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Noise Blankers that actually Work?
- Thread starter CTStallion
- Start date
:laugh: Well I went to the guy's Zed site thinking you wanted to show something he had made (like a noise blanker). Nope! But looks like he's helping kids learn, so it's not a total bust!
73,
Brett
Another thumbs up for the IC7000, I don't need to use it for my car as that's damned near radio silent, but for cell tower and other car interference it's great. I don't have it on normally, only using it when the need arises.
In the 1940's the Noie Limiter was placed int he audio chain and they where lack luster and did not work well. Everyone kept working to move them closer to the antenna. They kept incremently pushing them back more and more first downt he audio chain. Then they got into the if stages and found that the closer they could get tot he antenna the better they worked. When they first made the jump from tube to transistor the band width was smaller on units than before and they worked even better. So they started moving them back away from the antenna. Then DSP radio's started to get more borad band again and DSP came along. They had went with audio DSP first but you and than later on on high end gear rf DSP. By this time they had moved them too far away from the antenna. On top of that the various filters in the radio tend to distort and lengthen the noise pulse making it harder for the NB to see and react in time. If the noise is random it is hard to lock in on it as the pulse happens this is why NB's are great at ignition noise but suck at atmospheric white noise. Each stage int he radio that the noise goes through distorts and amplifies the noise and often it blunts the initial attack so it is not as sharp and easy for the NB or DSP to see and deal with. The distortion get's worse the more processing you do tot he audio which is why the people sound like motor boats by the time you get enough processing to deal with the noise. The same distortion that happens to the noise is also happening to the audio you want to hear.
In a perfect world you would have some form of noise blanking on the signal before it even made it into the radio. In the old days some hams built noise blanker that installed before the radio either internally if the chassis was large enough or externally. We are talking tube type noise blanker not just diode types long before DSP.
Compared to most ham gear CB's and Export radio's are not that broad banded so the NB is easy to get to work well. On top of that they use rather lousy diode detectors on receive that are not as sensitive as the Ham gear receivers. When you combine narrower bandwidth, less sensitive reciever and no DSP to depend on it makes designing a decent NB a must. It also means you can modify the NB on a CB or export radio much easier traditionally to improve it. Now that things are SMD that might not be as true.
Active synchronous NB might be worth investigating as an add on to Ham radio's as a separate black box ahead of the radio. I have to assume someone has done this already but I am not sure. I know military radio units had both types of processing and it was done before you got to the receiver in a separate rack. That was back int he 1990's. The operator did not have to adjust or tune anything it was down automatically. I have to think that with the advancements that have been made since the 1990's and the insane price of Ham gear that they could do this easily with one chip or one little add on board.
The reason I know this was done on military gear is because as you go lower and lower in freq. the noise has more energy. You have to have fantastic blanking preferably active when you get into LF and ULF/VLF etc..... Obviously we do not need that level of blanking but we should be able to operate in a mobile with out having to distort the signal to the point of it not being usable for the bands the radio is designed to operate in.
In a perfect world you would have some form of noise blanking on the signal before it even made it into the radio. In the old days some hams built noise blanker that installed before the radio either internally if the chassis was large enough or externally. We are talking tube type noise blanker not just diode types long before DSP.
Compared to most ham gear CB's and Export radio's are not that broad banded so the NB is easy to get to work well. On top of that they use rather lousy diode detectors on receive that are not as sensitive as the Ham gear receivers. When you combine narrower bandwidth, less sensitive reciever and no DSP to depend on it makes designing a decent NB a must. It also means you can modify the NB on a CB or export radio much easier traditionally to improve it. Now that things are SMD that might not be as true.
Active synchronous NB might be worth investigating as an add on to Ham radio's as a separate black box ahead of the radio. I have to assume someone has done this already but I am not sure. I know military radio units had both types of processing and it was done before you got to the receiver in a separate rack. That was back int he 1990's. The operator did not have to adjust or tune anything it was down automatically. I have to think that with the advancements that have been made since the 1990's and the insane price of Ham gear that they could do this easily with one chip or one little add on board.
