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High power video transmitters


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#1 Marcin Brauer

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Posted 26 November 2005 - 05:02 AM

Hi guys!

Any of you use those products?
http://www.rf-links....ransmitters.htm

There is a 2.4GHz transmitter with a 10W of power!!! The range is 20miles in open space (from air). Anyone tested this in our field?

Not to mention those designed for "Steadicam use":
http://www.rf-links....deo_senders.htm
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#2 RobVanGelder

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Posted 26 November 2005 - 05:33 AM

Though theze transmitters are now incredibly small and even powerful, the main problem with the 2.4GHz band is that it is full of other sourses and links. All computer and security camera´s seem to be relayed on this frequency and many times you have something different on your screen as what your Steadicam transmitter is sending out.
And then there is the problem with Follow Focus systems like Preston and Scorpio. They interfere seriously and only a few channels or sometimes even none at all are useble.

However, it´s the only LEGAL system, as long as you stay under 10 mW!

Now most of us, if not everyone, is not really concerned about the legal aspects, it just has to work!

Therefore the older -analog - systems are still usable if you find the right channel and I work with the 1,3 GHz system, which is not so cluttered with all kinds of S#$T.
And one thing is sure, in this pricerange: the lower the frequency, the better the reception and lesser drop-outs due to blocking the Line-of-Sight.

The transmitters on 1,3 Ghz are most of the time from the same manufacturer as the 2,4Ghz stuff.
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#3 thomas-english

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Posted 26 November 2005 - 07:53 AM

The UHF systems in your links seem very interesting. I worry that some old lady around the corner complains to the authorities because she s picking up your picture on the TV. I would be interested to know the effective range they give and thus the safety zone.

The lower the frequency the more "flex" the transmision has. Super high frequencies you get a lazer. very straight. hence my desire for the lowest frequency possible.

The big problem I have with my 1000 mW 2.4 ghz TX is not that the reciever is picking up the picture. The problem is multipathing. Where the signal is bouncing around the place, some signals are going longer routes to reach the reciever and thus getting there slightly out of time with the main signal, causing interference with its own signal. In that sense having a weaker TX can sometimes be an advantage. The secret is having super uni directional recieving ariels and have a runner point it at the rig.

Rob, I assume you have no problems buying 1.395ghz ariels in thailand. This is my problem here in the UK. Have you found anywhere selling diversity 1.395ghz recievers? Where you have 2 ariels an awkward wavelengh distance apart and the reciever chooses the finest signal. looks like I am going shopping when I come over at xmass.

The other problem I have with all these cheap recievers is their voltage range. I burn through 2.4 ghz recievers at a rate of one every 2 months and I reckon its because I run it off PAGs which are fairly high voltage relative the the 12v these guys are made for. especially hot off the charger. I have directly lost a few RX s by putting a battery straight off the charger.

By the way 10mW TX RX ranging 20 miles in open space would only be possible with 2 huge highly unidirectional antennas. In the kind of setups we use you ll have difficulty ranging over 50 yards.



thomas
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#4 RobVanGelder

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Posted 26 November 2005 - 09:37 AM

Rob, I assume you have no problems buying 1.395ghz ariels in thailand. This is my problem here in the UK. Have you found anywhere selling diversity 1.395ghz recievers? Where you have 2 ariels an awkward wavelengh distance apart and the reciever chooses the finest signal. looks like I am going shopping when I come over at xmass.



I cannot remember i saw a diversity receiver yet, but I did see some directional antenna´s
I will try to find out if they are for 1,3 or 2,4 GHz.
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#5 Marcin Brauer

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Posted 26 November 2005 - 11:35 AM

Curently I`m useing two transmitter systems one UHF and the other 2.4GHz.

The UHF is similar to those on the page I linked to, and it is ok. With directional reciver antenna it performs very well.

As for the 2.4GHz it is a simple 1000mW security camera set. I`m useing it high gain WiFi antennas - TX 7dBi, RX sector 18dBi. And they work great. - Not so many WiFi networks here to interfere with.

As for the 20mils range I was rather refering to that as it could cover 250m with great image quality/stability.
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#6 Emery Soos

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Posted 26 November 2005 - 02:37 PM

I don't think you want to be anywhere near 10 watts of video RF. You may also be interested to know that the company of which you speak has no refund policy.

Edited by Lentequip, 27 November 2005 - 12:59 PM.

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#7 JobScholtze

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Posted 26 November 2005 - 04:47 PM

From Januari the new Modulus 4000 will be released. But i am not sure i want that, still waiting for some new channel selectors for my 3000. CIT told me the send it over for free, 6 month ago :P
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#8 Brad Grimmett

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Posted 27 November 2005 - 12:00 AM

Is that news about the 4000 official? I know it's been in development for a long time. Is it finally ready?
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#9 JobScholtze

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Posted 27 November 2005 - 07:56 AM

Is that news about the 4000 official? I know it's been in development for a long time. Is it finally ready?

Click Me I am New

Thats what there website says
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#10 Erwin Landau

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Posted 27 November 2005 - 10:02 AM

I heard a lot of rumors, but non are good so far.

