[Lf] Re: Further results on monitoring 136.745kHz

[Frank Gentges]

I have several thoughts.  First, I notice that the spectrum of /6 beacon 
has a big zero and then peaks out where the /12 frequency is.  If the 
keying rate were to be cut in about half the zero would be right where 
the /12 signal is.

Second.  Add a capacitor of small value to the oscillator circuit and key 
it with a reed relay.  I can come up with a timer from my junkbox to key 
the realy on and off at a rate of several minutes at each point.  That 
would give a really distinctive pattern to ID our beacon.  Just a clock 
motor on a shaft with a cam and a microswitch to key the relay.

Frank K0BRA


On Sun, 2 Jan 2000, Andre' Kesteloot wrote:

> 
> 
> Alan,
> thanks for your efforts.
> I need to think on how to achieve that shift with the minimal amount of
> problems.  The transmitter on 136.745 is about 70 minutes from my QTH, so I do
> not want to have to go and come back too often the same day :-)
> I shall try and think of a simple mod, then try it at home, and then send it to
> the transmitter site.
> Around what time in the morning did you see those traces of interest?
> 73
> Andre'
> ***************************
> Alan Melia wrote:
> 
> > Hi Andre' , hope you enjoyed the festivities.
> >
> > On the morning Sunday of 2nd Jan 2000, the locals seem to have had a surfeit
> > of TV or have gone to church, because I have the lowest local noise level
> > for some time. I have continued to experiment with long integration time
> > monitoring using Spectrogram. This morning I have a fairly clean plot of the
> > 'daytime' Loran-C lines in the area between 136.7 and 136.8kHz. My surmise
> > is that because I am within about 500 kms of both the German and French
> > Loran-C sites I should get very little diurnal change in signal strength
> > (BIG assumption!) as the signal should be received by ground wave. I can in
> > fact read off the lines and they check against the frequencies measured on
> > my overnight plot that I advised you of earlier.....except that there is
> > distinctly only one line received in the vicinity of 136.745kHz !! My
> > over-night plot showed two lines with one seeming to fade away at dawn. So
> > far so good but I am not really convinced yet!
> >
> > The permanent lines around your beacon frequency showing here read off as
> > follows:-   (Hz only)  734, 739, 741 very weak, 745, 749, 751
> > I guess that they are accurate to about 0.5Hz I have a calibration line on
> > the plot from a synthasised generator which is calibrated against an off-air
> > standard to about 0.2Hz, the rest depends on the linearity of the plot from
> > Spectrogram. At least the lines seem to appear repeatably on my system.
> >
> > In order to get a definite identification, I am suggesting that a frequency
> > shift of between 2 and 4 Hz to the hf, for a period of at least 100 seconds.
> > This would move your beacon into an area between the lines that is
> > relatively clear, as far as I can ascertain. (+3Hz for 2 minutes would
> > probably be ideal with my present parameters)
> >
> > I have copied this to Dave Pick G3YXM for information
> >
> > 73 de Alan G3NYK (ever the optimist!) in JO02PB
> > Alan.Melia at btinternet.com
> 
> 
> 
> 
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