Sunday, May 28, 2023

Building another YU7EF duoband antenna (4)

  Finally I had some time today to finish this project. Actually I though it would only take a few hours. But after all I was busy most of the day. I made some photos from the progress. I can't tell much since the whole build went well and SWR/Resonance was as expected.

Of course this connection will be covered by rubber seal after the final installation.

After examinating the above photos I saw the second 4m director was not really in line for the SWR test. I really don't know if things would change much if it was. I'm satisfied with the result. SWR/Resonance will change after all when it is mounted at height in the tower of PB7Z. The last photo is the whole antenna disassembled. Longest part is about 1,8m so I can transport it in the car.

This is the second YU7EF duoband I made. I can recommend this build as it is quite easy to make and this antenna works really very well on both 50 and 70 Mhz,

Saturday, May 27, 2023

#6m Argentina & Uruquay worked

Both +11000km distance on VHF. Suddenly incredible propagation. It was over 10 minutes later. Both are new ones on 6m for me. This is the fun of the magic band!

Thursday, May 18, 2023

ES season here I am

  I continued building the YU7EF duoband antenna this morning but things didn't work out like I thought. So, I decided to exchange my experimental multiband halo for my own YU7EF VHF duoband 6m/4m antenna.

The multiband halo is a succesful project which has to be finetuned a little. I had a comparisation with the inverted-V in mind but time didn't allow it and I probabely do that another time. I actually want to rebuild the complete antenna using another kind of wire. Probabely 300 Ohm ladderline. 

On the photo it's me with the halo. 


  Assembling the duoband beam took some time. Mounting in the tower was no problem. Everything went very smooth. So I quickly brought all the tools, ladders and other things into the garage. It was almost dinner time and I wanted to test the antenna quickly. Next time I should check the antenna with an analyzer because the SWR was 1:4 on both 50MHz as 70MHz. Stupid me. After dinner I did the usual checks with the analyzer to see if there was a faulty coax or connector. Of course everything was alright. So I had to bring the tower down for the second time. In the end I found a PL259 connector which had a bit of corrosion on the pin, bad enough. I cleaned it and SWR was back to normal.

I quickly made some QSOs on 4m/6m to test the antenna. It seems to work well. But propagation was not that good this evening.

Tuesday, May 16, 2023

Building another YU7EF duoband antenna (3)

   Slow progress is made. I wish I had this antenna ready before the ES season. But unfortunately it takes time to build and time is a precious thing. I can't help experimenting with this design as well. I had no angle aluminium to mount on the boom to fit the (6m) dipole elements on. So I thought of angled weather resistant plastic. Side effect is that it probabely prevents disturbance from the boom. I really don't know how much and of course I don't know how this plastic behaves over time. I decided to take the risk. The material is also used for cladding on buildings.

Of course this gave me a mechanical challenge. The plastic looks solid but it isn't. The outside is solid 1mm thick plastic but the inside is a kind of foam. When you mount it on the boom with the bolts and nuts, like I did, the long end will move downward along with the pressure of the nuts. I needed to invent something to push it back to a straight position. I used tiny pieces of angled aluminium for that and bend it up a little. It worked out very well so far. I could nicely tune the plastic parts till they were flat with the boom.

When writing this post I just thought about the plastic foam. I think I need to protect the sides with a rubber like coating. I have some liquid gasket material in stock. I think that would be perfect.

Update 18-5-2023

I abandon this experimental plastic dipole mount. I tried it today but it did not work out like I had thought. Searching for angled aluminium thick enough to use now.

Wednesday, May 3, 2023

Building another YU7EF duoband antenna (2)

 Of course another antenne build by me always goes slow. I have to do this in between all my other chores. Unfortunatelty there is always something that happens like a water tap leakage, a faulty switch, a light that suddenly breaks and this weekend we had a leaking kitchen sink. You see, it always happens just when I want to build something. Anyway, some progress has been made. This time with the boom of the antenna. On request I made it extra strong. And because of that I had the possebilty to cut the boom at the center because it needs to be transported of course.

You see, it is still quite cold in the Netherlands. That's why I have my wood stove burning in the garage. The wind comes from the cold north for weeks now and since I'm living at the northern coast you can imagine that we get that coldest air first...

The boom of this antenna is aluminium 30x30mm over 4,15m long. Bernard wants it as strong as possible so I mounted another piece of 30x30mm with a length of 1,85m below the center. I bolted 2 pieces of thick angled aluminium at the center with clamps to mount the antenna in the tower. I probabely need to add weight at the front to get the whole antenna in balance when it is finished. I did that with my own antenna as well.

I have a antenna loving visitor for quite a while every evening. It is a blackbird that sings a beautiful song...probabely not because it is loving the antennas but to impress the blackbird ladies. Enjoy...