TS440 with PIN-Diods

TS440 Increase the power by ALC controlRecently i read about an upgrade for the ts440 concerning the bandswitc-diods.
Originally, there are simple switching types built in. For better high level performance i decided to replace D2,3,4,5,6,7,…23,68 by the
ECG553 PIN Diode.
The result was not so doubtless positive. i could not really confirm an advantage. unfortunately, i have no measuring equipment for
determining the intercept point.
But on 40m , where i sometimes have problems using a 160/80/40/30/20m 5-band fullsize dipole, i still suffer intermodulation effects.
I can not really say, if it is much better after the replacement, but i'm sure, it isn't worse (hi).
Some remarkable progress was the usage of the built-in tuner in the receiving pass. that really helped espacially on the 10mc band to
overcome the problems of interference.
But best results and a final solution i found in using an external preselector as described in the cq-dl several times.
That really did it! Of course you need to add on to cinch connectors at the rear panel.
It is no real problem.
so, my advice:
dodn't modificate the diods or use of the tuner for reception.
The result is too poor compared with that of an external preselector.
BC-stn(s) heard regardles of VFO qrg .
I mounted a new 1st mixer, a highlevel injection module type and used old tstrs as as aplifiers and got rid of the bc-stn in the
background regardless of VFO setting .
I think there is an oscillation,parasitic,somewhere around the first mixer or that diodes therearound for filterswitching goes into
mixing and "resend" their mixing which then is heard.Will more current through these diodes cure the problem ?
  
GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information