Author Topic: Camera Car Build  (Read 8641 times)

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eric220

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Re: Camera Car Build
« Reply #30 on: January 19, 2013, 11:41:02 AM »
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I just had an idea. Peteski (or anyone else, for that matter) do you know if the antenna on the camera can be replaced or extended?
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peteski

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Re: Camera Car Build
« Reply #31 on: January 19, 2013, 01:37:00 PM »
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I just had an idea. Peteski (or anyone else, for that matter) do you know if the antenna on the camera can be replaced or extended?

I'm not a radio-frequency electronic engineer but I don't think that coudl be done easily. I'm sure the current length was chosen on-purpose.  Designing antennas is a science in itself (especially in the multi-Gigahertz range) and unless you know what you're doing, your version might be worse off than the original.

I already asked if RF System Lab would be willing to increase the transmitting power of their camera. They said no.  Probably to keep this unit compliant with some government rules.

The other solution is to increase the gain of the receiving antenna. That is why I recommended the receiver which has a F-type screw-in antenna connector.  The camera operates on 2.5 GHz (same frequency as all the WiFi networks) so there is a wide range of larger antennas available for fairly low cost.  The only problem is to get one with F-type male connector. But adapters can be made.  That is how worked things out on a friends layout.

When you look for antennas, their specs give their gain in decibels (dB).  The higher the number the larger the gain. I think the rubber-ducky antenna included with the receiver is a 2 dB antenna. The one I used on friends layout was either a 9 or 11 dB unit.

I bought it from L-com. http://www.l-com.com/category.aspx?id=2073  They also offer custom services (such as F-type male connector installed on the cable) and cable extensions.
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eric220

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Re: Camera Car Build
« Reply #32 on: January 19, 2013, 02:00:19 PM »
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Yeah, you're probably right. The performance actually wasn't the issue. The train of thought went something like, "If I'm going to install trainphone antennas anyway..."

I do think that getting a higher dB antenna on the receiver would be a good idea.
-Eric

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GaryHinshaw

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Re: Camera Car Build
« Reply #33 on: January 22, 2013, 05:20:41 PM »
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Just catching up with this thread...  A higher gain antenna is not necessarily desirable in this context. In the RF world, the gain of an antenna is a measure of its directionality, not its overall power output.  A 2 dB antenna will broadcast over a very wide "field of view" with almost equal power; a higher gain (e.g. 9 dB) will focus the same amount of power into a smaller beam, hence broadcast more power in certain directions, less in others.  It works the same way for a receiving antennas: the higher the gain, the more sensitive it is to incoming signals, but over a smaller area.  If your transmitter and receiver are not properly aimed, you'll actually get poorer performance with a high-gain system -- it really depends on room/layout geometry.

To get higher signal-to-noise over the whole room you need either a higher power transmitter or a more sensitive receiver (or both).  Of course this only affects getting the data from the camera to your computer, not the quality of the picture that is being transmitted.

-gfh
« Last Edit: January 22, 2013, 05:25:01 PM by GaryHinshaw »

peteski

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Re: Camera Car Build
« Reply #34 on: January 22, 2013, 06:10:46 PM »
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Just catching up with this thread...  A higher gain antenna is not necessarily desirable in this context. In the RF world, the gain of an antenna is a measure of its directionality, not its overall power output.  A 2 dB antenna will broadcast over a very wide "field of view" with almost equal power; a higher gain (e.g. 9 dB) will focus the same amount of power into a smaller beam, hence broadcast more power in certain directions, less in others.  It works the same way for a receiving antennas: the higher the gain, the more sensitive it is to incoming signals, but over a smaller area.  If your transmitter and receiver are not properly aimed, you'll actually get poorer performance with a high-gain system -- it really depends on room/layout geometry.

To get higher signal-to-noise over the whole room you need either a higher power transmitter or a more sensitive receiver (or both).  Of course this only affects getting the data from the camera to your computer, not the quality of the picture that is being transmitted.

