Se sitten kannattaa tosiaan kokeilla eikä vain uskoa olevan hyvä koska
tuossakin Maunon lainaamassa jutussa kuitenkin vain puhutaan toimivuudesta
amatöörialueilla ei keskiaalloilla.
Amatöörit harvemmin kokeilevat MW:llä lukuunottamatta meikäläisen
kaltaisia jota amatööriliikennöinti ei kiinnosta lainkaan.....
Suuri osa hakkurien tuottamista häiriöistä on sijoittunut kokeiluissani
alle 1 MHz taajuuksille joten vaimennus siellä on erityisen tarpeellista.
73,s IJL
Joko kokeilitte sitä Fair-Rite 31-tyyppiä, jota täällä kehutaan:
<http://www.audiosystemsgroup.com/RFI-Ham.pdf>http://www.audiosystemsgroup.com/RFI-Ham.pdf
New #31 Material is a Problem Solver The relatively new #31 material made
by Fair-Rite Products
is extremely useful, especially if some component of your problem is
below 5 MHz. Measured
data for the new material is displayed in Figs 18a and 18b. Compare it
with Figs 19a and 19b,
which are corresponding plots for the older #43 material. By comparison,
#31 provides nearly 7
dB greater choking impedance at 2 MHz, and at least 3 dB more on 80
meters. At 10 MHz and
above, the two materials are nearly equivalent, with #43 being about 1 dB
better. If your goal is
suppression or a feedline choke (a so-called current balun), the #31
material is the best all round
performer to cover all HF bands, and is clearly the weapon of choice at 5
MHz and below. Between
5 MHz and 20 MHz, #43 has a slight edge (about 1 dB), and above 20 MHz
they're equivalent.
We'll discuss baluns in detail in Chapter 6.
The new #31 material is useful because it exhibits both of the resonances
in our equivalent circuit
that is, the dimensional resonance of the core, and the resonance of
the choke with the lossy
permeability of the core material. Below 10 MHz, these two resonances
combine (in much the
manner of a stagger-tuned IF) to provide significantly greater
suppression bandwidth (roughly one
octave, or one additional harmonically related ham band). The result is
that a single choke on #31
can be made to provide very good suppression over about 8:1 frequency
span, as compared to 4:1
for #43. As we will learn later, #31 also has somewhat better temperature
characteristics at HF.
12.12.2011 13:53, Roland Sandberg kirjoitti:
Tämmöinen palaute tuli TJ:ltä Ruotsissa- tosi aktiivinen kuuntelija ja
ferriittitestaaja ( mutta kaveri on totta kai Pietarsaaresta kotoisin)
joka taas todistaa että 3H2 on tosi hyvä ferriitti..
"Stort tack för 3H2 ferriterna. Har gjort några korta tester med Perseus
S-meter. It´s a keeper! Jag jämförde med en stackad BN-73 och kunde
genast notera en något höjd signalstyrka, mest märkbar på det lägre mw-bandet".
73'
RS
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http://www.hard-core-dx.com/redirect2.php?id=wrth2011
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