Hello, Petr,
about your loop: I think your 18 turns with size 1,75 x 1,75m are enough. My
portable loop has 24 turns size 0.6 x 0.6m, made from telephone cable
(should have 30 to 40). Is your loop tuned by a good variable capacitor
("steam-radio"-type,hi) and has a sharp maximum at 137KHz? The signal
strength from the loop normally is much lower than from the longwire, but so
is the noise,too. Therefore with the loop you should hear most of the
stations you receive with the longwire, too. I even do that with my small
one. What happens when you disconnect the middle from earth? After realizing
my loop I found out, that the capacity of the loop itself between the turns
was already 800pF. That generates losses. Do you know that capacity in your
loop? Maybe your flat cable will be better than my telephone cable. My loop
is coupled with 2 turns to a lf-converter (SO42P) without preamplifier. It
does a good job, but with low signal strength. Your last question: My
experience is, normally not. But in case of noise problems it sometimes can
be even better than the Marconi.
Hope you find the bug. 73 Walter DJ2LF
-----Ursprüngliche Nachricht-----
Von: Petr Maly <[email protected]>
An: 136 group <[email protected]>
Datum: Montag, 10. Januar 2000 17:50
Betreff: LF: Bad experience with loop ant
Hello LowFers.
I have made loop ant for rx and it seems not to work satisfactorily. Size
is
1.75m x 1.75m. Everything is done as usual, with grounded middle and
amplifier with 2 x BF245, tuned properly, etc. Output level from the
amplifier is high enough. I can hear Greek RTTY, also galloping horses a
little, but no poor HAM sigs. My LW 40m, that is in average height of about
6 m only, is much better. The only thing I am in doubt is the number of
turns. It has got only 18 turns (I used flat cable that was available at
the
moment). Could this be reason for the bad results? What are your
experiencies with loop ant? Can loop ant be as good as "big" Marconi?
73! Petr, OK1FIG
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