Cable connector for Flight aware USB stick, filter, &antenna


#1

Just curious, so when my FA USB dongle comes in, I plan to have a the FA filter on it, and then SMA to something connector. I probably need about 30-40 feet of feed line to get it to my mast. Are folks using LMR 400 and N connectors ? I’m asking because I haven’t gotten my antenna yet, waiting on Amazon to stock the FA one.
Or are the PL259 connectors’ loss at 1GHz still acceptable?
thanks in advance for some ideas
-Kevin


#2

I’m using an N-SMA adapter at the antenna, and LMR240 between the antenna and filter, followed by a short run of PIC wire with SMA ends into the dongle itself (mostly to go from outside to inside). You can buy LMR240/400 with an N male on one end and SMA male on the other end to connect your antenna directly into your filter without an adapter, then directly into your dongle. It’s all about routing convenience at that point.

As to your second question, the manual gain on the SDR maxes out at 49.6dB (AGC maxes out around 70dB), with FA recommending 45dB upon installation. You probably won’t see >5dB loss on your receive path unless you do something crazy or break something, PL259 or not, so you can always bump the gain up a bit more if you want to.


#3

I believe that the gain setting of 45db was without a filter. Max should be fine as a starting point, if you have a filter.

For the coax I use N and the antenna and SMA at the filter end. I am using LMR400UF, however, it is expensive at around $US1 per foot.
N connectors are better outside as they are weather resistant. I will, however, be adding some sealant to the N threads as I have heard of one user having water/ice issues with his antenna.

Be sure to get the correct N connector. There are two types, 50 and 75 Ohm. The Antenna is 50 Ohm.
The pin on the 50 Ohm version is thicker(so is the socket or receptor in the antenna). The 75 Ohm plug may not contact the 50 Ohm socket.


#4

Yes, exactly.


#5

I seem to be doing best at 42 with my setup. 1400msgs/sec getting hits from over DC and Boston from NYC. with the filter, the “max” setting was getting a lot of overmodulation.


#6

Isn’t 1500msgs/sec about the limit? I suppose it depends on how long the messages are.


#7

Theoretical limit is around 8000/sec (for long-form messages, about twice that for short-form), but collisions are going to make things melt well before that.


#8

Before the change to the FA dongle, I was getting a max of 1200 msg/sec.

I would post graphs for a real comparison, but by a frustrating happenstance, when I rebooted the Pi after changing the dongle my SD card seems to have corrupted (yes, I even shut it down correctly!)

My last backup was about a week ago, so there’s a big ol hole in my graphs.


#9

Thanks to everyone for the replies. I appreciate the advice. While I built my own antenna for fun, I think I will wait for the FA one to be back in stock at Amazon so I could complete my setup in a weatherproof way.
I was thinking about placing it up on my fiberglass mast, somewhere between the discone (lower) and UHF/VHF antenna (upper).

-Kevin