Hi Stefan
We try to spread interest by
publishing information and results in the URE forum, which has a
dedicated area to long waves
But you are right. Active
motivation is the key. You proved it clearly on your Christmast
transmission last winter
Noted. I'll try to do something
when I be grown up ...in ERP :-)
Did you measure the RF current into
your loop? Is the loop vertical or horizontal? What is the height above
ground?
This was a great help to know were was the loop
resonating and tune it correctly
I have installed it permanently in the loop and
have the milliamperimeter down in the shack connected by two wires
The variable capacitor is motorized, so I can
fine tune the loop from the shack. And yes .... tunning is sharp !
But the RF current system is not calibrated. So
I use it as differential indicator
The maximum current I can get in the DC line is
5mA. Don't know which is the relation of the ferrite transformer
I'm using 10 turns as secodary
Capacitors are good QRO ones. All is ready
to "grown up". Life is too short for QRPPPP :-)))
I'm living in the antenna tower. Or better
said, the antenna is on top of a building tower which makes 28th floors
.... about 80m high
As I can not simply hang it from top, the
loop is installed horizontally using as much as possible of the free
terrace area on top
The loop uses 70m RG59 coax cable using
braid+inner shorted at the ends. I use 1 m PVC tube poles on top of
ventilation
chimmenys to support the loop. It is
terminated in a cabinet were I have room enought for the variable
capacitor and future PA
This links to pictures showing the box
And this is the variable capacitor + 800pF
fixed caps + motor speed reducer/controller + Sensing current +
Coupling transformer
I choosed the loop because at this height
from ground, any ground referenced antenna would hardly work (or that's
what I suppose)
It is not easy visible to the neighbours
and not disturbing as a vertical pole or any other top loaded antennas
would be. And highly
resistant to winds. It actually uses five
support poles and the RG59 is not a heavy load
Like it ! :-)
73 de Luis
EA5DOM
Hi Luis,
Am 28.04.2015 10:34, schrieb VIGILANT Luis Fernández:
The closer station is Maxi
EA5CV. But he lacks a good Rx and antenna for MF
As long as the frequency of the RX is stable, it should work well. A
deaf RX can produce good results if the input signal is strong, you
know. For example, if he has a IC706 and a dipole for the 40m band, he
could make a T antenna out of the dipole, with a resonated
tuning/matching. This should provide enough signal strength and prevent
QRM / RX overload due to the spectrum limitation.
Unfortunately there is no
interest at all in the local hams for activities other than DX pileups
in HF
599!
But i think there are good chances to find new stations in EA! You just
need to search them actively. For example: Use the WSPR map, select all
bands and 24h, and see which station is active in EA. Then contact
him/her by qrz.com and ask for a cooperation, generate some motivation
to try something really new and exciting... If you contact such a
station, you know that it is active, it has a internet connection and a
running PC and knows what WSPR is. Then it is more likely to get a
positive feedback. Maybe it's better to focus on stations being active
on the lower bands rather than 10m or so.
I just made the test and found 14 from EA and 2 from CT :-)
If you decide to find one from EA, i will go to find one from CT. I
know it works because i have done it in the past, on LF :-)
and summit activations on 40m
during weekends. Ah! .... and some digital voices modes too
Beeing outside the shack is a good first step! But 40m is the wrong
band ;-)
My best reference is my own Rx
site at 7Km using MiniWhip and Perseus + SDR-Console V2
which provides up to 6 VFOs
sending each the audio stream to a different decoder
The nice side of QRPP is that
any small change worth the efforts. And there is plenty of room for
improving !
Oh yes indeed, i also noted that it is easier to improve the signal by
20 dB if you are starting at 1 mW TX pwr rather than 100 W :-)
Tx running 7/24. Water cooling the 2xBS170 but
it worths !!! ;-)
Yes, a BS170 is a good choice for a 3.3V output and it also has a very
low input capacity. It was my first idea to use a BS170 for the
Raspberry project too. But actually i find that a ICL7667 is a better
choice, even if the output is 4*f, i.e. ~ 1900 kHz for MF.
My 12V 100W PA is using an ICL7667 as the MOSFET driver (2x IRFZ48N),
so you can use your
QRPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP signal and
realise a (power) gain of > 40 dB :-)
Did you measure the RF current into your loop? Is the loop vertical or
horizontal? What is the height above ground?
I recommend to watch the antenna current because at higher power
levels, the C can warm up and detune the loop. The resulting mismatch
will then reduce the power taken from the PA...
Nice hobby :-)
73, Stefan
73 de Luis
EA5DOM
