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Author Topic: Crazy RF event last night...insight appreciated.  (Read 985 times)

Russell Ault

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Re: Crazy RF event last night...insight appreciated.
« Reply #10 on: May 07, 2018, 12:59:16 am »

RF bars went to 0? Not interference then. You had a loss of RF.
I'd say most likely a bad antenna cable.

In my mind if simply reprogramming the mic to a different channel makes it work again, then it's not likely to be bad hardware (or, for that matter, a loss of RF). Sounds like classic de-sens to me.

-Russ
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Samuel Rees

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Crazy RF event last night...insight appreciated.
« Reply #11 on: May 07, 2018, 09:53:48 am »

IShort of coming in on a previous day and doing a 24hr scan, there was nothing that could have prepared me for this.

Except coordinating with wireless workbench or similar to avoid your local TV channels altogether

Sent from my iPhone using Tapatalk
« Last Edit: May 07, 2018, 11:21:25 pm by Samuel Rees »
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Loren Miller

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Re: Crazy RF event last night...insight appreciated.
« Reply #12 on: May 07, 2018, 11:05:46 pm »

In my mind if simply reprogramming the mic to a different channel makes it work again, then it's not likely to be bad hardware (or, for that matter, a loss of RF). Sounds like classic de-sens to me.

-Russ
What is a classic de-sens??
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Loren Miller

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Re: Crazy RF event last night...insight appreciated.
« Reply #13 on: May 07, 2018, 11:24:22 pm »

RF bars went to 0? Not interference then. You had a loss of RF.
I'd say most likely a bad antenna cable.
Did you say "Combiner"? I hope you mean "Distributor"... Combiners are for transmitters, not receivers.
Was it a 2-ch receiver? Why did you need a distributor, the Shures are built in.
Were you using 2 antennas?

2 channels of QLXD, which is two 1/2 rack boxes, so instead of 4 1/2 wave antennas, I purchased a kit from RF Venue that eliminates 2 of those antennas by using 2 passive antenna combiners https://www.rfvenue.com/products/2x1split
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Russell Ault

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Re: Crazy RF event last night...insight appreciated.
« Reply #14 on: May 08, 2018, 12:48:20 am »

What is a classic de-sens??

(Ripped straight from Wikipedia):

Quote
Desensitization is a form of electromagnetic interference where a radio receiver is unable to receive a weak radio signal that it might otherwise be able to receive when there is no interference. This is caused by a nearby transmitter with a strong signal on a close frequency, which overloads the receiver and makes it unable to fully receive the desired signal.

-Russ
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Loren Miller

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Re: Crazy RF event last night...insight appreciated.
« Reply #15 on: May 08, 2018, 10:28:38 am »

(Ripped straight from Wikipedia):

-Russ
Got it, wasnít familiar with that term!

Anyone know of a place/website etc other than mfgr website that lists out clear or used freqs by area?
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Paul McDermott

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Re: Crazy RF event last night...insight appreciated.
« Reply #16 on: May 08, 2018, 11:27:48 am »

Got it, wasnít familiar with that term!

Anyone know of a place/website etc other than mfgr website that lists out clear or used freqs by area?


Rabbit ears has a very easy to navigate site, with the current and post-repack TV stations in each market. This site is full of useful information and is updated regularly. It is my go to for a quick lookup. the following link is to the page on the rabbit ears site that I go to the most for a quick reference.

https://www.rabbitears.info/repackchannels.php?country=B&city=&state=&mktid=39&owner=&sort=oldch&ph=&lss=&status=

Goole Spectrum Database is sometimes useful for markets with land mobile licenses public safety.It also shows local TV stations in their current broadcast spectrum location.
https://www.google.com/get/spectrumdatabase/channel/

You can also to a radius search on the FCC's website. This option is not quick of user friendly but will give you very detailed information motion if that is what you are looking for
https://www.fcc.gov/media/television/tv-query

I would avoid both current TV Stations and the post re-pack locations of your local channels.
« Last Edit: May 08, 2018, 11:38:22 am by Paul McDermott »
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Paul McDermott
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Andrew Broughton

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Re: Crazy RF event last night...insight appreciated.
« Reply #17 on: May 08, 2018, 11:39:04 am »

(Ripped straight from Wikipedia):

-Russ
Seems to me the rf bars wouldn't (or shouldn't) go to zero in that scenario, since the receiver is still receiving RF, just not the signal it wants.
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-Andy

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Paul McDermott

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Re: Crazy RF event last night...insight appreciated.
« Reply #18 on: May 08, 2018, 11:53:55 am »

Seems to me the rf bars wouldn't (or shouldn't) go to zero in that scenario, since the receiver is still receiving RF, just not the signal it wants.


It could be the aggregate of several less than optimal setup and operation practices. It may not be as simple as finding one root cause.

Have you tried to recreate the failure?

When you test your setup try to create a worst-case scenario, turn you back to the antenna, cover the antenna on the HH mic with your hand, etc.

 
« Last Edit: May 08, 2018, 11:59:39 am by Paul McDermott »
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Luke Geis

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Re: Crazy RF event last night...insight appreciated.
« Reply #19 on: May 08, 2018, 02:57:25 pm »

Wireless is one of those things where when it hits the fan, it is usually too late to save yourself. You can do everything right and there is no guarantee it will be 100% reliable. The biggest issue is not typically being able to scan the environment as if you were in show and deploy the mics accordingly in a timely fashion. Typically people are walking in the door filling the venue just about the time you are deploying the mics on the presenters. Too late now, you are cooked. You can scan the room for three days and not be able to account for what happens when 300 people walk in the room.

It should be noted however that the RF power you utilize should be set accordingly for the distance between the mic and the receiver. The goal is to use the lowest amount of RF power possible for any given distance. If you were within 50' of the receiver, you could have been cooking the antenna's. There is some math involved, but typically anything between 50' - 100' only needs about 10mw of RF power. After that, you can start cranking it up if you are noticing weak signals.
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I don't understand how you can't hear your self
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