It is true that I am just a newly
licensed ham, but I have been doing work on my elder father's
ham shack equipment that was left to me after he pasted away. I have been
under his license for many years and I worked with communications
while serving in the military. I work from a practical but experimental
approach.
In this case I found that several
of my older Kenwood 7800 /7950 two-meter radios did not like the heat
and lack of airflow in my shack. When the inside temperature of one of the
radios hit 120 degrees Fahrenheit on transmit, the led screen on the
radio started to flash and generally act up.
I was not
dismayed; I had more than one of these radios which I use as base
stations so it was time to experiment a little to see if I could cure the
heat problem that builds up in the radio.
As I have the radios
hooked up to larger external speakers, the tiny little speaker inside one
was redundant so I unbolted the top of the case and just removed it in
hopes of installing an internal cooling fan. I surveyed the size of the
space created by the removal and came up with the next part of the
plan.
I placed one of those thin, low draw, high speed,
quite, little computer CPU fans like the example picture below,
over the vacant space.
Example
of CPU cooling fan {Note that is
should be 12 volts DC rated.}
It fit and it covered the speaker grill
work on the underside of the top cover so well I figured I was on to
something here.
After bolting it up to the case top and
running the leads out through the small hole in the back of the finned
case, I hooked the leads to the same 12vdc source the radio used and I was
impressed. It works and the temperature dropped. The project
could have ended happily there but would that be the amateur radio way.
I went further with the
project. I wanted a way to turn the fan on and off. I then found
a small little hole in the back of the radio case on the flat spot
next to the fins that appeared to have nothing much next to it, so I
CAREFULLY drilled it out just a little bit to a more usable
size in which to mount the switch.
Sub-miniature toggle switch - not to
scale
Then I inserted a micro flip switch similar to the
picture above and it looked like it should have been made that way.
On further inspection inside the rear of the radio while
looking at the power section, I saw a good location point off of the power
main lead connector before it reached any electronics inside the
unit, so the soldering kit came out, and I soldered one side of the switch
connector to the DC power input (positive side) and the other switch
connector to the (hot fan wire), then I found a suitable case ground for
the other end of the circuit. See photo below for final
installation.
Location of fan switch on rear of radio
at end of white "arrow".
You can use your choice for the style and size of the
switch that will fit your radio. When the radio gets too hot, I flip
the switch, when it is cool enough, I just turn it off. You may forget
that the fan is running due to their very quiet operatiion....no
problem!
Cooling fan shown installed in top cover. Notice 4 mounting
bolt/nuts.
Now I am not going to
recommend that everybody go ripping out the speakers of all their radios,
especially since many newer radios already had internal fans hooked to the
transmit side of their boards these days. Also many radios may not be
as troubled by the heat build up in the case as the older radios, however
for my money I think this fix is hard to beat in the heat we have been
having of late. Onward to the next radio, it will get a thermistor
controller to turn it on automatically, so what do you think?
What
a concept! A twenty year old 2-meter radio saved from the
hottest summer weather in years by a $1.95 used CPU fan! Canadian Radio
Shack part number 273-248.
Not so bad for guy who has not
even had his ticket for a month.
Parts used 1 ea Canadian Radio
Shack 273-248A fan.
1 ea Switch (on/off) of
your choosing that will fit your particular location in your
radio. Enjoy and 73.......
Ian J. Turner VA7FSM "Just your
Basic ham"
Editors note: Many
radios will suffer heat related problems in hot weather that causes all
kinds of problems to show their ugly face. Most all transceivers have a
temperature range specification that they are designed to work in.
Excessive heat beyond the specifications will quickly destroy solid
state devices if not properly cooled or operated within their temperature
range. Some components are more sensitive than others.
It is advisable to insure
that if you do want to install an internal cooling fan that you do not use a fan rated at other than 12-15 volts DC.
Many "CPU' fans may be rated at much less voltage than
your radio's supply voltage which will usually burn them out
quickly.
So be wise and check the
"specs" on the fan you intend to use! Remember, if you plan to use the DC
power that supplies your radio, use the same voltage fan. In some
cases, you may not have room for an internal fan so the only other option
you have is to install an external cooling fan.
Another location option for
the fan is the back of the radio attached to the cooling
fins provided for most radios. These fins act as a heat sink and the
additional air movement across them will certainly help to dissipate more
heat. The "forced air" from the fan should move between the fins if
possible. Use your own ham ingenuity in the mounting process and
location and provide a way to shield fingers from
the fan blades for safety if they are external!
