Newbie question regarding picture quality...

[obsolete man]

Is there a common component we can pinpoint that is responsible for why a picture is clear versus a picture that has some static in it? I recently started getting a few old tvs, just due to nostalgia, not because of any technical knowledge. This was my set-up:

- Fire stick goes into...
- HDMI to RCA adapter...
- Then it goes to the RCA input off a RF Modulator..
- RF Modulator then goes out via coaxial...
- This coaxial goes into the 75 to 300 ohm VHF adapter...
- The adapter is then connected to the VHF terminals.

First tv I tested was a Zenith black and white from the late 70's. The picture came out perfect! Not a freckle! I call static freckles. LOL! The second TV is also a late 70's by Sharp. Both are small 9 inch tvs. But this Sharp TV required a lot of fiddling with all the knobs. The picture I get is okay, but I can see freckles/static. Actually, the picture the Sharp produced was closer to my expectations coming into this new hobby. Something that's decent with some static. But now the Zenith made me realized even old tvs can have crisp, clear pictures. It just blows away the Sharp picture. Do you guys have any recommendations what I can do? I exhausted all the available knobs on the Sharp, including the black ones in the back for vertical, horizontal, etc. Even on the VHF channel knob, there is an outer knob for fine tuning, and I messed with that as well. Could it be as simple as some component inside that's dusty that needs to be cleaned? How about an agile modulator that allows me to pick something else other than channels 3 or 4. Could that help picture quality? Please advise, thank you in advance.

[Graham G3ZVT]

Originally Posted by obsolete man

How about an agile modulator that allows me to pick something else other than channels 3 or 4. Could that help picture quality?.

I think that could be the answer.

The "snowy" picture might not be insufficient signal from your modulator, it might well be because there is a strong digital signal on each VHF channel you are trying, and they may be strong enough to interfere with your analog signal even without an antenna.
It may be that some of your sets fare better than others because of better front-end screening etc.

We use a different digital system in Europe, (and we only use UHF in the UK), but I suspect like our DVB-T, your ATSC system will look like snow when viewed on an analog set.

[obsolete man]

Originally Posted by rambo1152

I think that could be the answer.

The "snowy" picture might not be insufficient signal from your modulator, it might well be because there is a strong digital signal on each VHF channel you are trying, and they may be strong enough to interfere with your analog signal even without an antenna.
It may be that some of your sets fare better than others because of better front-end screening etc.

We use a different digital system in Europe, (and we only use UHF in the UK), but I suspect like our DVB-T, your ATSC system will look like snow when viewed on an analog set.

Wow! I was just throwing darts at the wall. Surprised that you think the agile modulator idea may work. I'll give this shot. Thank you.

[cheerfulcharlie]

Another problem might be that the modulator is probably the finest Chineseium and have a spec that some old sets might not tolerate so well.

So you could try an analog antenna distribution amp preferably an old pre-digital one ( used for feeding different rooms off the one antenna) some of these have a gain control you can twiddle around with to try and balance the signal. The modulator would feed into this then the outputs would feed the TVs.

[obsolete man]

Originally Posted by cheerfulcharlie

Another problem might be that the modulator is probably the finest Chineseium and have a spec that some old sets might not tolerate so well.

So you could try an analog antenna distribution amp preferably an old pre-digital one ( used for feeding different rooms off the one antenna) some of these have a gain control you can twiddle around with to try and balance the signal. The modulator would feed into this then the outputs would feed the TVs.

Can you show me what one looks like? Especially the pre-digital one? But if you can't find a pre-digital one, the newer ones could help as well?

[kan_turk]

Blonder Tongue AM series agile modulators are often offered on Ebay for reasonable money - these are professional quality units and most have a high level signal output which can be used to feed a passive splitter without further amplification

Rgds
John

[obsolete man]

Originally Posted by kan_turk

Blonder Tongue AM series agile modulators are often offered on Ebay for reasonable money - these are professional quality units and most have a high level signal output which can be used to feed a passive splitter without further amplification

Rgds
John

I'm looking at them on eBay, but I'm not sure how to use them. My current RF modulator has RCA composite inputs. How would I connect my source to those Blonder Tongue models?

