i shall be starting to do the major solder work anytime soon. but first i would like to get some inputs regarding installation of the peripherals:

1. i am using the HM EP1 dual diversity receiver. since this quad will have battery strapped to the bottom, i plan on having the receiver conveniently located on the open top deck with both antennas vertically polarized for the best unobstructed location. to this i have a few concerns:

a. will there be any operational issues having the receiver directly exposed to sunlight for very extended periods of time? 

b. since the top deck shall be shared by the receiver and gps module, where would be the most optimum placement of either? so its a choice between directly on top of the stack or the caddx vista for either of them. my gps happens to be an M10 unit which at least has better resistance to RF noise so that may work in its favor on a top deck install.

2. would any of you have inputs, ideas, actual installs (tpu prints, etc.) regarding vertically polarized T-antenna installations? i would be after function over form or crash resistance. 

for the time being my planned receiver installation above may be interim only for range test purposes where i can easily rearrange stuff. this build may also end up with a diy dipole antenna moving forward once i get to build one.

Hi Hawk,

First, my thoughts on the GPS placement. From my past research, locating the 
GPS low and to the rear as one sees on almost all BNF and even frame kits is 
less than optimal. Also, many of the larger "450" quads have the GPS mounted 
on a pole and high above the top deck frame plate.  Consequently, I have always 
mounted the GPS high. Often, I will use the supplied TPU holder, but mount it on 
additional (long) standoff columns above the top frame deck plate and to the rear. 
This location seemed to work quite well even with the receiver antenna also 
mounted high and to the rear. At first, I thought that taking 60 to 90 seconds 
was a long time for SAT Fix until I started comparing that to the times others 
were getting, like 2, 3 minutes or more. So, I guess the location that I was using 
was pretty decent. 

Yes, I have tried all of TMac's GPS Module Satellite Fix (FAST!) in an effort 
to get faster SAT Fix. None of these actually seemed to make much difference; 
still took 60 to 90 seconds depending on the day and location. I came to believe 
that the actual physical location of the GPS module was the single most important 
consideration and that I had chosen wisely. 

Additionally, I have tried all sorts of assorted "shielding" methods that did not help.
In fact, many just made things worse. So, I learned a lot about shielding. Any type
of shielding that I might do today is focused on the analog video system rather 
than for the GPS.

Now, let's take a look at the new GEPRC Tern LR40 which is touted as a 4-inch 
Long Range craft. Ah, Hah. They have located the GPS module high, but moved
it to the front of the quad on a TPU pedestal (column). The reviewer in one of
the videos indicated that the satellite fix was a lot faster in the high/front location
than other positions that he had been using. In my next GPS build, I will try the
high/front location.

Moving on to the RX receiver location, again, I mostly use the high/rear location
especially for my long range, R9, "T" style antennas. Now, I can not attest to the
range as I didn't get that far out, but the signal was always at the top, no loss.
Interestingly, I do not really see this location being used much. It seems one of 
today's popular locations is at the front, under the camera, with the active elements 
going out towards the front motors. There is some logic here, but not sure how the 
location compares to the high/rear location. Consider that the low/front location
keeps the antenna closest to the ground and is never blocked by the quad itself
regardless of the craft's orientation. 

NOTE:  I use JJRotoGeek's method to keep the antenna wire/shaft "stiff" enough
           to maintain shape while still having a decent measure of flexibility. I have
           never broken an antenna using this method. 

Later, iFly  

My latest AlfaRC Fi-118 2.5" build is giving me a lot of problems with GPS position fixation. The GPS receiver located in the printed tail never picks up a signal. I soldered longer wires to move the GPS receiver around the body to find a good position . And I still haven’t found it. I have interference both in the power supply and on the air. I installed the “GPS test” application on my phone, when I bring the phone to the quadcopter, I see on the phone screen how the satellites are dying one by one ...
Now I'm waiting for a thin shielded cable from Aliexpress to move the GPS to the front of the quadcopter and ground the shield.
I usually place the GPS receiver on top of the battery, but in this last case it didn't help much.

(08-Mar-2024, 08:29 AM)LiPoFly Wrote: My latest AlfaRC Fi-118 2.5" build is giving me a lot of problems with GPS position fixation. The GPS receiver located in the printed tail never picks up a signal. I soldered longer wires to move the GPS receiver around the body to find a good position . And I still haven’t found it. I have interference both in the power supply and on the air. I installed the “GPS test” application on my phone, when I bring the phone to the quadcopter, I see on the phone screen how the satellites are dying one by one ...
Now I'm waiting for a thin shielded cable from Aliexpress to move the GPS to the front of the quadcopter and ground the shield.
I usually place the GPS receiver on top of the battery, but in this last case it didn't help much.

what gps module did you install?

latest build update as of 03/08/2024 1730H. my first day melting solder on this official first build attempt. i did all the peripherals first. it took me a full four hours of mulling over the routing possibilities and this is the result. hopefully the receiver will reside permanently behind the camera taped to the tpu canopy. i routed the gps to the rear to use the inclusive tpu print (not in photo).

i must say it is not the most beautiful soldering work. BUT it did pass the meticulous multi-tester for continuity (or better yet lack thereof!). this is back breaking work for a middle-aged, shaky fingers fpv hobbyist like me. i had to be crafty in making a blu-tack jig to aim every single FC pad against the tinned wire tip in order to assure i hit the mark. it is painstaking work while others do this menial task free hand!

i hope the patience reaps rewards in the end. tomorrow i finish the ESC and motors.

