Connecting RTL-SDR V3 on master antenna system in the building

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sys-49152
Posts: 2
Joined: Thu May 06, 2021 10:49 pm

Connecting RTL-SDR V3 on master antenna system in the building

Post by sys-49152 » Fri May 07, 2021 9:17 pm

Hello, I am new to this forum and recently I got my RTL SDR V3 dongle. I am using Noeelec indoor antennas and I have one question:
I live in a building that was made in the 80s of the last century and the building has a common antenna (master antenna system) at the top of the building for TV and radio and in every apartment, we have two connectors in the wall: one for FM, one for TV (PAL connectors, males for TV, and female for FM).
I don’t know what condition the antennas are up on the roof since they are more than 30 years old.
I measured currents with a multimeter and there is no current in the connectors on the wall.
I would love to try and connect my RTL-SDR V3 dongle to those ports for the radio antenna but I'm not sure if it's safe.
Is this recommended at all?

Thank you!

DL2ZBK
Posts: 3
Joined: Sat Nov 16, 2019 11:15 am

Re: Connecting RTL-SDR V3 on master antenna system in the building

Post by DL2ZBK » Sat May 08, 2021 5:53 am

Hi,
the antennas onnthe roof are a good chance of improving your reception. The signal levels are exactly the levels you need. The radio connector should work for 0-30 MHz and 80-120 MHz, the TV connector for frequencies above 470 MHz and something between 30 and 80 MHz.
You simply need a gender changer for switching between the two connectors.
You can replace the wall outlet with a single BNC jack for easier use and maybe you can remove band filters in the distribution system on roof for wider frequency range.

Joerg.

PS. : Seems you are a C64 user?

snn47
Posts: 253
Joined: Tue Dec 27, 2016 11:00 pm

Re: Connecting RTL-SDR V3 on master antenna system in the building

Post by snn47 » Sun May 09, 2021 8:03 pm

Even though you will not meassure a voltage when you meassure it with a DVM, you should consider also damage by an Electrostatic Static Discharge, (ESD), when you connect your receiver to the house antenna ports. Only if the receiver is powered by a notebook which is solely operated by it's batteries and the notebook is not connected to any other device or power supply will you not have to consider ESD.

rtlsdrblog
Site Admin
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Connecting RTL-SDR V3 on master antenna system in the building

Post by rtlsdrblog » Mon May 10, 2021 4:07 am

The roof antenna will most likely be a Yagi directional antenna pointing to a TV tower. So it will receive the TV signals well, but everything else not in that direction poorly.

That said, reception of other signals may still be better than with the indoor antenna.

It should be safe to connect to your RTL-SDR, just be careful that there is no voltage on the line exceeding 5V, and that the line is not prone to high ESD.

hamradionl
Posts: 26
Joined: Fri Nov 22, 2019 12:42 pm

Re: Connecting RTL-SDR V3 on master antenna system in the building

Post by hamradionl » Fri May 14, 2021 10:39 am

These days in the 1980's use on top of the common antenna there whas a center whipe antenna, these used for radio RX. If yours have a center whipe, that will do the jobe fine.

sys-49152
Posts: 2
Joined: Thu May 06, 2021 10:49 pm

Re: Connecting RTL-SDR V3 on master antenna system in the building

Post by sys-49152 » Fri May 14, 2021 6:13 pm

Big thanks to all of you for your answers!

I've made the cables two days ago and finally plug the dongle into connectors.
First I've tried FM, and the reception was quite OK for FM radio stations, but when I scan the other freq's it was not so good.
Usually, I am testing two frequencies, one is the morse beacon on 145.45 MHz of the old local radio amateur club which is just 2km from my apartment and I have a clear path into the direction of their antenna (from the top of the building probably it could be seen). Interesting thing is that I did not receive well that signal (?) so probably either the roof antenna is in a bad condition or something else...
After that, I've tried a TV connector and I was expecting a good reception from local taxi drivers and utility services which are mostly around 440-470 MHz but no. Again, I got a much better reception with my ANT500 antenna and RaTLSnake M6 v2 bundle antennas from Nooelec.

So, for now, I will stick to my basic antennas on a balcony.

Thank you for helping!
Now I am discovering signals and creating a list... a lot is changed since I last time did this in my hometown 20-30 years ago. When I was 18 years old I was a 'radio-relay listener' in military service (I am not sure how to properly translate my title in corps) and I was using an old USA "SR-50" from the Vietnam war as a radio receiver. A lot more was there to listen than nowadays... I found very little voice communications but a lot of some buzzing/screeching signals that sound digital or encrypted. I need to learn new things :)

for DL2ZBK: Yes, I was a C64 user in the 80's - you have a good memory! :D SYS was a BASIC command to start a machine program at a memory location and SYS 49152 was a famous disassembler. I was using it to find code that is responsible for a number of lives in video games and creating POKE command for cheating ;)

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