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DVB-T: MUX 2 Issues with RTCN Poznań Śrem Signal - Antenna TELKOM-TELMOR, Possible Interference?

dyspozytor 25104 18
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Why does only MUX-2 from RTCN Poznań-Śrem break up intermittently even though the other multiplexes work fine, and how can I fix it?

MUX-2 is most likely weaker at your antenna position than the other multiplexes, not a decoder fault or proven weather/interference problem; the reported MUX-2 level was about -76 to -78 dBm with SNR 22.2–26.1 dB, while MUX-1/3/8 were around 48–52 dBm with about 33 dB SNR [#16924494][#16924561] A small change in antenna direction or position is the first thing to try, because even a slight horizontal or vertical shift can greatly improve one mux while changing the others [#16924584] The asker later confirmed that re-aiming the antenna to get the best average results across muxes made reception good again [#16924602] If that is not enough, the replies suggested using an antenna with an openable housing so the balun can be replaced by an amplifier, or asking Telmor for an amplifier for that antenna model [#16924570]
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  • #1 16924085
    dyspozytor
    Level 13  
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    My problem is with MUX-2. I am receiving a signal from RTCN Poznań "Śrem". I live within 5 km. Antenna: TELKOM-TELMOR. All other MUXs work fine. On the other hand, periodically on MUX-2 (TVN, Polsat, etc.) the program can not be received. It hangs up, breaks. Mostly in the evening. Sometimes the reception is very good. Surely this is not a decoder issue, because I tried with different ones. Also TV with a built-in decoder.
    Could it be a matter of some disturbance? weather influence?
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  • #2 16924155
    Włodzimierz Wojtiuk
    Level 32  
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    dyspozytor wrote:
    Antenna: TELKOM-TELMOR.

    more specifically?
    ie what exactly and how placed?
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  • #3 16924216
    dyspozytor
    Level 13  
    Posts: 280
    Help: 1
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    Passive terrestrial TV antenna Telmor DIGIT Passive
    - Full HD
    - UHF (channels 21 to 69).
    - Uniform signal amplification in the whole frequency range
    - Profit / effectiveness - 4 dB
    - Strong attenuation of GSM signals thanks to the appropriate shaped characteristics.
    - Good fit (WFS pound: 2.2).
    - Discrimination of back radiation
    I have so much in the description of the antenna
    Antenna in a horizontal position, just like on a photo. It hangs on the 4th floor.
    DVB-T: MUX 2 Issues with RTCN Poznań Śrem Signal - Antenna TELKOM-TELMOR, Possible Interference?
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  • #4 16924281
    Włodzimierz Wojtiuk
    Level 32  
    Posts: 1421
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    dyspozytor wrote:
    Antenna in a horizontal position, just like on a photo. It hangs on the 4th floor.

    I understand that he "sees" the transmitter?
  • #5 16924321
    andpol 33
    Level 39  
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    In the place where the antenna is hanging, the signal is insufficient.
  • #6 16924338
    Włodzimierz Wojtiuk
    Level 32  
    Posts: 1421
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    Rate: 271
    andpol 33 wrote:
    In the place where the antenna is hanging, the signal is insufficient.

    Are you sure? Really?
    dyspozytor wrote:
    I am receiving a signal from RTCN Poznań "Śrem". I live within 5 km.

    because in my opinion it can be too big .

    At the time when the reception gets worse let the author of the thread check his strength and signal quality on the tuner (of course on the right channel).
  • #7 16924363
    andpol 33
    Level 39  
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    I'm not sure because I was not there. The fact that it is 5km to the transmitter does not testify to anything? It is enough to build buildings. I have such a case even in the family. Skyscraper 5th floor, to the transmitter can also from 5 km. From the kitchen side, a beautiful view of the EC4 chimney and from the side of the living room where there is no stable picture antenna. Of course, the apartment after renovation and there is no chance to drag the cable from the kitchen. :cry: I do not know from where such a view that like 5km must already receive it.
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  • #8 16924369
    _kli_
    Level 41  
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    They receive mux-y on low channels 23 and 27, no reception on k.39. It looks like a weak signal.
    So the questions remain
    Włodzimierz Wojtiuk wrote:
    how placed?
    Włodzimierz Wojtiuk wrote:
    "sees" the transmitter?
    Is it mounted outside? What cable and what length? Are the connectors correctly made?
  • #9 16924404
    dyspozytor
    Level 13  
    Posts: 280
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    The antenna sees the transmitter. However, the signal goes along the block. And so I think, is there any interference from neighbors? Cable about 1.5 m. Installation repeatedly checked.

    SNR - 22.2 dB to 26.1 dB
    Signal strength -76,0 dBm to -78 dBm

    At the moment there are such results and the reception is excellent. Unfortunately, I can not give other data, because now everything is ok :-)
  • #10 16924406
    Włodzimierz Wojtiuk
    Level 32  
    Posts: 1421
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    andpol 33 wrote:
    I do not know from where such a view that like 5km must already receive it.

