Hello Markus, |
Thanks. This is helpful for many people trying to improve their RX
equipment. A QRPP beacon!
Don't we have a nice hobby?!! :-)
PS: Tomorrow ordering parts for a stereo MF RX!
Am 24.06.2015 21:07, schrieb Markus Vester:
this is a single turn loop, around
3.5 m wide and 3 m high, now consisting of the braid of a piece of
RG-216 coax cable. Required capacitance for 475 kHz is 7.1 nF, made
from five 33nF FKP capacitors from the junk box, plus a couple of
styroflex for fine tuning. It's fed through a small ferrite toroid,
32 turns primary, 4 secondary. Loop resistance at MF is about 0.57 ohm
(Q~83), presumably largely affected by losses from the nearfield
environment (reinforced walls, house wiring, etc). Using 35 W RF the
loop current is 7.8 A. Some pics of
the former LF loop tests (32 A, 250 uW) are at http://df6nm.bplaced.net/LF/Indoor_Loop/ .
The purpose of this experiment
is mainly to be able to provide a signal for receiver testing, which
(unlike my Marconi) can be left on air during unfavourable weather. But
it's really inefficient: An old ENI broadband linear amplifier
converts 140 W DC into 35 W of RF, of which only ~ 2 mW are radiated.
Yes it works also for WSPR -
a couple of nights ago I did get spotted by DK7FC, F59706 and SP5XSB.
During the daytime the range would be much shorter, and the signal is
definitely too weak for a decode in Heidelberg.
Sent: Wednesday, June 24, 2015 7:30 PM
Subject: Re: LF: 476.181 kHz from indoor loop
very interesting for WSPR tests !
- mono-turn or multi-turn ??
- what are you using for match to TX ???
many thanks and
73 de Mauro IK1WVQ
At 12:11 24/06/2015, Markus Vester wrote:
>I am currently running a DFCW-60 beacon on 476.181 kHz, using the
>same 10m^2 indoor transmit loop as previously on LF. With 35 Watts
>of RF input, estimated radiated power is around 2 mW, with lobes
>pointing west and east.
>The daytime groundwave signal is visible in the bottom panel of the
>DK7FC MF grabber. Going by the CCIR plots for 3 mS/m conductivity,
>the groundwave attenuation for this distance would be about 23 dB
>excess off lossless 1/r propagation, resulting in approximately 0.2
>uV/m in Heidelberg.