<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=US-ASCII" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 9.00.8112.16440"></HEAD>
<BODY style="FONT-FAMILY: Arial; COLOR: #000000; FONT-SIZE: 10pt" id=role_body
bottomMargin=7 leftMargin=7 rightMargin=7 topMargin=7><FONT id=role_document
color=#000000 size=2 face=Arial>
<DIV>Hi Ken</DIV>
<DIV> </DIV>
<DIV>I have now resolved the 5dB filter ripple problem on my unit to less
than 2dB for both SSB and CW filters. A replacement SSB filter produced the same
result as the original filter.</DIV>
<DIV> </DIV>
<DIV>I connected 3.395MHz tuned circuits to both the input and output sides
of the filter switch and adjusted both for minimum ripple using a signal
generator with a narrow sweep facility driven by the X output of my scope. The
sweep width was set to about 4KHz and a sweep speed of about three per second.
The AGC was disabled and the RF level at the product detector displayed on the
scope, making sure that the IF system was not overloaded.</DIV>
<DIV> </DIV>
<DIV>Although both tuned circuits had an effect on ripple, the best result
was obtained with the tuned circuit connected to C506. I ended up with a 75uH RF
choke (two 150uH chokes in parallel) connected from the switch end of C506 to
ground and no correction on the other end of the filter.</DIV>
<DIV> </DIV>
<DIV>This is a test of one unit so other Heath owners may need to carry out
similar tests to see what works best with their units.</DIV>
<DIV> </DIV>
<DIV>I do not know the exact spec for terminating the Heath filters other that
the stated 2000 ohms but it would appear to be 2000 ohms in parallel with a very
low value capacitance. The 75uH inductor suggests that it has corrected for
an excess capacitance of about 29.5pF. On other solid state units where I have
used the same Heath filters in a 50ohm signal environment, a matching L network
on each end produced an almost flat passband response so my 47 year old
filters seem to be fine.</DIV>
<DIV> </DIV>
<DIV><FONT lang=0 size=2 face=Arial FAMILY="SANSSERIF"
PTSIZE="10">73<BR></FONT><FONT lang=0 color=#0000ff size=4 face=Arial
FAMILY="SANSSERIF" PTSIZE="14"><I><BR>Bob</FONT><FONT lang=0 color=#000000
size=2 face=Arial FAMILY="SANSSERIF" PTSIZE="10"></I><BR>Bob F Burns<BR>C Eng,
FIET, MSE<BR>Amateur Radio Callsign: G3OOU<BR>Registered RSGB
Instructor<BR>G-QRP Member No: 6907; Zone: 14, QRA: IO91WH; WAB:
TQ25<BR>Secretary of Crystal Palace Radio & Electronics Club: <A
href="http://www.g3oou.co.uk/">www.g3oou.co.uk</A><BR>Technical web site: <A
href="http://www.qsl.net/g3oou">www.qsl.net/g3oou</A></FONT></DIV></FONT></BODY></HTML>