Rob2160

I recently purchased a 2nd hand JR9303.

I tested it fully, range checks perfectly and have flown a few planes to the limits of my vision with no issues.

Yesterday I turned it on in a completely silent room and noticed a soft humming sound. almost like a monotone "prrrrrr" coming from the radio.

I honestly don't know if it always made that sound and I just noticed yesterday or if the sound recently started.

I checked all my other radios and every one of them is silent when on..

The radio still works perfectly and range tests normally

Should I be worried or is this normal for the 9303?

Its about the same type of hum that comes from a small wall charger but softer.

Giant Flyer

My Feedback: (6)

Well...until I saw your post, I never noticed.
But guess what????????????
It does have a slight electrical sound.
Sort of a very faint buzzing sound.
I bought this radio new and it has never gave any problems whatsover.
So I guess it is normal!!!

Giant

Rob2160

Hi Giant,

Thanks for taking the time to check your radio and reply.

Sets my mind at ease that it is probably normal for the 9303.

Cheers.

Rob

Rob2160

A further update for anyone interested..

I closely tested all my radios again..

Futaba's are absolutely silent

DX7s and 2 x DX8s are totally silent.

two JR11X's - inaudible when held in the normal flying position but if you put your ear directly to the back of the radio they make exactly the same hum as the JR9303 just much quieter.  

So it is just the JR Radios that make the hum.. It must be normal.. the 11x's are probably 1 / 10th the volume of the 9303

AndyKunz

The DX7 makes the hum too. It's normal. If you listen closely, you'll see that it matches the frame rate.

Andy

Rob2160

Thanks for the peace of mind Andy.. I guess you mean the original DX7, not the newer DX7s? I only have the latter and can't hear a thing..

Aerocal

Yes the DX7(original).Mine had a slight hum to it.Some are louder than others. New generation Airware/DX radios are quiet.

Rob2160

Thanks, being eternally curious, what component actually causes the hum?

Aerocal

I havent specifically traced the hum but I kind of came to the assumption that it was likely the voltage regulator.

Rob2160

Thanks.. good enough for me..

AndyKunz

I think the fact that it matches the frame rate (45Hz) should be a pretty good clue ...

Andy

4*60

My Feedback: (41)

http://www.helifreak.com/showthread.php?t=278587

Good thread there and they give the reason for getting it serviced(joke!)

slarty

Ye Gods.... I forgot I posted that !!!

Just made me smile....

Dave Harmon

I tested my 9303 today and it is dead quiet.....not a peep outta that thing.
It has a 72mhz module in it so perhaps the 'noisy' radios are on 2.4g?
Dunno.....

1320Fastback

Ill check my 9303 out tomorrow on both 72 and Spek with the module.
I haven't noticed a humm but doesn't mean I just haven't listened close enough

AndyKunz

Your DX7 and DX7SE make the same sound, too. That hum is about 45 Hz ...

Andy

1320Fastback

I tried both modules in mine today and can't hear anything at all.

slarty

With a conventional module, the RF is transmitting 100% of the time, with the 2.4 GHz it transmits 2 pulses every 22 msecs or so. It is this pulsing that you are hearing,