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12./08/2004 2223z
Hello Ingolf,
Thanks for the infos, indeed,i should
appreciate some additionals
comments if you have some
time...
My system use very old 75 Ohms Andrew ( or something
like that)
coax cable out of order for VHF
activity.( normaly i use it for 80
or
160m dipole!)
Only the braid is used, with a space of 3.5 time
the diameter between
every turn. The spacers are PVC
type, but
without lead ( you test it
in
the µwave oven, it must be cold!).
The number of turns is always even,
for a central pick up to the ground. The tune
capacity must to be a
very good one to keep high Q ( very important). I use
PTFE capacitor or
mica type. The variable capacitor is a little one (
around 150 pF air model with
very good ground contacts). I use a little DC motor
and a gear box to tune
this system from the station ( essential if you want
to have the peace with
your neighbouring, otherwise take the audio to the
maximum, open the window
and tune for max noise... at 2 o'clock in the morning
it's super! :0) )
A little relay switch a additional capacitor to
increase the band.
On the middle of the loop, i put a little second loop
( around 30 cm of diameter),
one turn, connect to a simple coax cable, this loop is
used to tune the RX
equipment to the desired frequency with the transmit generator ( ultra
QRP
of course!), then the tune for max is very easy from
the shack ( and more
sociable!).
At the two end of the loop i put a preamplifier (
not exactly preamplifier, rather
Z translator ) to convert the high Z symmetrical from
the loop to 50 Ohms asymmetric.
I test many configurations (valves, bipolar and MOS)
but at this moment no significant
results...( say you more in the 10 futures years...)
All this thingamajig ( loop, tune system, preamp
,rotator) is at about 1.5 meter AGL.
I must continue the investigations, but XYL ( F6IFR )
find me some other entertainings
during the freetime! (hi!)
To be continued...
Vy 73
Jeff / F6CWN
----- Original Message -----
Sent: Thursday, August 12, 2004 9:28
PM
Subject: LF: Re: Re: RX in OZ
Hi Jeff,
Thanks for your reply
Yes I think I can receive him to but at the moment there is
to much crack from thunder storm her in the array.
I have made the loop out of VE7LS http://www.lwca.org/miscdocs/ve7sl.htm idea,
but with 40 turns 0,5mm in a special way to avoid internal capacity for
the tuning coil, and 2 turns for the RX coil.
I don't have data or picture of my antenna yet but if you
are interested I can produce some specification for you.
Vy 73
Ingolf OZ7QC
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