Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

LF: AW: RE: RE: W1VLF 9 Khz Antenna update Putting inductance near the

To: <[email protected]>
Subject: LF: AW: RE: RE: W1VLF 9 Khz Antenna update Putting inductance near the top.
From: Stefan Schäfer <[email protected]>
Date: Mon, 5 Apr 2010 16:26:28 +0200
References: <38A51B74B884D74083D7950AD0DD85E82A1BD1@File-Server-HST.hst.e-technik.tu-darmstadt.de>,<[email protected]> <BF4A524700075746A6467658DFC7102C19A043E511@ICTS-S-EXC2-CA.luna.kuleuven.be>
Reply-to: [email protected]
Sender: [email protected]
Thread-index: AcrT35yWRmHp8hCST8Ccpvq77MwkpwADIb1OAAYNgSAABDjxzwAHEICAAAM9Z5gAItoBow==
Thread-topic: RE: W1VLF 9 Khz Antenna update Putting inductance near the top.
Hi Rik, 
 
I think on VLF it could be even useful to place the L as high as possible when 
there is "nothing" lossy in the near surrounding. I think the difference to LF 
is, that the coil losses on VLF can be some 100 Ohms. If the "lost" capacitive 
current, that comes out of the lower part of the vertical section comes back to 
the coil without crossing too much earth resistance (due to the short way back 
to the coil) and if the coil losses are low (on LF often in the near of 10 
Ohm), there is not much lost and it behaves almost as a fixed parallel C 
(assembly part). Thus the benefit is rather small.
On VLF, the same equivalent capacitance causes much more losses due to the 
higher coil resistance. The Xc is higher but U also. 
I have not practically proven that and maybe the effort is not worth, don't 
know.
 
Sometimes it is better just to generate some 10W more power than installing a 
structure that will break down in the next storm ;-)
 
73, Stefan/DK7FC

________________________________

Von: [email protected] im Auftrag von Rik Strobbe
Gesendet: So 04.04.2010 23:40
An: [email protected]
Betreff: LF: RE: RE: W1VLF 9 Khz Antenna update Putting inductance near the top.


Hello Paul,
 
after I published my experiences several hams tried elevated loading coils on 
137kHz.
Significant improvement was observed when the antenna was surrounded by high 
obstacles (trees, buildings), when the antenna was "free" there was little or 
no gain.
I have no idea what the effect will be on 9kHz, but if you can install an 
elevated loading coil it whitout too much effort I would suggest to try it.
In my case most stations  noticed a signal increase of about 1 S point and 
PA0SE measured the field strength and noticed a difference of 5dB.
 
73, Rik  ON7YD - OR7T
 
________________________________

Van: [email protected] [[email protected]] 
namens Paul A. Cianciolo [[email protected]]
Verzonden: zondag 4 april 2010 22:28
Aan: [email protected]
Onderwerp: LF: RE: W1VLF 9 Khz Antenna update Putting inductance near the top.


Stefan 
 
On page 60 and 61 of the Low Frequency Experimenters Handbook Peter Dodd RSGB  
there is an example putting a coil near the top of the antenna
In this case the transmitter is on 137 Khz and a of a portion (1/2) of the "L" 
needed to resonate was moved near the top. According to measurements by Rik 
Strobbe ON7YD  an increase of 4 to 5 db  was measured.
 
Do you think it would be worth the effort to put 1/4 of the total "L" needed 
near the top
I could do that very easily.
 
PaulC
W1VLF

 

    -----Original Message-----
    From: Stefan Schäfer [mailto:[email protected]]On Behalf 
Of Stefan Schäfer
    Sent: Sunday, April 04, 2010 12:49 PM
    To: [email protected]
    Subject: AW: W1VLF 9 Khz Antenna update
    
    
    Hello Paul, 
     
    This sounds really improving!! And this will give a much more efficient 
antenna as before. Also the HV problems will be reduced. Note that the goal 
should not be to make the C as high as possible but first to make the antenna 
efficiency as high as possible. This is done be increasing the effective height 
and reducing all the losses. Thus i would recommend now a combination out of 
option 2 and 3. Maybe you could check with G3YNKs R-C bridge, if the losses are 
increased with option 3. You could use a braid of some meters to keep a 
distance to the trees although the wire is mounted on the trees. 
    But all in all it sounds very promising! 
    Option 1 is not so much improving i would say. The C would slightly 
increase but not the antenna efficiency i mean...
     
