Antennas and outside mounting

FlightAware General
1

there have been some other discussions but they all seem to be a little old.

Plan is to mount ALL of my antennas outside preferably on a single mount location.

Antennas to mount -

  1. TV antenna (Style TBD, Yagi?)

  2. 1090mhz (most likely ground plane but open to ideas)

  3. 978mhz (most likely ground plane but open to ideas)

  4. scanner antenna (ground plane)

Currently antennas 2, 3, & 4 are in the attic which is not the best location for them and since I am getting tired of paying for a cable TV bill I’m seriously considering the installation of a TV antenna which would of course give me a mast to mount antennas on.

What I have done for the antenna’s today is for the ADS-B antennas I simply purchased a BNC female 4 hole panel mount connector and turned it into a simple ground plane antenna, I then got a male BNC to male SMA connector and attached the SDR directly to the antenna. From the SDR I use an 8 ft USB type A extension (male to female) and I connect the SDR’s to a USB hub (40ft active extension hub), in the attic and the connection from the hub is to the RPi in the basement (hence the active extension hub). The scanner antenna I’m simply dragging RG-8 to the basement where it connects to the SDR).

I’m looking for suggestions on how to connect everything and keep the SDRs dry. Do I move the SDR’s off the antennas and move them to inside the attic? I am really concerned with grounding I have a ground block on the outside of the house that sits on the ground wire between the breaker panel and the ground rods, the ground block is on side of the house I would mount the antennas on. Other than knowing the antennas need to be grounded, my concern is with the electronics so close to the antenna will the ground actually work or would any potential lightning strike follow the electronics as it might be a shorter path to ground.

I am looking at a chimney mount (brick chimney), can I mount all 4 antennas on a common mast? can I put 2 masts on the chimney?

I know there are a lot of questions posed here and only 2 of the 4 antenna relate to the ADS-B feed, one relates to a liveatc feed, and one for my wife’s entertainment.

Thanks!

2

Is this a single story home?

3

Two story (w/basement)

4

Interesting thoughts. A similar question was posed a while ago that I answered in a similar fashion. The antennae would benefit from being on a pole outside, yes, especially if your loft is metal-film (or chicken-wired), as both will have an impact on your signal strength (and hence range), but at the same time, the antennae cables should be kept as short as possible to reduce interference.

My best approach would be to put the yagi on a pole, with the 1090MHz & 978MHz antennae below outside on one pole (I see no reason why not, provided wind loads are not an issue). The scanner antenna, with its existing ground plane could cause a wind load, but it should be possible to set up radials to act as a ground plane in lieu of the plate on a second pole.

Receivers wise, run the cables into the loft/attic, put the SDR’s and the RPi up there, thus eliminating the need for waterproof external boxes, and run a single ethernet cable from the RPi back to your hub, eliminating the need for the long USB (or use Wi-Fi, if wifey doesn’t like the idea of the cable).

Unless you’re in a high-risk area as far as lighning is concerned, I think you’ve probably taken as many reasonable precautions!

5

Tony,

Thanks for the response. The whole reason for this exercise is since I am putting up a TV antenna that means I will already have an antenna mast, can I take advantage of it and more importantly does it make sense?

In my case the roof construction is typical asphalt shingles, no metal in the roof, and even if the sides of the house had foil backed insulation, the antennas are above that. I’m sure being in the attic attenuates the signals, question is how much of a difference will it make? Currently I have graph 1090 running and the majority of my traffic is 20 to 60 miles away with an average of ~37nm, but when you consider I’m roughly 13nm NW or EWR and I can pick up aircraft down to about 1800ft going into EWR. Because of my location I’m not surprised most of my traffic is close in.

range
range619Ă—324 23.1 KB

You mentioned putting the RPi in the attic, I’m going to refrain from doing this, because of where it would need to be placed it becomes a very difficult to access due to an A/C air handler up there, this is why I use an active USB hub (40ft - Lindy 42783) to extend the USB ports to the attic, it works well and I supply it with power via ethernet using PoE and one of the cheap PoE splitters available on eBay, this gives the the ability to cycle the power on the hub remotely should it be necessary (it hasn’t yet).

The scanner antenna is simply an old Radio Shack ground plane antenna, I don’t remember if it has 3 or 4 radials coming off of it and it has an SO-239 for a connector, not sure where it is tuned but it seems to do a reasonable job on the aviation bands. I would continue to use RG-8 on the scanner antenna even though it is PITA to work with as it is so thick.

I have about 30ft of both RG-400 & RG-58, I know the RG-400 is a much better choice for the ADS-B frequencies but if I’m less than 10ft between the antenna and SDR is there that big of a difference? The RG-58 is a fraction of the cost fo RG-400.

I am not in a super high risk area for lightning strikes although there was a tree just outside my yard that was struck by lightning, knocked a chunk of wood onto my deck, so it does happen. Maybe I’m over thinking it but I’ve been looking at the lightning arresters/discharge unit, they seem to be $20 to $30 each use a gas tube of sorts and obviously need to be grounded. Am I overthinking everything?

