jt

RF Interference and Teradek Bolts

33 posts in this topic

Currently working on a show with many RF sources and getting intermittent but persistent bad interference. My wires are Lectrosonic and Audio Ltd in Block 21. With nothing turned on I get a typical mostly clean scan for my location. Turning on one of our Bolt 300's show broadband but low signal. Can work with that. Turning on only one of our Bolt 600's shows a higher level of broadband signal. Can work with that. Turning on both Bolts shows an additive increase in signal which is now problematic.

The level fluctuates through the day, sometimes more (very bad interference) sometimes less(not too bad).

There are other rf sources. Many wifi internet routers, spx rf triggers, wireless contolled dimmers.

I have contacted Teradek but without reply yet.

I am trying to get hold of a spectrum analyzer to track this down.

In the mean time, has anybody run across this before or have anything to suggest?

And should a product that works in the 5ghz range be spewing out noise in the 500mhz range.

Thanks in advance.

Share this post


Link to post
Share on other sites

I made a few enquiries and never had the courtesy of a reply. please do forward any info you might receive to this thread.

Share this post


Link to post
Share on other sites

The Teradek Bolts are nasty sources of spurious RF. Try a different band and see if it helps. I had good luck on Block 19.

Share this post


Link to post
Share on other sites

Also make sure they are using good shielded SDI cables, have had RF issues before from shitty cables.

Share this post


Link to post
Share on other sites

+1

Poor sheild on SDI cable has been a culprit in past. Quality cable is a must.

Share this post


Link to post
Share on other sites

I just worked with 2 bolts on 2 x c300's.

I had no issues with my talent mics (blk 25) or Comtek. I had a Zaxcom hop (blk 28) on one of the cams, no interference as far as I know.

Share this post


Link to post
Share on other sites

I wonder what would happen if Zaxcom and Lectro and others built radio mics that affected the remote focus and HD monitoring?

We have to contend with clicking range finders, RF spray from remote focus and video transmitters, etc., yet they're always fond of saying, "Can't you just wire them?" - Next time I'm going to say, "Sure. Turn of all the crap that interferes with my radio mics, and I'll wire them."

Share this post


Link to post
Share on other sites

jt : " Turning on both Bolts shows an additive increase in signal which is now problematic. "

yes.

" In the mean time, has anybody run across this before ...? "

yes, it is RF interference, and we talk about it here quite a lot.

" And should a product that works in the 5ghz range be spewing out noise in the 500mhz range. "

maybe, maybe not, but they frequently do... the FCC (USA) does have some regulations regarding such "spurious emissions", but even with good RF design (quite a complicated topic itself) there are frequently RF emissions present at harmonic, sub-harmonic, and intermediate frequencies.

there are numerous other factors, including...

TV: " Also make sure they are using good shielded SDI cables, have had RF issues before from shitty cables. "

there are typically significant differences amongst cables, connectors, and adapters; and price can be a clue...

AVU: " Quality cable is a must. "

 

RPS: " I wonder what would happen if Zaxcom and Lectro and others built radio mics that affected the remote focus and HD monitoring? " these devices are not only sources, but also must contend with all the other stuff out there, including our's.

Share this post


Link to post
Share on other sites

"Can't you just wire them?"

OT: Had this line thrown at me a few times by a DP recently who exclusively used prime lenses. I compared using prime lenses with using a (or two) boom(s), whereas asking me to just use wires would be kind of like asking him to use a zoom lens all the time (which he would never do). Of course it's totally different, but he kind of understood that...

Share this post


Link to post
Share on other sites

<<the FCC (USA) does have some regulations regarding such "spurious emissions", but even with good RF design (quite a complicated topic itself) there are frequently RF emissions present at harmonic, sub-harmonic, and intermediate frequencies.>>

 

which basically says the FCC don't know SHIT about what they're doing. and probably so. 

 

which mean the FCC knows TOO MUCH to do too much?  heh... 

