My Week in Radio
- ARRL RTTY RoundUp
- Testing and repairing a piece of coax
- no damage in the middle
- NanoVNA, Smith chart, compared ends
- one side showed along spiral
- other end
- compared to a working cable
Questions
- KC3OOK, Bill:
- For lifepo4 batteries, what’s the proper way to charge and discharge?
- W3QP, Tim:
- depends how often you use the battery.
- for storage, 50% capacity is good
- otherwise charge it up full.
- don’t keep it full all of the time.
- not much of an issue, though
- W3MOW, MIKE:
- researching electric vehicles.
- whatever you do to treat it better will just prolong battery life a bit
- there will be better replacements in a couple years.
- KC3WWC, John:
- I’m using my 71-foot random wire with a 9:1 unun.
- I can give it 5W on many bands without the tuner.
- It’s working, so not all loss.
- Checked it at with the NanoVNA at different points and it stayed pretty low.
- Disconnecting the wire definitely ruined SWR, proving to me that power is getting out into the wire, besides it otherwise working.
- What am i seeing?
- W3QP, Tim:
- SWR is great for a rough indicator for reflected energy
- reactance is more important for efficiency
- losses can mislead you with SWR
- any piece of wire will resonate at different harmonnics
- had a shorter wire was resonant at some harmonics that happened to work
- KC3SQI, Wayne:
- with a random wire, the balun takes SWR of the antenna and reduces it by a factor of 10.
- Tuner can offer extra protection for the radio
- a random wire antenna is to be a bit off and close enough for most radios
- he uses his random wire 71-foot random wire he uses for POTA, but barely needs the tuner.
- NA3CW, Chuck:
- every SWR meter is measuring voltage, current, and time.
- ratio of voltage and current = resistance
- a resonant antenna can have a high SWR because it’s feed impedence is not matched.
- measuring voltage, current, reactance.
- meters can be calibrated for other impedences, not just 50ohm.
- SWR compares voltage, current, phase (time) with internal 50ohm reference.
- watch amplitude of voltage and current on scope, and see it out of phase.
- can have a low SWR on non-resonant antenna
- can have high SWR on resonant antenna
- longer pieces of wire can have more resonances
- resonances may or may not fall in useful places.
- low SWR does not mean efficient. could be losses.
- all lengths of wire will have certain resonances.
- everyone went with 50ohms as a standard.
- TV coax is 75 ohms.
- transformers get it close to what the radio wants.
- I’m using my 71-foot random wire with a 9:1 unun.
- KV3JGB, Matt:
- He has a Vibroplex, single lever, usually thumb is dit, finger is dah, but he’s reversed the dits and dahs for comfort.
- Does it matter if he works reversed?
- AF3Z, Jim:
- probably doesn’t matter
- he learned left handed first then right
- WA3KFT, John:
- read about telegraph keys and bugs (semi-automatic keys)
- Vibroplex made a mechanical key that’s left-handed
- AB3AP, Mike:
- left-handed bugs are more expensive
- KC3WWC, John:
- I key left-handed, and I’ll have to reconfigure anyone else’s radio, or flip the key.
- I just flipped the key to reverse it, and was able to adjust with a moment of practice.
- KD3AIS, Tim:
- Who would you suggest to help install an antenna on the chimney?
- KV3JGB, Matt:
- lots of people are willing to help
- antenna launch parties
- Matt would help
- KC3WWC, John:
- try compromised installations for some more independent capabilities
- NA3CW, Chuck:
- come to a breakfast
- let’s talk about your intentions, site, etc.