[AMRadio] Ground(Or Lack Of)?


Jim candela jcandela at prodigy.net
Mon Feb 21 22:42:54 EST 2005



Tony,

    You bring up an interesting point. If we knew that
a pace maker or insulin pump was suceptable to RF, and
we operated anyway, and the patient died as a result,
then who ultimately is responsible? Maybe the
manufacturer might be liable legally, and the ham
might be held liable when trying to cross through the
pearly gates? :-(

Jim WD5JKO

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of Tony Golda
Sent: Monday, February 21, 2005 3:34 AM
To: amradio at mailman.qth.net; jcandela at prodigy.net
Cc: glowbugs at piobaire.mines.uidaho.edu
Subject: Re: [AMRadio] Ground(Or Lack Of)?



   Hello Bob,

        A big concern of mine would be the RF. Your 20X20 shack, is it in
   a retirerment home? If it is, are there alot of people with electronic
   medical devises.

         I  was  told  at  a  seminar, that the pace-makers, varges nerve
   stimulatars,  and  automatic drug dispensers are highly subseptible to
   RF. I wouldn't want to get blamed for killing some of these old people
   with a QSO!


   Tnx,


   Tony
   >From: "Bob Macklin" <macklinbob at msn.com>
   >Reply-To: Discussion of AM Radio <amradio at mailman.qth.net>
   >To:  "Jim  candela"  <jcandela at prodigy.net>,"Discussion  of AM Radio"
   <amradio at mailman.qth.net>
   >CC: GlowBugs <glowbugs at piobaire.mines.uidaho.edu>
   >Subject: Re: [AMRadio] Ground(Or Lack Of)?
   >Date: Wed, 16 Feb 2005 18:40:21 -0800
   >
   >Thanks to everyone for their comments on this subject.
   >
   >My  apartment  is  20'  by 20'. A RETIREMENT CLOSET! My desk with the
   station is
   >in  the  SE  corner of the livingroom. That's where the center of the
   antenna
   >is.  The  antenna  is on the wall about 6" below the ceiling. One leg
   goes west
   >almost  20'  then turns north for the remainder. The other leg starts
   in the
   >same  corner  and  goes  north  about  18'  then  turns  west for the
   remainder.
   >
   >The  antenna  tuner  will be on a shelf directly below the feedpoint.
   There
   >will  be  no  transmission line. The antenna will connect directly to
   the
   >balanced line terminals on the back of the matchbox.
   >
   >There will be RF in the shack. I have put the DX-60 on the single leg
   and
   >have  barely  noticable heringbone on some TV channels. And I have no
   TVI
   >supession  on  the TV yet. I am not going to mess with it until I get
   the full
   >antenna/matchbox system working.
   >
   >What  ground there is will only be for safety purposes. I don't think
   the OLD
   >LADIES can see well enough to see the heringbone.
   >
   >Thanks again for you comments.
   >
   >Bob Macklin
   >K5MYJ/7
   >Seattle, Wa.
   >
   >"REAL RADIOS GLOW IN THE DARK"
   >
   >----- Original Message -----
   >From: "Jim candela" <jcandela at prodigy.net>
   >To: "Discussion of AM Radio" <amradio at mailman.qth.net>; "Bob Macklin"
   ><macklinbob at msn.com>
   >Cc: "GlowBugs" <glowbugs at piobaire.mines.uidaho.edu>
   >Sent: Wednesday, February 16, 2005 6:17 PM
   >Subject: RE: [AMRadio] Ground(Or Lack Of)?
   >
   >
   > >
   > >
   > >    Bob,
   > >
   >  >      I  do  something  that  is a bit out of the ordinary, and on
   occasion has
   >  >  helped.  My  shack usually runs off a 10 outlet power strip with
   three prong
   >  >  120 v 15 amp jacks. I have found that making a common mode choke
   for the
   >  >  three  wires in the power strip helps keep my RF from conducting
   into the
   >AC
   > > power in my home. I do this with a suitable ferrite rod similar to
   a G-G
