Hi Daniele,
I felt real guilty.. and added a reference to the author’s site on my
webpage.
73’s Minto pa3bca
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Ceterum
censeo Carthaginem delendam esse
Sent: Sunday, August 14, 2011 21:54
Subject: Re: LF: Re: 137 grabbers
Don't worry Minto, this circuits
was re-published a number of times on the web :-)
Anyway, I agree that a reference
to the original article may give a more complete background and might be helpful
to the reader.
Best 73
Daniele
From: Minto Witteveen
<[email protected]>
To:
[email protected]
Sent: Sunday, August 14, 2011 9:18
PM
Subject: LF: Re: 137
grabbers
Hi Daniele,
Yup that’s the one. My shameless theft is exposed
J
I see
that the only thing _I_ did was re-draw the schematics (I use Kicad).
Of
course I should have acknowledged the original author on my webpage – will do
that next time I update my website.
Regards,
Minto pa3bca.
Sent: Sunday, August 14, 2011 19:51
Subject: Re: LF: Re: 137 grabbers
Minto,
this is the M0AYF page I referred to:
May be you "stole" the original schematics from there?
:-)
Best regards
Daniele
From:
Minto Witteveen <[email protected]>
To:
[email protected]
Sent: Sunday, August 14, 2011 7:33
PM
Subject: LF: Re: 137
grabbers
Stefan, LF
Not my own design, I don’t remember exactly where I
got it but I am pretty sure I stole the idea ‘from the Internet’ and possible
made some changes. The bc337 was used as I have a lot of them lying around, and
they are much better than for instance the bc547 (my other jellybean
transistor).
The reason I used a -43 type toroid is because I built it for
use on 500 KHz and up. Especially for 80 and 40 meters.
Type-43 is better here than Type-77. On HF this loop is _much, much_ better than
my end-fed TX wire in terms of S/N. The wire picks up a lot of noise from the
house (and from my neighbors houses). The loop is placed to null- out this QRM
as much as possible.
Above 10 MHz the gain drops off rapidly, it is nearly
useless at 14 MHz. a -77 type would be much worse there I think.
As for the
Q: I did a comparison between an FT50-43 and a 14 mm 4C6 (for my 137 KHz
low-pass filter, see my website). The Q of the FT50-43 coil was abt 50, the 4C6
– with a lower Al - was 140 !! Needed more turns ofcourse. On the other hand the
Q of this toroid is not very important here as it is used as a broad-band
transformer.
This is only my hobby… Originally I am a Civil
Engineer (but my job now is in IT).
73’s Minto pa3bca
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Ceterum
censeo Carthaginem delendam esse
Sent: Sunday, August 14, 2011 19:03
Subject: Re: LF: Re: 137 grabbers
This looks like a very good design. Fascinating
easy!! Is it completely grown in your head or have you seen it somewhere in the
web? What is the gain, about? I know the BC337 as a low noise NPN
transistor. Your loop is 2m diameter? How many dBs is the background noise
abovethe soundcard noise? Another question: Why are the T37-43 (the 43
types in general) preferred to the 77 types? The 77 types have a higher AL value
and should come out with less turns. I tried to wind a band pass coil with but
of the types (T50-43 and T50-77) and achieved about the same Q. Is it just a
question of an available distributor? And what is your job? Do you have
to design electrical circuits? ;-) 73, Stefan/DK7FC Am
14.08.2011 18:07, schrieb Minto Witteveen:
Sent: Sunday, August 14, 2011 18:03
Subject: Re: LF: 137 grabbers
Mal, LF,
I am now using a single-turn loop in the backyard (hight abt 2 meters)
instead of the miniwhip.
One of these days I will test again with the
miniwhip. First impression (testing the noise against DCF39) was that they
dont differ very much.
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Ceterum
censeo Carthaginem delendam esse
Sent: Sunday, August 14, 2011 17:51
Subject: LF: 137 grabbers
LF
My signal seems consistant on the PA3PCA grabber but
varies a lot on the DK7FC grabber, sometimes stronger on this grabber and
others like now barely visible. Could it be the type of antenna in use ie one
is more prone to noise es qsb than the other?
de
mal/g3kev
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