Two instances of pfclient on same computer

freddoair

freddoair

New Member
I think this might be heading for ab cd :)

Has anyone installed two instances of pfclient on the same computer? I couldn't find any pointers during a search yesterday so here am I asking.

Why, you ask? My station has been in service since 2017 using a RPi model B, and works just fine, although Jessie is a bit long in the tooth now and totally unsupported! I had a RPi 4 gathering dust so it now sports the latest headless Raspbian/Raspios (or whatever they call it this week) from the RPi foundation and is running dump1090-mutability and a RTL-SDR dongle with a temporary ground plane antenna about 15ft lower than my main antenna. My objective was for the RPi 4 to replace the old model B, and it will do that. Running a simple antenna has proven that antenna theory works, and it irons out the inevitable nulls in the vertical radiation pattern that are a product of running gain antennas such as my five halfwaves in phase collinear at the top of the mast, which temporarily nulls out low-altitude aircraft at critical altitudes just a few km away from me. The ground plane provides perfect fill for those null moments and got me thinking about leaving the old model B in service for that purpose. Then I got dangerous and decided the RPi 4 had lots of reserve energy so why not run two dongles, two instances of pfclient and two share codes on the same computer?

I'm clear on running two dongles with one instance of dump1090-mutability but foggy on how to get Debian to install a second instance of the same deb package for pfclient. Debian's dpkg has an --inst option to install to a different directory but I don't know how hostile that might be to the pfclient. Maybe I'm looking down a difficult route and there's a simple way I haven't tripped over yet. So, any advice would be appreciated. If you're new to Linux, take heart. I've only been using it for 27 years :)
 
Lee Armstrong

Lee Armstrong

Administrator
Staff member
No the client is not designed to be run on the same system at once and will actually cause you issues.
 
J

Janos Konya

Member
Hi @freddoair ,

If you want to eliminate a minor problem with the radiation pattern, doubling both the hardware and the software is not the way of "solution". Why don't you simply modify things only at the source of your problem?

- Antennas, mainly colinear ones are sensitive to their height. Not just for the reason of clear wiev around and coverage distance.
At this frequency, you can fine tune the height easily for getting more acceptable lobes - still with less sensitive angles but far from getting zero signal. Stay close to the original height, within plus/minus 60 cm - changed in 20 cm steps.

A radiation pattern can be changed also by the change of ground quality.
e.g. before and after a rainy day, you'll get different results.

A plane just a few km away from your position (as you mentioned the distance in your post) can be detected by a piece of wire, even without tuning, so your 5-element antenna is able to do the same. Think of the planes exactly above your antenna... They are detected even in the direction of the theoretically least sensitive angle!

Your problem can appear in case of a reflection too, but this phenomenon is not circular but exists in certain directions only.
(metal objects close to the antenna, or even tiles containing some metal in their mass or in the painting burnt into their surface) Not all of tiles are so antenna-friendly at L-band frequencies...

Above my station, 7m (AGL) is also a special, less preferred height. Both below and above it, reception is better.

Anyway, in my experiences - antennas with odd number of radiators always have a more unfavorable characteristic. Your 5 element antenna may belong to this category.
- After playing with height perhaps unsuccesfully, you still have a method for eliminating the zero signal level angles by tuning the distance between middle-points of half wave parts. About 0.8-0.85 WL is working best for me with 4 elements. (vertical, phased-stacked colinear) In practice, it means about 0.35 wavelenght distance between endpoints of two neighbouring half-wave elements.

Before you start trying to modify all the things above, check again if there are obstacles on the way between your antenna and the "low-altitude aircraft at critical altitudes just a few km away from" you. The mentioned "low altitude" makes it more than possible that it can be the case. Multi-element colinears are more sensitive at low angles, so it is not really about your antenna type. Due to the small distance, a large signal should be detected even if the source is partially covered.
e.g. One of your antennas mounted at a lower position might see the plane without nearby power lines crossing the field of view, but your 5-element one at a higher position can not...
 
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ab cd

ab cd

Senior Member
freddoair said:
I think this might be heading for ab cd :)

Has anyone installed two instances of pfclient on the same computer? I couldn't find any pointers during a search yesterday so here am I asking.
Click to expand...

No, I have never installed two instances of pfclient on same computer, but yes, it is possible. However arrangement should be made to avoid conflict of 2nd instance with the default instance.

When I find some spare time (possibly this weekend), I will attempt to do it. I have already successfully done 2nd instances for dump1090-mutability, dump1090-fa, piaware data feeder, and fr24feed, so doing it for pfclient should not be difficult.
 
ab cd

ab cd

Senior Member
OK, here is how to create 2nd instance of pfclient on a Linux Computer or RPi.
This procedure assumes that you have already installed pfclient, and 1st instance is running, and you want to run 2nd instance.


Method deleted in view of comment by planefinder staff nember Lee Armstrong…
 
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ab cd

ab cd

Senior Member
This is how i run two receivers on single Pi. It has 2 instances of dump1090-fa and two instances of piaware data-feeder

For details please see this:
https://github.com/abcd567a/two-receivers




1-Pi-2-Receivers-c-2.png
 
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