The gain of this preamp is the gain of a common source configuration. That's not critical, and you can use this maximising and minimising to cancel out a disturbing carrier on a nearby frequency.
Pointing the ferrite rod towards Sweden will give you minimum reception, it's a sharp null, the rod needs to be perpendicular to SAQ. Its rechargable, the preamp uses small power, you can listen the whole day outside and recharge it over night. The preamplifier is using a 9V battery to keeps things portable. The Coil I connected to the preamplifier.
Maybe I should repeat my first Rod conclusion: buy the longest and fattest rod you can get, do around 900 - windings and be happy! Maybe easier than looking for the holy grail. This means that also this rod needs around 900 - 1000 windings. This is not what I expected, as the mu = 350 or so. The results are: to get an L of 82mH, number of windings n = 1030. The week is over and I have tested the 3B1 rod from. What I learned here, you can not always trust what is written. After making a small coil and measuring the inductance, I thought hmmm. Update: Don't get it, it needed 1200 turns, website shows not correct information.Īfter I wrote the words above, I did buy 3 of the 3F3 Rods above. The 3F3 rod on (C) only needs 522 turns and is cheap. When you buy a 8mm diameter 3B1 rod, it only needs 665 turns, MnZnC. The 10mm diameter rod i bought has a mu of about 250, 4B1, NiZnī. It will not get much lower, dear readers!Ī. He sells various ferrite material, when you seach for "FERRIT" AND "3F3" you will find a great ferrite rod of 3F3 material with a length of 100mm. Here you can buy a rod of 3B1 material and diameter of 8mm: number of turns: 665.ī. I went to the page with the ferrite rods: I did do around 900 turns, analysis correct, this rod on my picture has mu=250.Ĭlearly not a rod with a mu of 900, 2000 or more.Ī. Diameter coil former is the same as rod diameter: 10mm, shift =11mm(?), wire diameter=0.25mm, winding pitch:0.26mm. I used L = 74mH, length rod = 600mm(long), diameter rod = 10mm, mu = 250. I measured the inductance of my creation and it is only is 74mH. I went to the website: COIL to calculate the inductance L for a mu of 250 (4B1) or 900 (3B1). This website Ferroxcube gives good info on material and mu. The datasheets will tell what materials are used. MnZn so Mangan Zinc, mu value of around one thousand or so, used for some kHz mu value of a few hundred, used for some MHz What material the rod is made from? I believe this gives a good indication: So we see quite a difference and we want to go for a rod of 3C90 or 3F3 material, otherwise we wil go for a 3B1 rod, that's also fine.You can also look at it from a material perspective. The permeability mu is the important parameter, the higher the mu, the less windings to make for the same induction L. Well, I did some more searching and the list is a bit larger: Over here in Europe, most ferrite rods are made of only a few ferrite materials,Īll from Ferroxcube Philips: 4B1 and 3B1. The third option is to upconvert this low frequency and convert it to a frequency that most short wave receivers can handle.Īfter everything was working, I tried to reverse engineer the Coil. As most sound cards sample on 44.1 kHz or 48 kHz, the spectrum up to half of the sampling frequency, so 22 or 24 kHz can be received.
#Sm6lkm vlf receiver Pc
It suggest to use a PC or laptop, take the build in sound card, and receive it directly. More information can be found using this link: The PC then can use a simple SDR programme to process the incoming frequency. The transmitted frequencies are that low that they can be directly received by a laptops soundcard. This solution comes from the Alexander association, the guys that run and maintain the old Grimeton Station. Using a short whip receiving the E-field. It is a classical super heteodyne receiver with an IF of about 455 kHz and a BFO. Look for: A very simple VLF Pocket receiver by By Wilfried Fritz, DJ1WF. The Receiver: I checked several web sites to see what other people are doing and I saw 3 solutions:
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