FAQ
TL;DR: In Ostrava, co‑channel k48 suffers because Hladnov transmits at 10 kW while Hošťálkovice uses 100 kW; “Both transmitters broadcast on the same channel and almost from the same direction.” [Elektroda, nomudrek, post #16920568]
Why it matters: This FAQ helps over‑the‑air viewers diagnose why one DVB‑T multiplex breaks up while others look perfect, and what to try.
Quick Facts
- Channels in play: k37 = 602 MHz, k48 = 690 MHz, k54 = 738 MHz. [Elektroda, makar42, post #16919996]
- Site powers noted: Hladnov ~10 kW on k48; Hošťálkovice ~100 kW on k48, same bearing. [Elektroda, nomudrek, post #16920568]
- Lysá hora carries Mux 1 and Mux 2 at ~25 kW from ~1300 m elevation; Mux 3 not from there. [Elektroda, MICHAŁ, post #16928981]
- Real‑world obstacle: the Rydułtowy spoil heap blocked Mux 3; moving ~2 km west restored 100% quality. [Elektroda, makar42, post #16937203]
- Example setup: mesh antenna + AWS‑1031 mast amp (12 V, three UHF inputs, adjustable output). [Elektroda, makar42, post #16920438]
Why is k48 reception weaker than k37 and k54 in Ostrava?
Because two Ostrava sites share k48. Hladnov (10 kW) and Hošťálkovice (100 kW) arrive from nearly the same direction. Their signals can clash, so your tuner locks inconsistently on k48 while k37/k54 remain clean. “Both transmitters broadcast on the same channel and almost from the same direction.” [Elektroda, nomudrek, post #16920568]
Can two same‑channel DVB‑T transmitters cancel each other out?
Yes. Co‑channel signals of similar arrival strength can create self‑interference. When they come from near‑identical bearings, your antenna cannot spatially discriminate, so MER drops and errors rise. As one expert put it, “Both transmitters broadcast on the same channel and almost from the same direction.” [Elektroda, nomudrek, post #16920568]
Could terrain or structures be the real culprit for my Mux 3 issues?
Absolutely. A documented case showed the KWK Rydułtowy spoil heap blocked the Ostrava path. A quick field test 2 km west delivered 100% Mux 3 quality, confirming obstruction. Use terrain profiling to verify your line‑of‑sight. [Elektroda, makar42, post #16937203]
Why are Czech Mux 1 and Mux 2 strong, but Mux 3 is weak or missing?
Mux 1 and Mux 2 can arrive robustly from Lysá hora, which sits around 1300 m. That elevation and takeoff angle extend coverage. Mux 3 is not broadcast from Lysá hora, so you rely on other sites and paths that may be obstructed. [Elektroda, MICHAŁ, post #16928981]
How do I confirm a terrain blockage is causing my reception problem?
Try this: 1. Check the path on a terrain‑profile tool and note obstacles. 2. Test from a nearby location offset by 1–3 km to change the path. 3. Compare Mux quality; a jump to 100% strongly indicates obstruction. [Elektroda, makar42, post #16937203]
Will changing my power supply or gain help DVB‑T stability?
Yes. An adjustable, regulated PSU and proper gain staging prevent overload or under‑drive in mast/indoor amplifiers. If k37/k54 are strong, too much gain can compress the front end and worsen k48. Start by fitting a regulated supply and trimming gain. [Elektroda, LeDy, post #16920307]
Does a higher site with lower ERP beat a nearer, higher‑power site?
It can. Lysá hora’s ~25 kW carries far thanks to its ~1300 m elevation and clear path, often outperforming lower, urban sites for some locations. Elevation and line‑of‑sight can outweigh pure power on UHF. [Elektroda, MICHAŁ, post #16928981]
Could a Polish k48 transmitter be interfering here?
Unlikely in the cited case. The user checked and found no Polish k48 within ~100 km. That points back to Ostrava co‑channel conditions or local terrain as the drivers. [Elektroda, makar42, post #16920851]
What antenna and amplifier setup was used in the thread’s tests?
A mesh antenna with a balun fed an AWS‑1031 multiband amplifier. The amp runs on 12 V, offers three UHF inputs, and has an adjustable output level for balancing muxes. [Elektroda, makar42, post #16920438]
How should I aim the antenna when two Ostrava sites sit on nearly the same bearing?
Fine‑tune azimuth to favor Hošťálkovice on k48 while minimizing Hladnov’s contribution. Small azimuth shifts and antenna pattern nulls can help separate arrivals when bearings are close. Expect iterative tweaks and re‑scans. [Elektroda, nomudrek, post #16920568]
What does “Mux” mean in this discussion?
Here, “Mux 1/2/3” refers to Czech DVB‑T multiplexes—bundles of TV programs carried together on one RF channel. The thread contrasts their sites: Mux 1/2 from Lysá hora, while Mux 3 is not. [Elektroda, MICHAŁ, post #16928981]
What was the final diagnosis and resolution path in the thread?
Terrain was the key factor. A spoil heap blocked the Ostrava path at the original location. Testing 2 km west yielded 100% Mux 3 quality, confirming obstruction and closing the case. [Elektroda, makar42, post #16937203]
