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Author Topic: Can I use the wa5jvb LogP antenna to transmit?  (Read 1237 times)

Tim Weaver

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Can I use the wa5jvb LogP antenna to transmit?
« on: February 25, 2018, 11:56:48 am »

http://www.wa5vjb.com/products1.html

Most of us know about this guys PCB LogP antennae. Can these be used to transmit for IEM's as well?
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Bullwinkle: This is the amplifier, which amplifies the sound. This is the Preamplifier which, of course, amplifies the pree's.

Pete Erskine

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #1 on: February 25, 2018, 12:12:50 pm »

http://www.wa5vjb.com/products1.html

Most of us know about this guys PCB LogP antennae. Can these be used to transmit for IEM's as well?

sure....
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Tim Weaver

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #2 on: February 25, 2018, 12:16:07 pm »

sure....


Cool. Thats what I though, but just wanted to ask. Thanks.
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Scott Helmke

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #3 on: February 25, 2018, 01:43:42 pm »

Antenna reciprocity. As long as there isn't an amp or something you can use an antenna either way.
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Henry Cohen

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #4 on: February 25, 2018, 04:28:33 pm »

Although the antenna data sheet does not specify RF power handling - key to using any antenna for transmit applications - the PCB trace should handle a couple of watts without problems.
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Henry Cohen

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Mike Caldwell

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #5 on: February 26, 2018, 08:24:57 am »

Those antennas have a low pass filter built into them, that's the small S shaped traces on the board at the end of the main elements. That makes the antenna appear as a DC short to what ever it is connected to, depending on the equipment it is connected to that may or may not be an issue.
 The biggest possible issue could be if the receiver or transmitter supplies DC power at the antenna jack for powering an inline RF amp.

frank kayser

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #6 on: February 28, 2018, 05:14:29 pm »

Those antennas have a low pass filter built into them, that's the small S shaped traces on the board at the end of the main elements. That makes the antenna appear as a DC short to what ever it is connected to, depending on the equipment it is connected to that may or may not be an issue.
 The biggest possible issue could be if the receiver or transmitter supplies DC power at the antenna jack for powering an inline RF amp.
I had some back-and-forth with Kent about his PCB antenna - a relevant reply to my question.  Nice guy and answered my emails within 1/2 hour.
------------------------------------------------------

Hi Frank
While they originally designed for EMI and Field Strength measurements, they have become quite popular in the Audio world.  Also used in several Superbowls hunting for interference.
(Not everyone made sure their favorite frequency was open or even authorized)


Yes, they work well for transmit as well.


Diversity reception has been around since the 1930's.  Basically you want the antennas to be at least  a wavelength apart, or at different polarizations.  For most wireless mics, this is about 2 feet.
Farther is nice if practical, especially if there are objects in the way. Or from a central area point one at the left of the stage and one to the right.


The only issue has been replacing active antennas with these. Some systems send a DC voltage up to the antenna to power a preamp. Most of our antennas are designed as a DC short.  Someone walks across a thick carpet, touches the antenna, and ZAP there goes a few transistors.  Making the antenna a DC short helps protect your equipment.   Take a volt meter and put it at the end of your coax.  Nothing?  You're fine.


Got several DC volts?   We have a little pigtail at the back of the antenna.  Just cut it.
They can be painted black, or any other color.  Just use enough paint to get the color you want and
avoid extra coats of paint.

Good luck with your project, Kent
------------------------
Also Kent noted that painting the antenna changes its tuning.  I can't find it now, but it does not affect the performance in the wireless UHF range.
« Last Edit: March 01, 2018, 10:00:30 am by frank kayser »
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Henry Cohen

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #7 on: February 28, 2018, 07:20:00 pm »

Also Kent noted that painting the antenna changes its tuning.  I can't find it now, but it does not affect the performance in the wireless UHF range.

In addition to other minerals in the paint that might act a s high impedance bridge between the radiating traces and thus affect the tuning, black paint generally contains charcoal, which will absorb RF energy (and heat up), reducing the antenna's ERP. Try to find black paint that contains no charcoal.
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Mike Caldwell

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Re: Can I use the wa5jvb LogP antenna to transmit?
« Reply #8 on: March 01, 2018, 09:41:02 pm »


Got several DC volts?   We have a little pigtail at the back of the antenna.  Just cut it.
They can be painted black, or any other color.  Just use enough paint to get the color you want and
avoid extra coats of paint.



I took a Dremel and ground it away on mine.
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