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Enthusiast
Posts: 7
Registered: ‎02-20-2017
Message 11 of 20 (1,012 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

Hi Nez,

 

Yes that was our first suspicion, but Pyers at Raycom tested my set of cables and for the test on the monitoring system we used his. Both were sound and well shielded. I also wrapped a ferrite core around my cable in a vain attempt to combat the problem.

 

Our struggle continues!

 

I also heard on the grapevine there were reports of the SDI blowing a couple Zacuto viewfinders. Not sure if that's true but could be worth investigating, as I feel there is something very fishy about that HIC board!

 

Phil

Expert
Posts: 1,602
Registered: ‎06-12-2013
Message 12 of 20 (1,012 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

Has there been similar reports from fs7 owners.. presuming its the same board..? maybe it isnt .. but there are alot of fs7,s around so it should be a known problem by now.. if the same boards that is..

 

I think your tests and others reports show it is a problem.. and not just cables.. but really the way Sony is.. and certianly the way Sony Japan is.. (they will deny all knowledge of making any camera,s and blame aliens )..your in for an up hill struggle.. but good luck.. fight the power !..

Enthusiast
Posts: 7
Registered: ‎02-20-2017
Message 13 of 20 (1,010 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

Hi Robbie,

 

Yes it does affect the FS7, one of my colleagues actually sold his F5 to go to an FS7 in the hope it would solve the problem. Sad to say he wasn't happy when it occur again. 

 

I heard the new F5 incarnation is coming out soon, it will be interesting if that also suffers...I would take bet it does!

 

Re dealing with Sony, I liken it to the VW fuel emission test, burying their head isn’t going to make it go away. In fact it only makes things worse. There are several of us together on this one, as it’s severely affecting our ability to work. I hope being on this forum will brings it to a wider group who could also be affected without realising.

 

As they say in Japan-  Shouda mo tsumoreba taiboku o taosu - With many little strokes a large tree is felled.

Expert
Posts: 1,602
Registered: ‎06-12-2013
Message 14 of 20 (1,006 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

[ Edited ]

Unfortunately there is also .. the all embracing excuse .. shoganai... (it cant be helped)..  lets have a meeting.. s u c k  air over our teeth.. and wonder off to the station.. 

Expert
Posts: 2,251
Registered: ‎11-23-2012
Message 15 of 20 (842 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

[ Edited ]

Sorry but I don't get what the fuss is about. The report says the RF is leaking from the video sender, not the camera. You should be addressing the problem with the leaky/poorly coupled video sender. The report states that the video sender only offers approx 10db of isolation between the HDSDI and it's antenna, that is shockingly bad isolation. It's not a camera problem, it's poor RF design in the sender unit.

 

 The HDSDI is a serial digital interface passing data at in this case up to 3GB/s. So inside the cable there will be a significantly large RF square wave signal centered on approx 640Mhz and 1.2Ghz with harmonics and other noise extending well into the microwave bands, that's the nature of the beast and perfectly normal. Without this RF signal the HDSDI wont work, it is a radio signal. Unfortunately the RF signal is very close to the frequencies used by our radio mic systems and because is digital data it generates a lot of RF noise, that is the way it is. The f800 and F55's SDI are different, F800 is 1.5G and F5/F55 are 3G, so the signals will be very different, all of this is normal and expected.

 

So to keep this RF in check you need very good quality cables with very high quality shielding. Most of the very thin cables that many of us use are really quite terrible, a 10m run of a thin coax like RG179 will loose almost 50% of the signal passing down it. In addition the cables must have the right impedance and the device connected to the end of the cable mst be correctly terminated at 75 ohms. Many of the thin coax cables used for video are actually 50 ohm cables meant for ethernet, not 75 ohm SDI. If the cable or device have the incorrect impedance then a high standing wave ratio (impedance miss-match) may be produced which will cause RF radiation on the outside of the attached devices and cables.

 

The Raycom report shows the RF to be leaking from the antenna of the video sender. This points to poor isolation/screening, an impedance miss match or lack of termination in the video sender unit, not a problem with the camera. RF will be travelling down the coax from the camera - it has to - the SDI connection is a UHF RF feed. When it gets to the video sender it should be terminated and should go no further. But somehow it is getting coupled to the video senders antenna where it is being re-radiated. That's a problem with the sender, not the camera.

 

Ferrite beads etc will only isolate/choke surface currents on cables, it won't make a leaky cable or attached leaky device less leaky.

 

Blame seems to be pointed at the camera when the report clearly shows the leak to be from the video sender. 

Expert
Posts: 1,602
Registered: ‎06-12-2013
Message 16 of 20 (835 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

I thought the problem was coming from the camera SDI outs.. isnt that what the OP was saying..? .. I hope its not that.. but thats what he was saying was it not.. regardless of any video sender.. confused..?

Expert
Posts: 2,251
Registered: ‎11-23-2012
Message 17 of 20 (828 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

Well that's what I don't understand. The OP is blaming the camera but if you read the report it clearly states that the RF is leaking from around the antenna of the video sender, not from the camera. There's even a picture with arrows pointing to the video senders antenna. I suspect the senders antenna is somehow mutually coupled to the HDSDI entering the sender and as a result re-radiating it.

Expert
Posts: 2,251
Registered: ‎11-23-2012
Message 18 of 20 (827 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

HDSDI is a big fat radio signal. When you send it down a cable it will find any leaks just as high pressure water pooring through a hose will spurt out of any holes in the pipe or poor out of the end of the hose if you don't fit a plug of exactly the right size.

 

It's well known that the HDSDI frquencies are very close to the radio mic frequencies, so a little bit of interferrence is common, especially if everything isn't 100% screened. That's not a camera fault, just the way it is.

 

Specialist
Posts: 22
Registered: ‎02-27-2014
Message 19 of 20 (797 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

Hi Alister,

Thank you for your time explaining whats going on. It does hep me. 

Cheers,

Tim

www.mindseye.net.au
www.cameramansydney.com
www.redcam.com.au
Expert
Posts: 1,602
Registered: ‎06-12-2013
Message 20 of 20 (512 Views)

Re: RF Leak from SDI outputs reducing Radio Mic range F5 and F55

So in what way are, say the Amira SDI outs different from the Sony F55.. ? if they have both been passed by the standards that Alister has quoted before.. the "strength of the output".. 3GB..sorry not very techie be seems a not too ****** question.. ?

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