In this post, we will detail how we made our TX antenna mod to the Taranis. In Part 1 we detailed our objective to develop a simple long range antenna solution for the Taranis.
2.4ghz 5dbi antenna
Antenna RP-SMA to uFL/u.FL/IPX/IPEX Adapter Cable
In addition, we recommend using a u.fl connector on the board which is available free with the antenna kit:
Antenna 2.4ghz 5dbi Kit
The following tools were used:
Medium phillips (star) screwdriver
Soldering iron with precision (very sharp) point
Long sharp pointed needle or craft knife
Hot glue gun
Multi-meter with continuity test function
In order to achieve a base line, we did an initial range test.
We connected an X8R receiver and placed it around 1-2m above the ground on a non metal surface. We placed one of receiver antenna at 90 degrees to the direction of the range test. The range test was conducted using model menu on the Taranis. Select [Range] in page 1 of the model’s menu.
Depending on your RSSI warning levels, you should get at least 50+ metres before an RSSI warning. My settings were 42/45 for critical/low respectively. I was able to achieve 80 metres before a consistently low RSSI waring at 45 RSSI. This was facing the RX with the TX antenna horizontal and pointing left. To measure the distance, I used two distinctive locations and measured on google earth.
We also took note of our RSSI reading at around 10 metres.
Open the Taranis
Disconnect the battery and open the Taranis, review this blog entry here for instructions on how to open the Taranis.
After you open the Taranis, trace the antenna cable to the Taranis RF board. You will note a ‘blob’ of hot glue over the antenna cable join to the RF board.
Using a sharp item, very carefully peel off the hot glue from all directions. You want to be careful that you don’t remove any of the laminate from the board.
After this is completed you will observe three connections. The two larger left and right pads are ground and connect to the braided external layer. The inner core carries the signal and connects to
the smaller central pad just below the ground pad.
Heat each each pad one by one with the soldering iron and remove the connection with the antenna cable. You will note that the braided outer cable is connected to the ground and the inner signal cable is connected to the smaller centre pad.
Using your multi-meter, test the continuity of the two ground pads, you should get a positive. Also test one pad and the large copper square trace on the left, you should also get a positive result. Do the same with the centre signal pad and you should get no positives with the ground pads or the large copper square trace. (collectively, the “Continuity Tests”).
Remove the Antenna
Using a strong pair of pliers, grip the edge of the antenna on the inside of the Taranis. The Antenna is attached by a clip and by compressing the clip, with the pliers (see red arrows), it can be pulled out from the top.
You will need to use a fair amount of pressure to remove the antenna as the fit is tight. Do not twist the antenna as it has a small plastic tab to stop this (see blue circle).
Test the New Antenna Cable
We will be using our pre-manufactured RPSMA extension cable. On one side is an RPSMA connector and on the other side is a small u.fl (IPX) style connector. The RPSMSA connector is a common antenna style connector. The u.fl is used for small electronic parts, for example, the RX antenna use these.
We will be soldering a u.fl connector to the board on the three pads. the pads are perfectly designed for this purpose. Once the connector is on, we can quickly clip the antenna cable on or off. This is not really essential as this won’t be required very often. It’s also a challenging soldering task.
On the cable, test the continuity between the centre of the two connectors on each end of the cable, it should be positive. Do the same for the external housing, it should also be positive.
Mix up the housing and the centre pins to check for shorts, it should not be positive.
Test the u.fl Connector
The u.fl connector will be soldered to the board. On the bottom, you will see two matching sides that connect to the external plug housing. The internal pin connects to the single trace beneath the connector. Using the continuity function on your multimeter, test various combinations until you get the hang of the connector.
Install New Antenna u.fl Connector
Place a very small blob of solder on each pad (much less than we did in our image). You want an approximate 0.5mm pillow on each pad. Place the connector down on the board and hold it in place with a sharp object. The two ground connectors on the left and right pad and the signal connector on the centre pad.
Whilst holding the connector firmly in place. Heat the solder on one of the ground pads until molten. Now do a continuity test between the connectors external housing ring and the large square trace on the left. It should be positive. This confirms that the connection you just soldered is good.
Now do the same with the centre signal pad, this should not be positive. If postive, solder has got onto the central signal trace beneath the connector. Unsolder and clean it up and repeat.
Now do the exact same with the second ground pad and test all again.
Lastly solder the signal pin and test continuity again.
Connect the cable to the newly u.fl soldered connector. Be careful that you line it up correctly as it can be fiddly. Do a continuity test between the centre pin of the RPSMA connector and the centre signal pad, it should be positive. Do the same with the ground pads and the housing of the RPSMA connector, it should also be positive. Mix it up to test for a short and you should get no positives.
Connect the antenna firmly to the RPSMA connector and feed the cable through the top of the antenna hole. Connect the cable to the board and gently force the RPSMA into the hole. Ours slid in firmly enough to fit but still hold the antenna in place for testing. Once all testing is completed, hot glue is used to firmly hold it in place.
Connect the antenna firmly to the RPSMA connector and feed the cable through the top of the antenna hole. Connect the cable to the board and gently force the RPSMA into the hole, Ours slid in firmly enough to fit but still hold the antenna in place.
We then closed the Taranis for testing. In addition to, RSSI, we added SMA to the telemetry page readings.
The SMA reading was approximately one however did move around if we re-positioned the antenna, but always settled back to 1. This number should be very low with anything above 50 being a major problem!
We conducted our range testing again on the same basis of the baseline testing. We achieved around a 50% increase (40m) in distance before a consistently low RSSI warning.
Once the testing was completed, we added hot glue to the antenna slot from inside. This was done to firmly hold the RPSMA connector and antenna in place. You do not want the antenna swiveling around as the internal connector will dislodge….