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Cushcraft MA5B Noise floor?
"Owen Duffy" wrote in message ... "David" wrote in : The noise level does not change when I turn the beam 360 deg. You did give S meter readings, but with respect, they are meaningless in the context you have given. Radios are not iniversally well calibrated, and most hams could not tell us what radio setting (eg PREAMP ON/OFF) put the radio in the calibrated mode. Remember that a directive antenna does not reduce noise that is non- directional, for all that it reduces noise picked up off the main lobe, it increases noise picked up on the main lobe. Ok, we hear that the noise is not strongly directional. You didn't care to share how you worked that out. If you had an extremely high noise level, it would quite likely be local, that is the way of things. It it appears to not be directional, it is probably very close (ie under the antenna). It could be in your own home, it could be some kind of fault with the installation. If it is within your own home, resolution is somewhat simplified. To clear away your own home as a source, turn EVERYTHING off and run a receiver on battery. No prizes for missing something, turn things off at the main switchboard. Does the noise vary by hour, day? Is it the same level when all the TVs and Inverter Air Conditioners should be off. If the noise is excessive, and it is real local, you have the choice of dealing with the source, and/or reducing your pickup (eg minimising the effects of feedline common mode current... good coax, effective connectors, an effecive balun, system grounding). Owen If I can here a weak station on any of my other antennas that is fully readable but weak and I then switch over to the beam the station gets lost in the noise. On stations that are a bit stronger but under a S9 after switching to the beam then there is a noticeable amount of noise in with there audio. Of course the beam brings the whole signal in a lot stronger as it should do with but with this large increase of hiss/background noise that is some how mixed in with there audio that wasn't there before. I do not get the same noise on any of my other antennas even when they are positioned in the same spot as the beam and connected to the same coax line. I have tried the Cushcraft R4 and the R5 the Cobwebb and several mobile whips and I do not pick the same noise up.. I have had the MA5B down and I cannot see any thing wrong with the installation. I have ordered some Ferrite and I will make a coke balun up and see if it improves. I will let you know what happens. |
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