A horn antenna for 6cm PAL TV

Barry G8AGN and a few others hereabouts are experimenting with little Chinese TV modules & I thought I would have a go too. These are nominally 5.8GHz modules, designed for drone/helicopter use, so very compact & light weight. The transmitter module I’ve bought is rated at 0.6W. There is a useful overlap between the available channels & the 6cm amateur band. Apparently the BATC use “channel 33”, 5.665 GHz for these modules. (More info from the BATC). The transmission bandwidth is about 27MHz wide. I seem to remember the old 625 line broadcast TV channels were 8MHz each? Maybe the modules allow higher definition?

I’ve never tried the 6cm band & I’ve never tried amateur television either.

I took the opportunity to make a horn out of copper sheet. I used a design from  Brian G4NNS’s website. See “Details for feed horns…”.

I used 0.5mm thickness copper sheet & marked it out with a marker pen according to Brian’s template. Then I cut it out using tin snips (metal shears) & bent the pieces on the bench edge, on the vice & with pliers. I found the resulting two pieces a bit fiddly to assemble and they didn’t mate perfectly, so I decided to drill the connecting flaps at strategic points & secured them together with stainless steel screws and dribbled some liquid flux under the flaps.

I “cooked” the whole thing on a hot plate. The plate was turned on full blast (over 300C on my IR thermometer). I fed fluxed solder into & onto the joins & then let it cool. It went reasonably well. I got only one small dribble inside and there are only a couple of cracks between waveguide & horn where the two pieces didn’t quite mate. I doesn’t look as professional as Brian’s effort, but I was quite pleased with it for my first attempt at a horn. It looks like it should do something.

3-April-2018 update: I tried using my biggest soldering iron to fix the holes, but it didn’t work, so I bashed the cracks closed as best I could and then cooked the horn on the hot plate again & soldered over the cracks. At the same time I soldered in an SMA socket with a long protruding pin. The pin is about 12 to 13mm long, so I’ve left it untrimmed. I’ll try it as it is. I removed the temporary screws, so there are a few little holes through the horn now. I hope they won’t matter.

I bought a little box (a Toolstation “moulded enclosure”) which I hope will house the horn & the transmit & receive modules along with a sequencer & a relay in order to make a transceiver which will take the weather. Maybe it could go on the dish? I will need to feed & receive video, audio, DC & PTT. A monitor line would be useful. Remote channel control might be fiddly.

Perhaps the microwaves will pass straight through the plastic case & grommets? We’ll see!

 

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27-March-2018 SHF UKAC

The 2W on 13cm did not get me very far & I failed to hear Jon GM4JTJ & Gordon G8PNN to the north.

On 3cm I only made 4 contacts, made harder by the dish having been blown out of direction. Denis G3UVR is a surprisingly reliable contact over the Pennines. Keith G4ODA was my best DX.

First contact with Peter G3PHO on 3cm

After our usual chat with Peter G3PHO and Joe G3LLV on 2m, (this is the only group where I am known as “young Graham”!), I met up with Peter again to attempt to find a route around the geography using 3cm.

At my end (blue marker), I have the top of Crosspool hill in the way of the direct path, so to the south, well, 160 deg-ish, I am beaming into the houses of Mulehouse Road which are a bit higher up. Further towards Peter (red marker) is the hill above Coal Aston/Dronfield (green marker). We have had several attempts in the past to find a reflection route around these obstacles and failed. This is frustrating as it is only about 14km away.

The direct path looks like this:

At first I tried to access Mow Cop SDR in the personal beacon band. I saw & heard nothing of my own signals. I knew GB3FNY was peaking at 070 deg azimuth, rather than the 067 deg that it should be. So I aimed at 240 deg on the dial for Mow Cop. I believe it should be 237 deg to aim at IO83VC47nl.

Then Peter’s signal showed up on Mow Cop. With a bit of elevation and backing the dish a bit, I found my own signal too, bearing 222 deg on the rotator dial. The signals looked quite wide. Then we realised we could hear ourselves over about a 40deg swing of the dish. This was snow scatter!

Then I noticed I could hear Peter’s signal on my receiver about 20dB over noise. I peaked up on him at 242 deg on the dial (maybe 240 deg true) at about 20-something dB over noise & we completed our first 3cm QSO! The CW had a nice mushy sound. I noticed this on Denis G3UVR’s signals last night, again over the Pennines. It gets some snow up there!

Sweeping the dish through the scatterpoint moved the frequency of the reflection several hundred Hz, so there was quite a doppler shift going on. (All my kit was frequency-locked to the GPSDO).

Using a MiniVNA Tiny (from Mini Radio Solutions) with Ubuntu Linux

First I installed Java  8 (1.8.0-16).  If I remember correctly, I used these instructions.

