Author Topic: My home-made ferrite antennas  (Read 46497 times)

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Offline JonathanW

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Re: My home-made ferrite antennas
« Reply #175 on: August 24, 2014, 07:28:33 PM »
On the one hand, the interfering signals are really only showing up on the FFT when it's at its lowest range (+/- 91 mV full scale)-- at what looks like 22, 42, and 68 kHz (about).  On the other, when you're trying for long range specifically due to lack of additional local stations around you, anything's going to be problematic. 

Interesting signals - wonder if it's sub communications?  The consistent 24 kHz signal we see in the east is likely due to the 2 MW sub communications transmitter in Maine.

EDIT: I see Mike beat me to it :)

Offline Silversword

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Re: My home-made ferrite antennas
« Reply #176 on: August 24, 2014, 07:57:32 PM »
If it is some VLF signals for under water communications, they are still wrapping up the recent RIMPAC operations from last month. Should have been completed the first week in August.

Will see what happens when I can get the antenna out side in an enclosure.  Maybe next weekends project.

--Stan Y.
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Offline W3DRM

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Re: My home-made ferrite antennas
« Reply #177 on: August 24, 2014, 11:41:46 PM »
If it is some VLF signals for under water communications, they are still wrapping up the recent RIMPAC operations from last month. Should have been completed the first week in August.

Will see what happens when I can get the antenna out side in an enclosure.  Maybe next weekends project.

--Stan Y.
   Maui, Hawaii

Due to their nature, submarine VLF comms run at an extremely low baud rate. They transmit continuously and it takes hours or more just to transmit a single message. From what I have read, they operate 24/7 so, if it really is these comms causing the interference, they will never go away. It they stop, then most likely you are getting interference from something else.
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Offline Silversword

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Re: My home-made ferrite antennas
« Reply #178 on: September 09, 2014, 04:26:25 PM »
Hi All,

Update on my antenna placement.

Finally found the time to get it on the roof and above the metal of the roof.

Hope it will work out better at this location.  The metal roof is just under the enclosure.

The top cover seal is from ACE Hardware for camper top seal.

Now the antenna is more in open air and hope less interference...

Any comments welcome for this install.

See attachment.

Regards,

--Stan Y.
   Maui, Hawaii
Stan Y. - KH6HHG - Maui, Hawaii --- Blitzortung ID: 993 --- FlightRadar24 ID: F-PHOG1
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Offline W3DRM

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Re: My home-made ferrite antennas
« Reply #179 on: September 10, 2014, 12:49:55 PM »
Nice installation Stan. Is the antenna horizontal? I can't tell by the photo.
Don - W3DRM - Minden, Nevada --- Blitzortung ID: 808 --- FlightRadar24 ID: F-KRNO2
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Offline Silversword

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Re: My home-made ferrite antennas
« Reply #180 on: September 10, 2014, 03:32:35 PM »
Nice installation Stan. Is the antenna horizontal? I can't tell by the photo.

Hi,

Thanks Don for the comment.  Took a while to make the box and some what weather resistant.  Made from 3/4" marine ply that I had left over from another project.  Painted with Deck Over by Behr from Home Depot...Another left over from that same other project...  It is kinda heavy and really not secured to the roof but just laying on top.  Put a cinder block tile on top for more weight.  Will see how it holds up... It is 24" X 24" X 8" for the foot print...

The box is sitting on the roof so the antenna is horizontal and the ends are perpendicular to the power lines that kinda goes to both side of our place..

The photo is kinda looking down into the box...

--Stan Y.
   Maui, Hawaii
Stan Y. - KH6HHG - Maui, Hawaii --- Blitzortung ID: 993 --- FlightRadar24 ID: F-PHOG1
Weather Display 10.37s Build 42
WDL 6.05
MS Windows 7 Pro
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Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #181 on: May 23, 2015, 10:29:01 AM »
 :twisted: This topic needs to be bumped.  Especially with the new "Blue" system on the horizon... So, here... "BUMP", dang it...

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Offline orion_jb2001

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Re: My home-made ferrite antennas
« Reply #182 on: August 10, 2015, 05:37:26 AM »
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff

Offline miraculon

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Re: My home-made ferrite antennas
« Reply #183 on: August 10, 2015, 08:20:27 AM »
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff

I can't speak for this particular antenna since I don't have one, but the "magnet" wire is too small to be captured reliably by the screw terminals on the amplifier input. Normally, the magnet (coil) wire is soldered to a larger stranded section that is OK for the screw terminals. The solder joint is protected by shrink wrap.

