December 9, 2024

To Quad or not to Quad?

There is a clamor for a quad tuner ZapperBox. And, we are actively researching all the issues involved in offering a quad tuner DVR and gateway. This blog post is about the many issues one must consider in designing an antenna signal distribution system to feed a quad tuner receiver.

A quad tuner or even a dual tuner receiver poses some challenges compared to a single tuner receiver. Each RF splitter reduces signal power through insertion loss. Splitters do not reduce the noise figure by a corresponding amount, so you are directly reducing the signal to noise ratio of the TV signals by the amount of loss at each split.

In an ideal world, a 2-way split reduces signal by 3dB, 4-way by 6dB, and 8-way by 9dB. But we don’t live in an ideal world, and some splitters are better designed and use higher quality components than others. Actual losses are usually 0.5-1.0dB more per split. These losses are labeled as insertion loss.

We often get complaints from customers who compare the weak signal performance of their dual-tuner ZapperBox against their TV. That’s an unfair comparison because the TV is not splitting the signal internally. Further, as you add more tuners inside a single, size constrained, low cost, set-top box, it becomes difficult to avoid interference between the tuners. 

We spoke with Karlo Maalouf, the owner of Mr. Antenna at https://mrantenna.com/. Karlo has installed thousands of antennas during his 30-year career. He also installed many dual tuner and quad DVRs in his long career. He feels that a dual tuner receiver strikes the right balance between the number of tuners and number of channels. When he was installing quad tuner TiVo DVRs, he had too many customer complaints about pixelating channels.

What are some solutions to signal loss caused by splitters?

Use high-quality splitters: Higher quality splitters typically have lower insertion loss and better performance. Look for splitters with low specified insertion loss values.
Minimize the number of splits: Each split introduces loss, so use only as many splits as necessary. Excessive splitting will significantly degrade the signal.
Use high quality RF cables, preferably RG-6, to minimize signal losses through longer runs of cable.
Consider an amplifier: In cases where multiple splits are unavoidable, using an amplifier preceding the splitter can help compensate for signal loss. However, be cautious as amplifiers can introduce distortion from overloaded signals that spread across the frequency band. If you do use an amplifier, here are some additional tips:

Make sure it quotes the noise figure and choose one with as low a noise figure as you can find. Typically aim for something less than 3dB.
Consider using an LTE filter. Even if you don’t have strong television signals, a strong, nearby, cellular signal can also overload the amplifier
Choose an amplifier with enough gain to compensate for your splitter and losses for any long cable runs and no more. High gain amplifiers are typically unnecessary and can cause more problems with signal overload than they solve.

Use balanced splitters: Balanced splitters distribute the signal evenly, which can help maintain consistent signal strength across outputs.
Avoid daisy-chaining: Instead of connecting splitters in series, use a single splitter with more outputs if possible. This reduces cumulative losses.
Match impedances: Ensure all components (including cables) in the system have matching impedances (typically 75 ohms for TV systems) to minimize reflections and signal loss.
Use the appropriate frequency range: Choose splitters rated for the frequency range of your signal to ensure optimal performance.
Consider active splitters: For complex setups, active splitters (which include built-in amplification) can help maintain signal strength, though they require power.
Proper termination: Terminate any unused ports on splitters to prevent signal reflections that can degrade performance. 75 ohms F-connector terminators are available on Amazon.
Optimize cable lengths: Use the shortest possible cable lengths between splitters and devices to minimize signal loss in the cables themselves.
Finally, consider a high-end signal amplifier that can individually amplify each RF band so that no RF bands are overamplified, such as the Televes Avant X. See this blog post by Bob Haines about using Avant X with ZapperBox.

By implementing these strategies, you can significantly reduce the overall insertion loss in a system using multiple splitters and maximize the number of watchable channels.

Prologue – by Javier Ruano, GM at Televes USA

This is why a properly pre-amplified system is always preferred. Ideally a pre-amplified antenna, like the ZapperBox A1 antenna by Televes, which conditions the signal and separates it from the thermal Noise Figure as soon as possible. The reason is simple, in a purely passive signal captured from a passive antenna the noise figure is set. Any loss in signal, be it from splitter or from cable loss, is a direct loss of Carrier-to-Noise Ratio (CNR). The signal gets attenuated, the Noise Figure doesn’t. If you pre-amplify the signal at the acquisition point with a proper preamp, that only penalizes you for the Noise Figure of the preamplifier (which should be low in a properly designed unit), but the signal gets separated from the thermal Noise Figure and any losses in power due to splitting or cable, are not a loss of CNR anymore, they are only a loss of power. The CNR or signal quantity remains constant. Furthermore, the Noise Figure of the first element in the system determines the Noise Figure of the rest of the chain. A properly designed preamplifier establishes that and “negates” the detrimental effect of other actives in the chain downstream, such as the Noise Figure of the tuner itself. Pre-amplifying the signal at the antenna negates the Noise Figure of the tuner. That’s why sometimes it appears that a system “gains channels” by adding a preamp. Now, what are the potential issues of using a preamp? Obviously overload, under or over amplification. We solve that because we make our preamps self-adjusting, so that they never apply too much amplification. The other one is being overloaded by out of band signals. We avoid that with very strict filtering. 

For a “properly designed” preamplifier, consider the Televes 560383. Some things we like about this preamp: