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I'm considering buying the New Generation Hobbies video splitter, but I'm not certain if I need it. I guess you would technically call the NG Hobbies splitter also an amplifier. That's because it's trivial to split a signal with a $3 cable from Radio Shack.

When I split my camera's video signal between a monitor and a recorder, all I notice is a decrease in brightness. It doesn't bother me when I'm viewing it in real time with a monitor. And I can correct the brightness issues in the recorded signal. I guess I'm wondering if I'm missing something. Is there necessarily a loss of quality when you split a video signal without amplifying it?

I have noticed a loss of quality with other setups, depending on the source of the video signal and what you're sending the video signal into. But with my current setup, all I see is a loss of brightness.

Thanks for your help.

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Okay, that clears it up. There may be some loss of quality that I'm not picking up on right now. The NG Hobbies product is the only one I would consider because of its small size. I had been looking for a product like that for a year now until I stumbled on a post in this forum. Everything else I had seen was too big and bulky.

Has anyone tried NG Hobbies "2 channel video splitter"? How well is it made? Is it put together well? Does it run hot? Based on the components used, how long can I expect it to last (e.g. MTBF)?

I read a previous post by Kilrah stating that he built something similar using a Max4222 chip. I looked up that chip and saw that current consumption was about 5.5 mA. Would that be about right for the NG Hobbies splitter? I plan to use a higher than recommended voltage supply, then using a resistor to cut the voltage to around 5V. To do this, I would need to know how much current it uses.

Thanks

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I plan to use a higher than recommended voltage supply, then using a resistor to cut the voltage to around 5V. To do this, I would need to know how much current it uses.

I'd recommend always to use voltage regulators instead of a resistor to reduce voltage correctly with a reliable output. Not many devices will use a constant current all the time, it will vary depending on use. For example, the video outputs on the buffer will source some current to the attached devices, so the total current consumption of the module will be different whether there's 0, 1 or 2 outputs connected. OK, if the module is needed we can assume both are always used, but still...

Too bad they didn't add a reg on their board, as everybody's not using 5V gear. On mine I added a regulator that I could easily not fit and put a bridge across if the board was to be used in a 5V setup, in a commercial design a switch or jumper bridging the regulator would be an idea.

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I'd recommend always to use voltage regulators instead of a resistor to reduce voltage correctly with a reliable output. Not many devices will use a constant current all the time, it will vary depending on use. For example, the video outputs on the buffer will source some current to the attached devices, so the total current consumption of the module will be different whether there's 0, 1 or 2 outputs connected. OK, if the module is needed we can assume both are always used, but still...

Too bad they didn't add a reg on their board, as everybody's not using 5V gear. On mine I added a regulator that I could easily not fit and put a bridge across if the board was to be used in a 5V setup, in a commercial design a switch or jumper bridging the regulator would be an idea.

I guess a small change in current can make a big difference in voltage if you use a resistor. I'll have to run some tests on it (after I order it) to see how much current it consumes under different conditions.

I plan to use a 10.8V NIMH power supply anyway, which is still under the 11V maximum stated. But when the battery is fully charged, it could be over 11V. The monitor I plan to use the splitter with operates well from 9.6V to 14.4V. I plan to incorporate/integrate the splitter with my monitor (as a single unit), and I'm concerned that I may accidentally supply the whole thing with a higher voltage in the future, forgetting that the splitter takes 11V maximum. So, a regulator may be the best option.

So, I gather from your response that you own an NG Hobbies splitter. What do you think of the construction? I would hope that it could last for many years of use. How hot/warm to the touch does it run?

Thanks

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No I don't own one, I just got the data from the specifications and photos.

You're talking of this unit, right? http://www.nghobbies.com/cart/index.php?ma...84eb36d9a9adeee

I haven't found another splitter on their website, but on that one the specs state 5V power only, no mention of 11V, and from what I can see on the board photos there's no regulator that would allow higher voltages than 5V indeed. So I wouldn't be surprised if there's some confusion somewhere.

Edited by Kilrah

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Look at the manual (pdf) on the link you just posted. It states that the range of input voltage is 3.15 to 11V. As well, the Max4222 chip that you mentioned is stated to have an input voltage range of 3.15 to 11V. That's why I though they might be using that same chip (or possibly a very similar one).