-gfh




Does the same apply to the receiving antenna?  BTW, the antennas I researched (with various gain values) were omni-directional. Does what you say also apply to those?
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Zox

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Re: Camera Car Build
« Reply #35 on: January 22, 2013, 08:05:54 PM »
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I'm not a radio expert, but this is what I've picked up while working on my own camera car...

Does the same apply to the receiving antenna?

Yes--higher gain means more directional. Of course, if you can place the receiving antenna outside of the layout area, this might be a good thing, since you wouldn't need (or want) to pick up anything from behind the antenna.

Quote
BTW, the antennas I researched (with various gain values) were omni-directional. Does what you say also apply to those?

Omnidirectional antennas achieve gain by "flattening" the pattern--they're more sensitive radially outward from the antenna, not so sensitive above or below.

This is one reason they often say to put DCC radio receiver antennas upside down on the ceiling. These are usually "ground-plane" antennas, which pick up well anywhere above the base of the antenna and not as well below. Putting them on the ceiling gets them above obstructions (like operators); turning them upside-down puts the most sensitive part of the pattern toward the layout.
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eric220

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Re: Camera Car Build
« Reply #36 on: January 22, 2013, 08:38:48 PM »
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Omnidirectional antennas achieve gain by "flattening" the pattern--they're more sensitive radially outward from the antenna, not so sensitive above or below.

I saw some high gain antennas that were pretty tall, like on the order of five feet. Would it work to mount one of those behind the scenery or inside the helix on the lowest level such that the top of the antenna was above the highest level?
-Eric

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Re: Camera Car Build
« Reply #37 on: January 22, 2013, 08:53:31 PM »
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I was also told about mounting the omnidirectional antenna on the ceiling pointing down.  So that is how I did one of the installs.  Notice the antenna pointing down from the ceiling in the top center edge of the photo.  It seems to work well.

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Re: Camera Car Build
« Reply #38 on: January 22, 2013, 10:21:42 PM »
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I saw some high gain antennas that were pretty tall, like on the order of five feet. Would it work to mount one of those behind the scenery or inside the helix on the lowest level such that the top of the antenna was above the highest level?

That, I can't tell you, nor where to find out. However, I suspect that when the distance between the antenna and the transmitter is of the same order of magnitude as the length of the antenna, the usual calculations wouldn't apply.
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GaryHinshaw

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Re: Camera Car Build
« Reply #39 on: January 23, 2013, 05:57:35 AM »
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Does the same apply to the receiving antenna?

Yes:

It works the same way for a receiving antennas: the higher the gain, the more sensitive it is to incoming signals, but over a smaller area.

To be more specific, the directionality of any antenna is the same whether it is transmitting or receiving.   

BTW, the antennas I researched (with various gain values) were omni-directional. Does what you say also apply to those?

Strictly speaking, a high-gain, omnidirectional antenna is an oxymoron because, for antennas, high-gain is synonymous with directional.   However, I suspect that omnidirectional in this context means almost omnidirectional. 

Aside, the definition of antenna gain is as follows: imagine you have a transmitter propagating a certain amount of RF power, in Watts, down a co-ax cable to an antenna; an ideal omnidirectional antenna will broadcast that power uniformly over the full sphere, producing a certain flux, in Watts per square meter, a given distance away.   (There is no such thing as a *truly* omnidirectional antenna BTW, but we can imagine it.)   Now a directional antenna with a gain of 10 dB, say, will produce a flux that is 10 times higher in it's forward direction than the ideal omnidirectional antenna does.  But since the total broadcast power is the same, that flux must be concentrated in 1/10 of the sphere, so you can estimate the angular directionality from that number.  This omits a lot of detail, but it gives you a rough idea of the concept.  Note that a 10 dB receiving antenna would be 10 times more sensitive to incoming radiation in its forward direction than an ideal omnidirectional would be (but less sensitive off axis).  To confuse matters further, dB is a log scale: the gain in Watts is related to the gain in dB by G = 10^(dB/10), so 10 dB gives G = 10^(10/10) = 10^1 = 10, but 20 dB gives G = 10^(20/10) = 10^2 = 100.  So a 20 dB antenna has a gain of 100 and (roughly) covers 1/100 of the sphere.


