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Author Topic: Prefered RBW, TTi or other, for scans to use with wireless Tx  (Read 278 times)

Mike Kahrs

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Prefered RBW, TTi or other, for scans to use with wireless Tx
« on: November 24, 2019, 03:20:07 pm »

Greetings, I'm curious what RBW others use when scanning for clear air and headroom while looking for space to deploy wireless mics when the client/supplier provides ill advised frequency bands.  On my TTi a RBW of 280kHz gives me a floor very close to what I see when using a Shure product with WWB; I like the view a RBW of 15 when reviewing mics already tuned and transmitting.

In a five-story Las Vegas hotel last week, and with the higher less protected floors harder to find frequencies to use, I found that a RBW of 15 was fooling me into thinking a particular freq would work, only to find limited range or no range.

Thanks.
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Henry Cohen

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Re: Prefered RBW, TTi or other, for scans to use with wireless Tx
« Reply #1 on: November 24, 2019, 07:31:38 pm »

Greetings, I'm curious what RBW others use when scanning for clear air and headroom while looking for space to deploy wireless mics when the client/supplier provides ill advised frequency bands.  On my TTi a RBW of 280kHz gives me a floor very close to what I see when using a Shure product with WWB; I like the view a RBW of 15 when reviewing mics already tuned and transmitting.

In short, the lower the RBW value, the lower the displayed noise floor and the greater resolution of the scanned span. However, the scan time will be longer, and there's the chance to miss any intermittent signals, so the smaller the span the better. Generally, if looking to see occupied TV channels, a 60MHz span (one TV channel per division) works well to ID active channels in a relatively short sweep time. If you're looking for other co-located wireless mics (and similar type equipment), best to look at individual 6MHz TV channels with a low RBW.


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In a five-story Las Vegas hotel last week, and with the higher less protected floors harder to find frequencies to use, I found that a RBW of 15 was fooling me into thinking a particular freq would work, only to find limited range or no range.

This doesn't make sense; can you elaborate? It could be possible your span was too great to properly resolve the signals to the display. Try smaller spans.
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Henry Cohen

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Scott Helmke

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Re: Prefered RBW, TTi or other, for scans to use with wireless Tx
« Reply #2 on: November 24, 2019, 09:27:31 pm »

When I'm looking for TV stations I set the TTi bandwidth to 60MHz, as Henry suggested.  That way the 10 divisions on the screen line up with the 6MHz TV stations so it's easy to figure out channel #s.  RBW is basically the tradeoff between seeing narrow signals and getting a reasonably quick scan.
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Mac Kerr

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Re: Prefered RBW, TTi or other, for scans to use with wireless Tx
« Reply #3 on: November 25, 2019, 12:04:31 am »

When I'm looking for TV stations I set the TTi bandwidth to 60MHz, as Henry suggested.  That way the 10 divisions on the screen line up with the 6MHz TV stations so it's easy to figure out channel #s.  RBW is basically the tradeoff between seeing narrow signals and getting a reasonably quick scan.

Different ResolutionBandWidth values will also display different noise floors. The smaller the RBW the lower the noise floor displayed, since the noise displayed is the sum of the noise within the RBW window.

When you are looking for active TV channels use a wide scan window, and a higher RBW value to get a reasonable scan rate, but for looking at individual or a couple of TV bands to see your active transmitters and anything near them, use as small an RBW value as you can with reasonable scan rates. This will show you more detail, and a better idea of what the noise floor actually looks like.

Mac
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John Sulek

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Re: Prefered RBW, TTi or other, for scans to use with wireless Tx
« Reply #4 on: November 25, 2019, 01:05:03 pm »

In a five-story Las Vegas hotel last week, and with the higher less protected floors harder to find frequencies to use, I found that a RBW of 15 was fooling me into thinking a particular freq would work, only to find limited range or no range.
Thanks.

I have always found a span of 1MHz and an RBW of 15KHz to be pretty effective when checking individual frequencies on the TTi. The graticule lines end up being 100KHz so it's easy to check the spacing between adjacent freqs.

Even on a span of 60MHz, an RBW of 15KHz gives a scan update in just under 5 secs. I like it because you can see things that would otherwise get lost in the noise floor but might poke up a bit stronger in level as the day goes on (or the roving B roll crew gets closer).
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Re: Prefered RBW, TTi or other, for scans to use with wireless Tx
« Reply #4 on: November 25, 2019, 01:05:03 pm »


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