Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: VLF  (Read 540 times)
K5PEW
Member

Posts: 223




Ignore
VLF
« on: August 19, 2008, 06:00:50 PM »

Dear Elmer,

I'm wondering if any of you guys monitor the VLF frequencies (perhaps even 24/7?).

In particular have any of you used the Palomar Engineers VLF equipment like their LA-1 amplifier, VLF loop antenna or their VLF converter.

Also wondering if the sensitivity of a high-end rig makes it through the tranlation of such a VLF converter. In other words, if I use a really good 40 or 80 meter receiver with the VLF converter, will it still maintain it's hot receive character in the lower band?

Thanks.

Graham Welch - K5PEW
Logged
WB2WIK
Member

Posts: 20611




Ignore
VLF
« Reply #1 on: August 19, 2008, 06:40:06 PM »

No, it won't.  However that's not really important.

What's important on VLF is the antenna used.  Since most VLF "amateur" antennas (not huge commercial/govt arrays) are extremely inefficient, you may need a 20-30 dB preamp to hear much of "anything."  That wouldn't be the fault of the receiver, it's the fault of the inefficient antenna.

Now, if you can lay out a 4000' dipole, you're in pretty good shape...

:-)

WB2WIK/6
Logged
N8NSN
Member

Posts: 283


WWW

Ignore
VLF
« Reply #2 on: August 19, 2008, 09:03:05 PM »

QST July 2005 has a real good article on VLF work.  The title of the article is,
"Spanning the Atlantic on 2200 meters".  

That is really low frequency around 136 kHz.  A dipole at 136 kc would be... 468 divided by .136 ?  That is 3441.2 ft. approx.  To get that monster to 1/4 wavelength above ground would require the antenna to be 1720 and 1/2 feet up.  Is the theory is still consistent that a 1/2 wavelength up be more productive?  

Dipoles would not appear to be the solution for frequencies this low.  The height above earth would be very high.  Higher than physically possible in most "amateur" station situations.

I am wondering if a good "beverage" type antenna system would be the answer for effective RX and a helically loaded vertical with a huge capacitance hat and a huge ground screen would be the route to take on TX.  Or perhaps for TX one of the weather balloon vertical wires. Would that work affectively in the amateur arena?  The antenna used in the QST article was monstrous.  The average "in town" ham could never pull that one off.

I would really like to see some feed back on this posting.  VLF would be some really cool stuff to work.

Great topic.
Logged
WA3SKN
Member

Posts: 5494




Ignore
VLF
« Reply #3 on: August 20, 2008, 06:50:02 AM »

VLF is interesting from the low losses in the atmosphere, and the extremely high losses in the antenna system.  It appears we will be getting a small allotment at or around 135 khz.
Noise is a problem, as is the size of the loading coils!
73s.

-Mike.
Logged
K7KBN
Member

Posts: 2813




Ignore
VLF
« Reply #4 on: August 20, 2008, 09:08:12 AM »

How about ELF -- around 24-26 KHz?  Solve the size problems there, and VLF will seem a piece of cake!

Use Google Earth and take a look at 21 degrees 49 minutes South, 114 degrees 10 minutes East.

As Mick ("Crocodile") Dundee might say, "THAT'S an antenna!"

Visited there briefly in the mid-60s when it was just being built and powered up.  Had a chance to be a plank owner but didn't want to have to reenlist.  Sometimes I wish I had, but....

I did some USNR training at NLK (Jim Creek WA) in '67.

73
Pat K7KBN
Logged

73
Pat K7KBN
CWO4 USNR Ret.
N4UE
Member

Posts: 297




Ignore
VLF
« Reply #5 on: August 20, 2008, 02:24:43 PM »

Hi, I have a fairly new Paloma VLF converter, that I bought new a year or two ago, The output is configured to 4015-4500 KHz. So the input is 15 - 500 KHz. I use it with my 756pro. It works excellent! I DO have several looong wire antennas, but the Palomar provides ALL the gain you can use, and then some!!

I kinda wish it would tune BELOW 15 KHz, 'cause there are a lot of intersting natural signals there. Of course, I have some Sierra selective Level Voltmeters for that, and maybe SOME day, I'll actually connect them to an antenna. ha ha

Do a 'Google search on "VLF" and you'll find more than you ever thought existed. There are some small commercial receivers out there that will allow you to listen to the "dawn noise" or "spherics", but be advised, you better be a looooong way away from powerlines, etc.


Have FUN!

ron

N4UE
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!