Everything posted by David Chen
-
JS8Call vs FT8 for actually having a conversation — am i missing something
7.078 is right for JS8Call, thats the standard calling freq for that band. the problem is activity is just way lower than FT8, its not even close. you might sit there for 20 minutes and see nothing then suddenly 3 or 4 stations pop up. late afternoon on 40 can be hit or miss depending on where you are — i find evenings after 8 or 9pm local are better when the band opens up more regionally the decode rate thing is normal, JS8 is inherently slower and the signal structure is different so you wont get the same wall of decodes. but when you do connect with someone its a totally different experience. had a 45 minute back and forth with a guy in Montana last winter talking about antenna projects, felt like a real radio conversation. worth sticking with it honestly, just dont expect FT8-level activity
-
coax routing through firewall on my truck — anyone done this cleanly?
yeah the drip loop thing is important, learned that the hard way on my jeep lol. also on the f150 specifically there's a pretty well known spot on the passenger firewall that a lot of people use — if you search the f150 forums (not ham forums, just the truck forums) you'll find pictures of exactly where it is. saved me a ton of time when i did my install. good luck with it, the ftm-400 is a great radio for mobile, display is super easy to read while driving
-
finally getting serious about EME, what am i actually getting into here
okay so 10el yagi on 2m with the 9700 is actually not nothing, you're probably not going to be working random EME but on JT65 with a solid preamp and low feedline loss you can def get contacts during good windows, especially around perigee when the path loss is a bit lower. the math works out to maybe -25 to -27dB on your end which is tight but stations with big arrays will hear you if your noise floor is decent. the tracking question is the real money sink honestly. you need az/el, theres no way around it unless your yagi is on a tripod and youre willing to hand track which some guys actually do for a first contact just to prove the concept. the SPID RAU or RAS setups are popular, ive also seen guys use the Yaesu G-5500 combo which is cheaper but has some backlash issues people complain about. for software basically everyone doing serious EME scheduling is on the ON4KST chat for real-time coordination and using WSJT-X for the actual operating. the moon tracking part, most people use either WXtrack or PstRotator which talks to the rotator controller directly, pstrotator is kind of the standard now i think. dont expect to just fire it up and start making contacts though, the timing synchronization stuff in JT65 is critical and your computer clock needs to be GPS disciplined or at least ntp synced pretty tightly or youll just be confused about why nobody hears you
-
using a pi zero to log WSPR spots automatically — anyone done this?
yeah the relay board thing is a super common headache with the pi. those cheap boards usually have active-low inputs which trips people up constantly — the relay fires when the pin goes LOW not high, so if your GPIO is floating at boot it can trigger randomly. easiest fix honestly is just pull the input pins high with a 10k resistor to 3.3v and then drive them low to activate. or just buy a relay board thats explicitly designed for 3.3v logic, they exist and they're like $3 more. on the wsjtx side there's actually a UDP broadcast wsjtx puts out on port 2237 by default that you can listen to with python. it sends status packets including the current mode, so you can absolutely only log when the mode field says WSPR. there's a library called wsjtx-assistant or something similar, cant remember the exact name but googling wsjtx udp python should get you there pretty fast. i did something close to this for FT8 logging a while back and it works well once you wrap your head around the packet format.
-
finally broke a pileup after like 3 years of failing at it — here's what actually worked for me
so i've been chasing a VP8 for a while now and every time there's a decent DXpedition i just get stomped in the pileup, like completely invisible. running 100w into a G5RV which yeah i know isnt ideal but its what i have. anyway last week there was a VK9 activation and i actually got through and i've been thinking about why it finally worked. the big thing i changed was listening way more carefully to where the DX was actually pulling calls from. i used to just throw my call in whenever i heard him come back to somebody, but now i wait and try to figure out the pattern — like is he working up the split or down, is he favoring certain parts of the band. took me maybe 10-15 minutes of just listening before i even keyed up. also i stopped sending my full callsign every time and started just sending the last two letters when the band was really congested, seemed like it cut through better somehow. also timed my TX to be slightly after the big wall of callers, not right at the start. i read somewhere that the first half second of a pileup burst is basically just noise to the DX station. dont know if thats scientifically true but it felt like it helped. anyone else have techniques that actually work? especially curious if anyone runs QRP and manages to crack these things regularly because i feel like even at 100w im at a disadvantage most of the time