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Wireless Sennheiser G2/100 -- how many channels will it support?

Discussion in 'Sound, Music, and Intercom' started by jkowtko, Oct 21, 2008.

  1. jkowtko

    jkowtko Active Member

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    At some point I'm going to have to replace our old AKG WMS80 systems ...

    As an alternative to simply upgrading to AKG WMS400/450 systems, I'm thinking of just getting some Sennheiser G2 100s. (The theater can't afford anything more expensive).

    I would like to clarify the frequency selection options though, since the docs aren't completely clear --

    Within a "band" (of which a given wireless set can belong to only one band), the G2 100 series has "four preset" frequencies per each of eight banks.

    Does that mean I can theoretically (barring local TV station interference) be able to run up to 4x8 = 32 channels within a single frequency band, intermodulation-free? Or is there a much lower practical limit?

    In general, how many G2/100 channels can be run together?

    Do the 300 and 500 series Tx/Rx have better RF electronics allowing you to run more channels, or are the only differences in convenience features?

    I also assume that the manual frequency adjustment will allow you to set and store any of the 1440 frequencies within the band, in case the presets don't give you what you want.

    Thanks. John
     
  2. DaveySimps

    DaveySimps CBMod CB Mods Premium Member

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    After reading their specs, I would say your best case scenario (ignoring local RF issues such as TV stations,) would be 20 frequencies without intermodulation. 4 for each bank @ 5 banks total (bank 1 518-554, bank 2 626-662, bank 3 740-776, bank 4 786-822, and bank 5 830-866). This would, of course, also be ignoring all of the white space issues coming up in February. Again, this would be BEST case scenario, in an ideal world.

    http://www.sennheisernordic.com/india/icm_eng.nsf/resources/Serie_100_GB.pdf/$File/Serie_100_GB.pdf



    I must say that I have not used them before, so I would defer to anyone with hands on expirence with them.

    ~Dave
     
  3. jkowtko

    jkowtko Active Member

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    Okay, I get it now -- it works about the same as the AKG systems ... just different terminology and method of instruction.

    I think that only frequency ranges A and B (the two lowest ones) would be viable under the FCC ban. So the next question is, can you run more than four 100 series units within a frequency range?

    According to the doc, within a frequency range you can select a bank and have the receiver scan to see if all four channels are free for use. If they are, then you can set up to four channels in that bank. If not, you can switch to the next bank and scan again. The same method applies for the Series 300 (up to 8 channels) and the Series 500 (up to 20 channels).

    Now, other than the scanning, and slightly better S/N and rejection ratios, the RF specs for the 100, 300 and 500 series look about the same. So although you cannot scan for more than 4 channels in a bank with the 100, can you set more units manually to channels 5+ listed on the frequency sheet? Or by using a frequency mgmt program (which I assume Tech Support will have)?

    Thanks. John
     
    Last edited: Oct 21, 2008
  4. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    The short answer is that you can probably cram 20+ channels in, if you do it right (i.e., ignore the presets and coordinate it yourself).

    Here's the longer, but more detailed, answer. Looking at the specs, there are two frequency ranges available for use within the US - 518-554 and 626-662. This covers TV channels 22-27 and 40-45.

    The first thing you need to do is download this document: DTV Allotments. It is the latest list, issued by the FCC, of the FINAL DTV channels allocations for the country. You'll need to find your city, or closest cities, and see what channels will be occupied after February 17, 2009 (The "NTSC Chan" column shows the current analog channel, and the "DTV Chan" column tells you where they are moving to [may not be what DTV channel they are on now]).

    Next, use a program like SIFM (Sennheiser; Free) or IAS (PWS; 15 Day Fully Featured Demo Available; Otherwise very expensive), and plug in the channels that will be filled, along with the frequency ranges you have. IAS is generally considered better, but like I said, it's time limited. Tell it to chug out frequencies (and print them out if you're using IAS!). This will tell you EXACTLY how many channels you can get in. I'm going to bet it'll be in the 20 or so range, but I've been known to be wrong before. :)

    REMEMBER - use the channel allocations AFTER Feb 17, and NOT the current ones. They'll do you absolutely no good unless you're going to use these mics before then (of course, if you need them before then, you'll need to generate two frequency sets - one for before, and one for after).

    Please let me know (here or via PM) if you have any questions. Also, read over the FAQ if you haven't already.

    ...You know, I should add these steps to my FAQ....

    'Zat help?
     
    Last edited: Oct 22, 2008
    scottmcleod and (deleted member) like this.
  5. jkowtko

    jkowtko Active Member

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    Yep, that all makes sense -- thanks Mike.

    I downloaded SIMF and will play with it a bit ... yes I am looking at post-Feb17 as the option here. And there are going to be a lot of channels in the area (San Francisco, San Jose, San Mateo) but hopefully I can squeeze in around them. I'll have to run the frequencies to determine how many range A and B units to get.

    Thanks. John
     
  6. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    Yeah, it looks like there will be channels on 27, 40, 41, 43, and 44. So you might be able to get a few units into the upper split, but I would put most of your eggs into 500 MHz basket.

    One thing that can help is to buy directional "shark fin" antennas, and get them as close to the stage as possible. Run good coax back to your antenna splitter. That will help keep your signal to noise ratio high (where noise here is TV signals).
     

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