[Lowfer] Lowfer Digest, Vol 102, Issue 1

Fri Aug 2 12:50:32 EDT 2013

Hi Doug and all . . .

Interesting your e-probe observations, esp as I've never used one for LowFering.

However one thing I'd like to comment on is use of big ground level rx loops.

It's been my experience and that of others in written comment that loops are not used a directional antennas like, say, a HF beam or loop is used. To the contrary LF loops are best used to null some interfering signal (unaffected at my locale) not as an enhancing means. This was my experience at the watering hole too.

My two un-amp'd, multi-turn loops at about 4 feet off the ground and at 6 and 10 feet across were generally set E-W and picked up the active ones at night thru early mornings on an Argo screen.

--Peter, N Ill
-----------------------------
>>> "Douglas D. Williams" <kb4oer at gmail.com> 08/01/13 4:00 PM >>>
Re: e-probes VS loops at LF

No idea if this is going out to the correct persons or not, since I have
subscribed to the digest version of this mailing list until October....

All I can offer is anecdotal evidence, and a few minor observations.

My only experience with a loop at VLF/LF is the Wellbrook LFL-1010, a
couple of years ago.

It was, IMO, a fine performer. I was impressed at how quiet it was,
compared to e-probe antennas that I had built myself and commercial units
such as the L400B.. I received several "Lowfer" signals during the time I
used it, as well as a few overseas 136 kHz amateur signals. I was not
impressed by it's performance below 100 kHz.

I compare that to my experience with the Clifton Labs Z1501 active
"e-probe" antenna.

http://www.cliftonlaboratories.com/z1501_active_antenna.htm

IMO, the 1501 wins, and it is not even close.

All one really has to do is search these threads, and the LWCA web site,
 for my reception reports with the Clifton Labs e-probe.

Perhaps my location has something to do with it. I live on a hill
("mountain" to you city folks), in east Tennessee. I live on the top of my
"hill". My "e-probe" is about 15' above ground level.

As for loops, I find them cumbersome to turn and orient to desired signals.
I still work 40+ hours a week, and go to bed early, so "live" monitoring of
LF signals is not usually applicable to my habits.

-Doug KB4OER

On Thu, Aug 1, 2013 at 12:00 PM, <lowfer-request at mailman.qth.net> wrote:

