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Reviews For: JPS NTR-1

Category: Filters, Audio: (DSP and others)

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Review Summary For : JPS NTR-1
Reviews: 1MSRP: 160 USD
Description:
The JPS NTR-1 is a DSP audio filter to provide noise reduction and multiple tone removal for AM, FM, SSB, CW, or FSK. The unit is simple and user-friendly with just 4 buttons: power on/off, 6.6/3.4Khz passband, notch, noise reduction. All functions are independent and may be used separately or together. High/low impendance audio input is provided. Low impedance output for a 3 to 8ohm speaker is provided in the back of the unit.
Product is in production
More Info: http://www.universal-radio.com/catalog/filters/ntr1.html
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0015
KD7RDZI2 Rating: 2021-08-24
Updated review: 27Y treasury Time Owned: more than 12 months.
I bought it new in 1994 when I entered in the hobby as an SWL. It was pricey at that time, 159$. But I did not expect such a long 'duration' for this ham 'asset'! So considering the time I have been using it, I spent a mere 6$ per year!

Evidently it was built accurately, good components and good design. Well protected in the audio input and in the power supply input.

This was one of the first DSP filter appeared in the ham market, so it may be considered ancestral technology. Ads of that time exaggerated the about the effective noise reduction. But I have to say, the notch filter works spectacularly with multiple tones beyond imagination without distortion. The unit has two bandwidths, 6.4 and 3.3Khz and looking its spectrum with SDR software the filters are very effective. The ADC used has 14bits, so dynamic range should be theoretically 84db, which should be more than adequate being really the last stage be chain after the filters built in the radio.

Noise reduction in my opinion works well in digital modes and rather well with speech. The DSP has an AGC, which may become annoying if the receiver is in Slow AGC position. I prefer to use Fast AGC in the receiver. Actually I found it works even better with SDR receivers: I use Quisk for my Softrock Ensemble receiver. Quisk has a digital noise blanker but not a digital noise reduction. The JPS NTR works well with Quisk especially when the AGC in Quisk is set fastest or with AGC deactivated.

The unit, being external and well screened, does not interfere in any way with the circuitry of the radio.

Operatively it is very easy to use but still it is worth to understand its manual and circuitry. The audio input is an op-amp which is a very high-impedance. At audio level impedance mismatch is not an issue at all. You can either use a high impedance output or a low impedance output such as speaker or headphones outputs of the radio. The op-amp is a unity gain buffer amplifier. I have added a small audio (data) isolating 1:1 transformer between the high impedance output of the rig and the NTR to totally remove any possibility of ground loops, especially when I use the NTR1 after the soundcard of my laptop.

In the case I use the speaker output of receivers I have added a 4:4000ohm audio transformer between the speaker output of the rig and the NTR1. I could have used a simple 1:1 transformer, however, the transformer rising the impedance, rises the mV delivered into the NTR, so in practice it rises a lot the volume (the input level should receive between 100mVRMS and 2VRMS). Also I have added some homemade RC high-pass filters to remove basses (between 0 and 350Hz).

Overall I am very satisfied. I still use it nearly every day with any radios from surplus, homebrew, analog to SDR.

As a bottom line, has a low latency, in the sense that latency in the NTR is close to nil.