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[Solved] Will an external antenna increase the range of the Zamel Exta Life RCT 21 receiver?

kdziadosz209 588 11
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  • #1 21222638
    kdziadosz209
    Level 4  
    Posts: 20
    Hello everyone. I have a question regarding the Zamel Exta Life receivers. If I solder out the original antenna and insert an SMA socket and attach an external antenna, will this increase the range? Has anyone tried this? The RCT21 to be exact.
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  • #2 21222683
    max-bit
    Level 34  
    Posts: 4560
    Help: 116
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    Certainly :) .
    Take it apart and see what it looks like inside
    It may be that the antenna is on the PCB and there is not much space ...
    Take photos and we will combine
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  • #3 21223811
    kdziadosz209
    Level 4  
    Posts: 20
    The antenna is on an additional PCB soldered on two pins vertically to the horizontal main board. I'll send a picture of what it looks like after 5pm.

    Added after 7 [hours] 42 [minutes]: .

    Will an external antenna increase the range of the Zamel Exta Life RCT 21 receiver? Will an external antenna increase the range of the Zamel Exta Life RCT 21 receiver? .
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  • #4 21224820
    max-bit
    Level 34  
    Posts: 4560
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    Then you have to combine
    Somehow solder the connector

    But this does not guarantee an improvement in range at all:) .
    Especially if you solder a few metres of poor cable and put a poor antenna at the end :)
    Then it can be worse than now
  • #5 21224877
    kdziadosz209
    Level 4  
    Posts: 20
    I have an original extra antenna for this system but this particular module does not have an antenna socket Will an external antenna increase the range of the Zamel Exta Life RCT 21 receiver? Will an external antenna increase the range of the Zamel Exta Life RCT 21 receiver? .
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  • #6 21224982
    max-bit
    Level 34  
    Posts: 4560
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    it is of questionable quality :) .
  • #7 21225017
    kdziadosz209
    Level 4  
    Posts: 20
    So the original antenna is of questionable quality?
  • #8 21225030
    max-bit
    Level 34  
    Posts: 4560
    Help: 116
    Rate: 835
    :) .
    It's a Chinese product
    Cheapest cable
    Antenna with 0 dB gain
    So only on such a cable there will be losses :) a few dB
    So in total a few dB loss :)
  • #9 21225147
    kdziadosz209
    Level 4  
    Posts: 20
    In this case, what is the best antenna to fit to this unit. The system operates on the 868Mhz band
  • #10 21225153
    max-bit
    Level 34  
    Posts: 4560
    Help: 116
    Rate: 835
    Well the question is where this device is where the "base" is
    How far away etc ...
    If somewhere far away and as they say in ... on a pole then you would have to lead the signal out with a better cable
    But here too there is another question whether it is not better to give it somewhere else ...
    Many questions ...
    and too many unknowns
  • #11 21225167
    kdziadosz209
    Level 4  
    Posts: 20
    The base is in the living room and the device is 20 m from the house. There is a retransmitter outside the house that amplifies the signal. However, with this signal it is not as it should be. A couple of hours there is sometimes an interruption, there is no connection. The device is in an airtight box. The retransmitter and the device can see each other.
  • #12 21253387
    kdziadosz209
    Level 4  
    Posts: 20
    I soldered an rp-sma socket to the circuit board. I plugged an antenna dedicated to the receiver into the socket and it works without any problems.
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Topic summary

✨ The discussion addresses whether replacing the original antenna of the Zamel Exta Life RCT21 receiver with an external antenna via an SMA connector can improve its range. The receiver's antenna is mounted on a small additional PCB soldered vertically to the main board, without a factory antenna socket. Modifying the device by soldering an RP-SMA socket and attaching a dedicated external antenna is feasible and has been successfully tested. However, improvements in range are not guaranteed, especially if using low-quality cables or antennas with 0 dB gain, as losses can offset any potential benefits. The original antenna is a low-cost Chinese component with minimal gain and cheap cabling, contributing to signal loss. Optimal antenna choice depends on deployment conditions, such as distance and placement relative to the base unit, which in this case is indoors with the device 20 meters away in an airtight enclosure. A retransmitter is used but signal interruptions still occur. Using a higher quality antenna and cable, properly matched to the 868 MHz operating band, and ensuring good line-of-sight can enhance performance. The modification with an RP-SMA connector and a dedicated antenna has been confirmed to work without issues.
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FAQ

TL;DR: External antennas can help RCT21 range, but “Antenna with 0 dB gain” plus cheap coax means loss. Use quality parts and short runs, or range may not improve. [Elektroda, max-bit, post #21225030]

Why it matters: This helps Exta Life RCT21 owners fix spotty 868 MHz links without wasting time on ineffective antenna mods.

