I decided to measure the impedances in a typical #hamradio #antenna setup with an unmatched antenna, here simulated by a 270R resistor.

At 3.5MHz, the feeder (25m H155) transforms this to 30+j51 ohms. Using the #nanovna_v2, I adjusted the tuner to a 50 ohm match at the tuner input.
Terminating the tuner input with 50 ohm, I removed the feeder and measured into the tuner output. I got (almost) the exact conjugate: 33-j53 ohm 👍🏼🙂
So the tuner presents a capacitive conjugate to match the inductive part of the impedance presented by the feeder.

That’s all there is to it: the antenna tuner doesn’t ’tune the antenna’, it creates a decent match to the transceiver while presenting a complex-conjugate to whichever impedance is presented by the end of the feeder, thereby securing maximum power transfer 🙂

#testandmeasurement #antennatuner #antennabuilding #hamr #mfjenterprises #rohdeschwarz

A manual #antennatuner opens up for a lot of fun 🤩

With a VNA you can watch real-time what happens when you adjust the inductance and capacitor dials, gradually closing in on the desired 50ohm.

Did you notice something funny as I just did? I’m sweeping from 6.9-7.1MHz and initially the 270ohm load impedance shows up as a single dot when the tuner is in ‘bypass’ mode.
Once I switch the tuner to ‘inline’, I get a small line instead. This is the frequency response of the matching network (a T-section) inside the tuner itself.

Had this been a real antenna with its own frequency response, and not just a 270 ohm resistor, the final bandwidth of the system would have been a combination of the antennna and the matching network.

#hamradio #testandmeasurement #hamr #mfj #nanovna #rfengineer

Servicing my homebrew #AntennaTuner. Tunes a 6" nail on all the HF bands, most probably up to 2kW. #AmateurRadio #hamr #HF #CW #QRO
[03/01/2020]

It didn't work.

Tested extended control cable with radio outside: worked.

Moved inside with ~65 ft control cable: worked for a bit, then quit.

Switched to better coax: works again.

Either some signaling thing, or I'm jostling wires just right when fiddling with this stuff.

#ah4 #antennaTuner #troubleshooting #hamradio

Since #MCH2022 is coming up I got myself a new toy. Looking forward to testing it. #HamRadio #AntennaTuner

Balloon Antenna Doesn’t Need a Tower

What do you do with floral wire and balloons from Dollar Tree? If you are [Ham Radio Crash Course], you make a ham radio antenna. Floral wire is conductive, and using one piece as a literal sky hook and the other as a ground wire, it should do something. He did use, as you might expect, a tuner to match the random wire length.

The first attempt had too few balloons and too much wind. He eventually switched to a non-dollar store helium tank. That balloon inflates to about 36 inches and appears to have plenty of lift. It looks like by the end he was using two of them.

One of the difficulties with the wind was that the line kept tangling on other antennas. But if you really wanted to use a balloon antenna, we'd guess you don't already have some large antennas in the way. We do hope, though, that the utility lines you can see behind the yard are further away then they look. Tangling in those would be detrimental to your health and your radio.

It looks like the antenna did a good job, although using PSK31 can cover a multitude of sins since you don't need a lot of signal to make contacts with that mode.

We've seen emergency antennas lofted by kites and balloons, especially for the military. Not the first time one of those helium canisters has shown up, either.

400

#radiohacks #antenna #antennatuner #balloon #bpsk31 #hamradio #psk31 #radio