Very unlikely Luis
I work on efficiency about 1:500 for
the 40x60 ft inv L , a low thin loop , may
be 1:000 or less , at gb4fpr , there was 600 ft in
200x200x200 triangle at 90 feet abv ground ,
that produced a similar signal 25
miles east , as did my home station
The levels over the 200 mile sea path are quite low
, but the loop will make a good ground
to tune the vertical against !
73-G,
Sent: Wednesday, September 30, 2015 1:44 PM
Subject: RE: LF: Re: 23:35 477 EA5DOM de EB3FRN Op8 Deep Search -36
dB1489.0 Hz
Hi Stefan, MF
I have been calculating the loop area with the help of Google
Earth. Not a regular shape but counting on the known
perimeter
and measures it can be estimated as 224
m2
I detect the RF current with this circuit from G4HUP but have
not calibrated it
I don't use the meter and R3, VR1, VR2 and directly wire down
the shack the output from rectifier diode and use an analog
voltmeter. The transformer is made in the same way with a
ferrite clamp over loop wire and 10 turns as secondary
The 2x100R load was using 1/2w resistors and burned out when
using the PA. So changed them to 2x5W resistors
On the volmeter I can get 60V dc when the antenna is tuned
(minimum PA DC current). The 5W resistors still stand !
I'm using 800pF fixed caps and 490pF variable at about mid
value to resonate the loop. Bandwith is sharp but lets me
work
WSPR and Opera. So lets assume 3KHz
Have changed some parameters in Andy's Excel. Sized it down as
a 17m diameter loop to match 224m2 loop area
Power down to 75W which is what I get with PA under
50ohm. Conductor diameter 5mm, not 6mm (great difference)
And it reports 1dBW ERP with 11A and 2904V
Can it be that high ? Probably less due to mismatch in the
feeding transformer
Nice ERP but in the wrong direction, I'm afraid
:(
Hi Luis.
What is the loop RF current and the loop area? Do you
know it?
Is it problematic to match the loop? You just need a C and a ferrite
transformer. If you have such a relatively high perimeter, you probably need
about 1 nF to resonate it? Currents may be in the range of 10A at 100W? A
bandwidth of maybe 3 kHz?
73, Stefan
Am 30.09.2015 11:14, schrieb
VIGILANT Luis Fernández:
Hi MF
Probably not 2mW ERP Stefan ;-)
Have to reconfigure my U3 but really don't know which ERP
I'm getting right now
The PA outputs 60V RMS under 50Ohm load, but the loop is not
an ideal load and I can tune it
to about 80V RMS. When detuned, RMS runs up to >>100V
and PA gets into problems
I tried to get loop performance using Andy G4JNT excel and
this is what I got
Probably many things wrong there
What I use is a 70m perimeter loop made from RG59 coax
(braid and inner shorted on ends) but not a round circle
The resonate cap is very close to what I need to tuneit.
So the "equivalent" round loop diameter should be
21m
Go figure ! :-)
One detail to
mention:
Yesterday, it rained. Not very usual here and still
not tested the loop with this Tx power and with wet
terrace
It seems to me that my signals was better than
before. Could the wet terrace worked as a kind of reflector
or
re-shapped the radiation diagram of the horizontal
loop making it more efficient for Dx ??
The loop is not equidistant from terrace but keeps
about 3 to 4 meter high, and just 1m on the feeding
point
73 de Luis
EA5DOM
Hi Luis,
Ooh, very well! I'm glad that i
received you the first time! Is it really 2 mW ERP?
Oh and BTW it was in
WSPR, the super mode!!!! ;-)
73, Stefan
Am 30.09.2015 00:17,
schrieb VIGILANT Luis Fernández:
Even
with the loop we are on the way ;-)
| 2015-09-29 22:00 |
EA5DOM |
0.475611 |
-27 |
0 |
IM98wn |
0.002 |
DK7FC/P |
JN49ik |
1398 |
27
|
73 de Luis
EA5DOM
Am 28.09.2015 17:02, schrieb VIGILANT Luis Fernández:
[...]
Next in the list is going vertical. Coil and variometer on the
way. Keep tuned ;-)
Oh yes! Do
it!!! :-) Looking forward to a QSO :-)
73,
Stefan
