开云体育

Re: SX-117 noise limiter behavior

Mike Langner All Messages By This Member #30299 开云体育 True, but a good approximation of the noise in the vicinity of the receiver antenna can be sampled and used to reduce the noise coming in along with the desired signal from the main antenna.? The noise from the secondary system, must, as you point out, be as close as possible to the noise being picked up by the primary antenna.? Cancellation is, of course, incomplete, so elimination is not possible, but quite significant reduction is indeed possible and has been proven in the field.? Needless to say, the noise receiving system must not pick up much of the desired signal.? This can be effected both by operating the two receive systems on dissimilar frequencies, and also by utilizing a receive antenna location that will pick up the closest possible envelope to the noise the primary antenna receives but picks up a minimal amount of the desired signal. How much improvement is available?? Results vary widely with the nature of the noise and the environment in which the noise is being received.? Still, the reduction is often very, very worthwhile! As always, your mileage may vary!! Mike/ K5MGR _____________________________________________ ? Mike Langner 929 Alameda Road NW Albuquerque, NM 87114-1901 (505) 898-3212 home/home office (505) 238-8810 cell mlangner@... ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Mike Feher Sent: Sunday, June 9, 2024 6:11 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? It seems to me, that since noise is neither correlate-able or stochastic, elimination is not possible. Also the multiple antenna theory is out the window since RF generated noise travels at the speed of light. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 908-902-3831 ? From: [email protected] <[email protected]> On Behalf Of Maynard Wright, P. E., W6PAP via groups.io Sent: Sunday, June 9, 2024 7:31 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? Another technique for reducing or eliminating noise was to introduce local noise to the front end of a receiver from a local "noise antenna." The amplitude and phase of that noise could be adjusted to, hopefully, cancel the noise received by the signal antenna. Early BC-342 and BC-312 receivers featured a noise suppression circuit of this type. War Department TM 11-850 states that the noise antenna was intended to eliminate ignition noise when the receiver was mounted in a vehicle. By the time my BC-342-N was born (1942), the noise antenna and associated circuitry were omitted, so that circuit may not have worked well. The September, 1946 revision of the TM notes that spare parts were no longer available for the noise suppression circuit and recommends removing it if any of the components fail. MFJ has featured at least one similar unit, the MFJ-1026, which is now listed as sold out. There are other such units available but I have no experience with them. 73, Maynard W6PAP

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#30299

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