HA7TI

27/04/2026

Looking at the ARISS week ahead, there's a STEM contact with Australia on Saturday. US STEM educators can learn about the contact proposal process on Thursday. The week starts with an outage for the Progress 95P mission.

27/04/2026

ARISS radio outage upcoming.

On Monday and Tuesday, the ARISS repeaters will go offline in support of the Progress 95P docking activity.

Check the graphic for specific times.

27/04/2026

If you’ve ever wanted a simple, effective antenna that just works on multiple bands, the EFHW is hard to beat—and the secret behind it is that little box: the 1:49 UNUN. Building one might look like a small DIY project, but it’s actually the key piece that makes the whole system work.

Here’s the idea in plain terms. A half-wave wire, when fed at the end, has a very high impedance—usually in the range of a few thousand ohms. Your radio, on the other hand, expects around 50 ohms. That’s a huge mismatch, and without fixing it, most of your power would just reflect back instead of going into the air. That’s exactly where the 1:49 UNUN comes in—it transforms that high impedance down to something your radio can handle efficiently .

When you build it, you’re essentially creating an autotransformer on a ferrite core. The number of turns matters—a lot—because that’s what sets the transformation ratio. A typical 2-to-14 turn ratio gives you that 49:1 match, which has become the practical standard for EFHW antennas across the HF bands . Get that part right, and you’re already most of the way there.

Another detail people often overlook is that this transformer isn’t just about matching—it also has to handle real RF power. Poor construction, loose windings, or the wrong core material can lead to losses, heating, and even failure under load . That’s why careful winding and solid connections make a real difference in performance.

And here’s something important: the UNUN doesn’t work alone. The EFHW system still needs a return path for current—often through a counterpoise or even the coax shield—and managing that properly helps keep noise down and performance consistent .

In the end, building a 1:49 UNUN isn’t just about assembling parts—it’s about understanding how your antenna, feedline, and radio all work together. Once you see that, it stops being just a project and becomes a solid upgrade to your station.

73 from PY6CJ - João Grisi

25/04/2026

https://www.youtube.com/watch?v=eJ4xS1_amkI

11 likes, 1 comment. "Nulla modern alkatrész – mégis működik! Marconi coherer vevő építése lépésről lépésre”"

25/04/2026

📻 Simple 2-Transistor AM Receiver (MW Band)
This circuit is a simple AM radio receiver operating in the Medium Wave (MW) band. It uses a TRF (Tuned Radio Frequency) design, where the desired station is selected using an LC tuning network (L1 + tuning capacitor).

🔹 The varactor diode (VD1 - BB112), along with RP1, provides electronic tuning. By adjusting RP1, the reverse bias on the varactor changes, varying its capacitance and thus tuning the receiver frequency.

11/04/2026

https://www.ariss.org/upcoming-sstv-events.html
2026-04-09 SSTV Series 31 commemorates several space achievements
The SSTV event should begin shortly after 11:15 UTC on April 10.
The SSTV event should conclude around 13:55 UTC on April 14.
To adjust for Doppler, check out the summary sheet at
ariss-usa.org/ARISS_SSTV/SSTV_Event_437.550_MHz.pdf

10/04/2026

Jelentkezz még most!!! :)
www.mrasz.hu

18/03/2026

For many kids who fall in love with radio, the adventure doesn’t start with an expensive station — it often begins on a small workbench with a handful of spare electronic parts. Old resistors, a few capacitors, maybe a tube or transistor found in a drawer, and suddenly the idea of building a transmitter becomes irresistible. Others discover the same excitement through simple radio kits, carefully following the instructions and soldering each component into place. When that little homemade transmitter finally comes alive and a signal goes out into the air for the first time, something special happens. In that moment, curiosity turns into passion — and that’s where the real magic of radio begins.

73 from PY6CJ - João Grisi

07/02/2026

https://www.youtube.com/watch?v=s_z5MDjvHqg

Februárban csak a kisebb meteorrajok jelentkeznek, átlagosnak tekinthető aktivitással. Vajon a rádiómeteoros rendszereink és ezt fogják igazolni? Élő közvetí...

01/01/2026

https://www.facebook.com/share/p/1BzYG4xE2V/

New Year Resolution.

"Being tuned to same frequency with less qrm"

31/12/2025

Kedves Rádióamatőr és érdeklődő barátaim!
Vidám Szilvesztert és Nagyon Boldog Új Esztendőt kívánok nektek!