15 May 2019

Tools for planning 10 GHz "expeditions"


Activity on 10 GHz means portable operations. If you live near some mountains, it is a matter of finding a panoramic spot, clear of vegetation, open to possible correspondants. Besides asking for advice to "who has already been there", technology and Internet help a lot.

Street View on Google Maps allows to survey many places directly from home. You can get an idea of the possible presence of vegetation, parking place, pic-nic table or grass field for stuffing the equipment.

Once you're done you can run a coverage simulation with Radio Mobile online. You'll need some practice in order to get meaningful and reliable maps, but I am sure there are many tutorials to choose from.

Last but not least, the wonderful peakfinder.net website lets you name mountains/peaks surrounding any location of the world: without running a simulation you will know if two remote locations can "see" each other and stand chances for a 10 GHz QSO. This is also useful if someone will operate from home and wants to know if the portable station is visible.

06 May 2019

Just another 10 GHz test transmission

Yesterday I wanted to test again my HB100 signal and the online receiver 30 km away. No dish on either side. This is the result of my WFM signal modulated with a square wave (which generates two parallel traces on the waterfall).

Three beacons and me on 10 GHz.

My transmitting setup.
I did not leave it transmitting for long given its strength on the waterfall and the frequency too close to beacons. Moreover the TX beam was 60 degrees off, at least according to the theoretical/datasheet radiation pattern. 

Simply amazing.


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?