[CQ-Contest] Switching Power Supplies

[K9MA]

OK, Barry asked me for the resistor value, so I had to look it up.

73,
Scott K9MA

On 11/13/2024 6:41 PM, Barry W2UP wrote:
> Tnx!  I had a feeling you didn't include the value for a reason  :-)
>
> 73,
> Barry W2UP
>
> On Wed, Nov 13, 2024 at 5:10 PM K9MA <k9ma at sdellington.us> wrote:
>
>     I was afraid someone would ask that! According to my 2011 notes,
>     it was 50 Ohms, and dissipates about 0.5 W. I'd use at least a 2 W
>     resistor.  That runs a K3, K4, or IC-7610 in receive mode without
>     switching to full speed. (One radio at a time, maybe two.) If you
>     want to experiment, use the smallest resistance which reduces the
>     noise to an acceptable level.
>
>     73,
>     Scott K9MA
>
>
>
>     On 11/13/2024 5:22 PM, Barry W2UP wrote:
>>     Scott,
>>
>>     What value resistor?
>>
>>     Tnx,
>>     Barry W2UP
>>
>>     On Wed, Nov 13, 2024 at 4:17 PM K9MA <k9ma at sdellington.us> wrote:
>>
>>         Sounds like the fan of the 1235P-M works the same way as that
>>         of the
>>         1235M, so the resistor mod should work.
>>
>>         73,
>>         Scott K9MA
>>
>>         On 11/13/2024 12:41 PM, Steve Dyer W1SRD via CQ-Contest wrote:
>>         > It's not variable speed, but on demand. When it turns on
>>         it's full on.
>>         > Must be something about the pitch of that sized fan that
>>         annoys me.
>>         > Maybe all the years working on 1U server farms at data centers.
>>         > 73,
>>         > Steve
>>         > W1SRD
>>         >
>>         >
>>         > On 11/13/2024 9:47 AM, K9MA wrote:
>>         >> I did a very simple mod to 1235M:  A resistor in parallel
>>         with the
>>         >> thermostat. This causes the fan to run continuously at low
>>         speed,
>>         >> rather than cycling when demand is low. The fan runs at
>>         full speed
>>         >> only during times when I'm transmitting a lot, when the
>>         fans in the
>>         >> radio and amplifier drown it out.
>>         >>
>>         >> The 1235P-M may be different, but I doubt it has a
>>         variable speed
>>         >> fan, or this mod wouldn't be necessary.
>>         >>
>>         >> 73,
>>         >>
>>         >> Scott K9MA
>>         >>
>>         >>
>>         >>
>>         >> On 11/12/2024 8:00 PM, Steve Dyer W1SRD via CQ-Contest wrote:
>>         >>> My only gripe with the 1235P-M is the fan noise. Good PS
>>         otherwise.
>>         >>> 73,
>>         >>> Steve
>>         >>
>>         >>
>>         >
>>
>
>     -- 
>     Scott  K9MA
>
>     k9ma at sdellington.us
>

-- 
Scott  K9MA

k9ma at sdellington.us