Impedantie 7.451 MHz crystal

So here it is, The impedance of the cruystal measured with the metrovna:

impedantie kristal
Shown: light blue is the impedance in Ohm, and green is the phase, red is the reflection coefficient. Span is 10 kHz, from -5 kHz to +5 kHz centered at 7.447 kHz.

And here, the crystal is used as a filter, we measure the transmission characteristics:

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Red: reflection loss, Green: phase, Yellow: transmission loss.

Last update: 22-April-2018

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Field day at Maasvlakte

Antenna: 10 meter glasfiber pole with an antenna tuner at the base. Couple of radials. It is an easy solution that always works: 17 QSOs in a 5 hours, conditions were mediocre.

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The weather was just too good to let this opportunity pass by, blue sky beach weather in April, what more do you wish. Here is the log, worked the 40, 20 and 17 meter, heard some Canadians and Americans, but no QSO was established.

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Last update: 20-April-2018

Field day Brouwersdam

Today we (Chris, John, Adri and I) went to Zeeland to check the QRM level near the Ouddorp lighthouse (it was ok), and I wanted to check the performance of a 80m vertical delta loop. Included are some images.

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The 80 meter delta loop consists of 80m of wire, and a 1:4 current balun. It has two functions, it does the common mode rejection from a symmetric antenna to an asymmetric transmission line, and it transforms the 200 Ohm impedance to the 50 Ohm. The measured SWR was around 1.7 at the resonance frequency of 3650 kHz. Still confused? This is what we made:

 

The 1:4 Guanella balun (invented by Gustav Guanella, 1909-1982) was discussed earlier in this blog: link¬†Why this design? I never found an opportunity to test a delta loop in the field,¬† I didn’t have a good antenna for 80 meter, and I never tested my Guanella Balun. A significant advantage is also that the Delta loop only requires one mast rather than two (or even three) required for the dipole.

The radiation pattern of this design is interesting when you put it in NEC, it appears as if all power is radiated upwards and it has a little bit of directivity, so this is an antenna for NVIS (near vertical incidence skywave) activities. During NVIS you stay under the critical frequency which was about 4 MHz during the event.

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Azimuth pattern, the antenna has 7 dB gain apparently, but it changes by frequency (it sweeps over the full 80 meter band here)
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Charge intensity
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Elevation pattern, NEC suggests that most of the power is going upwards

Here is the log of the QSOs we made, all locally (of course because of the time of day and the frequency):

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For DX contacts on 80m you need to be there around sunrise and sun-set.

Last update: 20-April-2018