Topics

Keeping the finals cool


Zac T
 

This is a question that has probably been asked many times.  I'm thinking of adding a fan to the top of the ubitx 6 case and forcing air down onto the finals to keep them cool during digital operation.  Has anyone tried this?

Second question, could I just power the fan from the 13.1v header directly behind the power input on the board?  If not whats a good way to power a fan?

Or would just replacing the heat sinks with something bigger work just as well?


ajparent1/kb1gmx <kb1gmx@...>
 

Hint: heat rises.

Best case with fan on top is to pull air out.  That means a series of holes
under the finals for air to come in, past heat sinks and out the top.

Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO


Bill Cromwell
 

Hi,

Heat and hot air rises. If you put the fan on top above the finals use it to pull the air *out* up and away. Cooler air will then be drawn in form elsewhere across the finals and the heat sinks. If you point the fan down into the radio you will blowing the rising hot air right back down onto the heat sinks and finals.

73,

Bill KU8H

On 4/23/20 11:56 AM, Zac T wrote:
This is a question that has probably been asked many times.  I'm thinking of adding a fan to the top of the ubitx 6 case and forcing air down onto the finals to keep them cool during digital operation.  Has anyone tried this?
Second question, could I just power the fan from the 13.1v header directly behind the power input on the board?  If not whats a good way to power a fan?
Or would just replacing the heat sinks with something bigger work just as well?
--
bark less - wag more


Bill Cromwell
 

Heh,

High five :)

73,

Bill KU8H

On 4/23/20 1:48 PM, ajparent1/kb1gmx wrote:
Hint: heat rises.
Best case with fan on top is to pull air out.  That means a series of holes
under the finals for air to come in, past heat sinks and out the top.
Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO
--
bark less - wag more


vu3gwn
 

I have brushless fans that I can use. But am worried about RF interference from the fan. What kind of fan should I use?


Zac T
 

Ok, that give me an idea of where to place the fans and direction to point them.  I'll check the schematic and see if I can tap into the board for some power and put the little buggers into the case.

Thanks guys.


brad martin
 

Heat rises when its a static environment.  You add fans and its no longer static and the heat will go where its told to go by the fans.  Most times fans are pointed in a way that will keep the surrounding components cool (no blowing hot fan exhaust on them) and the circuit clean of dust.  Take a look at most CPU heatsink these days,  Most all high end and laptop CPUs blow or pull across the heatsink from the side and not from the top.  You also dont need to run the fan at 100% if you can reduce the rpm.  It doesn't take much airflow to cool this in most cases and usually good enough that the air is moving.  I know unless you have some 120mm fan that the smaller 40-80mm fans can get quite loud.

Brad

On Thu, Apr 23, 2020 at 3:48 PM Zac T <ztread01@...> wrote:

Ok, that give me an idea of where to place the fans and direction to point them.  I'll check the schematic and see if I can tap into the board for some power and put the little buggers into the case.

Thanks guys.



--


Dale Parfitt
 

I believe I would add an external amplifier and not have to worry about fans, higher Vdd etc on the basic unit.  

 

Dale W4OP

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of brad martin
Sent: Thursday, April 23, 2020 4:07 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Keeping the finals cool

 

Heat rises when its a static environment.  You add fans and its no longer static and the heat will go where its told to go by the fans.  Most times fans are pointed in a way that will keep the surrounding components cool (no blowing hot fan exhaust on them) and the circuit clean of dust.  Take a look at most CPU heatsink these days,  Most all high end and laptop CPUs blow or pull across the heatsink from the side and not from the top.  You also dont need to run the fan at 100% if you can reduce the rpm.  It doesn't take much airflow to cool this in most cases and usually good enough that the air is moving.  I know unless you have some 120mm fan that the smaller 40-80mm fans can get quite loud.

 

Brad

 

On Thu, Apr 23, 2020 at 3:48 PM Zac T <ztread01@...> wrote:

Ok, that give me an idea of where to place the fans and direction to point them.  I'll check the schematic and see if I can tap into the board for some power and put the little buggers into the case.

Thanks guys.


 

--


Arv Evans
 

Beithur

Uh...one that does not cause RF interference?  8-)

Some brushless fans convert DC to AC to run the fan motor.
  That AC may cause harmonics up into the LF range.
Some brush-type fans cause both RF and AF noise.

It really depends on what you have available, or what you 
want to purchase and try.  

PC power supply fans are usually the brushless type.  Less 
expensive small surplus fans may brushed type.

