RTL-SDR BLOG BROADCAST FM BAND-STOP NOTCH FILTER
Official Distribution by HamRadioShop Italy
STOP RF OVERLOADS: HAMRADIOSHOP IS AN OFFICIAL RTL-SDR BLOG DISTRIBUTOR!
We are pleased to offer digital monitoring and receiving enthusiasts the original products from the renowned brand RTL-SDR Blog. This high-performance band-stop (Notch) filter attenuates commercial FM signals from 88 to 108 MHz with exceptional attenuation of 50 dB and beyond, protecting the front-end of your SDR dongle from unwanted saturation and giving you the clean spectrum you've always wanted.
Why install an FM Band-Stop filter on your SDR?
In many urban areas or near repeaters, FM Broadcast band signals (88-108 MHz) are so devastating in terms of power that they completely overload wideband SDR receivers. This phenomenon causes a drastic drop in overall performance, raising the noise floor and causing annoying ghost signals (intermodulations or WFM "images") on totally different frequencies.
If, by increasing the gain of your dongle, you notice the presence of commercial radio stations or strong noises typical of WFM modulation within the aeronautical, marine, amateur radio VHF bands or in UHF, the diagnosis is clear: your SDR is saturated. The RTL-SDR Blog filter solves this problem at its root with almost zero insertion loss on other bands.
PRACTICAL TIPS FOR USE AND CONFIGURATION
-- PLACEMENT IN THE RF CHAIN
For maximum effectiveness, install the filter as close as possible to the SDR antenna input. This will prevent high-power commercial FM signals from overloading the internal amplification stages of the dongle.
-- USE WITH PREAMPLIFIERS (LNAs)
If you use a mast amplifier or a wideband LNA, insert the filter before the LNA if the FM stations are close and risk saturating the preamplifier itself, or immediately after to protect the receiver if the preamplifier works correctly in the linear zone.
-- BIAS-TEE CURRENT PASSAGE (DC PASS)
The filter supports the passage of DC currents up to a maximum of 80 mA (and beyond) with negligible DC resistance. This means you can use it in cascade if you power your RF accessories or remote amplifiers via the SDR's Bias-Tee function.
-- NOT SUITABLE FOR TRANSMISSION
This filter is a passive component designed exclusively for reception (RX) purposes. It must not be used in transmission (TX) to avoid permanent damage to the internal components of the filter due to the power output.
TECHNICAL SPECIFICATIONS AND RF DESIGN
| RF Parameter | Operating Values and Hardware Architecture |
|---|---|
| Filter Topology | Advanced design based on a passive 7th order Chebyshev configuration. |
| Roll-Off Frequencies (3 dB) | The -3 dB cutoff points are precisely positioned at 76 MHz and 122 MHz to maximize selectivity. |
| FM Band Attenuation | Band start at 88 MHz attenuated by almost 60 dB; band end at 108 MHz attenuated by a good 45-50 dB. |
| Out-of-Band Insertion Loss | Virtually zero below 500 MHz; less than 0.5 dB from 500 MHz to 1 GHz; less than 1.5 dB between 1 GHz and 2 GHz. Maintains excellent performance below 1.5 dB loss for most frequencies up to 3 GHz. |
| DC Voltage Pass (DC Pass) | Supports current passage for Bias-Tee power supplies up to 80 mA with insignificant residual ohmic resistance. |
INSTRUMENTALLY SUPERIOR QUALITY TO CHEAP TV FILTERS
Laboratory tests performed with a VNA Network Analyzer demonstrate the clear superiority of this product compared to cheap FM filters (typically used for TV systems). Cheap filters not only do not guarantee a deep and effective stop-band, but also introduce severe insertion losses on the remaining useful frequencies, ultimately degrading the weak signals you wish to receive. RTL-SDR Blog guarantees clear rejection combined with absolute out-of-band transparency.
YOUR ORIGINAL RTL-SDR BLOG REFERENCE IN ITALY
By purchasing from HamRadioShop you are assured of receiving 100% original products, shipped directly from our warehouse in Italy with official warranty, fast shipping and specialized technical support for any configuration of your receiving shack.
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