Hello Piotr, Daniele, LF,
@Daniele: It's fine, i searched for the loopstick article as well,
thanks for the link!
@Piotr: Hello, nice to see you again here!
And happy to see i caused some new activity in homebrewing ;-)
DCF39 is about 500 km distant to you. You should receive it some 10 dB
better as you did. This is probably caused by local QRM.
What is the gain of your amp stage?
And what is the Q of the antenna's LC circuit?
BTW this small antenna is good to find a quiet place in the local
region and help to find the location of local QRM sources. So once one
has found the quietest place in the garden, a bigger loop may be
instelled there...
I have some problems with the dynamic range of my soundcard which is
120 dB in 1 Hz. Not bad but DCF39 comes in at up to 97 dB and if i want
to stay 15 dB above the soundcards noise (in the passband) it becomes
critical.
I saw that there are big differences between different capacitor types.
Replacing a standard foil cap by a styroflex cap increased the Q from
130 to 480! I took a cheap variable cap (100 pF) with a foil
dielectricum to resonate the antenna and saw that Q decreases with
increasing C of this small cap. The styroflex type is 2.2 nF. Then i
found a 47 pF silver plated varable cap with air dielectricum which
even has a 6mm axis. Now i think about using this cap and some switches
and fixed caps (47 pF, 100 pF, 220 pF) for resonating...
About the winding on my antenna: I stopped optimising after getting
that Q of 486 at 55 turns but actually it could be useful to further
increase the number of turns as long as the Q doesn't decrease to much.
Have to do some tests with various C values and see how the Q changes
as a function of frequency. More turns would result in a higher output
voltage. Furthermore i would get a wider range of frequency variation
by that small 47 pF varicap. The current Z of my LC circuit is just
about 500 Ohm...
Will you further optimise your system and try to receive some DX
signals with it or was it just a test? :-)
73, Stefan/DK7FC
Am 19.08.2011 10:02, schrieb Daniele Tincani:
Sorry, now I understand that a PDF of the ARRL article
was looked for.
My apologies for having sent not the desired link.
Regards
Daniele
From:
Daniele Tincani <[email protected]>
To:
"[email protected]" <[email protected]>
Sent: Friday, August
19, 2011 9:53 AM
Subject: Re: LF:
Ferrite Receive Antennas
Hi Stefan, LF,
here it is:
Regards
Daniele
From:
Stefan Schäfer <[email protected]>
To:
[email protected]
Sent: Friday, August
19, 2011 12:49 AM
Subject: Re: LF:
Ferrite Receive Antennas
Can we get a link to a pdf about this article?
73, Stefan/DK7FC
Am 19.08.2011 00:06, schrieb Brenda Hayes:
> At 02:27 a.m. 19/08/2011, you wrote:
>> Hello LFers,
>>
>> Take a look at the article on page 45 of the ARRL Antenna
Compendium Volume 6 about a
>> very interesting receive antenna for 160 and 80 meters. LF
usage should be possible with
>> some component value changes.
>>
>> 73, J.B., VE3EAR
>>
>> LowFER Beacon "EAR"
>> 188.830 kHz. QRSS30
>> EN93dr
>
> Also see QEX March/April 2000, page 20 - "A Giant LF Loopstick"
by Richard Q.Marris, G2BZQ.
>
> 73, Kevin, ZL4MD
>
>
>
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