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Post by W4FJF » Tue Oct 09, 2007 1:14 am

I have many receivers, but none go below 200KHz. What would be the best way to listen to the not unforgotten world of VLF? Your suggestions and thoughts are very welcome. Also, do we have any frequency allocation below 160M? I had heard of something between 160 - 190 KHz, but do not know exactly where. Is there a "hobby" band there? Email direct to ffuhrer@elmore.rr.com if you can. Many thanks to all who can help.
Fred - W4FJF.
FRED/W4FJF - EMAIL: ffuhrer@elmore.rr.com
Be careful: The toes you stomp on today may be attached to the butt you may have to kiss tomorrow!

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VLF Receiver or Converter

Post by N9LCD » Wed Oct 10, 2007 9:40 pm

Each has it's own unique advantages.

Converters are simple, solid-state "black boxes" that up-convert everything within their bandpass. The problem is that there's no input selectivity unless you build an preselector. Otherwise, all the unwanted crud that comes in, goes out in to your receiver.

There are some good VLF receivers out there. Most of them are hollow-state mil-surplus units built for use on ships & subs. I had a WRR-3(?) that covered 10(?) to 600 KHz in about five bands. It had great selectivity but it was a pain to aline; you needed a frequency meter to check the frequency of the IF as you alined the front end. The WW II sets are VLCC-sized anchors, some coming in at over 100 pounds for receiver & power supply. Plus some used circuitry that isn't seen any more -- like a tuned RF front end into a regenerative detector.

You might want to start with a converter and put the emphasis into your antenna. I think that the antenna is more important in VLF/LF range than in others because of the wavelengths down there, 1000's of meters, versus the size of the antenna.

Then, IF you're successful and technically adept with the needed test equipment, you might want to try a VLF/LF boat anchor .



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Post by chloelly » Sat Aug 03, 2013 7:39 am

Metal detectors mostly are VLF and PI metal detectors today. Both VLF and PI metal detector can work as gold detector. The former is more suitable for detecting smaller golds, with advantage of discrimination and versitility. PI is more for finding large size of gold in great depth and capabilty in ignoring minerals.

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Post by n1nqc » Sun May 25, 2014 1:32 am

Hey Fred,
I do a LOT of longwave/VLF work.Trust me ,it is real "specialty" and NOT everyone's cup of tea. I am surprised that nothing you have goes below TWO hundred Kc ( but I don't know what you have either). Most modern rigs go down to 100 or 150 Kc. anyways.

Below 200 Kc you are missing the six lowest African/European long wave AM broadcast channels. You may not hear these very often- near the coast and in winter, maybe. Anyplace else ,it's a much more dicey bet.

Below 153 there ain't much of interest to most folks. There are land stations sending submarine data . You can "check propagation" by these, but otherwise they get old really quickly.There are a few "Lowfer" ( search) experimental bands, but these are a REAL specialty.

You can "track" lightning storms at long distances IF you are into static crashes/sferics. This is actually better done with simple home brew gear in the "audio " range centered around 7 Kc. Commercial rigs are NOT as good, but still "work". Search "tweeks", "whistlers", "natural radio".

I AM into all of the above, so I don't get bored. My ham friends think I am NUTS and will often "rib" me ( in a good nature) about how I listen to "static" for "hours".I am NOT trying to discourage long wave exploration, just a head's up.

I like radios that actually COVER long wave rather than up converters. I have had both .I use an Icom R-71a as my main "conventional" receiver.It is SPEC'ED to 100 Kc, but "responds" reasonably to around 20 or 50 Kc.I do 90% of my work on it.

I also have quite a bit of commercial and home brew LW stuff too.

FWIW, this is my first QTH post.


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Post by Jeramy1 » Wed Nov 26, 2014 7:52 am

frequency detectors can be an advavced stuff that was used in metal detecting ,and it will detect out metallic objects according to the frequency from it. You can come to have a look if you need one.

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