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Splitters, Filters and Multicouplers - For discussion of all inline devices used to split, combine or amplify a receive signal. This forum is not for any bi-directional (transmit) device. Use the Amateur or Commercial Radio forums for those.

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  #1 (permalink)  
Old 10-11-2018, 11:27 AM
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Default new RTL-SDR Wideband low noise amplifier

Wondering if anyone has seen the new RTL-SDR Blog Wideband LNA product yet?
Seems to have been announced on sept 4th.

https://www.rtl-sdr.com/tag/low-noise-amplifier/

Specs show:
Frequency range of 50 MHz to 4000 MHz
Noise figure = 0.6dB @ 900 MHz
OIP3 = 39.5 dBm @ 900 MHz
P1 Saturation = 22.7 dBm @ 1960 MHz
Gain = 18.7 dB @ 900 MHz
based on the Qorvo SPF4189Z LNA chip
metallic enclosure

Importantly for me its also powered by bias tee.

I'd be curious as to how it compares to others like GPIO Labs, Mini-Circuit, and those available on eBay, etc?
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Old 10-11-2018, 1:59 PM
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It would be the same as all others with similar specs. You can't do much different in the design than setting power to the amplifier chip.
If bias tee are important you can add that to any amplifier by adding a simple choke coil and a capacitor on the circuit board.

/Ubbe
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Old 10-12-2018, 8:06 AM
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Quote:
Originally Posted by Ubbe View Post
It would be the same as all others with similar specs. You can't do much different in the design than setting power to the amplifier chip.
If bias tee are important you can add that to any amplifier by adding a simple choke coil and a capacitor on the circuit board.

/Ubbe
Ah cool. Yeah I'm considering this as an option to overcome my RG-6 coax loss. My plan is to hook up both my Uniden bcd325p2 and a Noelec Smartee SDR device.

Powering the amplifier is the question though:
I was looking at the MFJ bias tee in line power injector & a decent AC adapter in combo
MFJ Enterprises Inc.

However I got to thinking using the Noelec Smartee SDR with its built in bias tee power output would be much cheaper route. I'm wondering if I can use the SDR device powered off a usb hub on an extension cable without the need too have my computer on also?
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Old 10-12-2018, 9:22 AM
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If the bias T power are under software control then you might need the SDR to be connected to a PC. I think the default at power on are bias T off if it's software controlled.

Get a $5 CATV 1-2 splitter with power pass on one port. Then you have the other port for your BCD325.
Or get a 1-3 splitter and power it from any USB charger you have and cut a USB cable and connect red wire with a choke coil to one of the free power pass ports and black to ground. Then you power the LNA independent of your SDR bias T feature and can use your scanner without the PC being powered on.

Get flexible RG174 RG316 or similar SMA connector cables and get additional F-SMA adapters for the splitter to the SDR and a BNC adapter for the scanner.

/Ubbe
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Old 10-13-2018, 1:51 PM
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I actually thought about it more the MFJ is probably the best way to go as its hardware based, I can power the LNA remotely over Coax, independent of having any SDR devices, and prior to any splitters. I cant power it directly due to being installed in the attic space on a 50' run.

I just have to find a quality AC Adapter that matches the LNA power specs with an output of 5V, 1 A, and a 2.1mm plug. Preferably on amazon. A task that seems easier said then done atm lol.
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Old 10-14-2018, 7:45 AM
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The MFJ is a bit expensive, probably because it is fitted with N connectors.
This $7.50 one uses F connectors. https://www.amazon.com/PCT-Inserter-.../dp/B07CX4DSYP

/Ubbe
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Old 10-15-2018, 1:12 AM
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Quote:
Originally Posted by Ubbe View Post
The MFJ is a bit expensive, probably because it is fitted with N connectors.
This $7.50 one uses F connectors. https://www.amazon.com/PCT-Inserter-.../dp/B07CX4DSYP


/Ubbe
Yeah likely so. They have one about $10 cheaper but it uses so-239 (UHF) connectors which aren't really that great for higher frequencies.

Seems like matching power specs are difficult with these devices. A gotcha with an LNA that has a 5V 1 A input.
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Old 10-15-2018, 7:09 AM
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Quote:
Originally Posted by crucialcolin View Post
Seems like matching power specs are difficult with these devices. A gotcha with an LNA that has a 5V 1 A input.
What type of problem do you have selecting a power supply? The RTL-LNA probably doesn't need more than 100-200mA. The RTL-SDR and the LNA are powered from the same USB connector of a PC and that USB port can only output max 1000mA and are supposed to power both devices and that RTL-SDR alone gets super hot from all the power it consumes.

/Ubbe
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Old 10-15-2018, 7:08 PM
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So far Ive been finding most of the injector/inserter power supplies have different output voltages. Often 12 volts or more which would oubviously not be good for RTL-LNA.

For example:
https://www.amazon.com/Mountable-Ada...dp/B06ZZXWNTX/

Speaking of heat I wonder how much heat LNA's themselves generate being that I would be placing it in attic space that can easily reach 120 F during the summer.
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Old 10-16-2018, 5:38 AM
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You can use any 5 volt 1A power supply and cut the cable and connect to a screw terminal. There are also universal power supplys, both 5v and adjustable between 3-12v that have exchangable tips and one of them are a screw terminal and use a short cable to an adapter from screw terminal to F connector or whatever are most suitable for you. I didn't try to find the most cost effective supplier so you have to seach for that. Use that cheap power inserter with F connectors I linked to earlier.

https://www.amazon.com/Power-Supply-.../dp/B078RF3QWH
https://www.amazon.com/Universal-CUG.../dp/B078MKNXLD
https://www.amazon.com/Haokiang-Spea.../dp/B07FQ7TCMS
https://www.amazon.com/Kenable-Compo.../dp/B008IVMP92
https://www.amazon.com/Yohii-Termina.../dp/B07GDN9NHB
https://www.amazon.com/DCFun-Convert.../dp/B07BMNRPRP

/Ubbe
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Old 10-16-2018, 11:45 PM
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Quote:
Originally Posted by Ubbe View Post
.. I didn't try to find the most cost effective supplier so you have to seach for that. Use that cheap power inserter with F connectors I linked to earlier...
/Ubbe
No worries. Dang thanks for the help! I got a good idea how to do it now

Btw I think an LNA is the best way to go.
Originally I had been looking at a TV Antenna inline based amp such as RCA/Channel Master/& Winegard. Those all have noise levels in the 2-3 dB range on UHF however.

I guess only time will tell on reliablilty between the two options. That's really my only concern.
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