In terms of keeping the spousal unit happy, as long as whatever is visible from the outside is neat, professionally done, and her TV works she won’t complain.

1 Like
6

I made a similar upgrade very recently– old setup had everything in the attic, now I’ve got the antennas mounted above the roof with KMR400 to a weatherproof project box.

Very little/ no change to max range, maybe 20% increase in positions per second and number of planes simultaneously tracking. Roughly doubled my rate of messages from 200+ miles.

Antenna placement: If they’re in the same horizontal plane, put them at least 1 wavelength apart (about 1 foot, for ADS-B stuff). Or mount one above the other. I’ve seen examples of masts with “branches”, but IMO that can start looking janky on top of a house.

Depending on your home and your location, Pi can run into temperature issues in the attic. Mine reported CPU temps above 80C pretty much every hot sunny day over the summer.

7

Yeah, that’s why I split my setup as follows: antenna, filter/LNA, and SDR dongle in attic, Pi in upstairs closet with long USB cable from SDR dongle to Pi (with powered USB hub). That way the Pi stays at about 40C and I can easily access it to change the SD card.

8

Jim, why not bring the SDR down into the closet so it too can enjoy the benefits of the cooler environment provided? I have mine indoors near to the Rpi 4B and the temperature there maintains at just above the 30C mark.

9

Well, then I need a coax run from LNA to SDR dongle (right now I have zero length coax in the setup). Granted that coax would be at the output side of the LNA, so a little loss shouldn’t matter. However the SDR dongle is the receiver, so it should probably be kept away from a noisy processor like an Rpi. At least that’s how I view things.

10

So i did some tests because i had some serious throughput differences. I own multiple noolec v5’s and spent an afternoon testing them against each other with different cables against my PC and my RaspberryPi. The RaspberryPi introduces way less noise compared to my PC. All combinations were tried with 0 coax involved at the same time. The noise produced by the PC that somehow makes it way through a 6m USB cable into any of the dongles is even slight visible in sdrpp. Just a thought.

11

My noise trouble shooting experience has shown that USB power generation is by far the biggest noise contributor in the whole system. Small USB power warts are using switching power supplies and that is the source of the ugly. USB power generation that uses transformer hardware are heavier and larger but don’t generate as much noise. Physical separation from any USB power generation source is key to minimizing noise contamination in the system. Have yet to find the RPi to be a source of problematic noise. Maybe others have found evidence of a different result.

12

Switching power supply (noisy) vs linear power supply (less noise). But isn’t everything today a switcher?

13

No sir. Everything is not a switching supply these days. They are lighter, cheaper and more compact so that makes them more prevalent in the market despite their flaws. I run amateur radio equipment powered with linear transformer based power supplies. I avoid switching power supply short cuts because of all the noise generated by the frantic switching electronics. The aircraft tracking hobby has caused me to be even more critical than ever of the noise generated by such devices. The sensitivity of a good SDR is especially subject to the ill affects of that noise. We work at filtering noise coming in from our antenna’s surroundings, but yet we induce new sources of noise with wall warts and USB power sources right next to our core system components. Truly it is self defeating.

1 Like
14

Granted you can still get linear power supplies, but I was mainly referring to the power supplies that you can buy for the RPi or for a powered USB hub. They are all switchers. As you say, they are much more compact than a linear power supply. The switching frequency is 100 to 500 KHz, much below 1090 MHz. However harmonics of the switching frequency are probably the problem. I guess I could buy a linear power supply and then lash up a home made cable with a USB-C connector to connect to the RPi.

15

You are forgetting about the legislation that applies to small power supplies that applies in both the US and Europe.
In the US there is the U.S. DOE Level VI
and in Europe:

These regulations are virtually impossible to meet using linear supplies, hence the almost universal use of switchers.

16

The noise from switch mode can usually be blocked by winding the DC cable on a ferrite core. You want to stop the output of the switch mode supply to radiate, so mount the core as close to the power supply as possible. Make the windings get a snug fit to the core for max attenuation.
You can also use clip ons, but you would need lots of them in series to get the same effect.

I buy some cheap green cores from Aliexpress, and they do work quite well for noise from my supplies.

image
image455Ă—301 54.1 KB

17

@jimMerk2 no, it isn’t. Equipment that handles low-level signals (amateur radio, vinyl pre-amp’s, mic amps, etc) all need very low-noise power supplies; this is exactly where linear power supplies come in. Sure, they’re less efficient than a switching supply, but they’re also a darn site quieter.

18

Good point, I forgot about using a ferrite core. Trying something like that would be a lot cheaper than buying or building a linear power supply.

1 Like
19

RFI and ripple on a power supply are not the same as we know. For the latter you can add capacitors and inductors to smoothen the voltage. I try to avoid switch mode if I can, but linear supplies are getting harder to find at a decent price.