[today’s run: 7.4 miles]
I ran with the group in Starkville this morning. Then I came home and went up the tower to install new feed line. After that I drove back to Starkville to do a driving lesson with Nephew N.
The running route today was to the rose garden and north farm. I took the loop through the technology office park on the way out, but trimmed that off on the way back. I felt like I ran really well.
After I got home, I worked on finishing up a small project (new capacitors in the spare Delta-44 sound interface box). Then I wrangled up all of the equipment and parts needed for the transmission line replacement project. I’ve been using some cable TV hard-line with a couple of home-brew impedance transformers on the ends. The normal of impedance of TV hard-line is 75 ohms and my radio station stuff needs 50 ohms. Without some kind of transformers or matching, that results in a 1.5:1 SWR which means a bit of reflected power. My hope was that I could get a better match by using some 50 ohm coax. The efficiency of the coax is not as good as hard-line, but it is not bad.
In preparation I got my ham radio dummy load and I switched the transmitter to the dummy. That allowed the streaming to continue even though the local broadcast was very attenuated.
I was going to replace all of the line all the way up to the antenna. I have two “sections”, the lower section goes from the shed, up the tower, to a junction point which is grounded on the tower. The upper section goes from there up to the antenna. I got the lower section in OK. But I determined that the antenna is too high for me to climb. I don’t remember how I put it up there. I think maybe I mounted the antenna on the pole and then mounted the pole. That would explain why I can’t reach the antenna connector point. (I should search back in this blog and see if I left any notes from when I installed it. Maybe I could have reached it on a really good day. But I didn’t have the gumption today.) Fortunately, the upper section is already 50 Ohm cable! All I needed was a connector/adaptor to do UHF to N connector conversion. And I happened to have on in my connector box. So, after a little rest I went back up the tower and got that installed.
I then came down the tower slowly and removed the old hard-line and two other cables that were not being used. I got everything nicely attached to the tower. I got the new feedline routed to the shed.
Then I switched back from the dummy load to the new feedline and ran the transmitter up to normal output power. I did not get my perfect SWR, but it wasn’t bad. And I had some other positive indicators*, so I’m glad I got it done. I think, with the feedline now all 50 ohm, the next thing toward accomplishing perfect SWR is to adjust the antenna. Unforunately, it is way way up on the top of the tower. So that may not happen soon!
I am glad I got that project done.
Late in the afternoon I went back to Starkville in the old truck and had a nice country drive with Nephew N. He is learning to drive. So we went out on the lonely roads and he did a good job. I was somewhat apprehensive that he would goof around. But he was serious and we went slow and everything went just fine. Then we went to the hamburger place and had a great dinner.
It has been a productive day!
*previously my transmitter power out was about 40 watts higher than what the in-line Bird wattmeter was saying. After this work the Bird and the transmitter are much more in agreement. So according to the Bird I am putting out more power now for the same indication at the transmitter.