8,85 km on 10 GHz

I've made it! Today 2019-04-13 at 11:20Z my bare HB-100 WFM TX was received with a bare LNB at 8.85 km (5.50 miles) over a pure line-of-sight path. Then I added the parabolic dish on the RX side and the signal became very, very strong. BTW, nobody was aiming the TX side, so the signal could have improved a bit.

The current world record is 204 km (HB-100+dish to LNB+dish) and I am longing for it. :)

The Gunnplexer Cookbook (1981)

The Gunnplexer Cookbook was published in 1981 (and can be found online in PDF form, but I am not sure if it has been relased into the public domain). In 2019 we are playing with HB-100 and low noise SAT-TV LNB's rather than Gunn diodes, but I think that book contains good old wisdom that still applies nowadays. Temperature stabilization, a simple and mechanical way to estimate a frequency at 10 GHz (useful for HB-100 transmitters too) as well as other pearls to enrich one's knowledge of microwave bands.

Have a look at it if you are interested in GHz operations.

Welcome to GPS Week #0

The second GPS Week Number Rollover (do a web search for more info) has just happened. Your GPS device might think it is in 1980, or in 1999. The first symptom would be the long time to acquire a GPS fix. Then a wrong date is shown.

How's yours?

800 metres with HB-100

Since I have discovered that from home I see a parking space 600 m away, I have just completed two tests with HB-100 TX and TV monitor+LNB RX.

At the parking spot the signal was loud and clear with plenty of SNR, so I can go further with this setup.

Then I took a longer route home and I stopped 800 m away on the same direction, and the signal could be received through reflections, but very very weak. Well, the TV monitor instrument is not as sensitive as an RTL-SDR, but there was no clear path between "me" and me.

NB: no dish was used on either side!

While measuring the distance on Google Maps I noticed that if you zoom in on the drawn path the line is black on "clear" and grey when there is an obstacle: helpful!

HB-100 RF polarization

The test at 200 meters distance with HB-100 TX and LNB RX helped me:

• to confirm once again that the 10 GHz signal can travel long distance
• identify which position corresponds to horizontal polarization

Two years ago I could communicate one-way HB-100 to HB-100. I did it again but this time I had an LNB on the receiving end: plenty of signal to try a longer distance. Unfortunately as long as I am alone doing these experiments, it is either 200 m or 8 km.

Then, since the LNB has a known polarity, with no bounces off the room walls I determined (I am 90% confident) the polarization of the radiated 10 GHz signal. The rule is: polarization is given by the position of the line joining the two mounting holes. Incidentally it is rotated 90° with respect to the position of patch antennas.
So, when the longer side of HB-100 is horizontal, you should expect horizontal polarization.

HB-100 vs Voltage

Having built a DFCW modulator for the HB-100 controlling the operating voltage, I could observe that a difference of +130 mV in the supply voltage causes about +200 kHz shift. The higher the voltage, the higher the frequency.

Besides the lack of temperature stabilization, switching voltages affected negatively the resulting RF frequency, causing all sorts of short-term drifts. Most likely I will switch to FM-modulated CW (audio tone over the carrier) once I want to have a real QSO and not just a reception test.

HB-100 vs Temperature

My simple observation of a single HB-100 module is that the frequency increases as temperature decreases. 

I think it has gained 150 kHz while cooling of 15 °C, so -10 kHz/°C. That's just one test of one specimen, YMMV, even MMMV. In any case the temperature should be stabilized as much as possible, at least for short term variations, by adding thermal insulation.

I wonder if the relationship between temperature and frequency is deterministic, therefore either parameter can be inferred if the other is known: frequency-based thermometer, or temperature-based frequency estimation.

There is life on 10 GHz around here

I am really excited: I received HAM signals on 10 GHz!

I needed to add a T-bias to my RTL-SDR box and the longest part was drilling a hole for the pass-through capacitor.

Here's the quick setup on my crowded desk: can you see the LNB and the RTL-SDR?

 

What did I receive, beaming free-hand the LNB out of the window? Three beacons! And two of them were bouncing off the mountains surrounding Torino.  The recording has HB9EI/B ID signal at 147 km while both the LNB and the RTL-SDR were warming up, so it drifts:

Cool! Next days I will try QO-100 satellite, but I need to move everything on the other side of the house.