Typed in a terminal box: java -version yields the information:
      java version “1.8.0_161”
      Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
      Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)

Then I downloaded JAR-file (vnaJ.3.1.19.jar) from the DOWNLOADS VNAJ page, where is says: “For Windows- OS X and Linux-Users downloading the JAR-file is suffcient”; click on the blue “JAR-file” link. There is probably a later version than vnaJ.3.1.19.jar now, so select as appropriate.

I connected the VNA via a USB cable. Its green LED lit up. Double-clicking the vnaJ.3.1.19.jar file icon in its directory executed the application. Selecting Analyser Setup, miniVNA Tiny showed ttyUSB0 had appeared as an Available port. I clicked test, but the ttyUSB0 port failed the test.

I tried executing vnaJ as root using the sudo command. Now the port passed the test.

I asked for help on the Yahoo group analyzer_iw3hev.

Andy Eskelson G0POY helped me out with the permissions. He told me to open a terminal box and type in:

sudo usermod -a -G dialout gray    , “gray” being my username.

After a reboot, I tried vnaJ again. I tried a calibration & it ran fine!

So it looks like I can use my MiniVNA Tiny again.

I might try N1MM contest logger on Linux next.

27-Feb-2018 SHF UKAC

Before the contest, I chatted to Peter G3PHO on 144.175 MHz (microwave talk-back). We hunted around for a reflection point using 3cm and again found none. We didn’t know it, but there may have been a scatterpoint in the snow over the Pennines as we found the next day!

In the contest it was hard going & with the cold snowy weather there were few portable stations out; very wise! I didn’t work any portable stations. The temperature here went down to -6C overnight, the lowest temperature we’ve had this winter.

I had the usual 2W on 13cm. Best DX was probably Keith G4ODA. I did try John G3XDY, but he had no chance of copying my 2W in those conditions. Usually John can just hear me. This time, I could only just hear him.

So 11 contacts:

And on 3cm, I put out the usual 3W into the circular waveguide & horn to the 80cm dish up about 10m agl. Only 4 contacts, but each in a different square:

Nick G3KUX was surprisingly easy copy & he heard me too. Nick was my best DX. It didn’t sound like snow-scatter.

Weather-proof boxes

I’ve found Toolstation provide a range of weather-proof boxes, but they don’t file them very well in their online catalogue, so it is not that easy to find the information.

If you search on “waterproof”, you get a nice range of waterproof coats.

A search of “weatherproof” throws up this “Weatherproof Box IP54 12 x 19 x 30cm” which I used for the 3cm transverter & amplifiers.  I added a strap around the middle to help hold it tightly shut. It gets shaken well in the gales. I also drilled some drain holes in the bottom to release any accumulated condensation. The box has a set of rubber glands on the bottom for feeding cables through. The hinged lid means you are not having to fiddle about with screws in order to get at the contents. I added a bracket under the box so as not to distort the dish (not in the picture).

A search for “moulded enclosure” offers these IP55 boxes. I have one on the main aerial pole housing the 13cm transverter (see banner picture above). There is a useful range of sizes and there are pre-cut holes handy for feeding cables through with grommets for encouraging the rain to stay out. Again, I’ve drilled drain holes in the bottom. The lid screws tend to rust, so I’ve greased mine, but stainless steel screws might be better.

I added one of the smallest IP55s to the lid of the 3cm box in order to cover a hole I made.

I have heard of people pumping dry air into their outdoor boxes to keep the electronics dry, but I haven’t tried this.

Fast Log Entry on Ubuntu 14.04 Linux

FLE is a useful little program written by Bernd DF3CB which I had running on Windows 7, but I wanted it running on Linux. It allows for the creation of an ADI file directly from text typed in.

I downloaded the program from DF3CB’s site into a new directory under .wine

I right-clicked the installation file & selected WINE and the installation ran. I skipped creating a Windows desktop file.

The files installed into:  \.wine\drive_c\Program Files (x86)\FLE

I used sudo nano to create fle.desktop in /usr/share/applications with the contents:

[Desktop Entry]
Name=Fast Log Entry (DF3CB)
Comment=runs FLE on WINE
Exec=wine “FastLogEntry.exe”
Terminal=False
Type=Application
Path=/home/gray/.wine/drive_c/Program Files (x86)/FLE
Icon=/usr/share/icons/fle.png

I didn’t know how to find the icon, so I right-clicked FastLogEntry.exe & ran it under WINE. Then I used the Print Scrn key to capture the screen including the icon displayed on the on the launcher bar.  Using mtpaint, I cropped just that icon & saved it as fle.png

sudo cp fle.png /usr/share/icons

copied it into the icons folder.

I ran fle.desktop from /usr/share/applications by double-clicking on it & then right-clicked the icon in the launcher bar to lock it there.

If there is an easier way to do this, do let me know!

Anyway, FLE runs on WINE on Ubuntu Linux now.