Joining two antennas to one receiver

[MRPV26]

Hi!

Got a question that I tried to see if this was asked before but got no clear clue. I got a FA Blue Stick and I have put a DPD ADSB Antenna which is outstanding for receiving planes up to 200nm miles away, but when it comes to planes that are right above me, it does not do quite good (doughnut effect).

I was thinking about getting a cheap antenna and use a combiner or something related, in order to pick up planes that might be right above me, and use the DPD to receive the ones that are far away. Does this make sense or am I saying non-sense things?

I was looking at these but not sure if they would work for me.

Thanks a lot,

[abcd567]

SMA_Splitter_Combiner.jpg

Combining two antennas with this solid "T" will work, but with much reduce range/plane count. Try it and see. No harm in trying.

[wiedehopf]

It's much more likely you have the gain too high resulting in overload for close by aircraft and it's not the donut effect.

Get yourself readsb or dump1090-fa and install graphs1090 to get some data, easier to judge any changes: https://github.com/wiedehopf/adsb-wi...ADS-B-receiver

https://github.com/wiedehopf/adsb-scripts/wiki/Optimizing-gain

https://github.com/wiedehopf/adsb-scripts/wiki/Automatic-gain-optimization-for-readsb-and-dump1090-fa

You can do it manually just fine some people just like automatic stuff for .... (i'd recommend doing it manually ... a gain of 38 is probably a good starting point for you)

[GK367]

Hello MRPV26,

this may have to reasons:
a) I meen the signal was send horizontal, from the planes ... and not strange to the ground ... so you "can't" recieve the signal from higher flying planes "well"
b) or the singal may be to strange ...

Can you tell me something about the size of the "donut hole" ... I mean the range around your location, where this problem happens?

PS:
1.) It's better to use a (passive) combiner/divider to connect two antennas on one reciever (I'd use a Mini-Circruits ZESC-2-11), otherwise you will lose the 50 Ohm impedance.
2.) Attention: Only combine two of the same antennas, and both "must" have the same cable length ... antenne <-> combiner ... otherwise signals from antenna "A" will degrade signals of antenna "B"

Greetings
Gerald