    Where did I write that he must receive?
    If the level is too high, it will also be k..a, and the idea that it is too big only because the Author / Reporter does not report any problems with the rest of the MUX channels / problems ...
    (I have very different {reception in direct visibility of 2 km, 4 km, and shadow for the scar 30 km} experience from the analogue TV period about the transmitter in Chotycze)

    Let us wait for the author to speak.

    Added after 5 [minutes]:

    dyspozytor wrote:
    SNR - 22.2 dB to 26.1 dB
    Signal strength -76,0 dBm to -78 dBm

    It's already a lot (as far as I remember the recommended levels)
    dyspozytor wrote:
    At the moment there are such results and the reception is excellent



    Well, we are waiting for corruption and results.


    I'm sorry because I've been buried too much by other units!
  • #11 16924426
    dyspozytor
    Level 13  
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    On MUX-3 TVP-1 and here it is always ok.

    SNR-33.1 dB
    Signal strength 48.0 dBm

    It looks like the power is much lower, and it's always ok.
  • #12 16924458
    andpol 33
    Level 39  
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    Small force and small SNR. link
  • #13 16924482
    dyspozytor
    Level 13  
    Posts: 280
    Help: 1
    Rate: 89
    On MUX-3 (TVP-1, TVP-2) and here it is always ok.
    SNR-33.1 dB
    Signal strength 48.0 dBm


    However, on MUX-2 (TVN, Polsat, etc.) these are the results now, when everything is OK. I do not know for how long :-)
    SNR - 22.2 dB to 26.1 dB
    Signal strength -76,0 dBm to -78 dBm
  • #14 16924494
    _kli_
    Level 41  
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    dyspozytor wrote:
    Signal strength -76,0 dBm to -78 dBm

    Feebly. A head with very good sensitivity if it is still receiving something. It is only about 31-33 dBuV, with the minimum required 45-47 dBuV (-64 / -62 dBm).
    dyspozytor wrote:
    Signal strength 48.0 dBm
    dyspozytor wrote:
    it's always ok

    Hence, good reception (-48 dBm = 61 dBuV).

    dyspozytor wrote:
    SNR - 22.2 dB to 26.1 dB
    It would be better if it was ? 30 dB - just like you have on mux-3.
  • #15 16924513
    Włodzimierz Wojtiuk
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    andpol 33 wrote:

    Strength small and SNR small.Link

    Thank you!
    I was too much caught in the ganglia of other units from the time of cable TV (dBuV)
    I apologize to everyone for confusion!
  • #16 16924561
    dyspozytor
    Level 13  
    Posts: 280
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    MUX-1
    32.9 dB
    49.0 dBm

    MUX-2
    24.1 dB
    77.1 dBm

    MUX-3
    33.1 dB
    48.0 dBm

    MUX-8
    33.0 dB
    52.0 dBm

    Does this mean that the antenna is weak? Why is it that only the MUX-2 receives so little? Is there any possibility of healing this situation? What can you do in this situation?
  • #17 16924570
    andpol 33
    Level 39  
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    You will not do anything with this antenna. I would suggest you buy an antenna with an openable standard can, so that you can replace the balancer with an amplifier, e.g. link .
    Or ask kol @ Telmor if they have amplifiers for your antenna on sale.
  • #18 16924584
    _kli_
    Level 41  
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    dyspozytor wrote:
    Why is it that only the MUX-2 receives so little?

    Well, sometimes it happens that one mux "sticks out" from the others.
    dyspozytor wrote:
    Is there any possibility of healing this situation? What can you do in this situation?

    Start with a slight change of direction. Often a small shift of the antenna vertically or horizontally causes a dramatic improvement. Experiment by observing mux-2 parameters. It may also be that it will improve and the remaining mux deteriorate.
  • #19 16924602
    dyspozytor
    Level 13  
    Posts: 280
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    Ok. I will try the easiest way. From changing the antenna setting. I will try tomorrow morning.
    For now, Colleagues, thank you.

    Added after 18 [hours] 56 [minutes]:

    I set the antenna so that the results are optimal (averaged in individual MUX). For now it's ok. The reception is great. We'll see what will happen. Thank you Kolegom once again for helpful comments.
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Topic summary

✨ The discussion revolves around issues with receiving MUX-2 signals from RTCN Poznań "Śrem" using a TELKOM-TELMOR antenna. The user experiences intermittent reception problems, particularly in the evening, while other MUXs function correctly. Various responses suggest that the signal strength and quality are insufficient, potentially due to interference from nearby buildings or neighbors. The user confirms that the antenna is correctly positioned and has checked the installation multiple times. Suggestions include adjusting the antenna's direction, considering the installation of an amplifier, and monitoring signal parameters. After experimenting with the antenna's position, the user reports improved reception.
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FAQ

TL;DR: MUX‑2 dropouts here traced to weak level (≈−76 to −78 dBm ≈ 31–33 dBµV); “It would be better if it was ≥30 dB” SNR. [Elektroda, kli, post #16924494]

Why it matters: This FAQ helps Śrem-area viewers fix DVB‑T MUX‑2 freezes on TVN/Polsat with quick checks and proven tweaks.

