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Fan noise on FT-847



Stan, WA1ECF wrote:

Consider the exhaust fan noise of the new TS-2000.
Go to HRO and give it a listen..

Wayne, W9AE replies:

One of the first things I did after getting my FT-847 was to put a power
resistor in series with the rear fan.  That reduced the fan noise to a level
I consider to be tolerable.  The resistor runs cool because the fan moves
air across it.  The radio is still cool after a long PSK-31 transmit session
(I didn't modify the front fan that comes on when the radio is
transmitting).  I think the "stock" airflow is overkill for indoor use.
Perhaps it's necessary for some mobile operations when the radio is in
direct sunlight and the ambient temperature is very warm.

The fan on my Astron power supply was even louder than the FT-847 fan.  The
fan was off 99% of the time, but it really roared during the 1% of time that
the thermal switch kicked it on.  I put a power resistor on that fan also,
and now it runs very quietly 10-20% of the time (much quieter than the
slowed-down FT-847 fan).

Yaesu should have made a 2-speed rear fan on the FT-847.  The fan should run
slowly when the radio is cool, and a thermal switch on the chassis should
make the fan run full speed in the rare event that the radio gets hot.  At
least there is a fairly easy "fix" for the fan noise on the FT-847.  I wish
I could say the same thing for the excruciatingly slow Sub Tune function.  I
have to press the "Fast" switch to operate the Sub Tune, then return to
"normal" tuning rate to operate the Main tuning.  Dumb software!

In case anybody cares, here's a list of my FT-847 modifications so far:

1. Slowed down the rear fan.

2. Added 2.2 kHz SSB and 500 Hz CW crystal filters from International Radio.
They have a shape factor of 1.5 which is much better than the Collins
mechanical filters sold by Yaesu.

3. Added 2 headphone connectors and a "spkr/headphone" switch to an external
speaker.  This isn't exactly an FT-847 mod, but I did this because it was
very difficult to operate the Mic Gain/RF power control when headphones were
plugged into the front panel.  I also padded down the speaker a bit to match
the volume when I switch from headphones to speaker.  Now I can easily
connect a second pair of headphones to demonstrate full-duplex satellite
contacts to a visitor.

4. Added a transistor to mute Mic audio when the HF data port keys the
radio.

5. Future: Add a "144 Mhz TX inhibit" connector for use with 13cm RX
converter.

Also, I no longer use the FT-847 satellite memories.  InstantTune provides
more and better "virtual satellite memories" than the FT-847's internal
satellite memories.
  
Wayne Estes
Mundelein, IL, USA

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