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

belthur@...
 

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