One month in 10GHz

Last weekend I completed my first month in 10 GHz, and now it's time to put all the experiences together trying to get some conclusions.

The hardware

The hardware seems to works nicely taking into accounts its limitations. The local oscillator seems to do its work, but it takes a long time to stabilize, maybe 30 minutes or more, so in most of the QSO it is slowly drifting down in frequency, making necessary to readjust the dial frequency every few seconds.

After an hour or two, it seems to stabilize, but each time I power it on, it seems to stabilize on a different frequency, so I'm never sure on what frequency actually I am operating.

The parabolic dish is a prime focus 60cm refurbished TVRO satellite antenna for 11-12GHz. It has a circular illuminator with WR75 output. The de-polarizer dielectric plate was removed to keep the linear polarization. The WR75 to coaxial transition is a home made one I brought on eBay some time ago. A bit ugly but seems to work nicely. For some contacts I used also a 17dBi horn antenna with a WR90 transition that worked pretty well too.

The Eyal Gal module does its job. It has a good receiver and transmitter outputs a watt in round numbers. When it is cold power is nearly 1.2 watts but it drops down to 900mW if it gets too hot. I was able to get 1.8 watts, but SSB quality was not good. To get reliable operation (and prevent damage), do not exceed 1W output.

The first QSO

The first try was on April 5, with EA1AWV/p, distant 299km with an ugly profile:

After several tries, nothing was heard at both sides.

An hour later I tried with EA4BGH/p, having this profile:

After several tries, we were able to find each other and a contact was made. I noticed two things in this contact. First, the 60cm dish is VERY directive. The smaller movement and the signal was lost completely. Second, EA4BGH's voice had a clearly audible distortion. My first thought was the TCXO, but later some hams with microwaves experience told me that distortion was caused by rain scatter. Apparently the contact was made by reflection on distant rain rain clouds. It was indeed possible: That day a lot of rain and heavy clouds were all around Spain.

QSO with EA4BGH/p via rain scatter

Looking for a beacon

Fortunately, the 10GHz group of Madrid was preparing a new beacon in 10 GHz, ED4YAE, and on April 17, it was powered on from a temporal location in IN80BN with 1 watt and omnidirectional antenna. I tried to receive it from my house, IN80CI, surrounded by buildings, but I was not able to hear it:

So, I took the transverter, a battery and the 17dBi horn antenna and moved to a more convenient location, with similar profile, but without buildings around:

I was able to hear the beacon, but very very weak, just at noise level. Trying to get a better signal, I moved to a high location in IN80DE, having now this profile:

The signal was somewhat stronger, but still a very weak signal.

Testing the new beacon location.

The next day (April 18) the beacon was moved to its definite location, in IN70WR at 1549 meters asl. To test the new beacon location, I went to the same place I was the day before, in IN80DE, distant 70km from the beacon. The profile this time was much very promising:

It was indeed. The beacon was received with very strong solid signal.

As a bonus, I was able to contact with Andrés EB4FJV, in IN80CP, who had the parabolic dish installed in his window, having this profile:

Signals were somewhat weak, but do not forget Andrés was pointing his dish to the north! I was 180 degrees from where he was beaming! The contact was clearly made via a reflection somewhere.

Later that night, I tried to receive the beacon from my home, from a window, surrounded by buildings. I was able to find the beacon, both with the transverter and 17 dBi horn, transverter and pcb log periodic 2-11GHz antenna and with a simple PLL based LNB. Signals were weak, but perfectly audible, ranging from about 10dB over noise with the pcb log periodic antenna , to nearly 27dB over noise with the 17dBi horn.

Looking from the direction of arriving, I figured out the signal come from the top of the buildings, from the area of the buildings having line of sight with the beacon.

A field day

On April 27 some stations were active on microwaves, including the 10 GHz band, so I went to the same place in IN80DE. I was able to contact again with Andrés EB4FJV/p, now in IN80DQ:

Signals were weak, weaker than the day we contacted from his house beaming at 180 degrees of my direction, but enough to make a QSO.

