Sennheiser G3 - no frequencies open.

Michael Carter

Michael Carter

Veteran
I just purchased a Sennheiser G3 setup.

On my initial frequency scan, only one or two banks showed an available frequency. Today I did a scan, and not a single bank had even one - every bank showed zero available.

I tried this in my home, a residential area about 3 miles from downtown. This seems a little odd to me... I've googled but found no info.

Is this normal for the G3, or is there a problem with my unit?
 
It depends greatly on WHERE you are! Do you mean "downtown West Undershirt, North Dakota"?
Or do you mean "downtown New York City"?

At least complete your user profile to reveal WHERE you are located.

It would also be rather helpful to mention what frequency block(s?) you are using.

Else the only response we can offer is: It depends. In some places that is normal. In other places that would be very strange.
 
Michael Carter said:
I just purchased a Sennheiser G3 setup.

On my initial frequency scan, only one or two banks showed an available frequency. Today I did a scan, and not a single bank had even one - every bank showed zero available.

I tried this in my home, a residential area about 3 miles from downtown. This seems a little odd to me... I've googled but found no info.

Is this normal for the G3, or is there a problem with my unit?
Click to expand...

Yes... where are you located?

In my area, which has quite a bit of RF spectrum utilized, there are 2 channels that are 'for RF mics', TV channels 35(596-602 MHz) and 38(614-620 MHz).

That said, if you are in close proximity to a transmitter, there may be adjacent channel interference. A spectrum analyzer would assist in 'finding' as 'clean' a channel as possible...

In the US, the FCC sites may not be 'returned to operation', as the Sennheiser site seems to indicate when using their channel finder web function.
 
I had a B set of G3's out from a rental house the other day. I had the same problem. Only one available channel and we got constant RF noise in downtown Burbank. The shoot was a bust. Gonna have to reshoot. The A channel version was fine.
 
Thanks - Dallas, TX. "B" channel system. 626-668.

Sheldon, you had trouble with the "B" as well. Is this fairly common? I may be able to exchange it...
 
Michael Carter said:
Thanks - Dallas, TX. "B" channel system. 626-668.

Sheldon, you had trouble with the "B" as well. Is this fairly common? I may be able to exchange it...
Click to expand...

According to my 'super secret' means, in the Dallas TX area, TV channels 33(584-590) and 47(668-674) are allocated for 'mic' use.

According to the same secret means... it looks like the spectrum for Dallas is 'pretty full'...

Here's one version of 'super secret means'...

http://whitespaces.spectrumbridge.com/whitespaces/#Search

In your case, if you can't select in the 33/47 channel ranges, you'd be looking for 'whitespace', which the above URL will indicate.

"Whitespace" means that at your power level, you can 'use'(*) the spectrum, but you don't have exclusive use, and so, may experience interference.

--- Here's the channel list for 'whitespace', as well as the 'mic' Reserved channels from that URL
33 584-590 Reserved **
47 668-674 Reserved **
5 76-82 Available **
7 174-180 Available **
10 192-198 Available **
2 54-60 White Space **
11 198-204 White Space **
12 204-210 White Space **
13 210-216 White Space **
24 530-536 White Space **
26 542-548 White Space **
49 680-686 White Space **
----

*Since I am not now, nor have I ever been an FCC 'official' source of information or certification for operation of any equipment, the 'can' should be interpreted to mean, 'physically able', whether or not it is permitted under FCC rules for your equipment, is a different statement...
 
Sheldon Charron said:
I had a B set of G3's out from a rental house the other day. I had the same problem. Only one available channel and we got constant RF noise in downtown Burbank. The shoot was a bust. Gonna have to reshoot. The A channel version was fine.
Click to expand...

For you in Beautiful Downtown Broadcast Central Burbank California...

----
30 566-572 Reserved **
5 76-82 Available **
---

So, you're pretty limited as to what you can expect with 'minimal' interference...

