[Icom] Mods for ICOM 756 PROII

[Adam Farson]

Hi Ray,

If you would be so kind as to e-mail me your Po vs. freq. measurements over
the frequency range you measured (hopefully 1.8 ~ 30 MHz), I shall draw up a
graph and convert it into a Web page, with full pubs credit, of course. Then
Bill will be "off the hook" for the work I laid on him. <g>

For Clete: As far as I am aware, the transmit LPF's in the Pro/Pro2 are
Chebyshev filters. What the constants or parameters are, I do not know. One
would need to sweep the 2 ~ 6 Hz filter to determine its exact -6dB point;
the graph referred to above should cover that. Redesigning the filter to
move the -6dB point into the passband of the next filter (6 ~ 8 MHz) would
involve calculating new constants, fabricating or ordering new inductors
etc. and some serious SMT work on the LPF board. One must ask oneself
whether the end-result is worth all that effort.

One unintended consequence of such a modification is that the radiated
third-harmonic energy on 160m may exceed limits specified in FCC Part
97.307(d). The roll-off in the 5.5 ~ 5.9 MHz range was probably intended to
address just this issue.

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Icom FAQ site:
http://www.qsl.net/icom/







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