    What about the option to place the coil on the 40m tower? That would be the 
best improvement you can do!
     
    Good luck!
     
    Do you already know who could be the next receiving ham station? ;-)
     
    73, Stefan/DK7FC

________________________________

    Von: [email protected] im Auftrag von Paul A. Cianciolo
    Gesendet: So 04.04.2010 17:18
    An: [email protected]
    Betreff: LF: W1VLF 9 Khz Antenna update
    
    
    Stefan,Group.
     
    An update on the W1VLF hopefully to be 9 KHZ antenna.
     
     
    The 55 meter wire sloping at 45 degrees measured 340 pf as you recall.
    The addition of 2 top hat wires has been made, each over 50 meters long 
with a slope to the ground.
     
    Wire 1 is terminates at 11 meters above the ground and wire 2 terminates 20 
meters above the ground.
     
    Antenna only = 340 pf
     
    Antenna and  Wire 1 West  = 650 pf 
     
    Antenna and  wire 1 West and wire 2  East  = 900 pf
     
    L to resonate at 9 KHZ now = 350 mHy.
     
     
    The L is now coming down to a reasonable size!!
     
    For the next step there are 3 possibilities:
     
    1) Change the top 30 meters from a single wire,  to 3 wires spread 1 meter 
apart at the top to gain perhaps 100 more PF?
     
     
    2) Get my neighbors permission to use his tree as a support for the end 
rope on wire 1.  This will increase wire 1 west  about 40 meters and raise the 
end from 10 meters to 20 meters. 200 PF more?
     
     
    3) Run 2 more wires  Wire 3 Northwest and Wire 4 Northeast  each would be 
20 to 30 meters long and terminate at 30 meters high.   These would be over a 
forest and I am not sure if this is my best option.
    It may yield more "C" and lot more losses??
     
    Goal is to try to get antenna "C" to 1200 pf or more
     
    All ideas welcome.
     
    PauLC
    W1VLF
    
     
     
     

        -----Original Message-----
        From: Stefan Schäfer [mailto:[email protected]]On 
Behalf Of Stefan Schäfer
        Sent: Sunday, April 04, 2010 7:44 AM
        To: [email protected]
        Subject: AW: Activity 3 Mar 2010
        
        
        Mike, LF, 
         
        Wow! 5641km is really impressing! Congrats!!
         
        Is there such an activity planned for the "west-stations" as well? We 
could do the same!
         
        I've never been slower than DFCW-10 on LF. Would be interesting :-)
         
        73, Stefan/DK7FC

________________________________

        Von: [email protected] im Auftrag von Mike Dennison
        Gesendet: So 04.04.2010 12:09
        An: [email protected]
        Betreff: LF: Activity 3 Mar 2010
        
        

        An excellent day's activity on 137kHz yesterday with 5 countries
        received, the furthest easterly station received here and a QSO with
        a new country.
        
        In the morining, OE5ODL and DJ6GT were received.
        
        During the UA tests, five stations were logged (see the attached
        screen grab - Argo set to QRSS30 and centred on 137.778kHz).
        The picture shows (from the top) UA0AET (5641km from me); RA3YO;
        RN3AGC; UA4WPF; and EW6GB who was first received as early as 1700UTC.
        
        After the formal test I exchanged 'O' reports with EW6GB at 1902km,
        using QRSS10.
        
        Well done to all concerned.
        
        Mike, G3XDV
        ===========
        

<<winmail.dat>>

<Prev in Thread] Current Thread [Next in Thread>