Prop'n seems to be improving.
Iceland and
Finland last night on MF, nearly
2000km on about 50mW ERP.
Roll on the cold dark
nights!
Simple set up @
G7NKS
IC706mk2g via current meter and home
brew 7 pole LPF into coax out some 15m to a tapped loading coil into an inverted
L (12m high on a fibreglass telescopic pole and 30m top wire across
roof)
Earthing via a mish-mash of stakes
& bonding to oil tank feeder pipe (buried) and some steel mesh under patio
slabs and block paved drive.
Checking via the RigExpert AA1000
analyser shows an impedance of 52 ohm and a return loss of -25dB @
474.2khz. For the local IO92 and Newark Sunday morning net with
G3XIZ, M0JXM, G3DXZ, G4GIR occasionally and M0FMT, we use around 473.3khz and
this occassionally warrants a quick tap up or down by half a turn. Also
when it rains like today, there's a tweak needed sometimes as the top wire
capacitance to roof changes as it becomes more electrolytic and less air
spaced!
PC is a Dell Studio 1749
running WSPR 2.12.
The IC706mk2G will run at about 25%
max power on 472 so about 25w but not all of that is at 472 of course, I
estimate I'm getting 50mW ERP using a very helpful spreadsheet/calc provided by
Stefan.
On a 15% duty cycle it all remains
happily cool.
It does have a tendency to fight
with our cheap home broadband router supplied by British Telecom, resulting in
the "Orange Light of Death" and subsequent grief from XYL and 2 teenagers as
their Netflix/Music stream/Online gaming has just fallen over!
Ferrite toroids have been spectacularly unsuccessful in remedying this.
The best solution has been to try to run the CAT5 cables in my office as
perpendicular to the coax feed and line of roof top wire as possible to minimise
pick up and cross talk, but this hasn't really been that effective
either.
A bigger issue on Rx is the
noise pick up from both Dell (genuine kit and not cheap copies
either, which is annoying!) PSUs that feed the Studio and the XPS17 which is my
main office PC. On batteries, I get about S1-3 of noise which is very good, but
as soon as the PSU's are used and are under "load" then this rockets up to
S7-9! If they are powered on, but not driving the laptops i.e.
disconnected, then they have no impact. I'm wondering if it is
the load that makes them noisier or whether the whole laptop acts as an
augmented antenna when they are connected to it?
I've tried putting them in shielded
earthed metal boxes (biscuit tins!) with no effect. (biscuits were nice
though!). Similarly, stacked ferrite toroids on the mains inputs and DC
power out have had zero impact. They both have a very bright blue LED on
the power cable whereas older units for my Dell D610/20 series did not have this
"bauble" and were much quieter, but also were lower rated at 60W or 90W as
opposed to these beasts which are around 120W to 150W, and run alarmingly warm
at times!
The Rx noise doesn't seem to affect
my WSPR reception but it does impact on me hearing G3DXZ (Chas) from Newark on the Sunday Net,
so for that I just run the show on batteries during the Rx overs.
When I get "a round Tuit" I am going
to follow the very detailed instructions from John in the US and feed the
706 into my recently acquired Hafler Transnova 3000 (approx
400w). Cheers John.
While I will unlikely get 400W I
suspect I might get 250W which is 10dB up on my current input power and
hopefully about 500mW ERP and that may be enough to hop the pond.
As for 137KHz and
down…….
The 706 will generate a very weak
signal at 137 probably only around 1mW but if I can get that into the Hafler
then that’s my net project, work and weather permitting. I acquired some
coils from the SK estate of the late great G3ACQ and they will happily resonate
my "L" onto LF.
My other (better) plan is to use the
0dBm output on my Elad FDM Duo and a 1W broadband RF amp off Ebay to give
me 1W output at 137 and feed that into the Hafler, so plenty to
do.
The ELAD will also go down to sub
9Khz on the 0dBm output so I may try to re-start my dreaming experiments and
also try some of Roger G3XBM earth loop electrode
arrangements
The local 472 net nr to IO92ub will
be on air from about 9am local today and most Sundays so feel free to join
in!
Chris G3XIZ is usually "Net
Controller" and "chief documenter".
Best 73s
Jim
Dr. Jim
Cowburn G7NKS IO92ub