[patrickgnl]

Originally Posted by rambo1152

I think that could be the answer.

The "snowy" picture might not be insufficient signal from your modulator, it might well be because there is a strong digital signal on each VHF channel you are trying, and they may be strong enough to interfere with your analog signal even without an antenna.
It may be that some of your sets fare better than others because of better front-end screening etc.

We use a different digital system in Europe, (and we only use UHF in the UK), but I suspect like our DVB-T, your ATSC system will look like snow when viewed on an analog set.

Actually you would be surprised.. the following pics show some results of mine in the UK using a UK digital tuner via HDMI and monitor. The black and white Sony is actually a US model so the picture has been converted…

I suspect a better modulator would improve thing further and possibly the newer the set, the more tolerant it would be…

A guy i was chatting to in the US definitely felt consumer modulators are much poorer than commercial ones. I suppose you get what you pay for..

Patrick

[simpsons]

Watching "Vintage" TV on early TV sets in the USA has quite a following and no less so than in LA.

For many, the technology itself is not so important as being able to demonstrate to others that it can be done and to make new friends through the hobby.

Because it has been some time since analogue TV has been switched off and replaced by digital, the reason why channels 3 or 4 can be chosen and or the different TV systems used around the world have "got lost in the either."

Your basic set up, as described, makes perfect sense and whilst the description "static" and "freckles" sound OK, it is worth remembering that it can be misleading to use such terms when trying to describe a fault.

For example, when a analogue TV set is switched on without an aerial, the freckles on the screen and noise from the speaker is in fact the noise generated by the circuits inside the TV. When connected to a signal stronger than the internal noise, the picture is free of the interference and, because the TV uses FM sound, the sound does not have a background of hiss.

Now, you say that the Zenith gave a good picture and sound which was not so with the other sets which it is said that the modulator you are using isn't good enough. This may be so or the channel 4 might be better than 3, but to prove the point, I would see the Zenith as your reference set.

Connect as you have and then tease out the 75 to 300 ohm adaptor so making the signal poorer. You should notice that picture starts to have black specks on the screen. This is noise from a weak signal. Note, the US analogue signal is negative modulation, hence black noise.

Now, with this in mind connect the other TV's and see what the picture is like. Black spots noise, white spots, something else.

A picture says a thousand words and so feel free to illustrate the pictures accordingly using the experience of the Zenith to get a feel of how the controls affect the picture.

Good Luck, my names Chris. What's yours.

[John123]

Originally Posted by rambo1152

it might well be because there is a strong digital signal on each VHF channel you are trying, and they may be strong enough to interfere with your analog signal even without an antenna.
It may be that some of your sets fare better than others because of better front-end screening etc.

This seems highly likely especially in a big city. This short comparison video is a good demonstration.

[cheerfulcharlie]

Originally Posted by obsolete man

Can you show me what one looks like? Especially the pre-digital one? But if you can't find a pre-digital one, the newer ones could help as well?

Being in the UK not that familiar with US equip, but this looks like it will do the job and being 'Radio Shack' it must be a few years old.

https://www.ebay.com/itm/14412213430...IAAOSwV6dg-L~e


If you look in the center you will see the gain control, and it looks like it has an FM blocker presumably to stop interference from radio transmissions. Looks like you will need some 'F plugs' (male) to connect it but they should be easy to obtain.



.

[kan_turk]

Originally Posted by obsolete man

I'm looking at them on eBay, but I'm not sure how to use them. My current RF modulator has RCA composite inputs. How would I connect my source to those Blonder Tongue models?

Video input is usually either BNC or ´F’ connector - adapters to RCA are readily available - audio input is usually RCA so no adapter needed
user manuals are available online

J

[simpsons]

I am sure that US ATSC digital TV uses UHF transmitters just as in the UK but unlike here, channel numbers shown on the TV don't. For example, as UHF transmission was phased in and VHF assigned to other services, the TV would show KVHD Ch3, the local station, when in fact UHF ch 60 was tuned. This was so the less technical could find their way around the new analogue UHF stations. This may be why a couple of UK posts refer to interference from existing high power Ch 3 transmitters.

