Wire-Lists #31: Improving Signal to Noise Ratios with PF25 Filters

Social Media WireLists31 300pxIn today’s list, we’ll discuss improving Signal to Noise ratios using PF25 filters.

Filter 1 List 32

This first image shows a wideband scan using a Venue 2 with A1, B1 and C1 modules, and a pair of SNA600a passive dipole antennas. The blue arrows indicate our intended carriers from transmitters about 10 ft. away from the receiver antennas.


Filter 2 List 32

In the second scan, we have included an RF Filter on both antennas, allowing mostly only energy within Block 20 and a bit on either side into the receiver. Our PF25-20 is a small, low loss bandpass filter with a width of approximately 26 MHz. (the same of the Lectrosonics “Blocks”), which decreases the RF signals above and below the determined width. For example, a Block filter 20 will attenuate frequencies below 512 MHz and above 537,500 MHz. You can learn more about Blocks for PF25 here.

Filter 3 List 32

In this third scan, we have replaced the PF25-20 filters with a similar pair on Block 25 (PF25-25). Here, you can see that most of the energy outside of Block 25 is heavily attenuated.

Filter Q&A

How does a filter help me?

When coordinating frequencies, our goal is to maintain the best signal-to-noise ratio of the carriers. By using a filter, unwanted noise is significantly reduced, improving the performance of the system since it must process less overall RF energy. This can increase the range of the system and reduce intermodulation and other RF noise sources.

How is it installed?

Being a passive filter, the PF25 must be connected between the antenna and the receiver without any additional requirement. Of course, one filter should be used for each antenna.

When should I use it?

Filters are ideal in spaces where the RF spectrum is heavily congested either by many wireless systems in the same location and / or by TV channels.

But won't I be losing RF bandwidth?

Applying the filter will reduce the selectable bandwidth, but you can make better use of the space that is actually available.

How do I coordinate the new bandwidth in the frequency calculation software?

If you are using our Wireless Designer software, simply assign the same “narrowband” filter block in the transmitter option of the channel (s). If you are using other software, you only need to adjust the bandwidth for that channel to match the one on the filter (most popular software contain our blocks by default).

I have free space in my RF spectrum and low noise floor. Do I need to use filters?

If this is the case, the filter will not make a major difference. The greatest effectiveness of the filter is in problematic RF locations.

Can I use this filter with equipment from other brands?

Of course! Just check that the filter bandwidth is compatible with your equipment.

My receiver already has built-in filters, should I use an external filter?

Any additional filters will help if your spectrum is difficult.

Will a filter give me more transmitter-receiver distance?

If the space is congested, the filter will always be useful in improving the Signal / Noise ratio by reducing the noise. But if the spectrum is clean, applying a filter will not make a difference and may even slightly attenuate the carrier.

We’re here to help with any questions about Signal to Noise or filters. Reach out by This email address is being protected from spambots. You need JavaScript enabled to view it. or open a thread on our Facebook group.