Arv
_._


On Thu, Apr 23, 2020 at 1:23 PM <belthur@...> wrote:
I have brushless fans that I can use. But am worried about RF interference from the fan. What kind of fan should I use?


 

I always blow cool air inwards, I dont want hot air heating the fan parts and causing premature death.

Running a 12V fan on 5V makes it real quiet!

Raj


At 24/04/2020, you wrote:
Heat rises when its a static environment.  You add fans and its no longer static and the heat will go where its told to go by the fans.  Most times fans are pointed in a way that will keep the surrounding components cool (no blowing hot fan exhaust on them) and the circuit clean of dust.  Take a look at most CPU heatsink these days,  Most all high end and laptop CPUs blow or pull across the heatsink from the side and not from the top.  You also dont need to run the fan at 100% if you can reduce the rpm.  It doesn't take much airflow to cool this in most cases and usually good enough that the air is moving.  I know unless you have some 120mm fan that the smaller 40-80mm fans can get quite loud.

Brad

On Thu, Apr 23, 2020 at 3:48 PM Zac T <ztread01@...> wrote:

Ok, that give me an idea of where to place the fans and direction to point them.  I'll check the schematic and see if I can tap into the board for some power and put the little buggers into the case.

Thanks guys.


ajparent1/kb1gmx <kb1gmx@...>
 

Then you have to blow the air in from the bottom.

From the top if the air exiting though the fan is over 35-40C you really
need a bigger fan!  Why?  becuase everything below it is very hot,
likely way too hot.

Fans are cheap and more likely to out last the over heated finals.

Allison
---------------------------------
No direct email, it goes to bit bucket due address harvesting in groups.IO


Tom VE3THR
 

A few of us have tried dc fans of every type on vers 4 boards and found the rf interference terrible. These fans when powered from the same DC power source results in terrible noise directly proportional to fan speed. We have not found the correct combo of electrolytics and resistors/choke.
In my case, I mounted the two IRF210's via mica insulators to an aluminum block in turn mounted to the rear metal back panel - no heat issue and no noise or fan. 
Always was wondering about the fan noise so here we are!
73 Tom


Rob French (KC4UPR)
 

Well, I guess this answers this... I have so far had no luck killing the fan electrical noise.  It's in the low-hundred Hz, with some harmonics (though at least on my digimode waterfall, the only spikes I see are < 500 Hz, and I don't see anything visible in the spectrum display of my TX output).  Very noticeable (audibly) when I turn my volume down, mostly unnoticed when I turn the volume to normal listening levels.

I use a 1000uF electrolytic.  No resistor in series, though I guess I could try 10 ohms or so... I had a larger resistor in at one point, and it slowed the fan down too much. I also have a 1N914 diode in series... not sure what I was thinking, but I haven't removed it.  Large (megaohm?) resistor across the electrolytic terminals.

I have found the fan indispensable for running digimodes.  I have my uBITX v5 setup for a solid 8-9 watts on most bands (except 10M).  FT8/FT4/etc, the finals stay cool to the touch, even with many many transmissions in a row... 15 second transmissions just aren't long enough, and with the fan running continuously, any excess heat is quickly shed during the RX periods. However, with long transmissions (3-4 min) using Olivia, the finals definitely get uncomfortably hot to the touch, even with the fan running.  Now, if the other guys transmits for just as long, the fan does manage to cool the finals back down pretty quickly during RX.

Is this fan EMI primarily conducted, or radiated?  I kind of assumed it was conducted, and that maybe some DC ground isolation would fix it, but I don't really have a good way to do that (though I know there are specialized ICs for this).  Would probably be way simpler to forego the fan and switch over to the aluminum block!

Thanks for humoring me,
-Rob KC4UPR


Evan Hand
 

Rob,
My solution is similar to your resistor, though used a PWM fan control module that I ran direct from the DC power switch on the rear of the case to the controller, ensured that there was a good ground, and installed toroids on the in and out of the controller.  Did not totally eliminate the noise, but could dial back the fan to reasonable audio levels that also had low RF interference.

Not perfect, but did reduce to tolerable levels.  It also allows me to adjust the fan speed based on conditions.

