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Assuming you did also small ground connection to near filter shield to make 

filter module straight and to ground it - this is the end of mod. So we ended up with 
filter board looking like below. 
 

 

 

You can mount the PCB in the chassis, connect all remaining cables and 

connectors and be happy with your FT847.  

Please be careful when You cover the upper shield with speaker. Sometimes 

You will need to turn the speaker around to move audio soldering points to another 
position avoid short circuit with filter board. 

There’s not much place to do anything, and we just added two small but PCB. If 

the speaker will be to close with filter PCB you can bent the RX PCB toward front of 
the radio. It will increase the space between the speaker and filter PCB and it will fit 
OK.  
 
Note : Although I am sure that this mod is repeatable, and anyone can get similar 
parameters, final result depends on fact if there was any attempt to modify RX gain.  
It will be good to get into service menu of the RIG and check RX-CHAIN parameter 
and correct the gain if needed. Standard Hex note for RX-CHAIN parameter is  
Something like 3E for model 9I and 4E for earlier 8G. The lower Hex, the lower gain. 
 

Disclaimer: This article is written for information purposes only. 
 Although all described mods were carefully tested myself on my own radio, back and 
forth in the period of last year of my activity on 4m, I shall not be judged responsible 
for any damages/failures of your transceiver, if something will go wrong.  
All mod’s you just doing on your own responsibility. 

  
If You are not sure You can do it yourself, better ask a friend. Or if You want to 

push more life in your 847 and you don’t know how, write me. We are living on the 
same planet 

  

 

Sincerely thanks for Marc PA1O, for his super job, and Hellar ES1II with Arvo 

ES1CW for many hints about 847 mods and Jacek SP3LYU for loan me his FT847  
to do  . 
 
Best DX DX, 73  
 
Greg SP3RNZ 

 

 

 

 

 

 

 

 

 Oct.2013 

Содержание FT-847

Страница 1: ...iginal filter in the 847 has bandwith of 54 76 MHz which should give reasonable RX quality But it s not Receiver sensitivity varies from about 0 3 to 0 5uV depending on the production model and Year o...

Страница 2: ...ion of the modification includes more than 30 TRX across the EU and probably worldwide which can assure that the solution is repeatable and effective To achieve these results filters should be made ac...

Страница 3: ...mm dia FTP ethernet cable should be good idea to get this wire in good isolation Filters base should be prepared in advance This should be done by removing the legs cutting any flanges and drilling ho...

Страница 4: ...ted against short circuit we can put the screens and solder terminals Final result can look like this On the project stage I had made some measurements using NWT500 Please note the attenuation frequen...

Страница 5: ...Close up image And this is the screen from measurement taken prior to filter modification FT847 signal spectrum with 10W output power...

Страница 6: ...king our transceiver Although this has not been proven empirically and many rumours are about is it true or not the authors of this article after hearing about four or more different cases of damage t...

Страница 7: ...gnals 45 600MHz 34 dBm 49 035 MHz 2dBm Transmitter measurements made after the modification of the track TX 10W power out QRG 70 1MHz QRG 70 100MHz 39 dBm Unwanted signal 45 600MHz 22dBm below 70MHz C...

Страница 8: ...of adjustable gain by changing the bias voltage of the first gate G1 by small potentiometer which may be replaced by a fixed resistor in some cases Coupling coil consist of 3 turns of 0 5 mm insulate...

Страница 9: ...Measured response of amplifier with 30dB attenuator NWT500 not calibrated...

Страница 10: ...of 0 12uV MDS and the TX power at almost 60W level with dramatically improved purity of the signal spectrum and efficiency of your TX Disclaimer The following article is for information purposes only...

Страница 11: ...5 2 x 47p SMD 0805 C7 C9 2 x 56p SMD 0805 L1 L3 2 x 2t Cu 0 5mm with isolation L2 L4 L6 L8 4 x 6 5t CuAg 0 5mm L5 L7 2 x 3t Cu 0 5mm with isolation Q1 1 x BF994s SMD SOT143 R3 1 x 10k PR R6 1 x 10k SM...

Страница 12: ...ndpass filter to modified one with LNA replace existing TX filter chain to sharper one to get clean signal Let s get it started 1 Unlocking your FT847 to get 4m for those who already have unlocked one...

Страница 13: ...th Isopropyl Alcohol IPA It will ensure that joints are clean and no any solder dust left on place You should end with similar result for version b mod 2 Next step will be increasing efficiency of Pow...

Страница 14: ...rews Then we should disconnect two HF outputs on the rear Be careful as these pins need to be bend a bit to suck the solder out At this point please look carefully for two small bronze spring soldered...

Страница 15: ...ted on two different 847 After cleaning the place You should get something like that 50 Job is done now But At this place I will propose that if we already made efforts to remove this PCB we should do...

Страница 16: ...f PA job another good idea As observed in all four 847 after some years of time beryllium oxide paste used as heat spreader on transistors is getting dry and hard NOTE I found that in 847 year model 8...

Страница 17: ...tors After removing PCB we will have access to TX and RX filters To do this mod we must remove almost all SMD capacitors and coils Which one Look at the picture part of service manual It will be easie...

Страница 18: ...d only to make two wire bridges from diode switch to make it working It s clearly shown below Of course it s good to check with any multi meter if no sudden short circuits accidentally were made Last...

Страница 19: ...we can see TX filter part If Any trouble finding it please refer to PA1O article This should look somehow similar Green SMD were omitted by Yaesu those are the caps marked with an asterisk on schemati...

Страница 20: ...After some cleaning PCB will look like this damned Japanese glue Next step after inserting and soldering the filter is to make two bridges similar as in RX chain...

Страница 21: ...meters final result depends on fact if there was any attempt to modify RX gain It will be good to get into service menu of the RIG and check RX CHAIN parameter and correct the gain if needed Standard...

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