No big deal really. I don't plan to use it at that high of a voltage. The lower I can make the input voltage, the better, in my opinion.

http://nghobbies.com/cart/datasheet/2ch%20...%20Splitter.pdf

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OK, I hadn't seen the link to the PDF.

Yes sounds fair. The same chip is indeed also available in 2-output version.

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Hi,

I meant to send this early this morning, but then I had to run to work.

The chip is a Max4217 video buffer/amplifier. The voltage is between 3.3 and 11.5 as it is required by the Max chip, there is nothing else which would be voltage sensitive on the splitter. Since there is barely any power consumtion on this, this will run as old as possible, barely any heat dissipation.

The splitter has a 75 ohm resistor termination at the input - some installations may not require this.

Some issues were reported on some situations, but the splitter works very well in most cases. The issues reported were incompatibility with some cameras, because some would require biased AC input signal to work properly even if the MAX chip does not require this.

The only way to see if this works o not in your particular installations is to try it out.

The splitter will require an external power source. The original design was to complement the SGTX type transmitters, so it will take the 5V coming from the transmitter, but since there is barely any power consumption, a simple LM2940 5V regulator can do the trick.

Sorry for the late answer, I did not have time lately to check this forum.

Kilrah, thanks for the support... :)

Attached is the design of the splitter, so this will give you a clear view on what's inside.

Zoltan

New Generation Hobbies.

OK, I hadn't seen the link to the PDF.

Yes sounds fair. The same chip is indeed also available in 2-output version.

post-2686-1228787862_thumb.jpg

Edited by oxxyfx

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Sounds good. I'll give it a try in a few weeks, when I get a little time to test it out.

By the way, I use a KT&C KPC-650CHQ, which I notice that you have on your site. So, I would presume there are no incompatibilities with this camera.

Thanks

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The issues reported were incompatibility with some cameras, because some would require biased AC input signal to work properly even if the MAX chip does not require this.

The exact ptoblem is that with a 0-xV supply (no negative), the chip won't be able to take negative voltages on the input. Now, if the camera has an AC-coupling cap, its output signal will go negative, and the signal will be clipped.

Most if not all of my cameras turned out to have AC coupling, so I added a bias on my splitter. I wouldn't have been able to use it much otherwise.

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The exact ptoblem is that with a 0-xV supply (no negative), the chip won't be able to take negative voltages on the input. Now, if the camera has an AC-coupling cap, its output signal will go negative, and the signal will be clipped.

Most if not all of my cameras turned out to have AC coupling, so I added a bias on my splitter. I wouldn't have been able to use it much otherwise.

This post is a little over my head, but I have a feeling I need to understand this to find the product I want. I'm not sure I understand the concept of AC coupling and how that affects a negative vs. positive voltage. Also, I'm not sure what a bias is. I guess I'll have to do some studying.

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Ok, let me try... :)

The signal of a standard video image is a kind of wave signal which is split horizontally in the middle into a positive (above the line) and negative (below the line) segment. Well of course it is not split in reality, the horizontal line goes in the middle and the signal goes up and down. The upper portion is the positive AC voltage, the lower is the negative.

So, if that is the signal which comes out of the camera - connecting it to this splitter will loose the signal portion below the horizontal line - giving you a picture with rolling lines and missing portions and colors. This is even thought MAXIM specifically states that this should not be happening.

For this reason we can electricaly raise the signal above the horizontal line to such a level that all the bottom portions would be above the horizontal line, so in this case you would get a the full picture without any losses.

I think this was descriptive enough. The solution is easy but it is required only in case you have those specific cameras with the ac coupling.

I will have to try to see if this works with the KPC650 - and let you know. If not, I can always quickly add two resistors to the input of the video signal to raise it "above the line" - and ship it like that to you. It will not be as pretty as it is now, but it will be heat shrinked and it will work.

Zoltan.

This post is a little over my head, but I have a feeling I need to understand this to find the product I want. I'm not sure I understand the concept of AC coupling and how that affects a negative vs. positive voltage. Also, I'm not sure what a bias is. I guess I'll have to do some studying.

