technologies concurrently, they will probably go all uhf.

[Whirled One]

I've got a Ramsey TVT-1, which I guess must be one of Ramsey's early versions of this kit. [And yes, transmitting TV shows to my old TVs was indeed the application I had in mind with it! ] It wasn't very expensive-- I think it was about $12 or $13 (in kit form, without the plastic cabinet which was an optional extra at the time) when I got it over ten years ago. It's a fun li'l device for twelve bucks, but quality-wise I'd rate it as rather mediocre, which is especially apparent when using it with a color TV. The kit shown in that eBay auction appears to have a significantly more complex circuit than mine, so hopefully this indicates that it's improved considerably over the old TVT-1.

It's also more expensive than the old TVT-1, as far as that goes-- looking at Ramsey's web site, the TVT-6C is the current version, and it's available for $39.95 direct from them (same price as the one in that eBay auction). At least now they throw in the the matching plastic cabinet in the basic price of the kit though.
http://www.ramseyelectronics.com/cgi...ction&key=TV6C
Ramsey kits are available from various amateur radio and electronics dealers as well, so you might find it slightly cheaper (or more locally) elsewhere.

There are certainly other products out there besides the Ramsey kits, I might add; I found a few by Googe-ing for "VHF TV transmitter low-power", including products ranging from other no-license <= 100mW kits up to LPTV transmitters. ...Which makes me wonder if the FCC would even continue to issue LPTV licenses once analog TV goes off the air.

[kbmuri]

Found this article on the Ramsey. Has schematic and PCB layout. -k

http://www.web-ee.com/Schematics/TV_...VTransmitb.pdf

[kbmuri]

I splurged last week and bought one of the Ramsey kits from eBay.

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5701533417

Arrived just now (photo). I'll build it tonight. Evaluation to follow...

[kbmuri]

Parts is parts.

Went together pretty easy. It doesn't come with a power supply. Gotta scrounge for that...

[jpdylon]

IMPORTANT: I think the center connector has to be positive. I accidently connected one with a negative center tap and roasted my power regulators.

A note for those building:
I built one of these, and though assembly was easy fine tuning was not. I was also getting limited signal range and a hard time stabilizing the picture. Once you dial it in its ok, but my old sets have a hard time syncing with the signal sometimes.

[kbmuri]

Disturbing that nowhere in the manual does it give the polarity of the power supply. Looking at the schematic, it has both major electrolytics with their negative sides to ground -- that's the only clue. The large-area sections of foil on the PCB are ground, the P/S jack's housing is soldered to ground, so jpdylon's assertion that the jack's center is positive is correct.

I went to Radio Shack, another $20 added to the price tag of the transmitter for this: http://www.radioshack.com/product/in...ductId=2049714 . I snipped the end off of it and soldered the bare wires directly to the PCB, bypassing the plug. No confusion for later.

As jpdylon alluded to, I'm having a helluva time getting the thing tuned. Four separate adjustments that all interact with each other, sort of like trying to crack a 4-digit combination safe. Hopefully there's a combination that works, and hopefully it can be found!

[peverett]

I also have purchased this. I still have not gotten it tuned correctly either, but have not worked on it much yet. I purchased the power supply from Ramsey, which was only and adder of $12 or so and no worries about polarity.