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Author Topic: Antenna Length  (Read 467 times)

Curt Sorensen

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Antenna Length
« on: March 08, 2017, 06:00:03 pm »

Apologies if this is not relevant to PSW folks, lock it if so. Iím trying to maintain some Sennheiser ENG wireless systems in the A range. The kits use SK3063 belt-pack transmitters [A=450-626, although the sixteen pre-programmed frequencies are between 500-530]; and more agile EK3241 belt-pack receivers [A=450-626]. There are currently a number of different length antennas in each kit, which canít be right.

I have an Ďantenna length chartí for the EK3241 that says to use a 135mm length. I have an SK3063 Service Manual with a formula that gives a result in centimeters after dividing 7500 by the frequency. It doesnít make clear how to accommodate a range of frequencies, however. Using 450 gives 167mm; 550mm gives 136mm. These results lead me to believe 135mm may be correct.

Sennheiser support says to use the 200mm 542181 antenna [which is actually 220mm], but doesnít mention trimming it to a shorter length. The formula then suggests a [200mm or] 20cm antenna is optimal for 375MHz. Retailers of the 542181 all state to include the frequency range to receive the proper length. Support also states that the SK3063 and EK3241 use the same length.

So Iíd love to know what length is optimal for these systems, and Iím curious how much difference the various lengths we currently have even matter. And [or?] finally is there somewhere I can learn more about this for myself without having to wade through in-depth RF theory thatís way over my head?

Thanks for any input as well as all the activity on this forum,
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Curt Sorensen
Madison, Wisconsin

Henry Cohen

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Re: Antenna Length
« Reply #1 on: March 08, 2017, 10:00:22 pm »

So Iíd love to know what length is optimal for these systems, and Iím curious how much difference the various lengths we currently have even matter.

Cut the radiator length for the center frequency of the transmitter's tuning range. The typical 1/4 wave antenna at UHF frequencies with a .1" (2.54mm) element diameter (excluding the insulation or cladding) will provide about 50-60MHz 3dB (1/2 power) bandwidth.


Quote
And [or?] finally is there somewhere I can learn more about this for myself without having to wade through in-depth RF theory thatís way over my head?

See the brand new sticky "Learning Resources" (Thanks to Diogo).
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Henry Cohen

CP Communications    www.cpcomms.com
Radio Active Designs  www.radioactiverf.com

Erik Jerde

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Re: Antenna Length
« Reply #2 on: March 08, 2017, 10:35:26 pm »

I've come across adjustable antennas in the past that could be hand tuned to the specific frequency of they system they were bein used on.  I never used them, they were more of a curiosity to me.  I've got great respect for the guys who really understand all the wireless stuff.  I'm thankful that the out-of-the-box antennas have always worked for me.  I also haven't ever done more than probably 20 channels.
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Curt Sorensen

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Re: Antenna Length
« Reply #3 on: March 08, 2017, 11:30:57 pm »

Hi,
Henry thanks so much for your clear and concise response. Your contributions [and many others'] have made many of the assigned events I've done recently go very well, while elevating my confidence in even attempting them. Diogo's links appeared about the same time as my post, and I've dug into them already.

What an amazing resource this forum and it's contributors are.
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Curt Sorensen
Madison, Wisconsin

brian maddox

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Re: Antenna Length
« Reply #4 on: March 09, 2017, 01:04:52 am »

Hi,
Henry thanks so much for your clear and concise response. Your contributions [and many others'] have made many of the assigned events I've done recently go very well, while elevating my confidence in even attempting them. Diogo's links appeared about the same time as my post, and I've dug into them already.

What an amazing resource this forum and it's contributors are.

Testify.

I make my living doing this stuff.  But this resource enhances my bottom line in ways I often can't predict....

Go PSW
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brian maddox
11brian.maddox11@gmail.com

'...do not trifle with affairs of dragons...

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Diogo Nunes Pereira

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Re: Antenna Length
« Reply #5 on: March 09, 2017, 06:59:23 am »

Henry thanks so much for your clear and concise response. Your contributions [and many others'] have made many of the assigned events I've done recently go very well, while elevating my confidence in even attempting them. Diogo's links appeared about the same time as my post, and I've dug into them already.

What an amazing resource this forum and it's contributors are.
Testify.

I make my living doing this stuff.  But this resource enhances my bottom line in ways I often can't predict....

Go PSW

Agree! This forum enhances job karma... D

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Diogo Nunes Pereira
elraval@gmail.com
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"I envy not those who own charriots, horses or land. I envy only those who drink water from every spring." - Popular Song from Portugal
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