Quick Facts

Why does only MUX‑2 (TVN/Polsat) break up while others are fine?

Because its received level and SNR are lower than the others. Here, MUX‑2 measured about −76 to −78 dBm (31–33 dBµV) with SNR 22–26 dB, while MUX‑3 showed much stronger figures. Low headroom makes evening fades or reflections cause dropouts. Aim for ≈45–47 dBµV and ~30 dB SNR at the tuner. “It would be better if it was ≥30 dB.” [Elektroda, kli, post #16924494]

How do I quickly fix MUX‑2 dropouts from RTCN Poznań Śrem?

Try micro‑aiming. Small horizontal or vertical tweaks often lift the weakest multiplex without hardware changes. Watch the MUX‑2 parameters live while nudging the antenna. This simple change restored stable reception for the thread’s author after re‑aiming for balanced averages across MUX‑1/2/3/8. [Elektroda, kli, post #16924584]

What antenna and setup was used in this case?

A TELKOM‑TELMOR DIGIT Passive UHF antenna (ch. 21–69), ~4 dB gain, GSM suppression, mounted horizontally on the 4th floor. The run used ~1.5 m of coax, with line‑of‑sight to the Śrem transmitter. These details matter because low‑gain antennas and building edges can reduce a single MUX. [Elektroda, dyspozytor, post #16924216]

How far was the viewer from the Śrem transmitter?

About 5 km. Close distance does not guarantee perfect reception if the antenna is shadowed by the building line or pointed sub‑optimally. Levels and SNR at the tuner still decide stability. [Elektroda, dyspozytor, post #16924085]

Could the signal be too strong at 5 km and still cause issues?

Yes, front‑end overload is an edge case. Very high levels can also break reception, even close to the mast. One expert cautioned that an excessively large level can cause problems indistinguishable from weak‑signal behavior. If symptoms persist with high level, add attenuation. [Elektroda, Włodzimierz Wojtiuk, post #16924338]

When should I consider adding an amplifier or changing antenna?

If micro‑aiming fails and MUX‑2 stays well below ≈45–47 dBµV, consider an antenna that accepts a masthead amplifier in place of the balun. A model like the ASP‑4 with swappable components was suggested, or ask TELKOM‑TELMOR about an amp option for your DIGIT Passive. [Elektroda, andpol 33, post #16924570]

What SNR should I aim for on MUX‑2 to stop freezes?

Target around 30 dB SNR for robust DVB‑T reception. In this case, MUX‑2 showed 22–26 dB during good moments, which left little margin against interference or fading. “It would be better if it was ≥30 dB.” [Elektroda, kli, post #16924494]

How do I convert dBm to dBµV for TV signal checks?

Use the relationship shown by the expert example: −48 dBm corresponds to ~61 dBµV at the tuner input. Minimum stable levels cited were 45–47 dBµV (≈−64 to −62 dBm). Keep your weakest MUX above that floor to avoid glitches. [Elektroda, kli, post #16924494]

Could neighbors or building reflections cause evening-only problems?

Yes. The author noted the signal travels along the block edge, which can introduce reflections and time‑varying multipath. These effects often worsen at night. Improving aim and height relative to the building line reduces reflection paths and stabilizes MUX‑2. [Elektroda, dyspozytor, post #16924404]

What is DVB‑T and what’s a MUX?

DVB‑T is the Digital Video Broadcasting standard for terrestrial TV. A multiplex (MUX) is a single RF channel carrying several TV programs. If one MUX is weak, only its group of channels (e.g., TVN/Polsat on MUX‑2) will glitch while others stay fine. [Elektroda, kli, post #16924584]

Is the TELKOM‑TELMOR DIGIT Passive suitable near Śrem?

It can work, but its ~4 dB gain offers limited margin for a weak MUX. With line‑of‑sight and proper aim, it handled MUX‑1/3/8 well here, but MUX‑2 lagged until re‑aiming. Consider higher‑gain or amp‑ready designs if margin remains low. [Elektroda, dyspozytor, post #16924216]

What’s the three‑step way to re‑aim for the weakest MUX?

  1. Show live MUX‑2 SNR/level on your TV/decoder.
  2. Nudge azimuth a few degrees; wait 5–10 seconds; log SNR.
  3. Try slight elevation/tilt changes; lock the best average SNR. [Elektroda, kli, post #16924584]

After re‑aiming, how do I verify the fix?

Watch MUX‑2 during the usual problem window (evenings). Confirm SNR sits near 30 dB and that picture remains stable. The thread author reported excellent reception after optimizing for averaged MUX results across the day. [Elektroda, dyspozytor, post #16924602]
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