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Author Topic: Yaesu FT-857D Low Power Mod  (Read 5439 times)
WA6MOW
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Posts: 0




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« on: October 23, 2007, 08:52:16 AM »

Can anyone verify that if I ground the brown power wire it will reduce the power output to 20 watts and turn off the fan?  I love my rig rig but have no need for 100 watts and the fan drives me nuts.
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WW5AA
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Posts: 2088




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« Reply #1 on: October 23, 2007, 09:22:48 AM »

I don't know about the brown wire? The FT-857D can be adjusted to any power level from 1-100 watts in the menu. You might want to check things out, mine never comes on in HF and only after a long key down on VHF or UHF.

73, de Lindy
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N1WOM
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Posts: 60




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« Reply #2 on: October 23, 2007, 09:27:28 AM »

Yaesu FT-857D operating manual
Page 96
Menu item number 75
RF Power Set

73, John
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W5RKL
Member

Posts: 888




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« Reply #3 on: October 23, 2007, 09:32:23 AM »

The "Brown" wire on the FT-857D side of the power
lead, is the "Battery Sense" wire. If this
wire is grounded the FT-857D will "Automatically"
switch to 20 watts output (10 watts on 430Mhz)
regardless of the setting in menu item #75. This is
discussed on page 32 of the FT-857D's manual.

Mike
W5RKL
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W5RKL
Member

Posts: 888




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« Reply #4 on: October 23, 2007, 09:40:10 AM »

The Brown wire is on the 857D side of the
power plug. You have to pull the black
cover back from the power plug to see it.

Yes, you can adjust the power out using
menu item 75 but that was not the
question. I've quoted, from the Yaesu's
FT-857D's manual page 109, menu item 75 below:

"
MENU MODE No-75 [RF POWER SET]
Function: Setting of the maximum power level for the current band.
Available Values: Depends on operating band and transceiver version
Default: Depends on operating band and transceiver version
"

73's
Mike
W5RKL
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2E0BSS
Member

Posts: 85




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« Reply #5 on: October 23, 2007, 10:28:42 AM »

Simply turn the power down to 1 or 10watts whatever power you want without grounding anything. With my 857D I can turn the power down to 5 oh HF 2 on 70cm's and 5 on 2m and the fan still comes on, no idea if the uk spec is different appart from the 5mhz and weather than the usa version.

Charlotte 2E0BSS
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N3OX
Member

Posts: 8852


WWW

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« Reply #6 on: October 23, 2007, 11:11:50 AM »

I think the fan always comes on anyway, but I can check it when I get home, but yes, it does turn the power down (though mine gets turned down to about 30W)

Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W5RKL
Member

Posts: 888




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« Reply #7 on: October 23, 2007, 11:34:11 AM »

Simply changing menu item 75 to say 10 watts will
only affect the power setting for the particular
band in use. This is clearly stated on page 109 of
the 857D's manual. Menu item 75 is NOT an automatic,
all band, setting. Changing menu item 75 power setting
for 40 meters will NOT automatically change the power
setting for 20 meters. This is clearly stated on page
109 of the manual!

On the other hand, the Brown wire affects ALL band
power setting as described on page 32! The Brown
wire overrides menu item 75 as long as it is grounded!

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N3OX
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Posts: 8852


WWW

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« Reply #8 on: October 23, 2007, 04:43:11 PM »

"Changing menu item 75 power setting
for 40 meters will NOT automatically change the power
setting for 20 meters. This is clearly stated on page
109 of the manual! "

It's actually incorrectly stated that way in the manual.

All 9 HF bands have one power setting.  Additionally, you can independently set 6m, 2m, and 432MHz power output.

But, anyway, grounding the brown wire reduces the power output and does, in fact, turn off the fan.  I never noticed that before... that's pretty interesting.

It is pretty annoying but I usually use headphones (home station DX) so I don't notice it so much.

Dan

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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WA6MOW
Member

Posts: 0




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« Reply #9 on: October 23, 2007, 04:54:19 PM »

Everyone that reponded, thank you.   A tremendous help.  Eham is awesome.
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KD8FZI
Member

Posts: 5




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« Reply #10 on: October 24, 2007, 01:07:24 AM »

Does this mod work for the FT-897D?
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N3OX
Member

Posts: 8852


WWW

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« Reply #11 on: October 24, 2007, 06:00:11 AM »

It's a design feature of the '897D that just happened to make its way into the '857 because they're the same rig inside.

From what I understand, the "brown wire" is what tells the '897D that it's running off the internal battery... so when you're using the battery it uses lower power for less current draw (and I guess, doesn't need the fan at that point)

I don't have an '897 so i don't know where the brown wire is... presumably it is inside and goes to the battery connector?

Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
KB4XX
Member

Posts: 1




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« Reply #12 on: October 24, 2007, 08:46:26 AM »

Has anyone measured current consumption with the brown wire grounded? It would be helpful to know current consumption figures for both receive (squelched or low volume) and transmit. I'm considering the FT-897D as a "camping radio" and battery life is important. I realize there is an internal battery option, but it's quite expensive, and I'd like more battery capacity than it provides. I also like the idea of being able to un-ground the brown wire and go "QRO" when needed.

Phil      
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KE3WD
Member

Posts: 5694




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« Reply #13 on: October 24, 2007, 10:05:09 AM »

You would do well to take your own measurements on that, Phil.  

Ground the wire and hook up the DMM as ammeter...

Quick and dirty calc, figure about 65% efficiency here, class AB power amp, right?  78.5% being max theoretical there, 65% figure makes a great rule of thumb that is still on the conservative side.  

Then factor in the ICS rating, too.  

Receive consumption spec is published and shouldn't change at all with the wire grounded, that bit about them cutting off the fan also is, of course, a good one, the original batpack couldn't drive that fan for very long, right?  (grin)  --And running ~125W rated finals at 20W max, fan wouldn't be needed.  


KE3WD
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