Antenna connector question


#1

I did some searching and found a lot of discussion about antenna connectors but none are 100% clear to me about what I need to use. I’ve been burned in the past buying “not exactly the right thing” so would like to get the expert advice here.

I have the FlightAware Pro Stick Plus with a Pepsi can antenna :slight_smile: It works pretty darn well. But I decided to try out the FlightAware antenna for comparison (and also because I might try to convince the HOA to let me put it outside). For the time being the Pi and Antenna are in my attic.

What is the best (and hopefully not too expensive) way to connect the Pro Stick Plus to FlightAware’s antenna when used in an attic? I can place the Pi quite close to the antenna so don’t need much in the way of cable length.I’d appreciate a link to what I should get as I just am not familiar with the different connector types and impedance issues.

My current connector/cable is pictured here (I don’t recall what these are called): antenna connector


#2

This is the shortest cable I have used

You want N-Male at one end and SMA-Male at the other.
This one is a bit longer

This is longer again

The thicker the cable, generally the better and less loss.
LMR195 is probably OK for 10 feet. Any longer and you should consider LMR400.


#3

Thank you for the quick and clear response!


#4

If you can install the Pro Stick plus to the antenna, no cable, it’s even better.

Then use this one:

It’s what I use.


#5

Be sure to stay away from any connectors with RP, for reverse polarity, in the description.

Stick a flag on the antenna and the HOA won’t object! :slight_smile:


#6

Yes, the description says it’s not RP, plus the picture shows it’s not RP.

Basically, the RP type looks like a male SMA without the center pin.

Below is a picture of the RP-SMA. This NOT/NOT what you need.


#7

@roadfun

DIFFERENCE BETWEEN SMA AND RP-SMA
The SMA-male has center pin.
The reverse SMA (RP-SMA) male does NOT have a center pin, it has a hole.

.

TEMPORARY WORKAROUND
The SMA-male has center pin. The reverse SMA (RP-SMA) male does not have a center pin, it has a hole. The center wire connection is open because of missing pin. A temporary workaround is to cut a short piece of center wire of coax and insert in hole of RP-SMA male. This piece of wire will act as the missing pin, and connection will be established.
.

RP-SMA Worksround


#8

Thanks for all the feedback. I’m going to set it up in the attic this week and see if it is an improvement over a Pepsi in my situation. Then maybe I’ll look for a flag :slight_smile:


#9

To close the loop - I installed the FA antenna in the attic right next to my Pepsi can antenna and ran it for a few weeks. I ended up switching back to the Pepsi can because the FA antenna routinely reported receiving fewer messages and saw fewer aircraft.

The high points on my roof are quite steep and difficult to access but I will likely try to put the FA antenna there in the future.


#10

Question - after install FA antenna, did you adjust your gain settings?

Often that will need adjusting due to the increased sensitivity of these antennae - resulting in an overloading the dongle resulting in reduced numbers.

With appropriate adjustment of gain you should see marked increase when using FA antenna.vs. cantenna etc. There are several very good threads in the forums explaining gain settings (abcd567 and others)


#11

@roadfun
Due to high gain, FA Antenna picks up lot of cell phone and TV signals and overloads the Dongle. This results in moderate to severe reduction in performance.

To overcome this problem, there is a two step solution.

First step is to reduce gain as suggested by @dongerrard204.
Use different values of gain like 50, 45, 40, 35, 30.
At each setting watch for some time to see the performance.
This way you will find the best setting for gain. It is quiet likely that by reducing gain, the performance of FA Antenna improves considerably.

Second step is to add a Filter, which will cut off most of interfering Cell and TV signals. This will make a big difference in performance if you have strong Cell Phone & TV signals in your location.


#12

Thanks for the responses, a couple of follow ups. My config file has -10 which I understand is automatic gain control. So based on the above I should adjust it manually instead when using the FA antenna? And the values I would enter from your example are positive in the config file rather than negative (I think…)?

I have the FA Pro stick which has a built in filter. Do I need a filter in addition to that?

I’ve switch back to the FA antenna so am ready to play with the gain and watch the results.


#13

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Yes, you got it right, -10 switches the dongle to AGC mode.

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Yes.

(1) If you have burned your microSD card with Piaware SD Card image, you have to use following commands to change gain (replace xx by the gain value)

sudo piaware-config rtlsdr-gain xx  

sudo systemctl restart piaware  

sudo systemctl restart dump1090-fa  

.

(2) If you have burned your microSD card with Raspbian (Jessie or Stretch), and then installed piaware and dump1090-fa add-on packages, then you have to edit file /etc/default/dump1090-fa and change gain value there.

sudo nano /etc/default/dump1090

In the file opened, you will find a line starting with “RECEIVER_OPTIONS”.
In this line gain value is given as --gain -10.
Change it to --gain xx (replace xx with desired value).
Save file (Crtl+o) and close it (Ctrl+x).

Now restart dump1090-fa

sudo systemctl restart dump1090-fa

.

.
Yes, only positive values from 0 to 50.
Any negative value will set the gain to zero, and you wont receive anything.
The only negative value it accepts is -10, which is a special value. It does NOT set gain to -10. It switches the dongle to AGC (automatic gain control) mode.

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In some cases, yes. You can only find by trial and error, like I found that using a filter with ProStick Plus (blue) was necessary. This varries from location to location. Trial & error only can tell.


#14

I have the FA ProStick Plus, and added the external FA filter. Best gain setting for me with this combination is 22.9 dB.


#15

Thanks, very educational and helpful. I’ll start experimenting.