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[...] This is even thought MAXIM specifically states that this should not be happening.

Sorry for nitpicking, but:

The MAX4214 family’s input range extends from

(VEE - 100mV) to (VCC - 2.25V).

And more specifically, in the configuration we use:

If the buffer is

operated in the noninverting, gain of 2V/V configuration

with the inverting input grounded, the useful input voltage

range becomes 20mV to 1.7V

Which means that with our single supply the chip won't be able to pick signals below 20mV... while an AC coupled video signal will be able to reach -200/-300mV easily.

So, it IS properly documented :)

-AT-ginger_marianne: Skip the technical gibberish and take on Zoltan's advice, he'll test it for you so you have no risk anyway. ;)

Edited by Kilrah

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I will have to try to see if this works with the KPC650 - and let you know. If not, I can always quickly add two resistors to the input of the video signal to raise it "above the line" - and ship it like that to you. It will not be as pretty as it is now, but it will be heat shrinked and it will work.

Zoltan.

I don't think I'm going to get it no matter how much you dumb it down. I just don't have the knowledge base. I tried reading "Monochrome and Colour Television" by Gulati, chapters 11 to 14 on Google Books last night. It looked promising. There was a chapter on video amplifier circuitry. I didn't understand a word of it.

I did however understand some of Mr.RC-Cam's description of the 75 ohm resistor in the monitor, and how each additional device you add adds another 75 ohm resistor in parallel, hence the need for buffering.

Okay, if you add the 2 resistors to the splitter, will it be compatible with all cameras or will the act of adding the 2 resistors make some other cameras incompatible? I don't really care how it looks, just that it functions well and is compatible with as many cameras as possible. If you're just adding 2 resistors to the video inputs, I could probably do that if you describe which resistors and where they go.

Thanks

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I didn't have time to test this out last night, but that will be the first thing I will do tonight, and report back.

I will better add the resistors, heat shrink it for you and ship it ready to use. That way I can assume warranty as well for my work.

Zoltan.

I don't think I'm going to get it no matter how much you dumb it down. I just don't have the knowledge base. I tried reading "Monochrome and Colour Television" by Gulati, chapters 11 to 14 on Google Books last night. It looked promising. There was a chapter on video amplifier circuitry. I didn't understand a word of it.

I did however understand some of Mr.RC-Cam's description of the 75 ohm resistor in the monitor, and how each additional device you add adds another 75 ohm resistor in parallel, hence the need for buffering.

Okay, if you add the 2 resistors to the splitter, will it be compatible with all cameras or will the act of adding the 2 resistors make some other cameras incompatible? I don't really care how it looks, just that it functions well and is compatible with as many cameras as possible. If you're just adding 2 resistors to the video inputs, I could probably do that if you describe which resistors and where they go.

Thanks

Edited by oxxyfx

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I didn't have time to test this out last night, but that will be the first thing I will do tonight, and report back.

I will better add the resistors, heat shrink it for you and ship it ready to use. That way I can assume warranty as well for my work.

Zoltan.

Okay. Thanks for your help. I look forward to trying it out.

I have another question for anyone who might have experience with this. With some equipment, when I split the signal, it just reduces the quality of the video. With other equipment, it seems to be introducing some type of feedback. In other words, it looks to me like the equipment is introducing an interfering video signal in the opposite direction. Does this actually occur or is it just a symptom of the same problem we were discussing before? Does a buffer help with this as well?

Thanks

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That could have to do with the impedance mismatch Mr.RC-Cam explained earlier inthe post he linked. On high-frequency and terminated signal lines, a missing termination or otherwise incorrect impedance one can induce a bounce of part of the signal that will start to travel back in the other direction.

By experience I doubt this would be the case here though, I'd rather say it's one of the devices not being happy to receive a signal that is only half the amplitude it expects, and reacting weirdly to it.

A buffer will firstly separate the lines for each device, and ensure correct wiring characteristics, so would definitely help. You just don't passively "Y" video signals, period...

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You just don't passively "Y" video signals, period.