Some magnet wire requires sanding or stripping to remove the insulation varnish (or poly), other types will solder-strip. Be careful not to nick the wire or it might break.

Greg H.




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Offline orion_jb2001

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Re: My home-made ferrite antennas
« Reply #184 on: August 10, 2015, 08:50:02 AM »
Thanks Greg.  I am aware of the problems with the magnet wire and the terminals.  What I am trying to confirm, will any wire do for this "link" from the magnet wire to the board or should it be a particular type of wire?

regards,

Jeff

Offline miraculon

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Re: My home-made ferrite antennas
« Reply #185 on: August 10, 2015, 09:00:44 AM »
Thanks Greg.  I am aware of the problems with the magnet wire and the terminals.  What I am trying to confirm, will any wire do for this "link" from the magnet wire to the board or should it be a particular type of wire?

regards,

Jeff

I just used some common 24AWG or so stranded "hookup" wire. On the original Blitzortung ferrite antennas, there was a knot on the "start" winding. I used a different color wire so I know which one it is after all the shrink wrap goes on.

The instructions from the developers say to not twist these two wires since it will increase capacitance. There may be some rejection benefit from twisting the signal pair and the capacitance effect has got to be very small at our frequencies. I have a gentle twist rate on mine as a compromise (about 1-2 twists per inch).


Greg H.




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Offline dfroula

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Re: My home-made ferrite antennas
« Reply #186 on: August 10, 2015, 02:47:03 PM »
Hey all,

interesting constructions.  What type of wire are you using from the winding wire to the actual amp. By the look of it, you don't have the winding wires going to the amp, so the wire these connect to, do they have to be shielded, specific type of wire....  ???


Jeff

I think you're referring to my station, as I first put these antenna's together. I used short lengths of shielded two-conductor microphone cable. The shield and ground wire of the cable are tied together and to the shielded tube and one end of the antenna on the antenna end.

On the other end, the shield and ground are tied together and connected to the ground terminal of the amp channel.

The red wire goes to the other antenna wire and the amp "hot" connection at the amplifier.

That said, I think the shielded cable is completely unnecessary. It is more for mechanical strength. Just solder the free ends of the antenna to a larger diameter piece of copper wire so the terminals of the amplifier and grip it properly.

Best,

Don
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Offline bobbinnd

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Re: My home-made ferrite antennas
« Reply #187 on: September 03, 2017, 10:22:32 AM »
Don,

I am just starting out with a new System Blue, and have been reading EVERYTHING I can find about antenna's and mounting them. I live, live in North Dakota, so the weather can be brutal due to wind, ice and snow, and I am trying to figure out the best way to mount everything outside. I bought 3 ferrite cores from Egon, as I knew this would likely be a one time shot at this, so I think I will try your idea of the "L" PVC but with the 3rd core going vertical. 

Do you still use you antenna's seen on the string, or have you modified them and am have missed that information somehow?

As I said, I live in North Dakota, and the Navy has a very large VLF tower about 19 miles away, it happens to be where I work. I image that I will have to deal with this issue as well, but won't be able to figure that out until after I get the System up and running.

Thanks for a very informative explanation of what you built. Can I mount the E-Field in the same container as the H-field probes?

Offline Cutty Sark Sailor

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Re: My home-made ferrite antennas
« Reply #188 on: September 03, 2017, 11:21:19 AM »
I would mount them separately... with the E field as far from obstacles, structures etc as is feasible... and at least 2-3 meters above ground or metal.... It's best to find a location, for antennas before 'permanently' designing an enclosure, in my opinion.  I'd hold off on the vertical H field until I determined H field environment fairly clean... in my case the 'vertical' H environment is incredibly noisy.
NML lists at 25.20 kHz which will be a pain in the antenna for you.... we're really concerned in the 3K to 30K bandwidth! might have to go 2 antennas at 90 and axial one directly at the transmitter... maybe install filter IC on that channel and cutoff off about 22kHz... I read that there was talk of converting that facility to 150 kHz in which case your could obtain more hi frequ with a cutoff set about 130... You are close, and it may be very irrating, as the ground wave component will be very strong.... good luc... Shouldn't bother E field as much

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