Share this post


Link to post
Share on other sites

Started taking the cart apart this afternoon, turning off one piece of gear at a time and doing a scan after each one. No luck until I pulled a pair of jumper cables that took the HD video signal from the back of the cart to the HD monitors. There was still evidence of the spill from the Teradek Bolts but at a much lower level. Reintroducing the cables amplified the spill to the point where it produced interference.

These cables are HD-SDI 75ohm rated and soldered by someone with much experience. No evidence of shorts or discontinuity.

This amplified rf field was very close to the receivers and caused the bad dropouts.

Also, the effect seemed to change over the day being bad at some times and tolerable at others. There was visual evidence of this on the scans.

Furthermore, the issue of the smarttune suggesting frequencies already in use seems to have cleared up.

So I am glad that I will not be facing this problem but quite curious as to how that amplification worked. That's a head scratcher.

Still irritated that the Bolts are so badly made that they dump out crap at 500 mhz when designed to work at 5ghz.

Perhaps Mr Fisher would like to wade in on this.

Share this post


Link to post
Share on other sites

Worked on a show recently where one of my 3 comteks would open squelch when near the Bolt.  Of course, it was the series director's feed- feeding a camera that was then transmitting to a control room via the Bolt.   I thought maybe the Comtek was the problem and had a talk with Comtek support and was even given an RMA to return the Comtek.  I decided to do a little more playing around with the Bolt and enlisted the camera assistant to help.  I had him turn the Bolt on and off while I listened to the comteks open squelch, (one of my least favourite sounds BTW) and was disappointed that power cycling the Bolt did nothing to help the problem.  

On a whim, he then UNPLUGGED the Bolt from it's power tap on the camera.   The squelch closed and the comtek worked perfectly.

 

In short, the Bolt was emitting enough RF at Comtek (216) frequencies to open the squelch when the damn thing was TURNED OFF!!!!!  It's not even transmitting, it's JUST PLUGGED IN for power!

 

Sorry for yelling.  I was astounded. Not to mention flabbergasted and incredibly dismayed. - So check that the power cable is shielded, not just the SDI cable.

 

Cheers,

Brent Calkin

Share this post


Link to post
Share on other sites

Do they want sound or do they want wireless video.  Cant have both.

Share this post


Link to post
Share on other sites

Do they want sound or do they want wireless video.  Cant have both.

 

They'd pick wireless video.

Share this post


Link to post
Share on other sites

The spurious RF may be low enough to meet FCC requirements but still high enough to affect close in receivers. On the other hand they may be unapproved. I haven't found anything on the Teradek web site indicating they have approvals. If someone is close to one of these critters, see if they have FCC markings or an FCC ID code. With an ID code, you can check the FCC site to see if the unit has been approved. Even in the unlicensed bands they must be approved since they are an intentional radiator. For instance, our FCC ID code on the LT transmitter starts with DBZ such as DBZLTA1 for the lower band of the LT transmitter. You can just enter the DBZ and it will come back with all our submissions (think big expenses). You can also enter just a company name. Teradek comes back with no entries. It is possible that they filed under another name. That is why the FCC ID code is so useful.

 

http://transition.fcc.gov/oet/ea/fccid/

 

The interference caused at 500 MHz just by being plugged into power sounds like a noisy switching power supply. That comes under Part 15 and again must be tested but not necessarily approved. If there are no FCC markings, then you can complain to the enforcement arm of the FCC anonymously. After all, you are a licensed service in Part 74 and they can't legally cause you interference.

 

https://consumercomplaints.fcc.gov/hc/en-us

 

The site is 99% for phone and cable TV complaints but they handle this kind of stuff also. Remember there was a high profile case several years ago in which some heavy fines were levied for an unapproved video transmitter (Modulus). Both the manufacturer and retailer got caught up in  a mess.

 

Best Regards,
Larry Fisher
 

Share this post


Link to post
Share on other sites

Everyone,

 

Apologies for the late reply - this post was just recently brought to my attention.