Some minutes later I was able to contact with Pedro, EA4BM, who was located very very near the 10 GHz beacon (as near as 10 meter away) with the same profile as the beacon:

There is no need to say the contact was easy, with very strong signals both ways.

QSO with EA4BM on 10GHz band

We where also able to contact in the 1.2GHz band, in FM, from walkie to walkie, from rubber duck antenna to rubber duck antenna, over the same 70km path with big signals, in a really remarkable contact, at least for me.

Testing a PLL based LNB

On April 30, Javier EA4AAE received his new PLL based LNB, so we went to the field to test it. We went to a clear location in IN80EJ, with this profile:

Of course, signal was very strong. Javier used an AOR-3000 receiver as IF for the LNB and once we added some attenuation worked fine (LNB conversion gain is huge!). A RTL-based DVB-T dongle worked very well too.

ED4YAE beacon received with PLL based LNB and AOR3000 receiver

In fact, there was no need to point the LNB to the beacon, neither to set the right polarization: wherever you point the LNB at, the beacon was audible.

Breaking a record

Since the beacon was installed, some hams have been breaking the distance record, first EA4EOZ (me) at 70km, then EA3MS at 74km, EA1RJ at 114km... so on May 2nd, we looked for a location far enough, near the beacon's line of sight limit. We choose a place in IM89NS at 153km. It was not the longest distance possible, but access was easy:

We took with us the PLL based LNB, my transverter with the little horn and the dish, but the beacon was received at first try with the bare LNB and a RTL based DVB-T dongle:

ED4YAE with a PLL based LNB from 153km away

Contest day

On May 3th, there was a VHF contest, and this time we went to the north, to IN81DK, trying to get in range with some hams active in 10GHz in the north of Spain. Unfortunately the weather was not good, so almost no portable stations were active on 10 GHz. Fortunately we were able to to run a sked with EA1ZO in IN72GH:

But no signals were heard at any side of the path. We tried to receive the beacon but this profile says it all:

Luis EA4BHG was also portable, and we tried, but:

No need to say no signals were received.

Some time later, I realized the mounting of the dish allow me to point it at high elevations over the horizon, so I pointed it to the sun. It was easy because the dish is a prime focus, so you only need to point the dish until the illuminator's shadow falls exactly at the center of the dish.

To my surprise, I was able to hear the noise produced by the sun. It was not really loud, but it was clearly there, and disappears when pointing the dish somewhere else. Also, I noticed sun's noise is quite different from thermal noise. It is much more "aggressive", not as soft as the thermal noise.

Hearing the sun's noise demonstrates the Eyal Gal have a good ear!

Conclusions

I can not hide my disappointment. The 10GHz band I have known during this month is quite different from the 10GHz band I have been reading about for years. For me, it is clearly an optical band, a totally line of sight band. Why? Because in the center of Spain tropospheric propagation does not exists: After nearly 20 years working on 144MHz band I can count on the fingers of one hand the number of times I have seen real tropo in the center of Spain. All contacts from here are by tropospheric dispersion. Just check Hepburn's tropo maps and check for propagation in the center of Spain. None. Nothing. Ever.

With line of sight contacts, I can see almost anything will do: Even a gunn based doppler transceivers with small dishes or even horns. Signals are very very strong, but if there is no line of sight, expect very very weak signals in short distances, maybe up to 40-50km, or no signal at all. I can see the DX enabler for this band is bad weather, rain. But because nobody has 10GHz at the fixed station, and everybody works 10GHz portable, there are no opportunities: Bad weather equals no portable operation, thus no 10GHz active stations.

Line of sight contacts are a big limitation in a country filled with mountains like Spain. They are limited to about 150km, and there is very very few 10GHz activity, so the chances to have an active station in range are very small. For now I will no invert more money on this band, and I cancelled the 24GHz transverter project. If I get better results during this year, maybe, but only maybe I can change my mind.

Microwaves far from the sea are hard, very hard!

Miguel A. Vallejo, EA4EOZ

Note: All path profiles have been made by http://www.heywhatsthat.com/