Tom,
THank you for sharing that build! Do you by chance have any PC boards
for the RX?
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On Fri, 2014-03-28 at 22:08 -0600, Tom Thompson wrote:
> Several of you have shown interest in the loop antenna. I have updated
> my web page to show more details. If you have it cached, you may have
> to refresh it. The URL is:
> http://tomthompson.com/radio/ReceivingLoop/loop.html
>
> Let me know if some of it is unclear.
>
> Tom W0IVJ
>
> On 3/28/2014 1:53 PM, Tom Thompson wrote:
> > Hi Ken,
> >
> > One thing to keep in mind when you choose a loop is the antenna
> > factor. I believe your RFI is mainly on 80m. A small (10") loop
> > that is not tuned will have a terrible antenna factor on 80 m. You may
> > not even hear the noise from your house. Also, your receiver probably
> > does not have a very good attenuator in the front end. When you get
> > close to the noise, you can detune the loop and get some attenuation.
> > You need to keep the signal right at the noise level in the null for
> > the AGC NOT to work if the S-meter is not very good. When the AGC is
> > NOT working, you can listen to the strength of the signal through the
> > speaker. Again, remember the null is looking through the loop with
> > the feed at the bottom. Also, I always put a choke balun right at the
> > loop so I don't get false readings from picking up signals on the coax
> > when the signal gets strong.
> >
> > When you start your hunt, find the direction of the noise by nulling
> > the loop. You now have an ambiguity in direction. Peak the noise by
> > turning the loop edgewise and walk in one direction. Keep rotating the
> > loop back and forth looking for the peak signal to get stronger. If
> > the peak is getting weaker, walk in the other direction. When you get
> > very close to the RFI, use the null feature of the loop and attenuate
> > the signal by switching in an attenuator or detuning the loop.
> >
> > I have been able to trace a grow light almost to the room in the house
> > by not getting on the residential property. Once I find the house and
> > if the RFI is on a timer, I will position myself in front of the house
> > and wait for the noise to appear to make sure I have the right house.
> >
> > If you get this far, email me and I'll tell you how I approach the
> > grower. That is sometimes tricky and could be dangerous so I do not
> > want to generalize here.
> >
> > Tom W0IVJ
> >
> > On 3/28/2014 1:17 PM, Kenneth G. Gordon wrote:
> >> "The unshielded loop will...respond to electrostatically induced noise."
> >>
> >> While:
> >>
> >> "The shielded loop , on the other hand, is almost insensitive to
> >> electrostatically induced noise."
> >>
> >> In other words, the shielded loop is NOT a good choice to DF the
> >> types of
> >> noise we are most often bothered by, while the un-shielded loop is
> >> specifically sensitive to such noise.
> >>
> >> So, my use of my NM-20B, with its shielded loop, was counter-productive.
> >>
> >> Kenneth G. Gordon W7EKB
> >>
> >> "Courage is being scared to death but saddling up anyway."--- John
> >> Wayne
> >>
> >> _______________________________________________
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> >> RFI@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/rfi
> >>
> >
> > _______________________________________________
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> >
>
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