QX7 Reduced range

[Hank]

I have an old FrSky QX7 that I purchased from Aloft when it first came out. I have used it mostly with a HITEC external RF module. I recently updated the internal module firmware for ACCST V2. A couple of years ago I retrofitted the gimbals with hall effect upgrades.
About the same time I replaced the small bios? battery. Finally, last year I replaced the old 600 mAh NIMH battery with a 2000 mAh battery.
All that worked great except in the past few weeks I noticed dropouts during flying (no rssi with old Hitec RXs). So I conducted some tests with the same plane but different receivers and transmitters and the conclusion is that transmitter range is bad with internal and external modules.
Can someone tell me if that is fixable and what I can do to correct it? The TX has never been abused or dropped or bumped, etc...

 

[HENNY]

I have an old FrSky QX7 that I purchased from Aloft when it first came out. I have used it mostly with a HITEC external RF module. I recently updated the internal module firmware for ACCST V2. A couple of years ago I retrofitted the gimbals with hall effect upgrades.
About the same time I replaced the small bios? battery. Finally, last year I replaced the old 600 mAh NIMH battery with a 2000 mAh battery.
All that worked great except in the past few weeks I noticed dropouts during flying (no rssi with old Hitec RXs). So I conducted some tests with the same plane but different receivers and transmitters and the conclusion is that transmitter range is bad with internal and external modules.
Can someone tell me if that is fixable and what I can do to correct it? The TX has never been abused or dropped or bumped, etc...

Have you conducted a ground based range check. Because both the internal and external RF modules have reduced range it points towards your receiver setup. Please advise how the receiver is mounted and antenna locations and any nearby batteries/ servos near the RX antennas. The Hitec external module wont provide RSSI back to the TX.

 

[Hank]

Have you conducted a ground based range check. Because both the internal and external RF modules have reduced range it points towards your receiver setup. Please advise how the receiver is mounted and antenna locations and any nearby batteries/ servos near the RX antennas. The Hitec external module wont provide RSSI back to the TX.

Yes, I did ground based range checks, with the internal and external modules. With the external module I just observed the throttle response dropout. I even did some flying with different RXs and TXs. In all checks, the QX7 using internal and external modules had low range
Receiver layout has not changed and this issue was detected on two other planes as well.

 

[HENNY]

Yes, I did ground based range checks, with the internal and external modules. With the external module I just observed the throttle response dropout. I even did some flying with different RXs and TXs. In all checks, the QX7 using internal and external modules had low range
Receiver layout has not changed and this issue was detected on two other planes as well.

There is no relationship between internal and external RF modules outputs. If the internal module has low RF O/P I could understand your situation but both does not point to a TX issue. Throttle response issue could be a linkage or servo issue. I believe you need to look further at possible causes of your issue.

 

[jure]

as both the internal and external RF modules show a similar behavior ( reduced RF Power output ) , I would suspect something in common to them :
check their power supplies, maybe their voltage regulator or filter capacitors have issues

 

[Hank]

as both the internal and external RF modules show a similar behavior ( reduced RF Power output ) , I would suspect something in common to them :
check their power supplies, maybe their voltage regulator or filter capacitors have issues

That's what I wondered. The drop in range happened without any other changes to the planes. All the planes on this radio have reduced range and I did not move the receivers after many years of dependable flying.
One thing I forgot to mention, and it's a biggie, all the Hitec and FRSKY MINIMA receivers lost their bind to the Hitec RF module about the time of the range drop. I re-binded all the receivers but now I can't explain why the FrSky ACCST internal module also is misbehaving.
When I tested the range of the internal RF module, I should have removed the external Hitec module to isolate any issue from it that might affect the whole radio.

 

[jure]

When I tested the range of the internal RF module, I should have removed the external Hitec module to isolate any issue from it that might affect the whole radio.

OK , now you know which is going to be your next experiment,
see if there is a power supply overload due to the Hitec module

 

[Hank]

OK , now you know which is going to be your next experiment,
see if there is a power supply overload due to the Hitec module

So, do a range check on the internal module with the external module removed?
Another test coming up...

 

[Hank]

So, do a range check on the internal module with the external module removed?
Another test coming up...

