Tunable Lowfer/LF Receivers and You

[KG4CGC]

Anyone monitor VLF/LF? (LW)?
What equipment did you use?
What wisdom can you depart amongst us?

Thank you for your time.

[kf0rt]

Long time ago (60's and early 70's), I used to listen to a weather station on LF using an old Knight-Kit Star Roamer. This was below 300KHz and I gathered at the time that it existed to provide weather to pilots. Marine use made more sense to me at those frequencies, but there's not a lot of that in the mountain time zone and the weather reports always had places like Chadron, Nebraska and they always included the cloud ceiling. Last I listened down there, the band was dead, so the weather station must have gone the way of some other technology.

More recently, did a little looking into the system behind the "atomic" clocks and watches that you can buy; the ones that automatically stay in sync with the NIST clock. This is all done at 60KHz using a VERY low bitrate by "power modulating" the transmitter. That is, they indicate the mark-space stuff by raising and lowering the transmitter power output. The odd thing is that, while I have a couple devices that USE this (and they do work), I'm unable to hear the signal on an IC-7000. You would think that a reasonably sensitive receiver would pick up a carrier when a $30 watch has no problem. (Must be something I'm missing).

Anyway, here's an interesting (fairly technical) paper on the whole atomic clock thing:
http://tf.nist.gov/general/pdf/1877.pdf

[HUGH]

Just setting up for 136kHz here with the intention of applying for 500kHz which is available on request. I have a Kenwood R5000 with all the filters and made a tuner for 136kHz to block strong adjacent signals. Reception should be on one of a pair of frame antennas and transmission on a long wire. That's where the fun will really start!
In progress at this moment is a 2-vxco mixer to generate 136-138 kHz and I have collected some IGBTs for power.

[KG4CGC]

Thanks and thanks.
Part of the question deals with the fact that although the average ham rig will tune down pretty low, they are deaf and in the case of an FT100, you just hear the internal oscillator.
So where do you go for a tunable receiving device. I already have the kit mentioned in another thread and as soon as I've tested that out I'll let you know what I think.
http://jacksonharbor.home.att.net/lfconv.htm

[kf0rt]

I've been meaning to check into the AM BCB attenuation in the IC-7K. As I recall, they attenuate that band by 20db or something (but it can be turned off?) -- explains KOA being S8. Could be the attenuation starts at 1.6MHz and works to the lower limits of the rig.

The converter looks like a fun project. What do you expect to hear?

[KG4CGC]

Aside from the usual stateside stuff, I want to hear LWBCB from everything to the east of me.

[KG4CGC]

Just heard about trying a Selective Level Meter. What is it and how would I use it?

[N8YX]

Look at getting an old marine receiver. Most will cover down to 10KHz and have a preselector built in:



A Harris RF-590, Collins HF-2050 or Racal 6790 is also a good choice.

You can often find the Mackay receivers available on the surplus market. I paid $650 for a 3031A and $550 for a 3030AR, which is a thumbwheel-tuned version of the 3031.

Both work extremely well for pulling in signals in the LF/MF region of the spectrum.

Neither has a noise blanker, but an outboard DSP unit takes care of that.

Unless you have a lot of room for a Beverage antenna, you'll probably want to utilize a magnetic-loop arrangement for purposes of noise cancellation.

Here's a page with a wealth of information on them:

http://www.nitehawk.com/rasmit/ws1_21.html

[KG4CGC]

Nice link. :) Thanks.

[XE1/N5AL]

Just heard about trying a Selective Level Meter. What is it and how would I use it?

Some suggested reading:

"Frequency Selective Voltmeters and their Uses in the Radio Hobby", by Don Moman
http://www.qru.de/selective%20level%20meters.html

"Off-the-air Frequency Measurement and the HP3586B Selective Voltmeter", by Jack Smith, K8ZOA
http://www.cliftonlaboratories.com/off- ... troduction

"A Practical Guide for Using the HP 3586 A/B/C Selective Level Meter", by Bill Feldmann, N6PY
http://www.k7jrl.com/pub/manuals/hp/358 ... 20V2.0.pdf

The Hewlett Packard 3586A, 3586B and 3586C units show up on eBay all the time. With luck, you can get one for less than $100 USD, but they are heavy and it might cost an additional $50 USD to ship it.