donderdag 27 november 2014

Inverted Vee repaired

300 ohm ribbon repaired
Today I repaired my inverted V antenna after a long time.
He is flying high again.
Before placing a new pole, I repaired the 300 ohm ribbon.
I smelled solder smoke for the first time in months.
The wear and tear on the roof had damaged one of the wires of the ribbon.

I glad I am in time for the CQ WW DX CW of this weekend

Doorvoer bij het dakraampje op zolder

zaterdag 22 november 2014

Measurement of attenuattion

At the top of the Blog, I have changed my Page List by adding a page on
(Click) measuring the attenuation of an attenuator.

After building an attenuator, the attenuation can be easily and accurately measured with a DC voltage.  Voltages can meausred accurately with a digital voltmeter.

Measure the attenuation with a DC voltage

Example calculation
V1 is adusted to to 3.2 V.
V2 is measured as 0.99 V
A (dB) = 20 * log (V2 / V1) = 20 * log ( 0.99 / 3.2)
A (dB) = 20 * log (0.309) = 20 * 0.5095 = -10.19 dB
These values were measured for a 10 dB attenuator.

zaterdag 8 november 2014

10m WSPR - 5 watts from M0DEV

Mark M0DEV uses WSPR with 5 watts.
Today he made more than 400 spots on 10 m.
I noticed this since Mark left a note on the Blog of Roger G3XBM.

Mark notes:
Interesting. I am running 5 W (it's as low as my rig will go) and our two 3 hourly plots on wspr are all but identical. Neither of us has made any headway with the west side of the states.
The conclusion I draw is that when the band is open, it's open, and when it is shut it is shut: 
there is no point trying to blast it open with QRO.

The analysis below shows the calculated lowest possible power.
The lowest possible power is calculated from the power sent and the SNR.
The better the SNR, the lower the lowest possible power, the better the propagation.

The analysis shows that the propagation was good this day and confirms Marks statement that QRO is not needed.
Please notice that even with 100 mW, Marks signal would be heard over a large distance.