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Old Feb 06, 2012, 04:29 PM
RC Farmer
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Guys what element on the picture will need additional cooling if i increase the voltage to the module?
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Old Feb 06, 2012, 04:48 PM
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For long life of the module, feed it with 3.3v.

Cheap as you like
http://www.hobbyking.com/hobbyking/s...ly_6_23v_.html

Much better than a failed module during a flight...

Nigel.
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Old Feb 06, 2012, 05:02 PM
RC Farmer
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Yes i agree with you, but if you apply proper heat transfer from hot component, you could drive it with slightly higher voltage, like 3.7V... On the original 200mw completed TX you just need to change resistor divider that dictates output voltage.
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Old Feb 06, 2012, 05:19 PM
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Quote:
Originally Posted by Farmer_Joe View Post
On the original 200mw completed TX you just need to change resistor divider that dictates output voltage.
Uhhm, could anybody post a picture which resistor you will need to change on the foxtech 200mW Tx to apply 3.3V to module? I've sort of missed that post...

ty.

regards,
Sibi
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Old Feb 06, 2012, 05:22 PM
RC Farmer
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There is already 3.23V on the module on my stock TX.... You don't need to change anything.
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Old Feb 06, 2012, 05:23 PM
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ahh alright thanks!
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Old Feb 07, 2012, 06:32 AM
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Quote:
Originally Posted by Farmer_Joe View Post
Guys what element on the picture will need additional cooling if i increase the voltage to the module?
The upper right corner chip in the first picture is the final PA of this module.
On the opposite side you will find a cluster (circled in red) of metalized through holes, that is the heat pump point, where the whole heat of this module is dissipated outside. The whole ground plane around that point, under the green mask, is actually the real module heatsink, not the tin cover as some might think.
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Old Feb 07, 2012, 07:04 AM
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So that metalic rectangle located to the bottom right of the top picture needs cooling right.
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Old Feb 07, 2012, 07:05 AM
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Quote:
Originally Posted by msev View Post
So that metalic rectangle located to the bottom right of the top picture needs cooling right.
Nope, that's the oscillator. The upper black small square chip in the UPPER right of the picture.

Markus
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Old Feb 07, 2012, 07:32 AM
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So we need to put the heatsink directly on the chip or on the opposite side of the pcb (where Renato draw his circle)...

So the tin case of this module doesn't help in transfering the heat and if would not be beneficial to add a heatsink on it..
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Old Feb 07, 2012, 07:59 AM
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Quote:
Originally Posted by msev View Post
So we need to put the heatsink directly on the chip or on the opposite side of the pcb (where Renato draw his circle)...

So the tin case of this module doesn't help in transfering the heat and if would not be beneficial to add a heatsink on it..
The so called 500mW variant of the transmitter does something similar. The chip is rated for what it's used with the module and if so does not need a special heatsink. The modules are actually pretty much ok with this regard. They get hand warm which is ok.

If you intend to overdrive it by supplying a higher voltage you can - acording to Renato - squeeze some mW more out of it, but remember, to double the range, you have to have four times the power. So going from 200mW to 250mW or even 300mW won't buy you so much more really. What it does buy you though is the increased risk of a failure. This module, with standard power and propper antennas is good for 15km and more of range. Unless you are after breaking the 5.8Ghz distance record, I really wonder why you think you need a heatsink?

If you want to add a heatsink because you intend to embedd this module deep into isolating foam or such of a fuselage, then you maybe could add one, but for this purpose adding one to the metal can type of cover should be sufficient as this cover is nicely connected to the ground planes on both sides of the PCB which as Renato correctly mentioned also serve as a heatsink.

I made the experience that exposing the metal can a little bit to the air or even a fuselage internal slight airflow is aboslutely sufficient provided you don't overpower it.

Markus
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Old Feb 07, 2012, 08:38 PM
The Dreamer
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@markus123456

Very well explained and correct 100% in my humble opinion. . Beware of overdriving IC beyond the manufacturers spec or you run the risk of a premature failure.

Note also I have commented in other post that the antenna VSWR is an important consideration. A poor Antenna VSWR will reflect power back into the RF amplifier output transistors and add more watts and cause the transistor to overheat and fail.

Heat is the enemy of silicon chip and causes either instantaneous failure and or long term failure of the IC transistor.

Lindsay
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Old Feb 08, 2012, 02:44 AM
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I didn't intend on doing it all the time, maybe once a year ...And I even don't have the equipment, so I'm just asking...And you've read that Renato has been using his module for over a year on 4.2 volts and he hasn't got any problems...But yes I agree the difference in distance would be very small...But would be interesting to see just as an experiment.
Again I don't have any equipment yet except the camera
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Old Feb 08, 2012, 04:40 AM
The Dreamer
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Sydney, Australia
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RC305 BCD Rotary Switch Mod.

I have replaced the RC305 ch switch with a BCD rotary switch.

Reason is so I can easily scan the channel number and check for adjacent channel interference.

This mod makes it easier to find out what channel other guys are set to before taking to the air.

This photo is a 10 position BCD 4 line switch. Also available is a 16 position BCD switch same footprint.

FYI
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Old Feb 08, 2012, 03:34 PM
Flying FPV or Dreaming I Am...
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Quote:
Originally Posted by whakahere View Post
Just used the helical. it is easy to stay in the beam of a 4 turn. 6 turn I don't have to many problems either. The 4 turn has a wide angle to it. I have even flown close behind myself no worries.

In the first post where I did 5.1km was a 6 turn helical. At the end of it I was playing with the edges.

My new model I made straps to my head too .... so when I get off target i move my head. Antenna tracker kiwi style.
I know this is an old post but I am wanting to go back to using my 200mw 5.8ghz gear on my quadcopter for the more compact antenna size. I currently use 300mw 1280 CL/SPW set but the size of the CL on the quad is just too big and fragile. So I do not want to invest in diversity, so If I put my 5.8ghz 200mw CL setup back on the quad and used a single 5 turn helical on the Rx, how far to the sides and behind me can I realistically go? 200M?
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