Yaesu FT-897 modification sheet

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

Directory

Introduction........................................................................................................................2

Some background informations about the FT-897 mods............................................................3

FT-897 à FT-857............................................................................................................3

AGC................................................................................................................................3

Speechprocessor...............................................................................................................3

ALC audio pumping...........................................................................................................5

Exciter Stage Protection.....................................................................................................6

Proper BIAS-adjustment....................................................................................................7

Replacing the stock MURATA filter.......................................................................................8

Using an Electret capsule...................................................................................................8

Battery modification from W4CNG.......................................................................................8

Service Menu Settings.......................................................................................................9

Freeband Mod..................................................................................................................9

Programming Software....................................................................................................10

FT-897 won’t Power ON...................................................................................................10

Modifications overview........................................................................................................12

TX.................................................................................................................................12

RX................................................................................................................................13

Miscellaneous.................................................................................................................13

Mods – Summary View.......................................................................................................14

Mods – Detail View.............................................................................................................18

Disclaimer · Disclaimer of liability......................................................................................24

Copyright..........................................................................................................................24

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

Introduction

I started on doing modifications of CB- and HAM-radios since 1980 at the age of 12 years. I mostly
wasn’t satisfied with the sound of the modulation or reception of my rigs. This is normally founded
by restrictions of the local law or by rationalize productions. Only expensive high-class amateur
radios have a good sound on their basic state.

Therefore there must be some possibilities for improvements. So I learned the basics of RF elec­tronics on myself and did a lot of modifications until today and I would like to spend my experi­ences to all other electronic interested people, CB- or HAM-radio stations.

You have to recognize your local laws. Mostly modifications aren’t allowed by the local law or by
the manufactures. So you do it on your own risk. Also the brand new HAM rigs are mostly build
with a lot of teeny-weeny SMD parts. You have to use special equipment and you also must have a
great expert knowledge. So some modifications aren’t for only hobby electronic technicians.

So this and all of my Modification Sheet are for education purposes only !

Used pix are mostly done with my Fujifilm „FinePix 6800 Zoom“ on resolution „3M/Fine“, but they are reduced on their size due
to minimize the total file size of this publication.

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

Some background informations about the FT-897 mods

FT-897 à FT-857

Both transceivers are based on the same circuit diagrams but they have a different mechanical
case. All my electronics modifications can be done on the FT-857 mobile transceiver too. But actu­ally I hadn’t the time to compare the numbers/names of the parts between those both TRX. So it
could be that some parts have a different number/name on the FT-857 than described here for the
FT-897. As many FT-897 just wait for this modification sheet I will check and compare this later
and just spend my men-power in finishing this modification sheet first.

AGC

A lot of users have criticised the “too fast SLOW AGC” on SSB mode. For my opinion, that’s true
too. The circuit is similar to the FT-817 portable TRX on which I recognized the same problem some
years before. But the fix is simple and easy by only adding an additional electrolyt capacitor (10µF)
parallel to the “SLOW AGC” capacitor C1503 (1µF). As this stock capacitor can be found and han­dled very easily and without the need to remove any PCB this fix could be done from everyone and
it only needs about 15 minutes including opening and closing of the TRX case. After that mod the
SSB receiving sound is much, much better – especially on strong signals. And the time constant is
still fast enough not to loose weak signals between those “big guns”. I don’t like those TRX which
needs 3 sec. or more to come back.

Oh, I just hear a lot of FT-897 owners breathing a sigh of relief…. Hihi.

Speechprocessor

A story what I better would call “..the mystery of the FT-897 speechprocessor..” !! You ask me
why !? Cause the stock FT-897 just has a speechprocessor-Button, but no build-in real speech­processor ! Or let me better say the FT-897 has no build-in circuit which would act like a real
speechprocessor.

You’re confused ?

Then you react like me as I first read some remarks about that fact on several ham discussion fo­rums – just a long time before I got my own FT-897. Prior to my own buying I had a QSO with a
ham from Sweden (SM4YPG, Lars-Gunnar) on 20m and he used a FT-857. As I told him that he
sounded distorted and “harsh” we did some on-air tests and comparisons on different menu set­tings. And the difference between “speechprocessor ON and OFF” wasn’t really significant, even not
on a speechprocessor level of “100”. This was the final proof for me.

