Icom IC-910H, Instructions

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Icom IC-910H (IC 910 H IC910H) Sensitivity
For those of you using this radio on SSB or CW in the weak-signal part of the bands, you probably
already noticed that the receiver needs some help. The overall sensitivity is too low, making the
need for preamplifiers obvious.
Actually, the radio has enough sensitivity built into it already; there are modern GaAsFETs ahead of
the mixers on every band, including 23 CM. The factory alignment of the radio does not exploit it's
full capabilities. This is a common phenomenon of almost all multimode VHF/UHF radios, including
those made by Kenwood, Yaesu and others. One might think this may be part of the way they
market their preamplifiers, but that is only my own speculation.
The adjustments described below will bring the overall sensitivity of the radio up to par, and will
eliminate the need for external preamplifiers. An external preamplifier may still help if your feedline
is lossy; in this case, you may still benefit from a mast-mounted one. After I made these
adjustments, I found that my limitation was external noise and not the sensitivity of the radio. This
was even the case on 23cm; in fact, it now hears almost as well as the transverter I usually use on
this band, which has an excellent front-end.
No magic here; all you will be doing is turning up the I.F. gain on each band, which is set lower at
the factory. The service manual contains pictures and descriptions of the trimmer resistors to
adjust. If you don't want the entire manual, the 4 pictures you need to see are here:
144-R547