(Since I don't keep up on Sennheiser specifically, I don't know if any of their equipment operates in the low VHF band(TV Channel 5) at all. )
 
Yeah I agree Burbank is pretty crazy full of mics in use at any given time. :) But the point is, A worked fine, while B did not, so if possible, I'll get another A, just in case. ;)
 
Sheldon Charron said:
Yeah I agree Burbank is pretty crazy full of mics in use at any given time. :) But the point is, A worked fine, while B did not, so if possible, I'll get another A, just in case. ;)
Click to expand...

In Burbank, it seems that TV Channel 30 is reserved for 'mics' and that seems to be corresponding to the G range on Sennheiser's frequencies.

You of course may get lucky due to shadowing, and the like in a 'downtown' setting.

On more 'open' areas, there could be a lot of interference.
 
I normally refer to the "Sennheiser Frequency Finder", and choose a channel with the lowest dB in a given region... However...
[h=2]"Frequency Finder is currently unavailable due to the FCC website shutdown."[/h]
 
The Sennheiser Frequency Finder is working fine now.

Also, please remember:

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Click to expand...
 
Rick R said:
I normally refer to the "Sennheiser Frequency Finder", and choose a channel with the lowest dB in a given region... However...
[h=2]"Frequency Finder is currently unavailable due to the FCC website shutdown."[/h]
Click to expand...

While not exactly as clear as the Sennheiser widget would be fore specifically 'wireless microphones', the following URLs do allow for finding 'white space' and do list those TV band channels that are 'reserved' for mics in a given area.

https://prism.telcordia.com/tvws/main/home/contour_vis.shtml

and

http://whitespaces.spectrumbridge.com/whitespaces/#Search

I believe these are using a captured image of the FCC database, and so, while perhaps is not up to date relative to the last 2 weeks, were( and are now) available during the FCC site shutdown.
 
That is a very good resource I was unaware of.
Thanks j1clar !

PS- I meant to state the highest dB of isolation.
 
Last edited:
Yeah my shoot was on the LA River. It was wide open with power lines overhead. It's interesting that wide open areas cause more problems than inside. Why is that?
j1clark@ucsd.edu said:
In Burbank, it seems that TV Channel 30 is reserved for 'mics' and that seems to be corresponding to the G range on Sennheiser's frequencies.

You of course may get lucky due to shadowing, and the like in a 'downtown' setting.

On more 'open' areas, there could be a lot of interference.
Click to expand...
 
Sheldon Charron said:
Yeah my shoot was on the LA River. It was wide open with power lines overhead. It's interesting that wide open areas cause more problems than inside. Why is that?
Click to expand...

I would have to get a spectrum analyzer to give 'details', but one of the fundamental principles of RF at TV frequencies is 'line of sight'. It's the same for your mic transmitter and receiver... just when you have Megawatt transmitters for TV the distances are greater...

So, in a downtown area with buildings all around one has reflections to deal with, but also there is shadowing, such that the resulting signal is very low, since the receiver is no longer in 'line of sight', and absent reflections, would not pick up the signal.

For example, In San Diego there is a place called Mt Soledad. It has long been used as a major antenna location for TV, Radio, and other licensed uses. There's a monument near by that people go, for the view of San Diego. There's so much RF that car remotes don't work until your right on top of the car.

Now to the north side there are streets and houses, and just 200 feet below the 'crest line', one can get TV reception from LA, 60-70 miles line of sight... with very little interference from the RF on top of the hill...

I looked at the Sennheiser site... I thought they may have made it 'easy'... but it looks like the FCC database with a few controls.

One option was 'distance'. So for example, given the mention of Burbank... I selected Burbank, CA, and with 70 miles of 'area' came up with a long list of channels occupied. I then changed the radius to 10 miles... supposedly totally 'free' of transmitters... well yeah... but go 30 miles out, and one has a number of broadcast TV channels entering the picture at reasonable signal strengths to cause interference with your mic.

Here's a 'coverage map' for KTLA operating on TV Channel 31 @ 1000KW.

http://www.tvfool.com/?option=com_wrapper&Itemid=80&q=call=ktla

Here's a screen shot of the coverage map:

attachment.php


And needless to say, that's just one transmitter in the greater LA area.
 
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