A real speechprocessor consists of either an AF compressor, an AF clipper, an AF lowpass filter, …or
the combination of all these parts. The better and what I call “real” speechprocessors would be the
RF speechprocessor which clip directly on the RF signal to prevent excessive distortions.

And what on the FT-897 so called speechprocessor, when looking into the schematic !?

It’s only an additional simple AF amplifier (MAIN UNIT, IC Q1118, NUM2902V, pins 8 – 10) with an
amplification factor of 100 (R1417/R1420), but the output level is reduced again with a resistor
divider (R1435/R1437, 1:15) !!
And what is the effect of this ? You get a real minimum additional amplification when activating this
speechprocessor. The real amplification factor is set by the BIAS-line and the menu item no. 074

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

(Proc. Level). But if the menu level no. 074 is set too high (up to 100) the audio sounded distorted
cause the IC is overdriven. But it don’t sounds much louder cause the output resistor divider “de­stroys” this higher AF level.

I think the Yaesu engineers called this a “speechprocessor” cause when an IC audio amplifier is
overdriven the signal “clips” as no more amplification is possible. This can be a kind of “processing”
but the resulting distortions are ugly and not understandable. The sound is getting more and more
“hollow” and the distortions reduce the total readability.

But a real speechprocessor should HELP on weak signal operations, …and should not additionally
DESTROY them. So this “overdrive” way is one of the simplest but most bad possibilities which can
be chosen for a speechprocessor.

C1412

from Q1087

R1417

6k8

µ1

BIAS

R1420

680k

Q1118

R1435
22k

R1437
1k5

C1475

µ1

to Q1098

The stock “mystery” speechprocessor

To change this unusable speechprocessor into a good and working speechprocessor the trick is
quiet simple.

I removed R1437 to get a much higher output level. Now you would hear a difference between
speechprocessor ON/OFF and the audio distortions are reduced significant cause you don’t need as
high menu levels on no. 074 than before. But now we would only have a switchable additional au­dio amplifier and nothing more. Does this make sense !? No ! So I had to limit the audio level to
get a real speechprocessor.
And I did this with two antiparallel lownoise diodes. As clipping on the audio side always produces
some distortions and a “high pitched” sound characteristics (like loosing all basses) I added a ca­pacitor to have an audio lowpass filter too.

C1412

from Q1087

R1417

6k8

µ1

BIAS

BAT85

D1

BAT85

C3

150p

R1420

680k

D2

Q1118

AF Clipping

Smooth Lowpass 1.5 kHz

R1435
22k

C1475

µ1
R1437
1k5

remove to raise audio level

to Q1098

The modified speechprocessor

So the resulting sound with “speechprocessor ON” is great now ! And it has a real DX punch now !

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

The stock smooth AF highpass filter, consisting of C1412/R1417, reduces frequencies below 230 Hz
and helps a little too. My AF lowpass filter with 1.5 kHz seems to be too low on the first view. But
as we have a strong high pitched audio sound while being in the clipping area this reduction is nec­essary and the resulting sound of this both effects (working in opposite directions) is great as you
can hear on my sample wav files I recorded.

I’m using a pair of BAT85 schottky diodes as they only have a forward voltage of 0,3V. So the clip­ping starts on the quieter voice parts too. But it should be possible to use 1N5711, HP2800-2810
or other lownoise diodes with 0,7V too.

On menu item no. 074 I’m using a Proc. Level of “35” now (with my audio modified MH-36 DTMF
handmike) and the difference between ON/OFF is absolutely significant. Of course YOUR final value
for no. 074 is depending on YOUR used microphone, its characteristics and its audio level.

The DX can come !….

ALC audio pumping

Another big fault of the 857/897 design is the REV ALC which is documented on several ham radio
forums too. The 897 reduces its output power when having a bad SWR. This is a real good and
necessary option. But this detector works too fast and the SSB modulation is “clipped” or some­times “cut” on its peaks. A QSO isn’t possible in this state, as many users told.

One possibility is to check and realign the REV ALC parameters as described in the servicemanual.
Normally 100W on HF should be reduced to 50W on a SWR of 3:1.