 

ALL Teradek products are approved by the FCC. We have never and will never sell or ship any device without the proper approval from regulating authorities in each region. 

 

Here are the FCC IDs for our latest Bolt: 

Grantee Code: VQS Product Code: AMNMGIN01 
Grantee Code: VQS Product Code: AMNKHIN1 

 

With that said, I have brought up this problem to our engineers and to our chipset manufacturer to get to the bottom of. This is the first time we have heard of Bolt causing problems in the 500Mhz band.

 

Specifically, which models are all of you using so we can get a better idea? Are they generation 1 or 2? What range?

 

And if you have any further questions, please email me directly so I can pass you onto our head of hardware engineering: mike (at) Teradek (dot) com.

 

-Mike

Share this post


Link to post
Share on other sites

Hi Mike,

Thanks for the prompt response to the posting. Hopefully, this can be solved for our mutual users on the sets.

Best Regards,
Larry Fisher
Lectrosonics

Share this post


Link to post
Share on other sites

Hi Mike,

Thanks for the prompt response to the posting. Hopefully, this can be solved for our mutual users on the sets.

Best Regards,

Larry Fisher

Lectrosonics

 

No problem Larry!

 

If any of you are based in Southern California, we would be happy to perform some tests with your gear if you'd like to come down to our offices in Irvine, CA.

 

Also, if you could give me a list of gear models that have had noticeable problems with our Bolt products, we will do our best to bring them in house for testing.

Share this post


Link to post
Share on other sites

I have had trouble with RFI from your gear and remote focus gear using Lectrosonics HM transmitter.

It is frequently used close to camera.

Your gear may not be the only culprit, but it'd be great if we can rule you out, or can go to set armed with the knowledge of what power and video cables to your transmitters are the "correct" or "approved" cables.

If it turns out to be RFI from the power supplies, it'd be useful to know if that occurs with receivers too. They are often on set too.

Robert

Share this post


Link to post
Share on other sites

With that said, I have brought up this problem to our engineers and to our chipset manufacturer to get to the bottom of. This is the first time we have heard of Bolt causing problems in the 500Mhz band.

 

Mike, thanks for your open response. If Teradek has the information, or will soon, it would be great to see a tech note along the lines of the one Sound Devices issued years ago when there were some RF issues with their audio recorders. This tech note provided detailed information, emission graphs, and suggestions that helped us (or at least me) work around those issues. Perhaps a good model for you all?

 

Check it out:

 

 

RF Emissions and the 702, 722, and 744T Recorders

Sound Devices 702, 722, and 744T hard disk recorders have broken new ground for size and performance of modern digital audio recorders. As with the introduction of many new product categories, however, some things that were taken for granted in the past may have to be re-thought moving forward. One area where the modern recorder is different than that of earlier generations is in its use of computing power.

The RF (radio frequency) emissions of hard-disk-based digital recorders are higher than that of the tape-based recorders they replace. This increased stray RF energy can cause interference with wireless receivers in close proximity (within the same bag), reducing the useable range of the wireless microphone system. Some customers experience no performance issues, while others need to take corrective action. With careful planning, however, the 702, 722, and 744T recorders can co-exist with wireless systems with excellent results.

Rest of the note:

http://www.sounddevices.com/notes/recorders/7-series-rf/

Share this post


Link to post
Share on other sites

Mike, thanks for your open response. If Teradek has the information, or will soon, it would be great to see a tech note along the lines of the one Sound Devices issued years ago when there were some RF issues with their audio recorders. This tech note provided detailed information, emission graphs, and suggestions that helped us (or at least me) work around those issues. Perhaps a good model for you all?

 

Check it out:

 

 

RF Emissions and the 702, 722, and 744T Recorders

Sound Devices 702, 722, and 744T hard disk recorders have broken new ground for size and performance of modern digital audio recorders. As with the introduction of many new product categories, however, some things that were taken for granted in the past may have to be re-thought moving forward. One area where the modern recorder is different than that of earlier generations is in its use of computing power.

