JR 8103 heats up
#1
Thread Starter
Join Date: Jul 2003
Location: Provo,
UT
Posts: 988
Likes: 0
Received 0 Likes
on
0 Posts
JR 8103 heats up
Just got a nice looking JR 8103 Radio off from the bay. While checking it out last evening (had it on with the antenna down for an hour or so) the freq modual got quite warm, not hot just warm to the touch. Everything seems to work ok and the batteries (2500 NImetal) seems to be holding a charge ok. I have never noticed this on any other JR Radio I have owned thru the years. Ya think this is Ok/Normal???
#2
My Feedback: (1)
RE: JR 8103 heats up
It's because the antena was not extended. You can actually damage transmitters by operating them with the antena collapsed. Extend at least one segment of the antena whenever you turn it on.
Having said that, RCU has a JR Support forum:
http://www.rcuniverse.com/forum/forumid_116/tt.htm
David
Having said that, RCU has a JR Support forum:
http://www.rcuniverse.com/forum/forumid_116/tt.htm
David
#4
Senior Member
My Feedback: (3)
RE: JR 8103 heats up
I was in the hobby for 20 years before I read about the antenna deal. I guess the explanation is that the load on the output amp goes up, beyond what it is designed to handle. RF is weird science, the first guy to come up with the radio concept would have EASILY been smart enough to hang out with us..
#6
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,425
Likes: 0
Received 22 Likes
on
19 Posts
RE: JR 8103 heats up
The reason it has more power dissapation is reflections in the antenna. RF systems have reflections in any wire or path. Inside the board the lengths are too small to matter but in cables and antennas it's important to match the transmission line, load or antenna to the frequency to avoid these power reflections. Running with the antenna collapsed you're reflecting maybe 80% of the power back into the output transistors. When it's extended and provided it's matched well you'll reflect back less than 5%.
It's all got to do with standing waves and stuff like dat. Hi tech ya knows....
Try it again with the antenna extended. After an hour feel the module. Chances are it'll still be a little warm but not as warm as with the antenna collapsed.
Before computers took over this was how I made my living....
It's all got to do with standing waves and stuff like dat. Hi tech ya knows....
Try it again with the antenna extended. After an hour feel the module. Chances are it'll still be a little warm but not as warm as with the antenna collapsed.
Before computers took over this was how I made my living....
#7
Thread Starter
Join Date: Jul 2003
Location: Provo,
UT
Posts: 988
Likes: 0
Received 0 Likes
on
0 Posts
RE: JR 8103 heats up
Ok, I tried it with the antenna fully extended and the freq mod still feels "warm" to the touch but not AS warm as with the antenna down. SO I tried another 8103 and experienced the same results. Guess I'm just being paranoid. The battery seems to be holding a normal charge so I'm just gonna mention it to the JR rep and shut the F**k up and go fly it!