So some users only raised the digital values of the servicemenu to make the REV ALC acting later.
This is done by servicemenu items 053 – 058.

Here’s an email from Mike (KM6AB) to me, as an additional statement to this fact:

Von: Mike
Gesendet: Mittwoch, 17. November 2004 16:37
An: Jochen - DG2IAQ
Betreff: Re: FT-897D - Reverse SWR alignment

Hi Jochen,
Hold down the A, B and C menu buttons during power up to get to
the alignment menus. The main tuning knob will now change align­ment parameters, be careful!
Use the small menu/vfo/ch knob to find the parameter HF1-REV-ALC.
This is the set point for SWR foldback on the lower HF bands and
the main tuning knob will change the numbers in the upper right
corner of the display. Factory settings are usually 40 to 50 and
higher setting will make the radio ignore higher reflected power
conditions. There is also an HF2 and HF3-REV-ALC for the higher
HF bands I moved mine to 75 on all three menus and the radio now
behaves fine with an LDG AT-897 autotuner into a G5RV on all
bands from 80 through 10m. I would recommend trying the radio
into the antenna you have (as long as the match is good) and move
the numbers up until the radio stops breaking up on transmit. Do
this mod at your own risk, you will be making the radio more sus­ceptible to damage from an antenna mismatch.
I have been very happy with my 897 after two trips back to Yaesu,
but this is a very early model. I also replaced the stock mic
cartridge with a Heil HC-5 element and it gets great audio com­ments and has a lot more audio punch, which helps with 20w bat­tery operation.
Good luck,

Mike KM6AB

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

Menue

No.

053 HF1-REV-ALC CW 1.8 MHz 47 75 60
054 HF2-REV-ALC CW 7 MHz 42 75 55
055 HF3-REV-ALC CW 21 MHz 48 75 49
056 50M-REV-ALC CW 50 MHz 48 40
057 VHF-REV-ALC CW 144 MHz 61 90
058 UHF-REV-ALC CW 430 MHz 61 115

é
on a 150 ohms

dummyload (= 3:1)

As Mike told this can solve the problem but can be dangerous too as you don’t have this good pro­tection on bad SWR than having before.

So I tried another way and I had lengthen the time constant of the ALC circuit a little bit. This pre­vents from acting too fast, but still having the “bad SWR” protection as well as you can see on the
table above.

The mod is done simply by adding a capacitor parallel to the ALC time delay capacitor C1061.

Description Remarks Value Modified

KM6AB

Realigned

DG2IAQ

Exciter Stage Protection

What a surprise !!
The FT-857/897 uses the same critical FETs 2SK2975 for the exciter stage as the FT-817 uses on
its PA module !

Have you ever heard of the “BFC”, the “FT-817 Blown Finals Club” !? Hihi.
Oh yes, …I think so…

So as I found out this fact on the FT-897 I decided to make a real necessary modification to pre­vent a damage of these FETs. Of course on the FT-897 these FETs never see a bad SWR as they
work “behind” the PA module, but on the 817 these FETs weren’t destroyed only by bad SWR. The
were also destroyed by overheat, overvoltage, voltage peaks, …or combinations of this even when
the FT-817 handbook tells about using this TRX on DC power supplies up to 15 volts. A real guar­antor to destroy them !

The 2SK2975 have their full RF output still on less than 10 volts ! Each higher DC voltage would
produce more heat but you won’t get more RF out. On more than 12V you get into the “critical
area” where the shown “combinations” above can produce higher RF voltages than the used DC
voltage. But I don’t want to bore you, you can read the whole stories on huge ham radio forums.
Just search for the “BFC” and you will find tons of stuff…

Of course you can de-solder the 2SK2975 and re-solder their follower (Mitsubishi RD07MVS1)
which is much more rough and can handle higher voltages. But I will only do that if my 2SK2975
would really die.

The solution is simple here too. Just add a 10V fixed voltage regulator into the +DC line.

