Right, so this is the situation: I still haven’t obtained my license here in Brazil, but I already have a Baofeng DR-1801 HT that can connect to dmr networks. Therefore I haven’t transmitted yet. But I’d like to clarify some doubts:
- When I get my license, even in C-class in Brazil, I will be allowed access to some frequencies in 40-10m bands. Should I get a low power QRP transceiver (e.g. uSDX) or go for an used rig from known brands?
- It’s almost impossible to find a transceiver project with a power rating greater than 10w. What would be the difficulty of, say, copylefting the schematics of an ft-7b?
- Can I really use a wire thrown over my house (of course, with baluns and stuff) as a monopole antenna or that’s just myth?
Hard to recommend, because it will depend on preferences. I went with a QRP Icom IC-705 because I knew I wanted to go hiking and do POTA with it. I will say that 10W can feel very limiting, and it can be tough to make the same contacts that others can easily hit. If down the line you want a stronger transmitter, you’d need to get an amplifier. The overall cost of QRP rig + amp might be more than a “base station” type model with higher xmit power out of the box. Again it all depends on your preferences. At the very least, I’d recommend something with good voice and digital mode performance. Plugging right into WSJT-X or JS8Call for digital is super fun, and I like it a lot more than talking to folks.
Never done a build project for xceiver, so I couldn’t say. All those 10W systems can always be amplified for more output.
That’s called a random wire antenna. It’s what I currently use when taking my rig out on the go. It consists of an antenna line and a counterpoise joined by a 9:1 unun (not balun). Keep it away from other metal parts like roof gutters or fences. The wire length isn’t actually “random”, but you can find tables online where people test for a length that gets ok SWR on several bands. You will still need an impedence matcher (aka “antenna tuner”) to actually get a usable SWR.
SWR is Standing Wave Ratio?
Yes, it’s the ratio of how much of the power that you transmit is reflected back towards your rig due to impedence mismatch of antenna <-> radio.
Ideally you want SWR < 2, but for simple voice modes at QRP power, it’s not the end of the world if you end up in the 2-3 range. However digital modes need a good SWR because they transmit at 100% duty cycle. If I don’t get SWR < 2 for my IC-705 during a digital transmit, the reflected power causes my computer’s USB port to reset. At higher powers it could damage my rig or my computer, so it’s definitely a thing to avoid.