Quick Facts

Will an external antenna increase range on Zamel Exta Life RCT21?

It can, but only if the antenna and feed add gain, not loss. As one member warns, “This does not guarantee an improvement in range at all.” Long, low‑quality coax and low‑gain whips can make it worse. Keep any feed short and use a tuned antenna. [Elektroda, max-bit, post #21224820]

Where is the RCT21’s stock antenna located?

It sits on a small daughterboard, soldered on two pins and mounted perpendicular to the main board. This affects where you tap the RF feed and how you mount a connector. Plan placement and strain relief accordingly. [Elektroda, kdziadosz209, post #21223811]

Has anyone added an RP‑SMA and confirmed it works?

Yes. A user soldered an RP‑SMA socket to the PCB, connected the system’s dedicated antenna, and reported it works without problems. This shows the hardware accepts an external feed when done carefully. [Elektroda, kdziadosz209, post #21253387]

Which connector should I fit: SMA or RP‑SMA?

RP‑SMA is proven in this thread. The poster fitted an RP‑SMA socket and used the matching antenna with no issues. Match your connector to the antenna you plan to use to avoid adapters. [Elektroda, kdziadosz209, post #21253387]

Is the original Zamel external antenna worth using?

One expert called it “a Chinese product” with “Antenna with 0 dB gain,” plus a cheap cable that causes a few dB of loss. Net performance can be negative if the feed is long. Consider a better 868 MHz antenna and short, quality pigtail. [Elektroda, max-bit, post #21225030]

How long can the antenna cable be before it hurts range?

Avoid “a few metres of poor cable.” That edge case can perform worse than the stock PCB antenna. Keep the pigtail very short and use quality coax only when absolutely needed. Long, lossy runs are a common failure after DIY mods. [Elektroda, max-bit, post #21224820]

My device is 20 m from the house with a repeater and sealed box—why drops?

In the reported setup, the base was indoors, the device 20 m away, and a repeater was used. Despite visibility, links sometimes dropped. Try moving the repeater or enclosure, test with the box open, and keep feeds short. Check antenna orientation and height. [Elektroda, kdziadosz209, post #21225167]

Is repositioning the repeater/base better than adding a long cable?

Often, yes. Shorter RF paths beat long, lossy pigtails. As one member noted, there are “Many questions ... and too many unknowns,” so experiment with placement first to reduce losses and obstructions. [Elektroda, max-bit, post #21225153]

How do I add an RP‑SMA to the RCT21?

  1. Identify the antenna feed where the daughterboard connects and expose a ground point.
  2. Solder an RP‑SMA socket or short pigtail to the feed and ground, keeping it very short.
  3. Attach an 868 MHz antenna and test link quality. [Elektroda, kdziadosz209, post #21253387]

Do I need to open the receiver, and is there enough space?

Yes. You must open it to inspect and plan a connector. “Take it apart and see what it looks like inside.” Space can be tight with a PCB antenna, so choose the socket location carefully and photograph the internals. [Elektroda, max-bit, post #21222683]

What frequency should the external antenna be tuned to?

Use an antenna tuned for 868 MHz, matching the system’s operating band. Pair it with the same connector type you install on the receiver to avoid mismatch. [Elektroda, kdziadosz209, post #21225147]

What was the result after the RP‑SMA mod in this thread?

After soldering the RP‑SMA and connecting the dedicated antenna, the user reported it “works without any problems.” That indicates the mod can stabilize the link when done correctly. [Elektroda, kdziadosz209, post #21253387]

If my module has no antenna socket, can I still use the optional antenna?

Yes. You can add a socket by soldering to the board. In this case, an RP‑SMA was added and the system’s dedicated antenna was used successfully. Ensure RF ground and mechanical stability. [Elektroda, kdziadosz209, post #21253387]

Where can I get help verifying my mod?

Post clear internal photos. A member advised, “Take photos and we will combine,” after suggesting disassembly. Community review can confirm the feed point and safe routing before you solder. [Elektroda, max-bit, post #21222683]
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