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DIY sma antenna

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On 7/17/2018 at 6:42 AM, roubi said:

 

The best Leatherman for me : strong, only what I need, and nothing to loose (like those with several screwdriver heads you can add to the body). And yes the pliers function is awesome : https://www.leatherman.com/crunch-1.html

 

I ordered one! Great to have foldable vice grips in my pocket.

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I use the "cable dipoles" in a bag, running the cables (A and B antennas) up the shoulder straps. It worked as advertised. I was using Lectro receivers, but they should work just as well with the G3.

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On 6/29/2018 at 10:01 AM, drpro said:

I have had good success with brake or deraileur cable from local bike shop. Cover it with heat shrink in your favorite color.

If you want to go crazy Plasti-Dip makes a wide range of colors and enhancements for covering your antenna wire.


Ohhhh.... that is a good tip, especially as I'm needing some tomorrow for my bicycle anyway!

 

On 9/26/2018 at 6:19 AM, Glen Trew said:

I use the "cable dipoles" in a bag, running the cables (A and B antennas) up the shoulder straps. It worked as advertised. I was using Lectro receivers, but they should work just as well with the G3.


You made this yourself? Do you have a pic to share?

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On 10/23/2018 at 8:10 AM, IronFilm said:


Ohhhh.... that is a good tip, especially as I'm needing some tomorrow for my bicycle anyway!

 


You made this yourself? Do you have a pic to share?

What I think Glen was meaning to say is a dipole antennas made from 50 Ohm Coax cable. The Lectrosonics YouTube site has a DIY video on the subject.

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On 6/29/2018 at 12:01 AM, drpro said:

I have had good success with brake or deraileur cable from local bike shop. Cover it with heat shrink in your favorite color.

If you want to go crazy Plasti-Dip makes a wide range of colors and enhancements for covering your antenna wire.

what cross section did you find and use it?

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what sma connectors have you used,  there are many quality and prices around, sold online from China like 3 $ for 10 pieces and there also pieces of 5 $ for each. 

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On 6/22/2018 at 3:02 PM, Shastapete said:

Looks good. What wire are you using? 

 

Also, always good to share is the diy dipole from Gordon at Lectrosonics


for what I  have read, that shield folded in that way is not acting like an effective dipole negative, it is useless. 
to be effective it has to be far from the cable shield ground and at 90 ° from the positive core. 
1

 

On 6/22/2018 at 3:02 PM, Shastapete said:

 

 

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On 4/13/2019 at 5:34 AM, alidav said:

for what I have read, that shield folded in that way is not acting like an effective dipole negative, it is useless. to be effective it has to be far from the cable shield ground and at 90 ° from the positive core.

Actually, the shield needs to be folded as we show it. The folded shield couples to the the cable shield of the coax to "choke" off the RF and force the unbalanced coax to radiate as a dipole. The ideal construction is to have a 1/4 wave cylinder around the coax cable with the shield tied to the top of the cylinder. Here's a long explanation that saves me a lot of typing:

http://www.hamuniverse.com/vertbazooka.html

 

This is a good antenna not a great antenna, but it is small, compact and bends easily for storage or placing on a strap. It is a marked improvement over a rusty coat hanger.

Best Regards,

Larry Fisher

Edited by LarryF
should have had "choke off" rather than "choke of"

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Made a few of these based off an article in a back issue of 695 Quarterly. The came in handy for a visor mounted transmitter where I remoted the dipole to the outside of the vehicle. Worked like a charm.

 

Ran a quick test in the driveway using RF Explorer for the visor setup and was averaging a 7 dBm difference on plain whip vs remoting the dipole to the exterior then a whole 13 dBm difference when using a piece of fuel line hose to help vertically polarize the dipole wedged in the car door. 

 

 

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If using that dipole DIY antenna on a UCR 411 receiver, I need to replace both the stock antennas to get better results?

On 4/13/2019 at 4:04 PM, LarryF said:

Actually, the shield needs to be folded as we show it. The folded shield couples to the the cable shield of the coax to "choke" off the RF and force the unbalanced coax to radiate as a dipole. The ideal construction is to have a 1/4 wave cylinder around the coax cable with the shield tied to the top of the cylinder. Here's a long explanation that saves me a lot of typing:

http://www.hamuniverse.com/vertbazooka.html

 

This is a good antenna not a great antenna, but it is small, compact and bends easily for storage or placing on a strap. It is a marked improvement over a rusty coat hanger.

Best Regards,

Larry Fisher

If using that dipole DIY antenna on a UCR 411 receiver, I need to replace both the stock antennas to get better results?

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Using identical antennas will give you the best results but just improving only one antenna will still help. Remember also that setting the transmitter gain according to our manuals will make what seems to be an "antenna" improvement as the correct audio gain helps reduce the affect of the RF noise floor, interferences and noise ups. You can find out how to set the audio gain in any of our transmitter manuals.

Best Regards,

Larry Fisher

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According to the ''how to'' for the dipole, is the gauge of the coax affecting the performance in the end ? 

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14 minutes ago, Boomboom said:

According to the ''how to'' for the dipole, is the gauge of the coax affecting the performance in the end ? 

I used a 50 OHM antenna tv cable, in a case i used the same cable soldiered directly on the Sennheiser g2 motherboard, to replace the broken stock antenna.

 

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Larry, all of my wireless video gear is now using circular polarization. The benefits are significant. Just curious if if CP antennas would also work as well for audio equipment?

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5 hours ago, nick kolias said:

Larry, all of my wireless video gear is now using circular polarization. The benefits are significant. Just curious if if CP antennas would also work as well for audio equipment?

Hi Nick,

One big problem is that for circularly polarized reception, ideally you should have circularly polarized transmission. That is nearly impossible to do with a body pack transmitter. Even if you could, when the talent turns around, the left hand polarization becomes right hand polarization with theoretically zero reception, or vice versa.

In multiple trials over the years at Lectro, we were never able to get improvements in performance using circularly polarized antennas at the receiver. YMMV.

Best Regards,

Larry Fisher

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