Topics

heat sink upgrade #parts #bitx40

Doug W
 

I've been planning on upgrading the heat sink on my BITX40 for a while and finally got around to it with my last digikey order.  This one https://www.digikey.com/product-detail/en/assmann-wsw-components/V7477X/AE10882-ND/3511452 fits quite well if you flip it upside down.  I pulled out the board mount pins since they serve no purpose sticking out of the top.  I mounted it with this silicone pad https://www.digikey.com/product-detail/en/t-global-technology/DC0011-08-L37-3F-0.25-2A/1168-1803-ND/3466713 and secured it with a nylon screw and nut I had on hand https://www.banggood.com/180pcs-M3-Nylon-Black-Spacers-Screw-Nut-Hex-M-F-Stand-off-Assorted-Kit-Box-p-1000806.html  It fits just fine inside my banggood EF01 case.  The only thing I planned wrong is that it barely brushes against C155. I put some electrical tape in between the two and nothing blew up when energized so I'm calling it good.

Doug W
 

As a follow up to my post about this heat sink, I did some testing of digital Tx'ing into a dummy load yesterday as I think I have my digital interface set up the way I want.  I did not use anything to test the temperature other than touching the MOSFET and heat sink and going by feel.  At a full 7 watts out nothing got more than just barely warm at FT8 cycles running for about 15 minutes.  At WSPR timing both the IRF510 and heat sink got hot enough I was double checking the junk box to make sure I had a few spare IRF510's.  Bottom line, I think this heat sink is ok for occasional FT8 operations at full power (which was all I wanted it for) but if WSPR is your flavor of choice you'll need to crank the power way down.  All in all I got what I wanted for about 73¢.  I should also mention that although it is hard to tell in the picture the MOSFET is fully sitting on the silicone pad.  I lined the pad up with the heat sink overlooking the fact the the IRF510 is angled coming off the board.  Fortunately the pad was wide enough to accommodate my error.

Tim Gorman
 

Doug,

Thanks for the info. I usually use jt65. It sounds like this heat sink
would work fine for that, correct? About 45sec transmit cycles
interspersed with 1 minute receive cycles.

tim ab0wr

On Sun, 22 Apr 2018 10:37:07 -0700
"Doug W" <dougwilner@...> wrote:

As a follow up to my post about this heat sink, I did some testing of
digital Tx'ing into a dummy load yesterday as I think I have my
digital interface set up the way I want.  I did not use anything to
test the temperature other than touching the MOSFET and heat sink and
going by feel.  At a full 7 watts out nothing got more than just
barely warm at FT8 cycles running for about 15 minutes.  At WSPR
timing both the IRF510 and heat sink got hot enough I was double
checking the junk box to make sure I had a few spare IRF510's.
Bottom line, I think this heat sink is ok for occasional FT8
operations at full power (which was all I wanted it for) but if WSPR
is your flavor of choice you'll need to crank the power way down.
All in all I got what I wanted for about 73¢.  I should also mention
that although it is hard to tell in the picture the MOSFET is fully
sitting on the silicone pad.  I lined the pad up with the heat sink
overlooking the fact the the IRF510 is angled coming off the board.
Fortunately the pad was wide enough to accommodate my error.

Doug W
 

Tim
I think for anything other then very infrequent use at that cycle I would look for something with more mass.  You might get by but I couldn't guess for how long. 

_Dave_ AD0B
 

The part that gets hot on both of my bitx radios (40 and micro) is the power supply chip on arduino board. it gets too hot to touch. The PA only get slightly warm after an hour long phone qso. 

I had thin sheet of aluminum that bolted to the power regulator and it is markedly cooler. 

I have not set my radios up for digital 

Run radios both at 13.8v regulated.

Skip Davis
 

The reason the Raduino regulator greats so hot is it has to dissipate the heat generated from in your case the 8.8 voltage drop across it. To cool it down you can insert a dropping resistor of about 56 ohms inline with the regulator input from pins 15 & 16 of the Raduino control board. Just cut the trace between those two points and solder in your resistor. You want to select a resistor value that will keep the voltage at the regulator input at about 7 vdc.


Skip Davis, NC9O 

On Apr 24, 2018, at 10:01, davesters@... wrote:

The part that gets hot on both of my bitx radios (40 and micro) is the power supply chip on arduino board. it gets too hot to touch. The PA only get slightly warm after an hour long phone qso. 

I had thin sheet of aluminum that bolted to the power regulator and it is markedly cooler. 

I have not set my radios up for digital 

Run radios both at 13.8v regulated.

_Dave_ AD0B
 

Thanks for the advice Skip. 
Did some long transmissions on 40 and indeed the power transistors did get pretty hot. I had not noticed it. 

Went to my box of computer parts and pulled out a nice brushless computer fan. Thought about putting a circuit to turn on the fan when the tx is on. After a couple of minutes I did the more expedient route and wired the fan directly into the power supply It runs anytime the PS is running. My experience with larger heat sinks is that a fan easily Trumps a larger heat sink. 

Skip Davis
 

Dave that’s a great idea with the fan powered on only when in transmit I might do the same thing here. I’ve got a few very small fans here salvaged from somewhere and they are quiet too. 
Have you done any other mods? I’ve done my version of the thump mod and waiting for parts to flatten out the driver amp response. I’m also doing the mic amp gain increase mod too.

Skip Davis, NC9O 

On Apr 24, 2018, at 23:15, davesters@... wrote:

Thanks for the advice Skip. 
Did some long transmissions on 40 and indeed the power transistors did get pretty hot. I had not noticed it. 

Went to my box of computer parts and pulled out a nice brushless computer fan. Thought about putting a circuit to turn on the fan when the tx is on. After a couple of minutes I did the more expedient route and wired the fan directly into the power supply It runs anytime the PS is running. My experience with larger heat sinks is that a fan easily Trumps a larger heat sink. 

_Dave_ AD0B
 

Hi Skip,
No sir everything is stock. I have only used 40 and and 80meters.  Have not noticed much else wrong, If it is not broke, don't fix it. I have worked 40 states and Ontario with it and my bitx40. I use a homemade full sized 40meter dipole with traps and 48" extensions on 80 meters Using television 75Ω coax. Maybe if I had some commercial radio, I would see some areas that needed help. 

Still learning ditties so have not done anything with that yet. 

I am a newer ham and every project starts from scratch. 

Skip Davis
 

Dave, I upgraded my firmware to Ian’s build which fixed a few instabilities in the original firmware. I also installed a thump fix which works well because I use headphones a lot and now it’s fine. I’m using an inverted V here made of 450 ohm twin lead with twin lead feeder, a nice quiet antenna.

Skip Davis, NC9O 

On Apr 25, 2018, at 08:24, davesters@... wrote:

Hi Skip,
No sir everything is stock. I have only used 40 and and 80meters.  Have not noticed much else wrong, If it is not broke, don't fix it. I have worked 40 states and Ontario with it and my bitx40. I use a homemade full sized 40meter dipole with traps and 48" extensions on 80 meters Using television 75Ω coax. Maybe if I had some commercial radio, I would see some areas that needed help. 

Still learning ditties so have not done anything with that yet. 

I am a newer ham and every project starts from scratch.