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> Today's Topics:
>
> 1. Re: e-probe vs loop (Garry Hess)
> 2. Re: e-probe vs loop (Alan Melia)
> 3. Re: e-probe vs loop (Garry Hess)
> 4. Re: e-probe vs loop (Paul Daulton)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 31 Jul 2013 11:14:24 -0500
> From: Garry Hess <k3siw at sbcglobal.net>
> To: lowfer list <lowfer at mailman.qth.net>
> Subject: Re: [Lowfer] e-probe vs loop
> Message-ID: <51F937E0.9030405 at sbcglobal.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hi Bill,
>
> Thanks for the comments.
>
> My loop has 20+ dB nulls orthogonal to the main beam. More careful
> construction could yield 30+ dB nulls, but what I have has proven
> helpful for decoding certain DGPS stations. Often there are at least two
> strong co-channel signals present sufficiently orthogonal that one can
> be nulled out. Ideally the e-probe is omni-directional but mine is
> within perhaps 75' of a 65' Rohn foldover tower and perhaps 50' of a
> triband beam roof tower. Both are higher than the e-probe and thus might
> influence it. However, the 9 stations I monitored so far are spread
> around in heading and all of them fared better on the loop. The loop is
> fairly isolated although there is a Linden tree within about 50'.
>
> I normally transmit a pair of hifer signals around 13.555 MHz. The one
> radiating from a horizontal dipole is close to the e-probe, the one
> radiating from a vertical antenna is close to the loop. Although they
> don't seem to produce noticeable spurs at LF they are turned off during
> data collection.
>
> The e-probe receive lineup is as follows: Clifton Laboratory Z1501
> e-probe, 100' of cheap RG58 coax, homebrew common-mode choke, Z1203 DC
> power coupler, 6 dB resistive splitter, 10 dB pad, SDR-IQ#1 externally
> clocked and locked to GPS, Dell E521 Windows XP computer#1.
>
> The loop receive lineup is as follows: 10' shielded loop and preamp a la
> VE7SL, 100' 9913 cable, homebrew DC inserter, SDR-IQ#2 internally
> clocked but well calibrated, Dell E521 Windows XP computer#2.
>
> SpectraVue version 3.00 runs on both computers and inputs data to
> Spectrum Laboratory version 2.76b8 via a USB driver and virtual audio
> cable. Text file export is programmed to save signal and noise powers in
> a 100 Hz bandwidth for spreadsheet post-processing. Carrier signals are
> centered at 400 Hz and a SpectraVue filter covering 200-1200 Hz is used.
> The Spectrum Laboratory FFT settings are size=32768 with unity
> decimation. This yields a noise equivalent bandwidth of about 0.5 Hz and
> covers through 5.5 kHz.
>
> Because both the hardware and software are so identical I don't expect
> there to be any significant measurement differences. But it's easy to
> swap antennas and confirm that for certain. If there is an issue I can
> switch between antennas and use a single setup but then the data would
> not be quite simultaneous.
>
> --
> 73, Garry, K3SIW, EN52ta, Elgin, IL
>
>
> ------------------------------
>
> Message: 2
> Date: Wed, 31 Jul 2013 18:29:50 +0100
> From: "Alan Melia" <alan.melia at btinternet.com>
> To: <lowfer at mailman.qth.net>
> Subject: Re: [Lowfer] e-probe vs loop
> Message-ID: <AA7E5EED53974145A2B055177F9F82A4 at gnat>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> reply-type=original
>
> Gary there are a number of other parameters that need to be considered
> otherwise you may be comparing apples with bananas :-)) I assume from you
> description that the loop is untuned, and I suspect it is a single turn.
>
> The loop sensitivity is not dependent on the height it is mounted above
> ground. The e-field probe however has sensitivity almost proportional to
> height. Also at low levels the e-field antena is likely to be screened by
> any adjacent foliage/bulidings etc Thus raising the e-field aove these
> could make a very significant difference. One plus point is that if the
> two
> antennas are untuned there will be probably little or no interaction
> between
> them.......this is not the case with tuned antennas.
>
> The usual choice depends on you local environment. If you have quiet
> surroundings then you are lucky to have your choice independent of any
> local
> problems.
>
> Alan
> G3NYK
>
>
>
> ------------------------------
>
> Message: 3
> Date: Wed, 31 Jul 2013 14:13:39 -0500
> From: Garry Hess <k3siw at sbcglobal.net>
> To: lowfer list <lowfer at mailman.qth.net>
> Subject: Re: [Lowfer] e-probe vs loop
> Message-ID: <51F961E3.3010107 at sbcglobal.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Alan,
>
> Thanks for the comment.
>
> Yes, the loop is a single, untuned turn, based on VE7SL's writeup at
> http://members.shaw.ca/ve7sl/loop.html.
>
> I've seen others comment that above modest height the e-probe
> sensitivity stops improving. Thus, an ideal location might be a large
> open field with the bottom of the probe up only 15' or so. That would
> place the antenna well away from local man-made noise sources but not
> too many of us have large open fields handy, hi.
>
> The bottom of my e-probe whip is currently about 35' AGL. That places it
> above everything but my 65' tower (a roof tower with triband HF beam and
> a couple of VHF antennas is close in level, but probably not really
> higher). I've thought about putting the e-probe at the top of the tower
> mast (~75') and may yet do that, but I'm not confident it would survive
> there for long. On the other hand I have a new winch for the tower so
> raising/lowering won't need Hercules any more, and replacing blown JFETs
> is easy, and cheap.
>
> --
> 73, Garry, K3SIW, EN52ta, Elgin, IL
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 31 Jul 2013 20:57:20 GMT
> From: "Paul Daulton" <k5wms at centurytel.net>
> To: "'lowfer list'" <lowfer at mailman.qth.net>, k3siw at sbcglobal.net
> Subject: Re: [Lowfer] e-probe vs loop
> Message-ID: <20130731165720.0dg8q5c0vt4wcgks at webmail2.centurytel.net>
> Content-Type: text/plain; charset=UTF-8; format="flowed"
>
> Garry my pa0rdt miniwhip quit working when the co-op installed a remote
> reading meter. It is on the tower about 8ft horizontal and 20ft above
> the meter.
>
> My 14turn loop with modified m0ayf preamp didnt perform until I moved
> it to the other end of the house and 20 ft to the rear, about 95 ft
> from the meter. the orientation for ne signals like WM and SJ puts the
> null broadside to the meter. I need to move the miniwhip to the same
> location and see if it performs when located out of the noise
> field.Before the loop I never got SJ WM or EAR. on 1750 meters. Before
> the loop I only copied HSA, 45 mile away, a couple of hours a day on
> long wire or miniwhip. With the loop 24/7.
>
> while I blame the meter I could have devices like the DSL and washing
> machine that are generating the noise.
>
> Two years ago I complained to the co-op about the noise, I couldnt work
> 80 meters and lf was gone. Tech came out and started to blame cable tv
> and phone on interference. I took my grundig g5 out to the street, I
> have underground entrance, and held it up to the ground wire tuned to
> high end of BC band.Noise full scale on meter. He said he would send
> out noise crew next day. I never saw them but two days later they
> replaced 7 poles and hardware across the road and 80 meter interference
> went away.
> Paul k5wms
>
> Quoting Garry Hess <k3siw at sbcglobal.net>:
> > Alan,
> >
> > Thanks for the comment.
> >
> > Yes, the loop is a single, untuned turn, based on VE7SL's writeup at
> > http://members.shaw.ca/ve7sl/loop.html.
> >
> > I've seen others comment that above modest height the e-probe
> > sensitivity stops improving. Thus, an ideal location might be a large
> > open field with the bottom of the probe up only 15' or so. That would
> > place the antenna well away from local man-made noise sources but not
> > too many of us have large open fields handy, hi.
> >
> > The bottom of my e-probe whip is currently about 35' AGL. That places it
> > above everything but my 65' tower (a roof tower with triband HF beam and
> > a couple of VHF antennas is close in level, but probably not really
> > higher). I've thought about putting the e-probe at the top of the tower
> > mast (~75') and may yet do that, but I'm not confident it would survive
> > there for long. On the other hand I have a new winch for the tower so
> > raising/lowering won't need Hercules any more, and replacing blown JFETs
> > is easy, and cheap.
> >
> > -- 73, Garry, K3SIW, EN52ta, Elgin, IL
> > ______________________________________________________________
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>
> Paul Daulton K5WMS
> beacon WMS 185.302 khz qrss30/slow 24/7
> Jacksonville,Ar 72076
> em34wu
>
>
>
> ------------------------------
>
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