Antenna and SDR application in "RFI rich" environment.

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Joined: Sun Nov 13, 2022 7:44 pm

Antenna and SDR application in "RFI rich" environment.


Unread post by REDOCTOBER »

Hello everybody,
Greetings and my best wishes!
Just registered, although was browsing this site for a while and like it very much. For some time, already, digging into SDR, but my interest, exclusively, in receivers. Have no intention to transmit. I would like to experiment with VHF/UHF SDR receivers, listen to air traffic, police, FD, utilities, Hams, but have a very serious considerations regarding location and surroundings of my apartment and related problems with reception and antenna to use with SDR. I am living on 14th, the highest, floor of concrete building in downtown Tampa, Florida, in small apartment. I do not have balcony, just huge windows, two sections on the sides can be slide up open to outside air. Apartment, practically, on the East corner of the building. Windows, looking, almost strait on the South. In 100 feet, you see expressway and after 200 feet is river and bay. Right over my apartment, on roof top there are , maybe, about 15 cellular or some communication (as far as I can correctly identify them ?) antennas (it is ,like 30-70 feet from my windows , on the roof top). On the East side of the building, (it is little North/East, just around the corner), is major TV station with all bunch of huge dishes, 8 of them, telecommunications antennas tower, weather radar and so. Looks like they transmitter is not in this area, far away from downtown. About 200 feet from this TV station, in same N/E direction, is high-rise, like 40 floors, 450-500 feet tall building, and it has VHF/UHF repeater on the roof. This repeater I am hoping to monitor.
So, guys, I will greatly appreciate your opinion on this “RFI rich” environment, and if I have any chance (with good antenna, have a lot of restrictions on this: can just stick it out of the window for the time of receiving) receive any audible content?? Or, that would be, mostly interference and noise? Regarding receiver, I am thinking something like WiNRADIO WR-G305e, WR-G315e. Could be any other SDR, VHF/UHF receiver with reasonable price and performance. Sorry for such lengthy description, just wanted to make sure you, guys, can better understand my situation.
Thank you very much in advance, for your time and consideration.
With my regards and respect ,

Posts: 612
Joined: Mon Aug 10, 2020 8:17 pm

Re: Antenna and SDR application in "RFI rich" environment.


Unread post by jdow »

If the distance from the repeater you want to monitor is small, say below 1 k', the signal levels from its transmitters should be pretty big. That means you can take advantage of this big signal, give up some sensitiviry and a little if any over all dynamic range to reduce the potential problems from other local sources. Get some attenuators to put in your receiver feed line. I suspect 30 dB would not be too much but don't use more than you need to get clean reception. The attenuators will help protect your front end from any potential burn out issues. (Built in front end filters may not offer the protection needed. External attenuators will usually tolerate much larger signals before they fry.)

I'd be surprised if 20 dB is too much attenuation. I'd expect 30 dB or certainly 40 dB to be completely sufficient to protect you depending on the power levels of the various stations that are actually transmitting.


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