In every case I can think of, I'd skip the preamp and use a better antenna. Always.
I don't think I was the one who made that comment. It's too brief and concise.
Point being that AM & SSB are more affected by the noise figure of a preamp than FM & Digital. Since noise is amplitude modulated and FM offers "no static at all" as the lyric claims, NTSC video as a w - i - d - e AM mode would be far more sensitive to preamp noise than FM radio.
I think you are confusing different things. FM isn't prone to AM noise (such as
ignition noise) as long as the signal-to-noise ratio (SNR) is high enough
for full limiting.
But for weak signals they are often more difficult to demodulate than AM at low SNRs.
That's why we use SSB or CW for DX work on VHF rather than FM. FM signals are
quite noisy when they aren't strong enough for full limiting.
There are two problems to be overcome: first, you need enough signal strength to reach
the limiting threshold to have a clean signal. This can be accomplished with an
amplifier or by using a better antenna, or both. The second is that all the amplifiers in
the chain must generate little enough noise so that the SNR isn't degraded: receiver
noise is more complex and isn't simply AM. It masks the desired signal, and noise
contributed at the first amplifier stage gets amplified by all successive stages along
with the desired signal. Adding an amplifier stage does NOT improve the SNR if the
noise figure is worst than that of the original receiver (unless the coax losses are
I've demonstrated this by cascading two preamps on a weak digital TV station: the
receive signal strength indicator went up when I used both preamps instead of one,
indicating that the received signal was stronger, but because the SNR stayed the
same (both had about the same noise figure) there was no improvement in the
Many of the problems encountered with adding external wideband preamps are due
to interference from other stations, etc., because the preamp typically increases the
strength of ALL signals from 30 to 1000 MHz, and some designs can be easily
overloaded (or the added gain can cause overload in later stages.)