Exit Polls of Radio Wave

(Coaxial transmission line attenuation)

Recently, my uplink to the satellite seems to be weak.  When I call the other satelliter, which I’ve been able to contact normally until now, sometimes I don’t even get a “QRZ?” response.
Well, in satellite communication, especially telegraphy, your own signal also serves as a sidetone monitor, so if this is weak or inaudible, you can’t even transmit.
Up until now, I’ve usually been able to pinpoint the cause somewhere, either my myself or someone else, like water in the coaxial connector, or, like the other day, a bad soldering on the N connector contact, but every weekend I’ve been checking here and there little by little, but I just can’t figure out the cause.
And since it’s not good for my mental health to be unable to pinpoint the location, I tried an exit survey for each section. This is shown in the figure below.
I adjusted the output of the IC-7100 to 20W using a pass-through power meter + dummy load directly connected within the dotted line, and measured this as the reference (0dB) by changing the connections one after another.


I knew from the Ham Handbook that came with CQ magazine that the 5D-SFA would have this much attenuation, but in fact the 20m was too much, and 11m would be fine…

Even though I’m using expensive coaxial cable with low loss, it’s a waste to cut it halfway because it’s expensive… (Hey!  What’s the point of the cable?) – this is the contradictory poor mentality. If I cut it down, I can improve by 1dB, right?

And then there’s “one-touch section”. When I made it, I was a little proud that I could switch the beam pattern between the zenith and horizon without a rotator… But it’s not good to lose 1dB in just 50cm.

Even with the coaxial switch, there’s a loss of 0.6dB. This is included so that the 5D-SFA can share the 1200MHz band, which is rarely used outside of contests, so I can connect it directly using something that isn’t necessary for everyday satellite operation.

By restructuring the transmission line as described above, I expect to improve by 2.6dB.   What has dropped from 20W to 6.3W will bounce back to nearly double that, around 11.5W, so don’t hesitate to give it a go this weekend!

(2021.12.13)

→Back to Index