Mini-Circuit Low Noise Pre-Amp 10% Off December and Other Useful RX Items

[studio1930]

Excellent info! I plan on setting something up in my attic for my 536HP as well. I'll probably add an LNA and a notch filter.

 

[rogress]

Did you ever move this setup to an outdoor antenna? I like your setup, but haven't figure out how to use it on an outdoor antenna.

I still have to relocate my antenna/antennas from inside the attic to outside, but while the antennas are in the attic it allows me quick and easy experimentation of amplifiers and filter without weather or daylight limitations. Much easier to prove the concept and performance before moving on to a more permanent and difficult to reach installation.

 

[JamesO]

Unfortunately I have not had time to move this configuration to an outdoor antenna.

Probably what I will do is put the LNA in a PVC pipe with the top capped off and have a short, low loss pigtail to connect the antenna to the LNA.

I have enough spares, I will probably just install the outdoor configuration and keep the in attic configuration until I know for sure I am happy with the outdoor setup.

 

[R0am3r]

Unfortunately I have not had time to move this configuration to an outdoor antenna.

Probably what I will do is put the LNA in a PVC pipe with the top capped off and have a short, low loss pigtail to connect the antenna to the LNA.

I have enough spares, I will probably just install the outdoor configuration and keep the in attic configuration until I know for sure I am happy with the outdoor setup.

How do you plan to send power up to the LNA?

 

[JamesO]

How do you plan to send power up to the LNA?

So I currently am running a phantom power feed up the coax via Bias T's. BUT I also have a 5 Volt regulator mounted directly on the LNA. See post #10 above for pictures of how the FM Trap, LNA and Bias T is configured. This assembly is currently mounted right on the antenna connector in the attic.

Another option for powering things at the antenna is another piece of coax or a single 16-18 gauge wire for the positive feed and then share the shield of the coax as the negative power path.

The nice thing about the regulator mounted on the LNA is it stabilized the temperature a bit in colder temps and it allows me to use 12 Volts at the Bias T feed point and if needed I can add a number of CATV splitters and/or drop Amps for splitting into multiple radios. At the moment I am feeding 8 radios with the LNA a LONG piece of RG6, probably around 125 feet, I have a tilt compensator installed to flatten out the loss of the RG6 in the higher frequencies, power passing attenuator that then feeds another higher noise figure distribution Amp that then feeds an 8 way splitting configuration.

So I have a lot going on, but it works well and it works correctly because I am not over driving any of the Amp stages and I am not running 30 dB Amps.

 

[jl2s]

Please note this Amp is a 5 Volt device so if can easily be powered by a small USB wall adapter or you can do what I did and mount a LM7805 Voltage regulator and a few capacitors directly on the amplifier so I could phantom feed the coax with an adjustable Voltage without worrying about the Amplifier that is located directly at the base of the antenna installed on a FM Broadcast band notch filter.

Do you have any schematics and parts list for this mod? Could you draw up a simple diagram to help me?

 

[JamesO]

See figure #1 page 7 of this PDF - https://www.sparkfun.com/datasheets/Components/LM7805.pdf

I ended up actually mounting the 7805 Voltage regulator to the rear of the LNA case.

This is the physical set up of the Voltage regulator and FM band trap/notch filter: https://www.dropbox.com/sh/hmvxvtev71z09z8/AACpt0RSsfk5BI5T2JD0WOfNa?dl=0

 

[jl2s]

See figure #1 page 7 of this PDF - https://www.sparkfun.com/datasheets/Components/LM7805.pdf

I ended up actually mounting the 7805 Voltage regulator to the rear of the LNA case.

This is the physical set up of the Voltage regulator and FM band trap/notch filter: https://www.dropbox.com/sh/hmvxvtev71z09z8/AACpt0RSsfk5BI5T2JD0WOfNa?dl=0

OK now I'm a bit confused. Please bear with me. This is all referencing your dropbox photo

You fed DC Power in the coax-cable center core. The DC Power road up the coax wire and into the attic, and hits the BIAS-TEE. At the BIAS TEE the DC Power is converted from the coax-center core spit out on the side of the BIAS-TEE at the power port. You connect a 2 cables + and - from the BIAS TEE power port and feed them into the 7805 voltage regulator. The 7805 proceeds to power the ZX60-P103LN+ LBA.

Do I have that part above ^^^^ correct, or am I way off course?

If so, why do you even need the 7805 voltage regulator? Why don't you just feed the LNA from the BIAS-TEE with a + and - wire?

 

[JamesO]

I could use a separate power supply and just fee the LNA directly with a few wires, but this means I would need to have a 120 Volt outlet somewhere reasonably close to the LNA location.

Why did I put the 5 Volt regulator directly at the LNA and not just fee 5 Volts up the coax? Well I have a fairly complicated configuration where I am feeding 8 scanners at the moment, so I have more than 1 amplifier in the chain. So the other amplifier I believe is a 12 Volt amplifier. This way I protect the LNA and I do not need to compensate for any Voltage drop via the coax.

There are many different types of Bias-T's, I chose to use the Mini-Circuits SMA containerized unit with side terminal for power connection.

There are many ways to skin the cat/solve the problem, I choose to configure my system in the way I did for a number of different reasons.

Keep in mind, depending on the coax run length you may need to add a 3-9 dB attenator at the input of your radio. Unfortunately most attenuators integral with radios tend to be 20 dB attenuators.