Best is always fanless for low noise of all types.  An aluminum block on the back of the case with the fans mounted to the block would be the best in my humble opinion.
73
Evan
AC9TU


Robert D. Bowers
 

I've used a tiny squirrel cage fan (a lot quieter running, and put a choke kit and small value resistor just ahead of the fan as it didn't need to run full speed to keep things cool.  That completely eliminated noise and still moved a lot of air past the heat sinks. Some fans are far noisier than others... I'm not sure why, as I've tried brushless and brush motors - found noisy and quiet ones for each type.  Maybe an AC fan using a small inverter circuit?  With the right circuit, that should be quiet.  The AC fans I've used - no noise problem (but then, I was running them off of the AC mains with a dropper resistor to slow them down a bit).

Good luck on killing that noise - sometimes it takes trying a lot of different things to get rid of it!  (I just wish there were more tiny DC squirrel cage motors available! That might be something to consider.)

Bob
N4FBZ

On 9/2/20 12:02 PM, Evan Hand wrote:
Rob,
My solution is similar to your resistor, though used a PWM fan control module that I ran direct from the DC power switch on the rear of the case to the controller, ensured that there was a good ground, and installed toroids on the in and out of the controller.  Did not totally eliminate the noise, but could dial back the fan to reasonable audio levels that also had low RF interference.

Not perfect, but did reduce to tolerable levels.  It also allows me to adjust the fan speed based on conditions.

Best is always fanless for low noise of all types.  An aluminum block on the back of the case with the fans mounted to the block would be the best in my humble opinion.
73
Evan
AC9TU


Rick Walker
 

I haven't dug into it yet, but the audio in my v6 sounds very metallic, noisy and distorted.  None of the high gain audio chain circuitry has any supply bypassing.  The situation might be exacerbated by the fact that I'm using a switching wall-wart type supply that has alot of noise on it.  I think the best engineering fix would be  active local supply regulation on all the critical nodes, such as the undegenerated transistor running at full beta after the final mixer.   I usually judge the clarity of audio by tuning down to one of the strong AM stations in the area (KGO here in the SF bay area).  The audio is noticeably inferior to any $20 AM radio and the problem is not just the 3kHz bandwidth - it is also noisy and noticeably distorted.  The entire design seems to assume ultra quiet battery power with no significant rail noise.  This is probably why adding a fan messes everything up.  There is basically no supply regulation on any of the critical nodes.

Rick
WB6GVI


Adrian Chadd
 



On Wed, 2 Sep 2020 at 14:29, Rick Walker <walker@...> wrote:
I haven't dug into it yet, but the audio in my v6 sounds very metallic, noisy and distorted.  None of the high gain audio chain circuitry has any supply bypassing.  The situation might be exacerbated by the fact that I'm using a switching wall-wart type supply that has alot of noise on it.  I think the best engineering fix would be  active local supply regulation on all the critical nodes, such as the undegenerated transistor running at full beta after the final mixer.   I usually judge the clarity of audio by tuning down to one of the strong AM stations in the area (KGO here in the SF bay area).  The audio is noticeably inferior to any $20 AM radio and the problem is not just the 3kHz bandwidth - it is also noisy and noticeably distorted.  The entire design seems to assume ultra quiet battery power with no significant rail noise.  This is probably why adding a fan messes everything up.  There is basically no supply regulation on any of the critical nodes.

Yeah, I've been experimenting with choking and RF bypassing on the power rails. (And I also use KGO; it's not too far from me :-)



-adrian
 
_._,


Jonas Sanamon
 

Hi Rick,

I would try to address the issue at the source instead, i.e. clean up the supply as close as possible to the wart. Or replace it for a better version. 
Should be a lot less work than "fixing" supply filtering at multiple modules/places, and it's usually better to stop interference/harmonics before it has radiated from leads and circuits.

Cheers,
Jonas - SM4VEY

Den ons 2 sep. 2020 kl 23:29 skrev Rick Walker <walker@...>:

I haven't dug into it yet, but the audio in my v6 sounds very metallic, noisy and distorted.  None of the high gain audio chain circuitry has any supply bypassing.  The situation might be exacerbated by the fact that I'm using a switching wall-wart type supply that has alot of noise on it.  I think the best engineering fix would be  active local supply regulation on all the critical nodes, such as the undegenerated transistor running at full beta after the final mixer.   I usually judge the clarity of audio by tuning down to one of the strong AM stations in the area (KGO here in the SF bay area).  The audio is noticeably inferior to any $20 AM radio and the problem is not just the 3kHz bandwidth - it is also noisy and noticeably distorted.  The entire design seems to assume ultra quiet battery power with no significant rail noise.  This is probably why adding a fan messes everything up.  There is basically no supply regulation on any of the critical nodes.

Rick
WB6GVI
__,_._,