I think I need to get some tee-shirts made with that printed on it. :)

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I think I need to get some tee-shirts made with that printed on it. :)

Funny... Send me one Thomas... :)

So I tested the Video splitter today, this time with properly set up signal line. As per Mr. Rc-Cam's instructions we added a 47uF cap, and 2 resistors. Connected to the 650HQ I've got excellent picture quality on both outputs.

This seem to work, you can go ahead an place your order at your convenience, I can send you this modified one or if you are not in a rush, please wait for 8-10 days till I receive the new modified PCB's and I can send you one without haking. I just re-designed the thing and reordered the boards, those should be in in 8-10 days.

This will work with any type of cameras this time.

Thanks,

Zoltan.

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Funny... Send me one Thomas... :)

So I tested the Video splitter today, this time with properly set up signal line. As per Mr. Rc-Cam's instructions we added a 47uF cap, and 2 resistors. Connected to the 650HQ I've got excellent picture quality on both outputs.

This seem to work, you can go ahead an place your order at your convenience, I can send you this modified one or if you are not in a rush, please wait for 8-10 days till I receive the new modified PCB's and I can send you one without haking. I just re-designed the thing and reordered the boards, those should be in in 8-10 days.

This will work with any type of cameras this time.

Thanks,

Zoltan.

That's just what I wanted to hear. I'll wait for the newly designed ones rather than the hacked old one. I just want to say thanks to Zoltan, Kilrah, and Mr.RC-Cam for your help.

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Hello,

just as an update, we have received the new Video splitters. Tested with the 650 and it works excellent. The product pictures are not yest updated on our website, but we will ship only the new splitters from here on.

Please add o your cart this item: http://www.nghobbies.com/cart/index.php?ma...products_id=168

Thank you,

Zoltan

That's just what I wanted to hear. I'll wait for the newly designed ones rather than the hacked old one. I just want to say thanks to Zoltan, Kilrah, and Mr.RC-Cam for your help.

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Hello,

just as an update, we have received the new Video splitters. Tested with the 650 and it works excellent. The product pictures are not yest updated on our website, but we will ship only the new splitters from here on.

Thank you,

Zoltan

I just got a chance to test it. Delivery was very fast from Canada to the US (about 5 days including holidays) with standard shipping. The picture quality is pristine with every video source I've tested so far. It can accept a wide range of input voltages. It worked perfectly at 3.1V to 10V (didn't test any higher), although it should work at up to 11V. It's about the size of a postage stamp, excluding the connectors coming out of the sides. It produces virtually no heat. Based on my calculations, the operating current is around 15mA.

The buffered video outputs are indeed independent. Regardless of what you do to one of the video outputs (e.g. short circuit the ground and video), the other video output will be unaffected. It can be run off of a 12V (+/- 25%) source using a 440 ohm (2 x 220) or 470 ohm resistor. Using a 440 ohm resistor, it should operate fine from 9V to 15V (assuming future versions of the splitter operate at the same current as this one). Note that I embedded the resistors in the wiring and didn't modify the splitter in any way.

It's small enough that it can be embedded in another device, such as a monitor. You can use the splitter to create a buffered video output from your monitor. It can share the same power source as the monitor, since its power usage is negligible. On my monitor, this can be done without ever touching the circuit board. Note that this will likely void the warranty of both the monitor and splitter and can easily damage both. This is actually an easier solution for me than finding the 75 ohm resistor (as Mr.RC-Cam mentioned), and making it switchable. I tried finding that resistor in one of my monitors but, for some reason, couldn't locate it. Perhaps some monitors are easier than others. It can probably also be embedded in the wiring of your cam to create a second, buffered video output. It can also share the same power source as the cam. Again, this will void the cam warranty and probably the splitter. Both of these ideas are probably also a fire/electrocution hazard if the wrong person does it. I know CRT monitors have areas of very high voltage, and I believe LCD monitors do as well. I'm just pointing out that this device is small enough to be permanently/temporarily embedded in another device and share its power supply, thereby making it much easier than using a separate buffer/amplifier box. But since I don't want to get sued, I'm not actually recommending this.

