Two quick basic audio questions: windshield, radio interference.

I

Iudex

Well-known member
Hi there, I was wondering if someone could answer some questions I had in mind.

The first one has to do with my windshield: I bought a WS7 for my NTG-3, to use in outdoors windy situations - mainly. Nevertheless, should I keep it on all the time or will I lose noticable audio quality using a windshield in a not wind-noisy shot?

On the other hand, I was wondering if there is any way of avoiding radio interference. A couple of months ago, shooting near a radio tower central sometimes my EX1+XLR+NTG-3 rig picked up radio signal. Is the XLR picking up the unwanted signal or is it the microphone?

Thank you very much!

I.
 
Most folks leave the zep on all the time. There may be some slight high feq. loss? but not much and one surprize gust will blow your whole take if it's off.

Could be a bad cable or it could be the mic. Some mics are more susceptible to RF than others. If your actually picking up the station rather than static/ noise I would bet on a cable with a bad shield.
 
For the windscreen, generally it's a better idea to use it only as needed, as you do lose some high frequencies. Although, that's a personal preference and you should do your own comparisons. If you like it, then go for it (plus the added protection is never a bad thing).

Hadn't heard of anyone with issues on the NTG-3 as it's supposed to be RF shielded...
Likely the XLR.
 
I've experienced RF interference issues with phantom-powered mics a few times, usually when shooting around Toronto's waterfront (with that pesky CN tower) or around arcing electricity (welding, streetcars, lightning). The couple of times I was using back-electet condensor mics, I found that switching to the internal battery would solve the problem nicely. Otherwise, the best solution I've come up with is using T-12 MKH-series sennheiser mics (MKH416t, MKH816t, as well as some of the older models).
 
Should go without saying but make sure you're using star-quad xlr cable, that will help weed out some interference as well.
 
Iudex said:
Thanks everybody, thanks SMuir, unfortunately the NTG-3 is only phantom powered :(.
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The question you have to ask your self is how good are the connections, how good is the shielding, and how long the lines are. In the case of connections, anything that leads to 'imbalance', will potentially allow for RF to 'sneak in'.

On the other hand if you standing next to the transmitter... like shooting on top of a building, (or like here in San Diego, Mt. Solidad, where everyone in the world has a transmitter...), it may just be almost impossible to get rid of...
 
Rippie said:
you could also try just putting a ferrite bead on the xlr near the mic end.
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You beat me to it. This is the most common fix when working in an RF environment. Both in the mike and at the end of the mike cable. It is debateable at which end since the Ferrite bead attenuates RF and that could be at either end of the mike cable. The cable being an antenna. Remember to loop a single conductor around the bead.
de WB9YRR,
 
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I have experienced the phenomenon (doot doo do doo doo) of picking up a radio station in my cables more than once. Strangely, it's always the same radio station, broadcasting on 102.9FM. It always seems to be caused by cheap cables.
 
Noiz2 said:
Now how would you do that with out cutting your cable up and breaking the shield?
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Yeah, you have to open the connector to do that. Only way, no big deal. Use a small bead that will fit in the XLR. Usually put one in the mike too.
 
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Captain Pierce said:
I have experienced the phenomenon (doot doo do doo doo) of picking up a radio station in my cables more than once. Strangely, it's always the same radio station, broadcasting on 102.9FM. It always seems to be caused by cheap cables.
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Whatever the reason you're picking up RF, a little impedence differences, funny electronics, etc. clearly it is tuned to that frequency... is this across cables and mics, or just a specifc mic and cable+<whatever you plug it into>.

The Wife wears a hearing aid, and on various occasions, claims to hear a radio station folding into her hearing aid. The nearest broadcast radio antenna is about 2 miles away... of course she could be hearing voices, and I should worry.

The hearing aid does have what is known as a phone switch, which switches in a loop which picks up the magnetic flux of the phone speaker, and that is then passed into the hearing aid, for her to better use phones... the problem is if there is some sort of noisy 60 cycle thing in the vicinity, she picks that up too...

Then there's the GSM switching noise... CDMA doesn't suffer from that problem...
 
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Thanks again! I will call the place that sold me the XLR and talk to them about putting a bead on it.
 
I can't find the small beads that I picked up years ago but you might use the split beads that most people are used to seeing on USB and VGA cables. In any case you need an RF choke that will attenuate the effect of radio interfearance.
 
Two things I alsways do now.

On all XLR cables I am now moving over to the new Neutrik EMC-XLR Series - this has a ferrite bead on pin-1, a small internal PCB with capacitors so that the shell is connected to pin-1 via these caps. that prevent hum loops - and - the female has a "toothed ring" that makes full and proper contact with the male; both keeping it tight and unmoving and providing a proper sealed "Faraday cage" connection to prevent RF pick-up.

The EMC-XLR Series is a specifically designed version of the XX series to give enhanced RF screening for critical applications in live performance and recording where there are particular problems with radio transmission or mobile phones. The design guarantees a continuous RF shield connection from the cable to the chassis connector housing via a circular capacitor around the cable shield. An EMI suppression ferrite bead between pin 1 and the cable screen provides a low-pass filter for improved RF rejection.
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With more and more RF floating about nowadays, any new cables I get will be fitted with these - and I have been doing this ever since the EMC series came out.

I also keep several Canford Audio in-line XLR RF filters with me all the tome and plug them in if ever I have an RF problem.

CANFORD XLR IN-LINE RF FILTER

Although input stages today can provide a high degree of RF rejection, they are never totally immune and location recording, temporary installations and outside broadcast can pose particular challenges. Even using good quality screened star-quad cables (from Canford) still leaves a degree of risks that an AM radio signal will get into your equipment and be demodulated and this RF rejection filter can then save the day, or more often the evening!
Radio breakthrough is normally caused by common-mode RF signals being carried through either input or output cables acting as aerials and with the active electronics of the mixer or recorder providing a demodulator. The Canford RF immunity filter is plugged into the problem circuit at the mixer end of the cable and provides an effective solution by greatly attenuating the RF signal entering the mixer. The rejection is primarily of common-mode signals so it has no effect on the balanced audio signal even in applications when it is considered necessary to maintain the frequency response well into supersonic regions.
The filter is built into a high quality, machined “barrel” with Neutrik 3-pin XLR connectors, male on one end and female on the other. The internal circuit is symmetrical making the device equally suitable for use on inputs and outputs.
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I hope this helps.

John
 
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