- 4 -
Noise Figure -
The ratio of equivalent noise power developed at the input to that generated by
thermal noise in the source resistance, usually expressed in decibels. If it were possible, a
perfect amplifier would have a noise figure of 0 dB. The RPA-2 is extremely quiet, and does not
contribute noticeable noise to receiving systems. Almost all HF antenna systems receive an
ambient noise level that is greater than the noise floor of the RPA-2.
Dynamic range -
The ratio of the faintest signal detected to the loudest signal amplified without
significant distortion, typically expressed in decibels. The RPA-2 allows you to hear faint
signals in the presence of adjacent strong signals.
Gain
- The ratio of signal input to output. The RPA-2 features a modest gain that may be
bypassed when not needed by removing power to the unit.
ATTENTION: Never transmit through the RPA-2.
The unit can be damaged by direct application of transmitter power.
Installation Location Considerations
Optimum electrical location of the RPA-2 varies with antenna system background noise level. A
good receiving system requires the antenna to establish system noise, not the preamplifier. A
common myth is that a preamplifier must be mounted at or near antennas to be effective. This is not
true at low VHF, HF and lower frequencies. A preamplifier is needed at the antenna only when
feedline loss is high and the antenna has very low background noise. Low band antennas rarely
suffer from feedline losses, so the preamplifier can normally be used at the radio. Another common
misconception is that mounting the preamplifier at the antenna feedpoint reduces feedline noise
pickup. The location of the preamplifier rarely makes a difference in feedline noise. Most feedline
noise couples back to the antenna at the antenna terminals, it does not leak directly into the feedline.
The RPA-2 prevents signal leakage when used at an antenna.
Normal Mounting Indoors
For typical indoor installations, mount the RPA-2 near the receive antenna input of receiver or
transceiver. For best results, use the RPA-2 in a well-ventilated indoor area away from direct
sunlight and moisture. Operation outside of the specified temperature range of -10°F (-23°C) to
150°F (65°C), non-condensing, will shorten the life of the RPA-2, and should be avoided.
Mounting at the Antenna
Ordinarily, the preamplifier should be mounted indoors at the operating position, rather than at the
antenna. There are few exceptions which include
Pennants, Flags, and K9AY Loops. These
antennas have relatively low sensitivity and will not provide much background noise to the
system when they are installed in quiet locations. If the feedline loss is high, performance
might improve with the preamplifier mounted near the antenna.
The RPA-2 may be mounted at or near the receive antenna under a cover or in a weather-protected
enclosure. Operation outside of the specified temperature range of -10°F (-23°C) to 150°F (65°C),
non-condensing, will shorten the life of the RPA-2, and should be avoided. Make certain that the
enclosure is vented to prevent moisture from collecting in the unit that would accelerate corrosion