   >  >  linear  filament  choke.  This gives me a good and safe 60 hertz
   ground for
   >my
   >  > equipment, and discourages the Rf from going into your power line
   as a
   >  >  common  mode  signal.  I would then direct any RF floating on my
   equipment
   > > chassis's to a close-by ground rod, and use 1" wide braid.
   > >
   >  >      In your case, you could try the 1/4 wave ground wire concept
   tied to
   >  >  your  rig  (or MFJ equivalent), and use the common mode choke on
   your shack
   >  >  power strip. I'm not too sure how much this might help since the
   proximity
   >  >  of the antenna to all sorts of building wiring (door bell, phone
   wires,
   > > cat-5, catv, ac power, gas pipes, furnace ducts, plumbing, re-bar,
   >I-Beams,
   >  >  etc)  will  most  likely unbalance an indoor dipole antenna. You
   might try to
   >  >  force the balance with a current balun as well, and maybe change
   the
   >lengths
   > > a little due to varying detuning on each end.
   > >
   >  >      Another  thought  (from Dr. Evil) would be to go around your
   apartment
   > > with a impedance bridge, and look at the impedance between any two
   points,
   >  >  like  the  CATV  shield, and the furnace ducts. You might find a
   combination
   >  > that is easily tuned to 50 ohms resistive on a frequency you want
   to
   >operate
   >  >  on. I know this sounds crazy, but realize that every FCC part 15
   device in
   >  >  the  complex  is  likely  to  go  nuts  with your transmitter on
   anyway... I can
   >  >  see the whole complex blinking on and off to your CW CQ...Aliens
   on
   >another
   >  >  planet might see your CW from the visual blinking! If you cannot
   get the
   >RF
   >  >  out  of  the  wiring,  heck use the wiring for your antenna, and
   operate VERY
   > > infrequently. :-)
   > >
   > > Regards,
   > > Jim Candela
   > > WD5JKO
   > >
   > >
   > > -----Original Message-----
   > > From: amradio-bounces at mailman.qth.net
   >     >     [mailto:amradio-bounces at mailman.qth.net]On    Behalf    Of
   k0ng at inebraska.com
   > > Sent: Tuesday, February 15, 2005 6:42 PM
   > > To: Discussion of AM Radio; Bob Macklin
   > > Cc: AM Radio; GlowBugs
   > > Subject: Re: [AMRadio] Ground(Or Lack Of)?
   > >
   > >
   > >
   >  >  Bob:  Dont  expect  any problem with your dipole (unless you are
   right under
   >  > it, then things might get hot). A dipole does not need any ground
   to
   > > operate.
   >  >  The "3rd wire" should only be used as a safety line to the radio
   chassis.
   >  >  It  would be best if you checked the 3rd wire continuity all the
   way back
   >to
   >  >  the  building  entrance  ground  but  I realize this is probably
   impractical.
   > >
   > > Good Luck,  DE Charlie,  K0NG  ..
   > >
   > > Quoting Bob Macklin <macklinbob at msn.com>:
   > >
   >  >  >  Back  to  my  4th  floor apartment problem. This building has
   plastic
   >  >  >  plumbing(which  seems  to  leak  at tleat once a month). This
   morning I
   >pulled
   >  >  >  the plate off one of the wall plugs. The building has plastic
   conduit
   > > also.
   > > >
   >  > > So the only ground is the third wire and who knows where or how
   it runs.
   > > >
   >  >  >  The  antenna  will be made to a full 40M dipole. What kind of
   problems
   > > should
   > > > I expect from the crappy ground?
   > > >
   > > > Bob Macklin
   > > > K5MYJ/7
   > > > Seattle, Wa.
   > > >
   > > > "REAL RADIOS GLOW IN THE DARK"
   > > > ______________________________________________________________
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   > >
   > >
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