Stefan, LF
I use
the 4C6 cores in my Lowpass filter for 137. I tried the FT50-43, and the 4C6.
The latter needed about 44 windings for 80 uH so it’s AL is 41 nH/T^2. (varies a
bit per core). The AL of an FT50-43 is about 10 times as high. 100 uH is
perfectly doable with a 4C6 core of 14 mm dia.
The Q of the FT types was
around 50, the 4C6 was 140 @ 137 KHz @ 80 uH.
4C6 (originally made by
Philips) is a well-known core type here in PA. The larger types are often used
for HF baluns. I understand that Philips no longer makes them so they are
getting harder to come by.
I bought a bunch of 14mm 4C6 cores at http://www.vandijkenelektronica.nl/ for € 0,50 apiece.
Pot cores are more expensive
but they have the advantage of being adjustable, which is nice if you want to
construct (small) bandfilters…
73’s Minto pa3bca
Minto,
Daniele,
@Daniele: Nice to read you also want to join in on LF! BTW VLF
is not forgotten here, i want to come back in September. But want to have the LF
system ready for the DX season and wat for lower QRN on the Dreamers
Band...
You don't have a licence and cannot TX? Wouldn't it be worth to learn
for a licence for that reason? :-)
And have you done further tests on sferics
and so on your remote VLF QTH? Any news?
Just got re-fascinated by John/F5VLF
about the earth antenna stuff and want to do more experiments on that antenna
again but LF improvements are very time consuming! But i have holidays now :-)))
I am curious how the earth antenna performs as a RX antenna on 137 kHz
(directional pattern and gain and noise). As a TX antenna i will be to lossy i
think and its not worth the effort carrying 100s of kg of batteries on the hill
for doing some CQ calls that are not answered....
@Minto:
Am
14.08.2011 19:33, schrieb Minto Witteveen:
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.
Sure. I just talked
about LF now. I read the -43 type is suitable for 40...400 MHz, at least this is
said in the catalog...
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
!!
Interesting! 140 at which L?
I am searching for ferrite cores to achieve a high Q on LF, in the range of
100...1000uH. Where can i get these cores? At RS? Where do you buy them? They
are usually samller, cheaper and easier to handle than pot cores.
BTW
what do you think about a ferrite RX antenna for LF? Now i'm opening an older
discussion i expect ;-)
73, Stefan/DK7FC
