Re: LF: good night on MF WSPR @G7NKS 1933km @ 50mW erp - winter plans

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Well done Jim. You sound pretty organised this season!

73s

Roger G3XBM

On 25 September 2016 at 08:11, James Cowburn <jim.cowburn@outlook.com> wrote:

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