I saw some high gain antennas that were pretty tall, like on the order of five feet. Would it work to mount one of those behind the scenery or inside the helix on the lowest level such that the top of the antenna was above the highest level?

A five foot antenna operating at 2.5 GHz would be **really** directional and is probably not a good idea.  Since 2.5 GHz radiation has a wavelength of 12 cm, a rule of thumb is that a 5 foot antenna (~150 cm) would have a "beam width" of about 12/150 radians (about 5 degrees), meaning it would be really sensitive within that 5 degree footprint, but pretty insensitive outside of it.

I agree that the best place for an antenna is the middle of the ceiling, aimed down.  Start with the most omni-directional antenna you can get, and try slightly higher gains if you need to.  But going higher than ~5 dB is probably not going to help much, because the extra sensitivity is increasingly focused directly underneath the antenna.

I doubt this info is very helpful, but hopefully knowing a bit more about the concepts can't hurt.

-gfh
« Last Edit: January 23, 2013, 06:22:47 AM by GaryHinshaw »

rogergperkins

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Re: Camera Car Build
« Reply #40 on: January 23, 2013, 07:37:59 AM »
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Will the following work for n-scale applications, i.e. on flat cat to be pushed by locomotive, etc.?
•Looxcie 2: Weight ~22g (0.8 oz.), Length 3 1/4″ (84mm)
I am not ready to budget for the $300+ version with HD,
but could consider this one which is about half the $$.

DKS

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Re: Camera Car Build
« Reply #41 on: January 23, 2013, 07:47:10 AM »
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Will the following work for n-scale applications, i.e. on flat cat to be pushed by locomotive, etc.?
•Looxcie 2: Weight ~22g (0.8 oz.), Length 3 1/4″ (84mm)
I am not ready to budget for the $300+ version with HD,
but could consider this one which is about half the $$.

Yes, it will work. You may, however, need to remove the earpiece in order to clear some bridges and tunnels.

Here's my non-disguised Looxcie camera car build. I clipped off the earpiece with a flush cutter; that's the only mod required for the camera, and does not affect operation in any way.



The car is an old MTL chassis, with a clip made of strip brass attached.



Because the camera is slightly offset in order to maintain clearance, a counterweight (scrap of lead) was needed to keep the car from tipping over.

« Last Edit: January 23, 2013, 08:00:32 AM by David K. Smith »
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VonRyan

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Re: Camera Car Build
« Reply #42 on: January 23, 2013, 10:58:31 AM »
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Interesting thread.

I had the idea to mount the smallest camera possible with the best resolution possbible to be mounded behind the engineer's window in a F unit.
The feed would be sent back to a modified briefcase with built in UT4R and LCD screen to allow for portability. It would be the DCC version of remote controling the train via virtual virtual-reality.

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Re: Camera Car Build
« Reply #43 on: January 23, 2013, 11:24:03 AM »
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Here is the picture of the camera I am working with...promised earlier in the topic.





This is the camera only. It measures 4mm x 4mm x 13mm, runs of 3.5-5v, has an optional LED light ring (shown) and I believe it is 800x600 resolution (may be 640x460 though, can't remember what the gentleman told me it was when he gave it to me). I still need to come up with a way to transmit the signal from the camera.

Yellow wire is video signal out, Red is 3-5V+, Black ground, and White 3-5V+ to power the LED ring.
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Re: Camera Car Build
« Reply #44 on: January 23, 2013, 11:33:58 AM »
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Run a long wire HF loop style antenna around the room on the RECEIVER antenna only. You should get a nice clean signal with DFQ and no issues. You must remember that you are playing with radio waves that pick up all types of interference with the all the stuff using power in the room. My HF radios do not like computers or even stuff they pick up through the house electrical wiring. With so much stuff these days plugged into the house and running, it makes an RF nightmare!
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