The reverse phase cancellation is not how I understand the blanker
to work although I think there are noise eliminators that do work this
way. My understanding is that the signal from the noise antenna is
detected and converted into a DC pulse which is applied to a gate in the
signal path which cuts it off momentarily for the length of time the
pulse lasts. Since both the detection and gating can be done where the
bandwidth is fairly wide the rise and fall times of the gating signal
can be made quite short. The device must be such that there is not an
excessive time delay between the noise pulse in the receive chain and
the muting or gating signal. Presumably, there is some delay in both
signal and noise channels and they can be matched by careful design. The
advantage of this system over the type of noise gate that picks up the
signal from the IF is that the bandwidth of the noise pulse can be
narrower and the rise and fall times of the pulse are shorter thus
reducing the amount of time the signal channel is cut off.
I am pretty sure Collins used this system, perhaps in its first
mobile transceivers. Also, since the kind of noise pulse the blanker is
supposd to work on is very short it will have a spectrum well into the
the HF or VHF range so that a short antenna antenna can be used and
desired signals will not get into the blanker.
Again the blanker works by shutting off the signal path briefly
during the noise pulse.
toggle quoted message
Show quoted text
On 6/10/2024 11:22 AM, Maynard Wright, P. E., W6PAP via groups.io wrote:
The operation of a noise antenna and associated circuitry are
independent of the nature of the noise, whether or not it's periodic and
whether or not it's random.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
