[Kenwood] ts 870 filters is any one have step by step info

[DL9FCC@aol.com]

Subj:   Re: ts870 kenwood   
Date:   27/5/02 9:27:16 GMT Daylight Time   
From:   <A HREF="mailto:K3BU">K3BU</A>    
To: <A HREF="mailto:DL9FCC">DL9FCC</A>  
    


Hi E.paim

I don't have step by step instructions described, only what was written in my 
original note.

Filter Modification.

Major improvement in selectivity and DSP performance can be achieved by 
replacement of 2nd and 3rd IF filters with sharp crystal filters, like from 
International Radio. The 2nd IF 8.83 kHz filter used in TS870 is the stock 
Kenwood crystal filter, while the 3rd IF 455 kHz filter is little ceramic 
Murata filter. 

I have ordered set of 2.1 kHz filters (8.83 and 455) from IR. The 
modification involves removal of printed circuit boards where the filters are 
located, unsoldering the old filters. In their place solder short piece of 
miniature coax to connect new IR filters. IR filters can be mounted between 
the circuit boards and the metal chassis using double sided sticky tape. Coax 
from old filter connections is then connected to new filters. Tweaking the 
matching IF transformers next to the filters ensures proper match and gain.

Other filters with wider bandwidth can be used also. For contesting I found 
2.1 filters to be the best and the mod works very well on CW also. 
Selectivity improves as well as functions of DSP. Now it is a decent radio, 
matching those costing thousand(s) more.

73  Yuri


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