RTL-SDR V3 long wire problems (SOLVED)

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Re: long wire problems

Post by rtlsdrblog » Sun Dec 30, 2018 10:03 am

snn47 wrote:
Sun Dec 30, 2018 9:42 am
RCND and all
It is interesting to note that the NooEelec 1:9 Balun claims to be with Antenna Input Protection, which if true should have protected your dongle. Does anyone have a scrematic or type list of the protection components used? From the picture on amazon I asume that they just used a resistor.

Sufficiently high static electricity takes only a few nano seconds of peak voltage to damage the semiconducters in a receiver.

From experience even prior to the first lightning bolts, sparks were continiously between the inner conductor of RG-213 coax cable several centimeter to the stone bottom below the roof. The antenna was just a small 10 m 1/4 wave groundplane, much shorter than what a long wire will pick up.
Pretty sure the ESD diode on that balun is a proper protection diode, BUT an antenna input protection diode isn't going to do much if the system isn't grounded properly on the antenna input side.

snn47
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Re: RTL-SDR V3 long wire problems (SOLVED)

Post by snn47 » Sun Dec 30, 2018 1:46 pm

pretty sure the ESD diode on that balun is a proper protection diode, BUT an antenna input protection diode isn't going to do much if the system isn't
Looking at the picture from the NooElec Balun One Nine - Tiny Low-Cost 1:9
Image there is only one SMD element antenna in use. To me it looks like a a resitor(capacitor which is unlikely) and this SMD element is located at the output side of the Balun towards the coax connector.

For a long wire antenna which is asymetrical a 1:9 UnUn (Unbalanced/Unbalanced) would be the correct use unless two longwires of indentical length would form a symetrical antenna for which a 1:9 (Balanced/Unbalanced) is used.

Has anyone read which frequency range the 1:9 BalUn is rated for?

RCND
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Re: RTL-SDR V3 long wire problems (SOLVED)

Post by RCND » Tue Jan 01, 2019 12:27 am

Hello All:

The SMD is a ESD protection device. It is a varistor on the 50 Ohm side of the Balun.

The SDR must have a ground for this device to protect it.

There is no ESD drain resistor on the antenna side as shown in their schematic.

For a long wire antenna, there is a trace on the bottom of the balun that is cut. Then one post is for the antenna, the other for ground.

A 1 Meg Ohm resistor should be installed between antenna and ground as a static drain.

Robert

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