Topic: My home-made ferrite antennas

[JonathanW]

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

[Silversword]

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

[W7DRM (old call was W3DRM)]

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.

[Silversword]

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

[W7DRM (old call was W3DRM)]

Nice installation Stan. Is the antenna horizontal? I can't tell by the photo.

[Silversword]

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

[Cutty Sark Sailor]

  This topic needs to be bumped.  Especially with the new "Blue" system on the horizon... So, here... "BUMP", dang it...

[orion_jb2001]

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

[miraculon]

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.

[orion_jb2001]

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

[miraculon]

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.

[dfroula]

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
WD9DMP

[bobbinnd]

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?

[Cutty Sark Sailor]

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

[Jim-Bob]

Hello all
1st post here.
A quick search reveals
https://www.fair-rite.com/product/antennarfid-rods-3078990891/
Which is available at
https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926

and many other RS component locations.

Is this close enough?

Part Number: 3078990891
78 ROD
Medium Permeability, 78 (ui=2300) material

[schaffer970]

Hello all
1st post here.
A quick search reveals
https://www.fair-rite.com/product/antennarfid-rods-3078990891/
Which is available at
https://uk.rs-online.com/web/p/ferrite-rods/4674059/?relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D626572266C753D656E266D6D3D6D61746368616C6C26706D3D5E285C647B362C377D5B4161426250705D297C285C647B337D5B5C732D2F255C2E2C5D5C647B332C347D5B4161426250705D3F292426706F3D3126736E3D592673723D2673743D52535F53544F434B5F4E554D4245522677633D4E4F4E45267573743D3436372D34303539267374613D3436373430353926

and many other RS component locations.

Is this close enough?

Part Number: 3078990891
78 ROD
Medium Permeability, 78 (ui=2300) material

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

See 3w3.we 3 33333

Sent from my SM-N950U using Tapatalk

[Cutty Sark Sailor]

The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 ±20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.

[Jim-Bob]

Thank you Cutty Sark Sailor
I have inquired about shipping to the UK from Surplus sales, but have not received a reply.
I'm rather wary about ordering them and not knowing the shipping cost until after they have been sent.
This is why I'm looking for an alternative supplier.

[W0BTU]

Do you think that there is any difference in the way these work compared to the antennas that can be ordered from Egon?

Or maybe I should ask if these are the ones you use on your System Blue? 

The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 ±20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.

[Cutty Sark Sailor]

Do you think that there is any difference in the way these work compared to the antennas that can be ordered from Egon?

Or maybe I should ask if these are the ones you use on your System Blue? 

The Antennas in this thread topic' were all built with 50mm X 7.5 mm rods from
https://www.surplussales.com/Inductors/FerRods/FerRods.html
item ICH) ROD7.5/50  ...

Phillips ferrite rod. Soft 3C80 ferrite material great for EMI suppression or tuned coils. EMI suppression DC-200 Mc. RF tuned coils DC-30 Mc. Initial Perm: 2000 ±20%. Saturation flux density: 500 mT. Residual flux density: 210 mT. Mfg. P/N: ROD7.5/50-3C80. 3C80 has been replaced by 3C90.  Here is a cross referenced specification on 3C80.  3C80 is equivalent to Cosmos Ferrite CF196 material.

This construction is exactly what I use on all my stations...  I have a pair of 120mm Wolfgang Friese builds which I ordered with my first red years ago... the performance is similar, but the 120mm, being smaller, didn't produce a large enough S/N ratio for my environment...
My blue 1439 runs Delta 250 x 7.5mm modified build, Red 689 runs 300 x 7.5mm modified build... currently the experimental 791 red  has 300mm unmodified build.. the signal image above: Green is a modified ("CSS THINGIE"   http://frankfortweather.us/blitzblitz/CSS%20Thingie.pdf   49MB) build, and red is an unmodified...

[W0BTU]

Very well! I plan on getting some of those. After I catch up with paying work here.

I'm in the process of moving my E-field antenna probe from that noisy location on the upstairs balcony to near the H-field antennas. Someday...

[quailvalleywx]

I wound a set of these antennas.  Thank you Don for posting the instructions!  Station 2319, https://www.lightningmaps.org/blitzortung/america/index.php?bo_page=statistics&bo_show=station&bo_sid=2319&bo_page=statistics&bo_show=station&bo_sid=2319 has been running with them for a few weeks now (300mm x 7.5).  For mechanical support inside the PVC I just wrapped the antennas in paper towel.  I've got some EMF from the ground level power company distribution transformer in my backyard that limits real good detection at the moment.  At one point I tried grounded aluminum foil for one rotation within an outer layer of the paper towel wrap but found the transformer noise was magnetic field (not 60Hz sine but more like an arcing impulse at amplitude peaks).  The aluminum foil is no longer in there.

Another observation - I found the twisted pairs in typical non-shielded CAT cable work fine for noise rejection.  Even with 75ft of CAT cable in my backyard noise was ~zero with the antenna/preamp not plugged in.  It definitely came in via the antenna and was worse closer to KCPL's transformer.  System Blue's differential input noise rejection (and power supply decoupling caps) are excellent.

If you are too lazy to make a trip to Harbor Freight to get a heat gun then a "half baked idea" is to throw the antennas in the oven with the roast    At ~275F the ends of the shrink tubing collapse first pressing the rods together.  Don't go too long though since the ferrites can warp (< ~1 min).  I had minor warping on one of the antennas.
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[W0BTU]

Wolfgang Friese
http://www.friese-electronic.de/sfericsempfang/komponenten/ferritantennen/

cu Robo

Latest archived copy of that website at https://web.archive.org/web/20200224202534/http://www.friese-electronic.de/sfericsempfang/komponenten/ferritantennen/.