Hello Stefan!

I have no words... :-)))))
just started a SL instance on 970 Hz, I have no idea if something can 
appears but I'm just a bit more far away from the end of first wave ;-
))

keep on

Marco IK1HSS

----Messaggio originale----
Da: [email protected]
Data: 26-gen-2018 14.45
A: <[email protected]>
Ogg: Re: LF: RE: 20 mA carrier on 970 Hz

Hello Jim,

Thank you. We will see if the experiment will be successful. It will 
be 
in 40 km distance, still near field. Then there will be another one in 
a 
few weeks, trying to cross the far field border.
One day it might be detected in > 1 wavelength (309 km). 'milestone' 
can't describe it. It would be rather a light-year-stone! :-)

73, Stefan

PS: The carrier is still on the air since last night. I increased the 
current to 23 mA. When going to 25 mA, the ferrite transformer between 
PA and HV transformer is starting to saturate (due to the non-resonant 
HV transformer) and is thermally drifing away (protected by the safety 
function in SpecLab)... I'll investigate...



Am 26.01.2018 01:04, schrieb [email protected]:
>
> Stefan,
>
> Very nice work on identifying ULF core materials, and on transformer 
> design, construction and testing. The transformer looks beautiful.
>
> How long did it take to hand wind the 4000 turns?
>
> Does the Kapton tape partially fill the 0.15 mm gap (such as with 5 
> mil tape), or completely fill the 0.15 mm gap?
>
> 73,
>
> Jim AA5BW
>
> *From:* [email protected] 
> [mailto:[email protected]] *On Behalf Of *DK7FC
> *Sent:* Thursday, January 25, 2018 4:34 PM
> *To:* [email protected]; Renato Romero
> *Subject:* ULF: 20 mA carrier on 970 Hz
>
> Hello dear friends of the *U*ltra *L*ow *F*requencies :-)
>
> Since 21:05 UTC i'm running a carrier on 970.005 Hz.
>
> With a lot of work i built a new ULF coil for 970 Hz. It's Q is just 
> 11! For the next experiment, the target voltage is 12 kV, that means 
> 36 mA antenna current and about *10 nW ERP*!!
> Since the Q of the coil is so low i decided to add a primary winding 
> in this experiment, so actually it is a transformer now.
> Here is an image showing the transformer inside the large waterproof 
> PVC tube on the roof: 
> http://www.iup.uni-heidelberg.de/schaefer_vlf/ULF/ULF_coil_970Hz.jpg
> The core material is that special stuff i bought a few months ago, 
see 
> the old mail below. The iron cross section area is 40 mm x 40 mm. 
With 
> acceptable upheating i can apply up to 4 V / turn, which means 0.4 T 
> at 970 Hz. Not much but better than ferrite and it has quite a high 
mu 
> r! Also i can form all wanted geometries, which is a bit hard when 
> using ferrite :-)
> On the core there are 4 windings which have 1000 (hand-wound!) turns 
> each. So i could apply up to 16 kV. But in the coming experiment i 
> stay at 3 V / turn.
> The core is floating, so its potential against ground is given by 
the 
> RC network of the geometry of the arrangement. I spent loads of 
Kapton 
> tape which is just excellent for all such applications!
> Oh, the iron core has two air gaps of course. It should be about 2x 
> 0.15 mm. The Kapton tape realising the air gap also helps to isolate 
> the two half cores from each other. This helps to reduce the E field 
> stress.
>
> I just made a frequency sweep and found that the actual resonance is 
> near 1100 Hz. But the Q is low and the TX power is low too. The only 
> disadvantage beeing outside the resonance should be a higher primary 
> voltage and higher PA losses.
>
> SpecLab and the antenna current regulator carefully holds the phase 
> and target current! This is important here. A view into the box 
> showing the PA, power supply, PA output transformer (yes, i'm still 
> using N30 ferrite at 970 Hz!! But just 1 V / turn on a AL=10800 nH 
> core), digital and analog antenna current measurement: 
> http://www.iup.uni-heidelberg.de/schaefer_vlf/ULF/[email protected]>
> I intend to run the carrier for a hour and then check the 
> temperatures. Later i want o rise to 24 mA and check again....
>
> More soon...
>
> 73, Stefan
>
>
> Am 16.11.2017 18:24, schrieb DK7FC:
>
> ...today i drove to the company and got that high permeablic 
strip. 
> http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/Powercore_H075-18_20mm_Thyssen.jpg
> Quite a large amount!
> To be continued...
>
> 73, Stefan
>
> Am 13.11.2017 16:03, schrieb DK7FC:
>
> Today i searched for suitable materials to 
build a iron band rod for a 
> coil for 970 Hz.
> I learned about kornorientiertes Elektroblech, 
> https://de.wikipedia.org/wiki/Elektroblechor 
> https://en.wikipedia.org/wiki/Electrical_steel> A normal 50 Hz 
transformer is using 0.5 mm plates. For higher 
> frequencies there are thinner plates available.
> I 
searched for a local company and quickly found this product catalogue:
> http://www.lohse-ringbandkerne.de/uploads/downloads/Lohse%20Prospekt%20D_web_2017.pdf
>
> Excellent! They offer 0.23 mm think plates.
> Then i sent them an email request and later i had a telephone talk 
> with the chief of the company. I asked if they have maybe even 
better 
> materials and he said yes, they have a band of the type H075/18/20. 
> This is a band which has a thickness of just *0.18 mm* and it is 20 
mm 
> width. Since it is grain-oriented it matters how the B field passes 
> through it.
> He said that this special band is worse at 50 Hz but can be used to 
up 
> to 4 kHz!!!!!!!!!!!!!!!!!!!!!!!!!!! So maybe this opens the 
frequency 
> range from 4 kHz down to the lower ULF!!!! :-)
>
> I got a good price, just 4 EUR for 1 kg but i have to order at least 
> for 100 EUR so i will order 25 kg of that stuff! Already done!
>
> My idea is to build a 0.5 m long rod. One piece of the band will 
then 
> have a cross section area of  3.6 mm^2. I will need about 1000 to 
1500 
> of these bands in parallel. This should fit into a PVC tube with an 
> outher diameter of 80 mm. Very handy!
>
> I'll keep you informed ;-)
>
> 73, Stefan
>