Alfa Antenna Mod

Joined
Nov 21, 2016
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San Diego, CA
#1
My P3S has always had an excellent range: here in the US (FCC mode) I was able to reach 5500ft/1670m, whereas in Europe (CE mode) the best I've done is 3250ft/990m. Keep in mind those numbers represent the absolute best, in areas with little to no interference, but they are still impressive. In CE mode in particular, you notice that the signal is just weak, all it takes is a tree between you and the AC, and you lose it. I tried Icarus (at 27dBm) and got mixed results: the first time it worked well (rock-solid 2.4GHz signal, all the way to the limit of the 5.8Ghz, which is not affected by Icarus), the second time not so good (constant "weak signal" messages, even at close distance - never understood why).

Anyways, I decided to try something new so I bought a used RC for $40 on Craigslist and the Alfa Antenna Kit for $35, from Rokland's eBay store. The kit comes with one Alfa APA-M25 for the 5.8Ghz control signal, two APA-M04s for the 2.4Ghz and three pigtails with RP-SMA connectors.

Installation is pretty easy, provided you take your time and do things carefully. I more or less followed the instructions provided by a guy named Rick Sisco, on YouTube:


The way he installs the 5.8Ghz antenna requires a non-reversible modification of the RC, something I did not like, even if my RC was a spare. So I mounted mine on the front: it's functional and it would allow me to put back the stock antenna if I want to, but it definitely doesn't look as nice.

I also purchased some 6dBi dual-band (2.4 + 5.8Ghz) dipoles on eBay, at $3 each. Once you have the RP-SMA connectors on the RC, you can try pretty much any antenna you want, and my idea was to have a long-distance setup (the Alfas) and a short-distance one, more versatile (the dipoles).

I still haven't done proper testing, but I wanted to share my first impressions. First of all, the RC is definitely bulkier with the Alfas, but still reasonably light. The 2.4GHz RP-SMA connectors are mounted where the RC handle originally was, so you don't have it anymore. Which also mean you need another phone/tablet mount (not an issue for me, as I use the Inspire mount). The RC would not fit in the P3S case with the Alfas on, so you have to mount/remove them every time (not a big deal). The cheap dipoles are better in that respect, but the one in the front (5.8Ghz) still had to come off for storage.

When it comes to range, so far the Alfas allowed me to reach 6100ft/1850m, whereas the cheap dipoles couldn't go past 4000ft/1220m. In particular with the Alfas, it seem that the moment you lose signal, you lose it forever: RTH kicked in and brought the AC back (at those distances, I have to admit it was a bit nerve-racking....) but I was able to regain control only at very close distance.
The Alfas are also directional, which means you need to keep them pointed toward the AC or you lose signal in a split second. Nothing crazy, though.

All in all, a decent mod for $35, but not stellar: the range gain is there, but it's not a game changer. And I personally never fly that far, anyways, unless I'm testing things out. At less extreme distances, you enjoy a slightly more robust signal, but on the downside you have to keep aiming at the AC.
With better quality dipoles, I'm pretty sure I can do better than 4000ft, and at that point you really have the best of two worlds: use the dipole for everyday use, switch to the Alfas when you want to go crazy far.
 
Last edited:
Likes: Rohanm
Joined
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San Diego, CA
#2
This is how you remove the stock 5.8GHz antenna without breaking it:
2018-02-19 17-59-39_resize.jpg

These are the stock 2.4GHz panel antennas, which I recommend NOT to remove as they are glued pretty well (as you can see, I broke a little piece off... nothing functional):
2018-02-19 18-03-36_resize.jpg

This is how I suggest you enlarge the holes for the 2.4GHz antennas (slightly offset, so I used a dremel instead of a drill bit):
2018-03-04 11-19-30_resize.jpg

Front hole for the 5.8GHz antenna... quite ugly, I reckon:
2018-03-04 11-44-58_resize.jpg

How to route the new pigtails inside the RC (I suggest you install them all in the front half of the RC, use a zip-tie to keep them where you want, and then mount the 2.4GHz RP-SMA connectors on the rear half of the RC before closing it):
2018-03-04 12-18-41_resize.jpg

To tighten the 2.4GHz RP-SMA connectors, position the two halves of the RC this way, then slide a screwdriver next to the connector on the inside, preventing it from spinning, and tighten the nut on the outside:
2018-03-04 12-19-35_resize.jpg

One more view of the new pigtails, nicely tied together:
2018-03-04 16-21-58_resize.jpg

A view of the cheap dipoles (I took one apart to see what's inside):
2018-02-20 16-22-08_resize.jpg

Final result, long and short-distance configurations:
2018-03-04 17-08-34_resize.jpg 2018-03-04 17-10-27_resize.jpg
 
Last edited:
Likes: Indiana_pyro
Joined
Nov 21, 2016
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#4
I was actually more interested in having a solid link at standard range, than breaking any long-distance barrier. This mod does help in that respect but, as I said it, has its downsides.
 
Joined
Jul 10, 2018
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Location
Sacramento area
#5
I am a new flyer but would like to extend the signal reach but don't have a lot of electronics build background. This sounds great but a bit intense for me to attempt to do. Is there an easier way to gety more reach?

Thank you
 
Joined
Mar 4, 2018
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#8
I was actually more interested in having a solid link at standard range, than breaking any long-distance barrier. This mod does help in that respect but, as I said it, has its downsides.
Which are ? Apart from drilling your controller. I think as well don’t hold me to this that the covers for the metal bar will still cover the holes I think a little glue will stop them from moving about inside the holes that’s my remedy if that’s the downsides I’m getting better distances and it looks better too I’m my mind anyway
 
Joined
Jun 28, 2018
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#9
where do u guys buy that alfa patch antenna ?
is it comes with the cable rp-sma ?
plz post the link
thanks.
 
Joined
Nov 16, 2018
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Age
56
#10
Hi Guys
just a quickie, ive done the alfa mod on my p3s and im getting 200m then video loss and break up across an open field, and 300m the rc signal loss nearly lost drone today, it was 350m away..
any ideas
 

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