I talked to people that claimed to have seen prototypes of the 4000. (Same interior, new Box)

I also heard something about better costumer service promises... but tell that to all the guys that are still waiting several months to get a simple repair done.

Also I heard rumors that all but one sales rep jumped ship here in LA...

In the moment you have to send the unit directly to Main for ANY kind of maintenance or repairs.



Erwin "Still using them, hope never have to repair them" Landau

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#11 Brad Grimmett

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Posted 27 November 2005 - 10:27 AM

Sure, the website says Jan., but it doesn't say what year. I hope you're right, but I'll believe it when I see it.
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#12 JobScholtze

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Posted 27 November 2005 - 01:40 PM

Sure, the website says Jan., but it doesn't say what year. I hope you're right, but I'll believe it when I see it.


Well, he wont answer my emails. Still waiting for some new channel selectors for my modulus 3000. If this is his costumer support no way i will buy the 4000. I hear nice things about the lentequipe but its way out of my budget. ( I think its to much for a transmitter personally )So, not many options left here. Does anybody knows where i can get some modulus support?
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#13 Erwin Landau

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Posted 27 November 2005 - 08:47 PM

I played with the Canatrans on a couple of occasions and I was very impressed with the technological advencement over the Modulus 3000. Remember when the TB-6 hit the business and out performed the then leader PRO 2 Monitor? Analog versus Digital.

Through my backround in designing and building complex units... he spend a shit load of money into the development. You really get what you pay for... I have to admit.

The Canatrans layout provides the owner with rock solid channel selection (new version coming next year with 31 channels, free upgrade for existing owners), no ghosting; internal output and channel selection with the push of a button. Menu driven. Sofware upgradeable in the future over the Internet, etc...

Also how do you put a price tag on Costumer Service? I was told he had a 24 hours turn around...

It cost me $2000.- for a second Modulus, just to be sure to have a back up in case of failure. With all the cable and aks for my Modulus, I'm in about $7000.-


Erwin "Saw the Light... can't afford it right now" Landau

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#14 RobinThwaites

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Posted 28 November 2005 - 05:22 AM

Hi All

That much power can create real problems for a moving transmitter application. Thomas really hit it on the head when he mentioned multipathing - more power equals more multipathing. I have been in situations with typically a 250mW TX where we have attenuated the output and got a MUCH better signal.

Digital systems seem to be the future usually using relatively low output coded signals - there are a few around and more coming on the market. You will have a small delay as the receiver decodes the signal but this is for monitoring so not important. Naturally if you want to record the signal for transmission then you will have to pay a lot more to get the tool for the job.

Robin Thwaites
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#15 thomas-english

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Posted 28 November 2005 - 04:35 PM

I have been studying this for a few days, as I plan too on upgrading. The major difference between UHF and 1.4/2.4 is they are AM and FM respectivly. "Amplitude Modulation", where the video signal is put by using the amplification of the frequncy carrier seems to be much more prone to multipathing/reflection interference than "Frequncy Modulation" where its more down the frequency changes to carry the signal. However the higher the frequency the better the bounce and hence the more multipathing, hence why 2.4ghz break up so much over the AM UHF s however the signal and colour gamut on UHF "CAN" be consistently worse than microwave as small reflections find it easier to remodulate an AM signal.

An ideal system would be an FM UHF , but I think the wavelengh may be too long to frequency modulate.

Another ideal system for our application would be a diversity 1.4ghz. AvalonRF do diversity 2.4ghz that are used on police helicopters and the like. It is however $4000 for the 4 ariel diversity reciever. Marell electronics have just started selling diversity 1.4ghz and 2.4 ghz systems at quite reasonable prices. approx 1900 sterling (RX and TX) as well as diversity directors monitors. Hopefully the ability for it to flick to the best reception antenna could eliminate most of the breakup.

has anyone yet tested the VATboy system on
http://translate.goo...e...cial_s&sa=G

I don t think you need as much power as I have, 1000mW on 2.4ghz. I think 400mW is about what would be best. better concetrate on your recieving antenna. My new configuration of my 2.4ghz has a unidirection ariel mounted on a PAG battery (so no bounce can get through the back) I am interested to see how this performes in real life.

What diversity recievers are used on the modulus? I hear chroiszel make one, xcs make one and avalonRF make one. Is a diversity noticably better on AM UHF? A clever chap I was chatting to at joe dunton reckons that if you plan your ariels right on diversity you could have a mobile feed going up the projectors at say a concert or the like. a good consistent enough picture at a concert.

My housemate just got back from stateside after doing the visuals for DefLeopard. He hung out with some kids using a UHF system Waveshot at a gig and he was putting the feed onto a screen perfectly. Transmiting through a crowd with only occasional breakup.

http://www.dvshop.ca...a/waveshot.html

However I think it may only be available on NTSC .

I feel the future lies in COFDM systems. No delay, No breakup, perfect signal until a distance is reached. However at the moment they cost about 6000 sterling, and weigh a lot more (1.5kg TX).

http://www.bbc.co.uk.../paper_15.shtml

sorry for the rant,

thomas
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