Help with RF-modulator needed...

Zeela · Post by **Zeela** » Tue Nov 30, 2004 1:47 am

Hi,

I just gotten a RF-modulator for my VIC. It's a UK one and I live in Sweden. When I try it out, I can't get the sound to work, but the picture is acceptable, if not perfect.

Someone suggested that it might some difference in the PAL format used in Sweden and the one used in the UK. Could that be what's wrong with my modulator or is it just broken?

// Zee

carlsson · Post by **carlsson** » Tue Nov 30, 2004 7:44 am

Yes. PAL exists in at least B, G, H, I, D, N and M subversions. I believe the UK uses PAL-I while Sweden uses PAL-B. The difference is on video bandwidth and sound carrier.

http://www.alkenmrs.com/video/standards.html
http://www.hamlet.co.uk/support/apps/Wo ... ndards.htm

Last time I visted Clas Ohlsson, I saw that they have a generic RF modulator which takes composite video and outputs the RF on your frequency of choice. I don't know if and how it works, but it sounds interesting?

Zeela · Post by **Zeela** » Tue Nov 30, 2004 8:15 am

Darn...

No more RF-modulators from the UK then... I just got one for my Amiga as well...

// Zee

Post by **Jeff-20** » Tue Nov 30, 2004 6:33 pm

carlsson wrote:Last time I visted Clas Ohlsson, I saw that they have a generic RF modulator which takes composite video and outputs the RF on your frequency of choice. I don't know if and how it works, but it sounds interesting?

Is that possible? I don't understand how that is possible.

Bacon · Post by **Bacon** » Wed Dec 01, 2004 2:14 am

Jeff-20 wrote:
carlsson wrote:Last time I visted Clas Ohlsson, I saw that they have a generic RF modulator which takes composite video and outputs the RF on your frequency of choice. I don't know if and how it works, but it sounds interesting?
Is that possible? I don't understand how that is possible.

Going out on a limb here, but isn't an RF signal just the composite signal modulating a carrier wave (the same principle as in FM radio)? In that case, it should just be a matter of changing the frequency of the oscillator generating the carrier.[1]

Right?

[1] It's been 15 years since I took electronics classes. I slept through many of them.

Boray · Post by **Boray** » Wed Dec 01, 2004 6:53 am

Cool! I have to check that rf modulator out! And of course it's possible - most video recorders can do that...

/Anders

Boray · Post by **Boray** » Wed Dec 01, 2004 7:11 am

From Scart to RF for 298 SEK.... Maybe a bit expensive...

carlsson · Post by **carlsson** » Wed Dec 01, 2004 11:03 am

Universal SCART to RF modulator : 298 SEK
Collection of nice games to play: 500 SEK
The joy of playing VIC-20 on your TV again: priceless!

(inspired by the credit card commercial)

Post by **Jeff-20** » Wed Dec 01, 2004 10:50 pm

Boray wrote:of course it's possible - most video recorders can do that...

/Anders

ok, now that I think about it, it makes sense.

Leeeeee · Post by **Leeeeee** » Wed Dec 01, 2004 10:56 pm

[quote]Going out on a limb here, but isn't an RF signal just the composite signal modulating a carrier wave (the same principle as in FM radio)? In that case, it should just be a matter of changing the frequency of the oscillator generating the carrier.

Right?[quote]

Right. In most modulators there is a separate sound subcarrier oscillator that runs at 6MHz for the UK and 5.5MHz for most of the rest of the world. The adjustment for this is usually hidden inside the can and covered in soft wax to disuade you from adjusting it.

To adjust the UK modulators you have tune in the picture on your TV then (after opening and removing wax as needed) adjust the sound oscillator (probably clockwise and not by much) until the sound quiets. Make a note of this point. Now carry on until the sound becomes noisy as before then come back again until the sound quiets, make a note of this point. If the two points were different set the modulator to about center between the two.

One thing to note is that this should be done with AFC or AFT on the TV turned off.

Zeela the Amiga modulator, which uses an Aztec RF modulator can certainly be re-tuned. I don't recall the original Vic modulator but suspect that can easily be re-tuned as well.

Cheers,

Lee.

Boray · Post by **Boray** » Thu Dec 02, 2004 10:04 am

carlsson wrote:Universal SCART to RF modulator : 298 SEK
Collection of nice games to play: 500 SEK
The joy of playing VIC-20 on your TV again: priceless!

(inspired by the credit card commercial)

Yes, but as you need to make a vic->scart cable anyway.... TVs that doesn't have any AV input must be as old as the vic20 by now... We don't have any color TV without an AV connection....

/Anders

carlsson · Post by **carlsson** » Thu Dec 02, 2004 12:07 pm

Bah. What about nostalgia, brownish white and superfluous blur?