LNA and Splitter Advice Appreciated

KenH999

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Nov 15, 2018
Messages
42
Still kinda new to the hobby but moving forward. My primary monitoring interest is MilAir but also CivAir.

I need to amplify and split my antenna feed for the below setup.

Note: Cost is a factor. I'm not going the Stridesberg route and am fine with the 'good enough' methods outlined in many of the posts here.

1. Tram 1411 with center whip removed. Mounted ~6ft above roof line, 24ft AGL.
2. ~30ft RG-6 thru attic almost to desk area with 6ft RG-6 patch cable w/barrel connector to reach desk and devices. Close to 40ft total run. I currently use a BNC - F adapter for the scanner and a F - SMA adapter for the SDR.
3. RTL-SDR V3. I use this alot for MilAir band searches and stored freq. scanning.
4. OLD BC-950XLT. Mostly CivAir only.
5. Will add a BCT15X soon.

So, need to feed a SDR and 2 scanners. I also want to amplify the signal. As an experiment I connected a ChannelMaster CM-3414 from our OTA TV setup to the Discone then to the SDR and BC-950XLT. I was able to receive the Charleston, SC airport (KCHS) Tower (noisy but readable) and the ARTCC RCAG channels as well as the Chas. Air Force Base "Palmetto Ops" channel. I normally cannot hear those. For MilAir I am midway between 2 MOAs. The Charleston/Beaufort coastal areas (50-60 mi) and the Gamecock MOAs in the Midlands/PeeDee areas of SC (~70mi). I have had decent luck receiving A2A comms of fighters doing A2A combat training in BOTH areas but it's sketchy. I'm convinced some signal amplification and hopefully noise reduction will help.

LNA
I read MANY posts in this sub-forum about antenna splitting, TV distribution amps, LNAs, etc., to the point of info overload. I'm not a ham nor well-versed in antenna theory and the engineering level stuff but do have a grasp of the basics. It seems a LNA of some type, ideally mounted at or near the antenna will give me the best signal improvement. I have these questions/requests:

1. Recommend a reliable wideband LNA, Noise Figure <1dB, around $30 or less? Model?
2. How do I mount the thing on the mast? The simpler the better. OR, if you know of one that comes in a weatherproof enclosure please advise.
3. Power: There is power in the attic. That would be approx. 20-25ft. from the antenna. The RG6 runs through the attic. What are my options to power a LNA?

Split Antenna Feed

Assuming I get a LNA up and running I need to split the feed for 3 or (future 4?) devices listed above.
1. Will I need to attenuate?
2. With my varied radios (SDR, old and new scanners) will the attenuation need to be varied for each device?? If so what do I need to do so?
3. Or, just use a quality 4-way TV splitter and good to go?

Will greatly appreciate advice and suggestions, the simpler the better.

Ken
 

Ubbe

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Sep 8, 2006
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Stockholm, Sweden
Easiest solution would be to have the amp at your desk and power from a USB 5v adapter. I suggest a PGA103+ based amplifier. You could probably find a water tight enclosing for it if you select to install it at the antenna and then feed power to it using a Bias-T, if the amplifier has that feature. But it is easier to handle and it would not be exposed to the weather if installed indoors. 30ft of RG6 have something like a 1dB loss at 350MHz. If you use a CATV splitter it will have a power pass port so you could just insert a choke coil there and connect a 5volt source to it if you use the amplifier remotly.
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You will need to attenuate the signal and it will be different for each receiver but it will probably work to set a single attenuation before the splitter to suit the BC-950XLT. The SDR-RTL's gain can be set to handle the signal level and a BCT15x will for sure handle any stronger signals that the 950 can handle. Choose a variable attenuator. Also you should use a FM trapfilter when monitoring VHF Air and choose one that doesn't attenuate the lower frequencies in the airband.

/Ubbe
 

KenH999

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Premium Subscriber
Joined
Nov 15, 2018
Messages
42
"Easiest solution would be to have the amp at your desk and power from a USB 5v adapter."

I may start with the LNA at desk and see how it goes. I've seen so many posts saying that putting the LNA at or closer to the antenna minimizes noise and maximizes the good signal so not ruling out doing that.

"I suggest a PGA103+ based amplifier."

What's the difference between a PGA103+ and a PSA4-5043+ based LNA. I found this one at GPIO and like it for its both USB and Output Bias Tee powering options. My RTL-SDR V3 is Bias Tee capable. That flexibility may help if I move it up to the antenna. It's PSA4-5043+, so far haven't found one w/same dual power in PGA103+. Low Noise Amplifier 10-3000MHz with USB, Output Bias Tee & ESD

"You could probably find a water tight enclosing for it if you select to install it at the antenna and then feed power to it using a Bias-T, if the amplifier has that feature."

Any reason why an appropriately sized one of these, or similar, wouldn't work? ABS Plastic Dustproof Waterproof IP65 Universal Electrical Boxes Project Enclosure

"If you use a CATV splitter it will have a power pass port so you could just insert a choke coil there and connect a 5volt source to it if you use the amplifier remotly."

Is this splitter acceptable or can you recommend a better one? BAMF 4-Way Coax Cable Splitter Bi-Directional MoCA 5-2300MHz

Please be a little more specific on the 'choke coil'? Type or model? Where exactly would it go? Between LNA and splitter? Would 1 or 2 of these work? I have a bunch left. Clip-on Ferrite Magnetic Ring Core RFI EMI Noise Suppressor Cable Clip

"You will need to attenuate the signal and it will be different for each receiver but it will probably work to set a single attenuation before the splitter to suit the BC-950XLT. The SDR-RTL's gain can be set to handle the signal level and a BCT15x will for sure handle any stronger signals that the 950 can handle. Choose a variable attenuator. "

Please recommend a reasonably priced variable attenuator?

"Also you should use a FM trapfilter when monitoring VHF Air and choose one that doesn't attenuate the lower frequencies in the airband."

Will this one suffice? FM Notch Filter 88-108MHz; Excellent Rejection 85dB



/Ubbe
 
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