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Author Topic: So this guy told me....  (Read 7700 times)

Mac Kerr

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Re: So this guy told me....
« Reply #10 on: December 12, 2017, 09:31:28 am »

I would guess though that this is simply from the mic/beltpack working a little harder to find a signal?  When they're put into the metal tray and cut off from talking to their receiver, I'd assume they either change/up their transmit power a little to try and get a better signal (as a mobile phone does in a low signal area) or page/attempt to connect more regularly, and this is what drains the battery.

No. RF mic transmitters don't know when they have a good transmission, they just transmit. There is no link back to tell the mic to go into high power, like there is on some RF comms systems.

Mac
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TJ (Tom) Cornish

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Re: So this guy told me....
« Reply #11 on: December 12, 2017, 09:52:15 am »

There are two ideas being floated:

1. That the radiated RF energy of the mic somehow drains and/or damages rechargeable cells (but doesn't affect alkaline cells)

2. That due to the RF shield, the mic tries to work harder and draws more power than it normally does.

Scenario 1 is voodoo of the same order as always wearing the same pair of socks on game day.  Scenario 2 seems almost as unlikely, as Mac has noted that though there are some mics with 2-way communication for status and control, wireless mics don't adjust their transmit power like cell phones do. 

Both of these scenarios can be tested by timing how long it takes to run a set of batteries down.  Scenario 2 can be tested more quickly by measuring the current draw of the mic both covered and uncovered.

I'm not sufficiently bothered to perform this test and even if it were conclusively proven it may not sway the more superstitious (cf the Big Ben craze), but as experiments go, this one isn't very difficult to perform if someone were so inclined.
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Stephen Swaffer

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Re: So this guy told me....
« Reply #12 on: December 12, 2017, 09:53:33 am »

What about digital xmtrs?  I know the Shure 2.4 Ghz sync with the receiver so that has to be 2 way?
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Steve Swaffer

Milt Hathaway

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Re: So this guy told me....
« Reply #13 on: December 12, 2017, 10:09:53 am »

Perhaps in some cases the proximity of the tray is detuning the antenna causing the transmitter to see an incorrect load.
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Samuel Rees

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Re: So this guy told me....
« Reply #14 on: December 12, 2017, 02:05:24 pm »

Perhaps in some cases the proximity of the tray is detuning the antenna causing the transmitter to see an incorrect load.

I’ve read the following from RF Venue:

“The only downside to adopting a tray system is that since the tray effectively becomes the antenna to the transmitter, and that antenna, for lack of a better word, sucks (is extremely inefficient), the current drawn from the transmitter is increased, and devices left in trays will bleed battery about 10% faster than when sufficiently isolated or insulated from metal surfaces.”

https://www.rfvenue.com/blog/2016/05/13/whats-up-with-the-tin-bins




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John Roberts {JR}

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Re: So this guy told me....
« Reply #15 on: December 12, 2017, 04:14:01 pm »

I’ve read the following from RF Venue:

“The only downside to adopting a tray system is that since the tray effectively becomes the antenna to the transmitter, and that antenna, for lack of a better word, sucks (is extremely inefficient), the current drawn from the transmitter is increased, and devices left in trays will bleed battery about 10% faster than when sufficiently isolated or insulated from metal surfaces.”

https://www.rfvenue.com/blog/2016/05/13/whats-up-with-the-tin-bins




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I still might be tempted to perform a few experiments. 

Maybe you need a bigger metal pan spaced with a gap away from transmitters.

JR
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Samuel Rees

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Re: So this guy told me....
« Reply #16 on: December 12, 2017, 05:37:24 pm »

I still might be tempted to perform a few experiments. 

Maybe you need a bigger metal pan spaced with a gap away from transmitters.

JR

I would wonder, though, if the pan interfering with the antenna is both the cause of the increased current draw and and the desired effect in terms of reducing intermods. All speculation, but it wouldn’t surprise me if this was two sides of the same coin.


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Keith Broughton

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Re: So this guy told me....
« Reply #17 on: December 12, 2017, 06:13:37 pm »

I’ve read the following from RF Venue:

“The only downside to adopting a tray system is that since the tray effectively becomes the antenna to the transmitter, and that antenna, for lack of a better word, sucks (is extremely inefficient), the current drawn from the transmitter is increased, and devices left in trays will bleed battery about 10% faster than when sufficiently isolated or insulated from metal surfaces.”

https://www.rfvenue.com/blog/2016/05/13/whats-up-with-the-tin-bins




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Learn something every day! :D
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John Roberts {JR}

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Re: So this guy told me....
« Reply #18 on: December 12, 2017, 11:12:50 pm »

I would wonder, though, if the pan interfering with the antenna is both the cause of the increased current draw and and the desired effect in terms of reducing intermods. All speculation, but it wouldn’t surprise me if this was two sides of the same coin.


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I am mostly speculating about inside the transmitter but the metal pan should short out the RF fields to each other so prevent the interference getting outside the pan.

Loading the transmitters is more subtle and seems like a little distance could reduce the effective coupling and loading, but this is mostly guesswork on my part.

Have we confirmed that this is real ?  I know that I don't know.

JR
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Scott Holtzman

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Re: So this guy told me....
« Reply #19 on: December 13, 2017, 12:07:50 am »

I am mostly speculating about inside the transmitter but the metal pan should short out the RF fields to each other so prevent the interference getting outside the pan.

Loading the transmitters is more subtle and seems like a little distance could reduce the effective coupling and loading, but this is mostly guesswork on my part.

Have we confirmed that this is real ?  I know that I don't know.

JR

The pan would have to be 1/2 wavelength away for it not to be considered "near field".  That's about 5"

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Scott AKA "Skyking" Holtzman
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