[NLRS] FT857

[Dr. Gerald N. Johnson]

I haven;'t seen it in my 857s yet, though I'm getting out poorly with a 
tangle of cables by showing an high SWR on UHF only at the radio whether 
the horizontal antennas with a duplexer or a dual band vertical. I need 
to check with a high quality dummy load along the various coax junctions.

The very last menu entry with extended menues is a toggle for 
transverter mode that limits the power output. I have suggested that got 
toggled for low power sometimes. For my transverter 857 I turned down 
the power on 2m using the TX gain setting (by band) in the alignment 
menu. Lowering by ALC or power setting lets it spike, lowering the TX 
gain prevents that spike. There are also settings in that menu for ALC 
levels, SWR protection trigger levels, and power readings IIRC. And 
things like SWR protection trigger is set to 1:1 when there us a super 
master reset performed. My second 857 that I bought second hand I found 
had been through that super reset, but I found a web page with a 
tabulation of settings and compared them to the 857 I bought new. There 
is one such table I have downloaded from mods.dk titled: "Second menu 
for FT-857"

While Yaesu Technical Supplement doesn't admit it, there are some 
differences in the amplifiers and filters between the 857 and the later 
857D that solved some of the power loss and filter crackling of some 
vintages of 857.

I discussed some of the alignment menu items and how I used them in my 
CSVHF 2010 paper:
www.geraldj.networkiowa.com/papers/CSVHF2010/xvtr857align.pdf

Other than these memory values having changed, I would look for low gain 
in the TX from a UHF side hardware failure, like a filter tuning voltage 
and for a SWR detector that was hypersensitive to reflected power and so 
limiting power output as a PA protection scheme the change due to the 
SWR detector, not the menu, but I'd look at the alignment menu first. 
Essentially low TX output can come from any stage in the transmitter 
from audio to PA, though most are shared and it works on VHF, but might 
be specific to mode as some exciter parts are different for FM than for SSB.

73, Jerry, K0CQ


On 5/14/2015 3:41 PM, S. Earl Jarosh wrote:
>
>
> I came across this question on another forum.  Since so many here have
> these, does someone have the answer?
>
> ----------------------
> I own a 2003 FT857 that only outputs around 2 watts on UHF any mode.  My
> friend has a radio with a similar issue from the same era and browsing the
> internet I see we are not alone.
>
> The radios all operate fine on VHF 2 meter with 50 Watts.  This band uses
> the very same power transistor as UHF, so this is not the issue.
>
> Anybody knows what component to replace to get this fixed ?  The unit draws
> around 4,5 A so probably the final stage is running but power gets stuck
> somewhere in an affected SMD part.
>
>
> Pedro ON7WP
>
>
> (please no stupid replies like "have you checked your antenna?"  I am
> testing on a 1:1 dummy load with calibrated power meters)
> ------------------------
>
>
>
>
>
>
>
> S. Earl Jarosh, N0HZ
> SEJ Industries, Computer and Business Consulting
> 1432 Quebec Ave. N.
> Golden Valley, MN  55427
> Cell:  612.868.1313
> Off:   763.545.3275
> Fax:  763.546.7897
> www.linkedin.com/in/earljarosh
> 6128681313 at txt.att.net
> earl at jarosh.org
>
> Turning Can't Do Problems into Can Do Solutions
>
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