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

J1004

TP1017 / TP1018

13.8V to PreDrivers Q1006/Q1007

L1890599 / C1021 / C1023

10V to Driver FET's
Q1001/Q1002 = 2SK2975

Jumper

78S10

2A

10µ

Fuse

self-resetting 1.85A

To be safe against damaged FETs and burned PCB lines as a result of a short I added a 1,85A self­resetting fuse into the 10V line too.

Proper BIAS-adjustment

Remark:
The BIAS adjustment of VR1001/VR1002 must be done again after you build in the
“Driver Protection” from the chapter before.

The 857 of the Norway HAM I told you above sounded “hard” and “breathing”. It sounded like the
operator didn’t get enough air to speak or he had a cough and his lung works hard. I can’t really
describe this sound but it always sounded that he “like to say more, but he hadn’t air enough to
bring it to end”. Or as someone permanently tries to retard his voice.

This is a result of wrong BIAS parameters. If the BIAS current is too low you would hear this effect
and the modulation sounds as being “retarded”.

The same was on my stock FT-897. The same I read on the ham radio forums as people told their
BIAS currents weren’t properly aligned, sometimes they weren’t properly aligned from the factory !

Time for me to check and re-align my BIAS currents. Here’re the results:

Adjust Description as told in the

VR1004 Pre-Driver

2SK2596

VR1003 Driver

2SK2973 (2x)

VR1001/1002 Exciter

2SK2975 (2x)

VR3002 HF/50MHz PA

2x 2SC5125

VR3001 VHF/UHF PA

2SC3102

servicemanual

30 mA 20 mA 40 mA

20 mA 56 mA 40 mA

2x 100 mA

(**)

300 mA 80 mA 400 mA

300 mA 270 mA 400 mA

(**) on the FT-817 the 2SK2975 are adjusted on a BIAS of 2x 38mA

Higher BIAS values give a more “smooth”, “warm” and full SSB audio so I raised all the BIASes a
little bit with great results.

I checked the datasheets of all the FETs or transistors and found sometimes even higher BIAS lev­els on their test circuits, so I don’t expect any problems, overheat or damage with my higher BIAS
levels above. I’m still UNDER those test levels.

DG2IAQ

from factory

2x 42 mA 2x 100 mA

DG2IAQ

re-aligned

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]

Modification Sheet Yaesu FT-897

last modified: 27. Dez. 2004

Replacing the stock MURATA filter

I’m not a CW man (..I never learned it, cause I never liked that mode). But still to have the option
to build in a CW filter later I de-soldered the stock MURATA filter and fit in an INRAD 706F
(2.6kHz). On the option socket #1 I’m using an INRAD 720F (2.0kHz).

The FT-897 has a great TX-FILTER / RX-FILTER switching method. You can either use the one or
the other filter independently targeted for TX and RX.

This makes me able to transmit with a “fixed” 2.6kHz “HIFI sound” and on the RX side I can switch
between the 2.6kHz and the 2.0kHz, depending on the crowded bands.

Using an Electret capsule

As the modified FT-897 has a great build-in speechprocessor now, I wasn’t forced to use any ex­ternal one. So the MH-31 stock microphone can easily be modified to get a strong and great audio
without any of the “strange” sounds of the dynamic capsules. No additional mic amp, compressor,
clipper and so on is needed.

R1

C2

4k7

470µ

C3

R2

1k0 - 2k2

47µ

C1
1n

+5V

MIC

R3

MIC GND

680

C1 should be an SMD type and should be directly soldered on the backside of the electret capsule.
This prevents any RFI.
R2/R3 is a resistor attenuator as electret capsules have much more audio output level than dy­namic capsules. Audio distortions and overdrive of the FT-897 mic amp would occur. The value of
R2 varies on the used electret capsule, as some has more or less internal audio amplification
(5.6mV or 7.9mV output). The resulting level should be some higher than with the dynamic capsule
before, but still under the level where the distortions begin to start. A value of 1k5 would give a
good “never-to-think-about-any-more” average.

Battery modification from W4CNG

I did the battery modification of W4CNG as described on http://www.eham.net/articles/4114.

© 12/2004 Jochen Heilemann, DG2IAQ Phone: [phone]
Jochen Heilemann P.O. Box 1106 Fax: [phone]
All rights reserved. D - 75218 Niefern-Öschelbronn Germany e-Mail: [e-mail]