The RF (radio frequency) emissions of hard-disk-based digital recorders are higher than that of the tape-based recorders they replace. This increased stray RF energy can cause interference with wireless receivers in close proximity (within the same bag), reducing the useable range of the wireless microphone system. Some customers experience no performance issues, while others need to take corrective action. With careful planning, however, the 702, 722, and 744T recorders can co-exist with wireless systems with excellent results.

Rest of the note:

http://www.sounddevices.com/notes/recorders/7-series-rf/

 

Thanks for the recommendation. Ill be sure to push for something like this once we get to the bottom of the issue.

Share this post


Link to post
Share on other sites

Hi Mike,

 

Thanks for jumping in here.  Fury has great respect for the entire Teradek family and was happy, as usual, to see your intervention,once he made you aware of this thread.  You may recall that Fury has a Zaxcom kit, with a Nomad 12 and wireless transmitters/ ERX pieces.   I know you recall that Fury has a Bolt 2000, which worked a treat on set, with all that gear... again today.  

At any rate, no problem for Fury to drop by your facility, with kit in tow, if that helps sort this out-perhaps with some Lectros there as well...   Call if you needed.

 

Thank you very much

 

Fury

Share this post


Link to post
Share on other sites

I've noticed interference from just about every video transmitter I've ever encountered...

They seem to pose the most risk to camera mounted receivers and sometimes just moving the two devices a few inches father apart or rearranging cable paths make the difference between usable range and severe dropouts.

Like others said here I've also noticed that the emissions often come from the connecting BNC cables and that when disconnected the interference disappears. Sometimes even with high quality cable this occurs.

It's a problem but the video transmitter and camera manufacturers don't seem too concerned.

Glad to see teradeck taking interest.

Share this post


Link to post
Share on other sites

I've noticed interference from just about every video transmitter I've ever encountered...

They seem to pose the most risk to camera mounted receivers and sometimes just moving the two devices a few inches father apart or rearranging cable paths make the difference between usable range and severe dropouts.

Like others said here I've also noticed that the emissions often come from the connecting BNC cables and that when disconnected the interference disappears. Sometimes even with high quality cable this occurs.

It's a problem but the video transmitter and camera manufacturers don't seem too concerned.

Glad to see teradeck taking interest.

Hi Derek,

It is very possible to get interference from a device that fully complies with FCC limits on radiated RF. The FCC is concerned that the device not cause interference to broadcast TV sets, let's say, at a distance of  10 feet. (I'm making numbers up here.) Then your laptop won't wipe out your "over the air" TV.  That way you can use your laptop to watch Spinal Tap and watch The Simpsons on TV with rabbit ears. This does not mean you can put a receiver mere inches from a digital device and not have problems.

 

On top of that, the FCC has two types of Part 15 compliance, A and B. "B" is for home use (consumer) and has a very low level for allowable RF radiation (interference).  "A" is much more forgiving with a higher level for industrial or commercial applications. The Teradek Bolt could be tested under A levels since it is not a home device. Some manufacturers will go ahead and test to B levels if the product easily meets those levels. Not to look like heroes, but we test our installed sound DSP devices to B levels since we hope our receivers will be also purchased by those same customers.

 

One would hope that manufacturers would reduce spurious emissions to levels vanishingly small not just because the Feds require it but also to play well together with other devices. I have seen that with some other devices where the first round of designs caused interference but newer designs were much better. A good part of that self improvement is because of social media; potential users (customers) learning about interference problems very quickly. Since the sound and video forums don't cross over very well, maybe we need to get Jeff to start JWSAV.

Best Regards,

Larry Fisher

Lectrosonics

Share this post


Link to post
Share on other sites

Hi Mike,

Thanks for sticking your head into the lion's mouth here!

 

I'll try to find out which Bolt(s) unit we had on set.(we actually had 4 running)

 

I was having troubles with a Comtek PR-216 Option7 setup

 

The Comteks are adjustable in a range from 216 to 217 Mhz.

 

Cheers,

Brent Calkin

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now