Some people had previously mentioned the FK655 video amplifier electronic kit. Here's why I decided against it. At 3" x 2.2", it's a giant compared to the New Generation Hobbies splitter. Also, the pdf stated that the FK655 uses 150 mA. This is not a trivial amount. Also, I believe it has a heat sink, indicating that it probably runs hot. Of course, the FK655 has 4 outputs, so it is different in that way.

Regarding the reasons why a buffer is needed, I've thought about it some more and realize my initial post was inaccurate. Whenever I edited footage (using Virtualdub) in the past that was obtained using a Y cable for splitting, I would always set the contrast to +43%. I always found this to yield the best result. I always attributed this to something in my camera or the lighting conditions. And even after my first post here, it didn't occur to me that this was due to using a Y cable. Without upping the contrast a great deal (in Virtualdub), everything would look very washed out. Even though about 75% of what I shot looked okay after I upped the contrast during editing, I realize now that I probably lost some dynamic range. Not to mention the 25% that was unusable. This is part of the reason why I didn't want to record in mpeg2. But now my hope is that if the contrast situation is fixed by using a buffered splitter, I can record directly to mpeg2 (instead of a low compression codec) and do all (or most of) my editing losslessly (i.e. just basic cutting).

So, all in all, I think it's an excellent product. And I give Zoltan credit for his customer service and for changing the design so quickly based on information he received from the experts on this forum (not me of course).

Edited by ginger_marianne

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Update:

In my quest to use this splitter with a 12V (+/-25%) source, I've made a couple modifications since my last post. I decided to lower the resistance from 440 ohm to 380 ohm (or 330 ohm) because the 440 ohm wasn't perfect around the 9V range. Also, I added a 100 uF capacitor from the ground to the +5V (pin 1 to pin 2 on the input side of the splitter). Again, I didn't modify the splitter and simply added the capacitor to the wiring.

Apparently, adding the resistor introduces a small amount of noise (low frequency?). The thing about the noise is that it usually isn't visible. It would probably work fine with just a resistor and no capacitor. In fact, I watched TV for hours with this device using just a resistor, and it looked perfect. I only noticed it with one specific thing produced by my cable box. So, I added the capacitor, and it disappeared. A 10 uF capacitor improved it but it didn't disappear completely. Also, I want to make it clear that it was my adding the resistor that introduced the noise. If you just feed the splitter 3.1V to 11V, the output is always perfect.

So, I found the simplest solution is to add 2 components to the wiring (no circuit board needed). Add a resistor to the middle wire feeding pin 2 (+5V) to reduce the voltage being fed into the splitter. Then add a 100 uF capacitor to eliminate the noise introduced by the resistor. The capacitor should be placed on the ground and +5V wires (feeding pins 1 and 2). The capacitor should be between the resistor and the splitter. It's actually very easy to build (just some minor modifications to a servo cable).

I also want to emphasize though that if someone uses a splitter with even a small difference in current usage than mine (e.g. slightly different components), then a different resistor will be needed, or else too much voltage (>11V) can be supplied to the splitter, possibly damaging it. So, anyone attempting this should measure it for themselves (with a good multimeter), starting at a higher resistance and working your way down. Go with the highest resistance that works.

There's also a very small 5V voltage regulator (7805) from Radio Shack that can take any input voltage from 7V to 35V and give you a clean 5V. All you need is the regulator and 1 or 2 capacitors. I haven't used it yet, but I've seen some good reviews. I decided to go with the resistor because I could make everything a little smaller overall. But a regulator is a safer option with a wider input voltage range. With a 380 ohm resistor, I get a range of approximately 9V to 17V.

If someone can explain the noise introduced by the resistor, I would appreciate it. I don't fully understand it. But my guess is that small variations in current usage by the splitter induce small changes in voltage across the resistor (because the voltage across the resistor is dependent on current). So, does this introduce a low frequency AC component?

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Okay, I'm sorry if I'm posting too much.

I tried the 5V regulator from Radio Shack. It's absolutely perfect. No capacitors are needed when used with the splitter. It provides a clean 5V. And there's no noise at all, even without a capacitor.

And it's tiny. So, ignore everything I said previously about resistors.

Thanks

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