As the Modulator you are using works well with the Zenith, personally, I would leave all alone and show screen shots of the other TV's. Buying new bits of kit in the hope of making another set better may not help.

Chris

[obsolete man]

Originally Posted by kan_turk

Video input is usually either BNC or ´F’ connector - adapters to RCA are readily available - audio input is usually RCA so no adapter needed
user manuals are available online

J

The more I'm looking into it, specifically the am60-550. I'm realizing people are using this to send signals instead of directly connecting the TVs? Is that right? So the TV would need a functioning antenna?

[obsolete man]

Originally Posted by simpsons

I am sure that US ATSC digital TV uses UHF transmitters just as in the UK but unlike here, channel numbers shown on the TV don't. For example, as UHF transmission was phased in and VHF assigned to other services, the TV would show KVHD Ch3, the local station, when in fact UHF ch 60 was tuned. This was so the less technical could find their way around the new analogue UHF stations. This may be why a couple of UK posts refer to interference from existing high power Ch 3 transmitters.

As the Modulator you are using works well with the Zenith, personally, I would leave all alone and show screen shots of the other TV's. Buying new bits of kit in the hope of making another set better may not help.

Chris

Thanks for the advice, I'll post some pictures as soon as I can. But I actually don't mind buying up some gear just to have. The current RF modulator I have was something I bought in the 1990's. And it wasn't for the RF feature, I don't even think I knew what that feature was when I got it. It was simply for the fact that it had four RCA inputs, and one output. Just used it to switch between devices. Fast forward two decades later, I'm now using the RF feature. LOL!

Brandon

[kan_turk]

Originally Posted by simpsons

I am sure that US ATSC digital TV uses UHF transmitters just as in the UK but unlike here, channel numbers shown on the TV don't. For example, as UHF transmission was phased in and VHF assigned to other services, the TV would show KVHD Ch3, the local station, when in fact UHF ch 60 was tuned. This was so the less technical could find their way around the new analogue UHF stations. This may be why a couple of UK posts refer to interference from existing high power Ch 3 transmitters.

Chris

While the above described channel number aliasing is in use, the use of real VHF frequencies is also employed and has in fact expanded in the years following analogue switch off - some channels which initially used UHF frequencies have switched to VHF for a variety of reasons including the vastly superior propagation characteristics of VHF - this has led to stiff competition for VHF TV transmission licences

J

[obsolete man]

Originally Posted by kan_turk

Video input is usually either BNC or ´F’ connector - adapters to RCA are readily available - audio input is usually RCA so no adapter needed
user manuals are available online

J

I see just one RCA input for audio in some of these models. So we just input either the white or the red?

[cheerfulcharlie]

Originally Posted by obsolete man

The more I'm looking into it, specifically the am60-550. I'm realizing people are using this to send signals instead of directly connecting the TVs? Is that right? So the TV would need a functioning antenna?

No the output of the modulator should be RF which would be just the same as what came down the antenna, so you should be able to just connect the output of the modulator to the input of the distro amp, then the outputs of the distro amp would go to your TVs RF inputs.

[obsolete man]

Okay guys, here is a picture of the Zenith picture quality...



Here is the Sharp...



Here is a link to a sample of the Zenith video: https://youtu.be/rxd6hPlz4Kc

Here is a link to a sample of the Sharp: https://youtu.be/kq9vkrIIh1A
Another Sharp sample video: https://youtu.be/NRbsyMHtNm8

Regarding the Sharp videos, you'll notice not just the snow, but some sort of glitch that looks like a lightning effect. Is that lightning effect a telltale sign of anything?

Thanks!

[Restoration73]

On your Sharp, if there is some EHT discharge caused by defective EHT rectifier or any
associated sparking that might lead to interference on the picture.
However the noisy picture gives the impression the tuner input stage is defective,
possibly a faulty transistor. The VHF tuner will also be used as an IF preamplifier on UHF,
so if that too was noisy, that might confirm the diagnosis. Note sure if you can obtain a
UHF modulator locally, they were standard in the UK.