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  #1  
Old 07-26-2014, 03:45 PM
MarioMania MarioMania is offline
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VCR as a VHF TV Transmitter

How strong are the modulator in the VCR's?

Any old VCR's have a Ch 2 Option on it?

200 ft is my Max
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  #2  
Old 07-27-2014, 10:24 PM
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old_tv_nut old_tv_nut is offline
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Quote:
Originally Posted by MarioMania View Post
How strong are the modulator in the VCR's?

Any old VCR's have a Ch 2 Option on it?

200 ft is my Max
1) not very strong - a few millivolts into 75 ohms
2) never heard of a channel 2 option, but I don't know
3) do you mean you want to broadcast 200 feet to a receiver?
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Old 07-27-2014, 10:33 PM
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I read that the signal from a VCR with rabbit ears will only reach a few feet. Would be interesting to know if they could be modded to output on other channels though for a hard-wired setup. I reckon a distribution amplifier would help with a wireless setup, but that just wouldn't be feasible.
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Last edited by Jon A.; 07-27-2014 at 10:37 PM.
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  #4  
Old 07-27-2014, 10:44 PM
MarioMania MarioMania is offline
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I'm just going to get a Blonder Tongue RF Modulator the one you can select your channel

Can I hook up a TV VHF Antanna to it?
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  #5  
Old 07-27-2014, 10:55 PM
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Quote:
Originally Posted by Jon A. View Post
I read that the signal from a VCR with rabbit ears will only reach a few feet. Would be interesting to know if they could be modded to output on other channels though for a hard-wired setup. I reckon a distribution amplifier would help with a wireless setup, but that just wouldn't be feasible.
The simple analog ch 3/4 units could probably be modded by changing a crystal, but you might not get full modulation depth if you go too high in frequency.

My Dish TV satellite box has an analog output that can be set to any UHF channel; obviously contains a synthesizer/modulator that can handle the high frequencies without stray leakage around the modulator element.
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Old 07-27-2014, 11:02 PM
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Too bad about those modulators that are set at the factory to a certain channel, lots of searching and waiting involved if you want to cover multiple channels with different video devices. Having a bunch of selectable units would just be an unnecessary expense.
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Old 07-28-2014, 02:34 AM
MarioMania MarioMania is offline
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Well I'm going to use it for my Pocket TV's like my Casio and my Sony

Besides I like the VHF Channels, Mainly Ch. 2, 3 and 4
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  #8  
Old 08-03-2014, 11:38 AM
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Phil Nelson Phil Nelson is offline
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Originally Posted by MarioMania View Post
I'm just going to get a Blonder Tongue RF Modulator the one you can select your channel
Can I hook up a TV VHF Antanna to it?
Yes, this article describes what you are talking about: a Blonder-Tongue agile modulator using a TV rabbit ear antenna to transmit:

http://antiqueradio.org/HomeTVTransmitter.htm

Easy to hook up and it works well.

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

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  #9  
Old 08-17-2014, 02:45 AM
centralradio centralradio is offline
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I remember I seen some mods online somewhere to boost up the VCR RF modulator but got to watch those.They probably pushing over the limits and get in trouble over it.

I have a Ramsey TV6 and it only goes 60 to 100ft if I'm lucky.

I picked up a UHF unit on channel 14 for about $30 bucks ant it does the same distance as the Ramsey kit goes.
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Old 08-17-2014, 09:28 PM
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wa2ise wa2ise is offline
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Quote:
Originally Posted by old_tv_nut View Post
The simple analog ch 3/4 units could probably be modded by changing a crystal,...
I've done it. Some VCR TV modulators get the carrier frequency from the tuner circuit's reference frequency, but the ones useful to us usually use a small SAW resonator. These look like a small flat metal rectangle. Remove it carefully (to not damage the circuit board traces). The pinout is usually 4 pins in a row, a drive pin, ground, then the last two pins are for channel 3 and 4 (I don't remember which order). I've used a 18.432MHz crystal (a small one about 1cm tall and 2/10 inch pin spacing for the leads) to replace it. It will run at 3 times that frequency, which is close to channel 2's. One lead goes to the driver, and the other one feeds one of the connections for channel 3 or 4. Then tune the TV to channel 2 and play with the ch 3/4 switch to see which way it needs to be to get a signal.

See if you can read the chip number off the modulator chip. and maybe you can find a data sheet, try http://www.digchip.com/. Googling it will likely give you dead leads, as various Chinese web sites fool the Google spiders into thinking datasheets exist at their web sites. If you luck out and find a data sheet, it should have a sample circuit that will show the video carrier and sound carrier output pins, and then you can trace out the circuit in your VCR modulator. They usually have attenuation resistors from each output feeding another resistor to ground, remove the to ground resistor, and strap resistors 1/10 the ohms across the other two, this should make the output stronger. If it's surface mount, I've salvaged resistors off junk boards (easy if you use a pair of soldering irons, one tip per end of the resistor to melt both solder joints), and in this case it's easiest to just stack the new resistor atop the old one and solder it down. This for the bigger ones, like 1/10 inch long, forget the modern micro ones...
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Old 08-19-2014, 06:28 PM
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Phil Nelson Phil Nelson is offline
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I would give a thumbs down to the Ramsey kit. I built one years ago and it was awful, compared to a Blonder-Tongue agile modulator. If you watch on eBay, you can find a reasonably priced B-T unit (and usually some very overpriced, ones, too).

Phil Nelson
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  #12  
Old 08-19-2014, 11:59 PM
centralradio centralradio is offline
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Quote:
Originally Posted by Phil Nelson View Post
I would give a thumbs down to the Ramsey kit. I built one years ago and it was awful, compared to a Blonder-Tongue agile modulator. If you watch on eBay, you can find a reasonably priced B-T unit (and usually some very overpriced, ones, too).

Phil Nelson
I agree.The TV6 is a piece of shieeze.I would like to get a B-T setup.
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  #13  
Old 08-21-2014, 08:53 AM
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dtvmcdonald dtvmcdonald is offline
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Channel 2, at LEAST 1/4 mile or nearest FCC inspector,
$35

http://www.ebay.com/itm/Audio-Video-...item4185c6ea12
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  #14  
Old 08-24-2014, 02:38 PM
Dude111 Dude111 is offline
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Since no one watches the analogue channels anymore it would be interesting to put a 5 watt transmitter on say channel 2 or 3 and see how far you could get one night
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  #15  
Old 08-25-2014, 01:38 AM
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Quote:
Originally Posted by Dude111 View Post
Since no one watches the analogue channels anymore it would be interesting to put a 5 watt transmitter on say channel 2 or 3 and see how far you could get one night
I've considered trying to make as strong of a booster as I can, and doing that.
I even modified an old test pattern to use by adding the call letters WTFt, and a jab at DTV to it. I thought it could be fun on some future April fools day to crank it up and transmit some stuff that files in the face of the ever diminishing profanity standards of the FCC ....Comedies that contain the F-word, and maybe some porn.
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