Ok did a range check with and without the external Hitec module installed. Range was bad in both cases, about 15 feet before RSSI dropped to bellow 40 and got the warning.
This time I used an FrSky RX8R Pro with the enhanced performance. But that didn't matter, still bad. Also the range is rapidly and progressively getting worse every time I check the range. Both TX and RX batteries are charged.

 

[HENNY]

as both the internal and external RF modules show a similar behavior ( reduced RF Power output ) , I would suspect something in common to them :
check their power supplies, maybe their voltage regulator or filter capacitors have issues

The TX warns you if the TX battery is low. I would setup a ACCST receiver outside of your air craft and perform a range check. You should get at least 100 to 150 feet in range check mode while facing the receiver, elevate the receiver at least 3 feet above ground. Just to clarify when you bind a receiver the UID is stored in the receiver so loss of bind indicates a receiver issue.

 

[Hank]

The TX warns you if the TX battery is low. I would setup a ACCST receiver outside of your air craft and perform a range check. You should get at least 100 to 150 feet in range check mode while facing the receiver, elevate the receiver at least 3 feet above ground. Just to clarify when you bind a receiver the UID is stored in the receiver so loss of bind indicates a receiver issue.

As suggested, I ran another test with the receiver out of the plane.
Range:
X9 Lite: 150+ feet
QX7: less than 20 feet
Everything the same except transmitter.

So to me the QX7 is TOAST.

 

[Wayne]

Maybe a bad antenna on the module, but it should warn you of that too.

If range has dropped more and more over some time, then it sounds like something is killing the RF chip. This is usually an antenna issue, but FrSky does monitor their antennas to make sure they will not run into this issue.

 

[Hank]

Maybe a bad antenna on the module, but it should warn you of that too.

If range has dropped more and more over some time, then it sounds like something is killing the RF chip. This is usually an antenna issue, but FrSky does monitor their antennas to make sure they will not run into this issue.

Both the internal module and the external Hitec module have the reduced range.

 

[Wayne]

Yeah, I really do not see a way for that to occur other than something not being discussed. Just bad luck perhaps.

It is not normal for a FrSky system to suffer from range loss. Does it happen? Sure, but it is not the norm.

 

[Hank]

Yeah, I really do not see a way for that to occur other than something not being discussed. Just bad luck perhaps.

It is not normal for a FrSky system to suffer from range loss. Does it happen? Sure, but it is not the norm.

I moved my models to my X9 Lite for now.

 

[jure]

UPDATE:
the transmitter was repaired,
the issue was a shorted transmission line at the connector from the internal RF board to the antenna.
Both the the internal RF module and the external Hitec module work now.

 

[Hank]

Thanks Jure for the help.
I flew an airplane successfully with the internal QX7 RF module.
But when I tried flying with the external module, a HITEC module and FrSky MINIMA RX, I almost lost the plane. It would drop out randomly. I know it is not the receiver because it happened on another plane before the repair.
So I am suspecting that the Hitec external module is bad (15+ years old).
Last winter I noticed that all the planes using this external module suddenly lost their binding. I can't explain why, but that's also when the range dropped.
So I removed the external module and will switch planes and receivers around.

 

[Hank]

What I need now is an external bay cover. Unfortunately I misplaced mine a long time ago because I used the external module continuously from the beginning.
The TX color is white, but I don't care what color of the replacement cover is. I looked in the replacement parts section without luck.
If anyone around this forum has a spare they are willing to sell me, I would appreciate it. Otherwise, I will have to use ugly duct tape.

 

[Wayne]

We could print one of these for you:

Taranis Q X7 bay cover FLVSS sensor mod by simpson1991

You have to remove the 6pins on the right side, I desoldered them.The chip itself is simply hotglued in place.I printed it with an infill of 60%No support required.

www.thingiverse.com

or this one:

Taranis QX7 upgraded module bay cover by twinkle_414

Upgraded external module bay cover for the FrSky Taranis QX7. Replaces the annoying wobbly cover that comes with it. Stress tested by doing 100 removal cycles and it is still going strong. Use tough/ductile filaments, such as PETG for best results. I used PLA, and while being pretty brittle, it...

www.thingiverse.com

Our 3D printers should be up and running early next week.

 

[Hank]

Sounds great