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n4vgb
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« on: February 26, 2007, 02:15:11 AM »

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w3jn
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« Reply #1 on: February 26, 2007, 07:34:02 AM »

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installed a halo ground system here and converted to an isolated ground system in the shack. Yes, I am familiar about how to properly do this, my telco background where we used an integrated/isolated/data return ground system came in handy here. I know there were some EE & electrician types that were about to jump down my throat on that one, cool your jets! I used 9 inch wide pieces of copper sheet for the ground system inside the shack with 4 inch wide pieces for risers and 2 inch wide pieces for connection to gear. All receivers operate via AC isolation transformers with only the isolated ground connection.

So long as you re-derive the neutrals and bond the ground/neutral at the secondary of the transformer, you're OK insofrar as the NEC is concerned.  Be advised you need to do this for ALL equipment hooked to that antenna/ground system - xmitters included.

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Has anyone else noted a general rise in the noise floor in recent years?

Yes.  The advent of switchmode power supplies and SCR power switching gear appears, at least to me, to be the big culprit.


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Do the modern Japanese HF DSP rigs do away with this problem completely?

No.  The noise DSP in my FT1000MP MK5 certainly helps a bit with the S-9 power line noise I have but that's at the far back end of the receiver.  The noise still reduces the sensitivity and thus the S/N ratio.  Worse, the DSP in that radio only works in SSB/CW modes, not AM.

My location was very quiet, noise-wise, until a couple of years ago.  My lake place, with a "shaded dipole" below the rim of the mountain and threaded amongst saplings, is very quiet but not entirely noise free either.
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K6IC
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« Reply #2 on: February 26, 2007, 03:11:31 PM »

Mr. R. -

YES !  The NOISE FLOOR is becoming the ceiling !

My semi-urban QTH has gone from being quiet in 1998, to Very NOISY in the past 5 years or so.  Here in the urban West,  the densities are very high.   My neighborhood has about 7 residences/acre on average.   We are all jammed together.   A lot of switcher noise is attenuated by distance.  Here,  this is conducted/radiated noise.  So we can hear each of the offending sources.  Not really raising the floor in the classic  sense.  It is just a din of discrete emissions,  each one of which is discernable on the band.   Below that din,  the floor is probably raised by the multitude of these devices,  but often that is not obvious due the local din.

First, there was awful Line NOISE from 75-100 intermittently-noisy power poles.  Now, there are ever more switching devices which are louder and more frequent problems than the line noise (which is still there, too).  Every week,  there seems to be a few more switchers polluting the local spectrum.

The worst of the switchers seem to lighting products ... probably trac lighting products,  followed by touch lamp dimmers and probably garden (garbage!) lighting. Plus the battery chargers, DVD players,  TV sets, and so on & so on. Many of these are on most of the day,  and almost all of them seem to come on before greyline,  and run til 11 PM or later  As a bit of a DXer,  this is horrible.  And in AM mode,  the din of buzzing drives one crazy.

There seems to be no regulation of the emissions,  and I cannot picture the ear-blowing that would be required to convince  even one  neighbor to replace one of these devices.  And,  it may be very difficult to find anything that was commercially available that would be much better than this Chinese,  bottom dollar junk


To me,  these junk switchers are a much larger threat to hamming than BPL would ever be.

Just my rant ... am building a remote,  off-grid site to try to reduce this problem.  At least then,  I will know who to strangle for making all of the noise that I make !

GL  Vic  K6IC
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