29 April 2019

32 km on 10 GHz

Still one-way, but it is quite outstanding: my bare HB100 signal could be received by a bare LNB at 32 km distance with a 13 dB S/N margin. I could increase the signal by adjusting the TX direction, but the RX side is fixed on a remote location (remote SDR receiver).

Also I think that the strong wind was waving some vegetation into the path because the signal would disappear with heavy QSB.

What is even more interesting is that the bare LNB is receiving a 3 cm beacon 300 km away! At least now we know a remote site where we could try a super-HB100-DX!

23 April 2019

Distorted readout on Tektronix 7603

I got to use my Tektronix 7603 analog oscilloscope over the weekend and started worrying.

I usually fire it for few minutes to check a signal and then off it goes for weeks. Not long ago, during longer operation, I heard a "clunk!" and with side-vision I saw the CRT display going blank and then back again.

Last weeks the "Trig'd" lamp on the timebase plug-in broke, but it triggers just fine.

Fast-forward to this weekend... when switching vertical plug-ings left-to-right I noticed the Tek was using a different font for readout:

Wait a moment! That's 1970's hardware, it cannot change font!

I am afraid I need to start troubleshooting from the PSU. This calls for a way to see PSU signals, that means I need another oscilloscope.

And dilemma: keep it or let it go? It will hardly sell as a single piece (to be re-capped, the least). I might sell individual plug-ins, 2x 7A18, 7A13, 7B80 (doesn't sweep), 7B53A. Or keep the beast since I can configure it to provide 4 channels at 100 MHz BW.

13 April 2019

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. :)

10 April 2019

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.

07 April 2019

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?

06 April 2019

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!

03 April 2019

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.