Hi Hawk,

First, the soldering job is first rate; looks Real Good. Of course,
passing the continuity test is where it really shines. 

All of your work is top notch. 

The dry fit looks really nice. 

Later, iFly  

(08-Mar-2024, 11:25 AM)iFly4rotors Wrote: Hi Hawk,

First, the soldering job is first rate; looks Real Good. Of course,
passing the continuity test is where it really shines. 

All of your work is top notch. 

The dry fit looks really nice. 

Later, iFly  

much appreciated sir!

again if i may ask the community, i am planning to install the EP1 dual diversity receiver on the top deck where i can conveniently experiment both antennas vertically polarized for good range. would there be any issues having it exposed to direct 34degC sunlight!??

latest build update as of 03/09/2024 1609H. i spent another 4hrs soldering the ESC, motors and filter capacitor. as usual everything was newbie slow. fortunately it passed the multi-tester continuity check. finally the most awaited moment plugging the 6S and hearing the much sought after three chime tone from the ESC! oh and i used a smoke stopper for good measure.




tomorrow i may start setting up BF4.4.1 which came default. hopefully gps rescue works with severely lowered expectations.

i also did some dry fitting of all the remaining components. empty weight is 209g. for comparison my AOS5 bnf weighs 375g. a significant 166g lighter for this build. hoping for good things efficient. the 6S li-ion it may haul weighs 300g! so here’s crossing my fingers the motors are up to the task.

(08-Mar-2024, 10:28 AM)hawk01 Wrote: what gps module did you install?

Any GPS receiver I have detects interference specifically from the new AlfaRC Fi-118 assembly: Beitian BN-220, Beitian BE-122, GOKU GM10 Nano v3, Matek M8Q 5883, smartphone receiver. I wrote my post to say that sometimes shit happens and you have to seriously deal with GPS signal interference.

once it meets my expectations i will figure out the final receiver location. it may well reside underneath the caddx vista since it is the most convenient location available. hopefully the long leads will not cause any RF issues.

Hi Hawk,

CONGRATULATIONS !!  

Excellent Build. 
Very Clean !  Good Job. 

I like the DIY receiver antennas. Very Cool 

Later, iFly  

Congratulaions, looking good. If you are running diversity, isn't the idea to have the second antenna in a different position or orientation? For example if your quad was heading directly back to you and pitched up slightly, you would have the battery and drone completely blocking both antennas as well as pointing directly at the null points of both, so reception could be very bad in that situation.

Hi Mstc,

Yes, I do agree with you as I generally have the two antenna pointing in different
directions; mostly either a "V" at the tail or a "T" on one of the arms (with zip ties).

Quote:if your quad was heading directly back to you and pitched up slightly

Would this be when the quad is moving backwards as it might when flying LOS 
and the antenna are pointed towards the transmitter? Is that where the Null 
situation occurs? Now my question is this, would the antenna need to be pointing 
directly at the transmitter? If the quad has some altitude, would the antenna not
really be pointing directly towards the transmitter? Or, would the RF LOS be
enough different from the direction of the antenna to avoid the Null area? 

When flying FPV, there would be very little chance of this happening since we 
don't normally fly backward when flying with the goggles. The quad would
basically be either level or, more likely, always in forward motion which pitches
the nose down and the tail up. 

Still, it is a good idea to point the antenna in different directions. He could 
position them slightly to form a "V" as we often do with the XM+ receivers.

Later, iFly  

Null point is in the directions along the antenna. And this is not flying backwards, but flying back towards you which in most cases you will do 99% of the time especially when flying LR.



apparently Dall-E thinks pilots should hold their radio backwards...

(10-Mar-2024, 08:55 PM)mstc Wrote: Null point is in the directions along the antenna. And this is not flying backwards, but flying back towards you which in most cases you will do 99% of the time especially when flying LR.



apparently Dall-E thinks pilots should hold their radio backwards...

a visually valid point that certainly presents the obvious. my use case for the boxer T-antenna is to null point pointing towards the sky (vertical polarization) during use for this particular quad. i think this alone already addresses the matter.

the present shallow angles of both diy antennas on the quad are also somewhat dry fit for testing (and photo op) purposes only. i only bent them well enough as the coax can handle on its own without stressing the material. today i am buying glue sticks to apply the hot glue antenna hack. after this i shall have both antennas pointing more steeply towards the sky in highly dissimilar angles. this should offer differing null points. just like the technically detailed photo below to illustrate my profound concept!  



i don’t think the final outcome will win any beauty contests. but hopefully will perform the intended task.