The reason I know this was done on military gear is because as you go lower and lower in freq. the noise has more energy. You have to have fantastic blanking preferably active when you get into LF and ULF/VLF etc..... Obviously we do not need that level of blanking but we should be able to operate in a mobile with out having to distort the signal to the point of it not being usable for the bands the radio is designed to operate in.
The Yausu FT-101EE noise blanker works very well on pulse noise 
Otherwise most operators just slightly lower the RF Gain or disengage the RF Pre-amp all together (IPO mode for later Yaesu's) to help alleviate white (really "pink") noise.
The noise blankers on my FT-857D, 897D, FT-1000MP are 99% useless. I guess they were designed to filter out the old OTH Russian Radar noise? You can mess around with the DSP and IF shift to help quiet things though.
Not an HF rig by any standards, but my Stryker's have incredibly great noise blankers especially when utilized with the stock Hi-Cut filter. Regarding the RCI/ Ranger stuff; I do not understand why they even bother to include it because it's basically useless on their products. Galaxy's "GNF" was another Galactic Noise Failure.
Otherwise most operators just slightly lower the RF Gain or disengage the RF Pre-amp all together (IPO mode for later Yaesu's) to help alleviate white (really "pink") noise.The noise blankers on my FT-857D, 897D, FT-1000MP are 99% useless. I guess they were designed to filter out the old OTH Russian Radar noise? You can mess around with the DSP and IF shift to help quiet things though.
Not an HF rig by any standards, but my Stryker's have incredibly great noise blankers especially when utilized with the stock Hi-Cut filter. Regarding the RCI/ Ranger stuff; I do not understand why they even bother to include it because it's basically useless on their products. Galaxy's "GNF" was another Galactic Noise Failure.
My Yaesu FT450D has a N.B. that works quite well. Off and I get 5-7 units of just crap from my truck, (09 ram), and the citys lights and so on.
N.B. on, and It's ALL gone. And I am Bonded like every place and where.
exactly correct,.... I always use at least 10 Db attenuation on 40 meters and lower.
the end goal is SNR, not max s-unit reading.
Yeah what BBB said: I have a Stryker 955 Radio and the NB works incredible well, the audio feeding a Sonic Cushion (a GE 47 light bulb and a pot type volume control 25 Ohms, that levels out the strong/weak station volume level) that feeds the Clear Speech DSP speaker unit, all mounted on my dash. It all works quit well allowing me to drive down the road and NOT hear ignition noise. Had to install two diodes across 955 audio output wires back to back, to prevent the snap pulse into the Clear Speech unit that has a 10 watt audio amp, when pressing the PTT switch.
Also added a toroid core with as many windings as I could get on it, on the audio input wire and power input wire to the DSP unit, about a 1 inch core, to attenuate any RF getting into the Clear Speech DSP unit.
Then after all was working well, I installed two 100 watt solar cell units on top of the roof on the camper, with a solar cell controller (voltage regulator/battery charger) and that thing is so loud generating RFI/EMI noise that I am sure the military would want a few. Installing input/output filters and installing a metal box with the controller inside the metal box the noise level went from 20 over on every band to a slight noise in the background on some frequencies. Heads up.
Jay in the Great Mojave Desert
Also added a toroid core with as many windings as I could get on it, on the audio input wire and power input wire to the DSP unit, about a 1 inch core, to attenuate any RF getting into the Clear Speech DSP unit.
Then after all was working well, I installed two 100 watt solar cell units on top of the roof on the camper, with a solar cell controller (voltage regulator/battery charger) and that thing is so loud generating RFI/EMI noise that I am sure the military would want a few. Installing input/output filters and installing a metal box with the controller inside the metal box the noise level went from 20 over on every band to a slight noise in the background on some frequencies. Heads up.
Jay in the Great Mojave Desert
The Yausu FT-101EE noise blanker works very well on pulse noise
The noise blankers on my FT-857D, 897D, FT-1000MP are 99% useless. I guess they were designed to filter out the old OTH Russian Radar noise? You can mess around with the DSP and IF shift to help quiet things though.
Not an HF rig by any standards, but my Stryker's have incredibly great noise blankers especially when utilized with the stock Hi-Cut filter. Regarding the RCI/ Ranger stuff; I do not understand why they even bother to include it because it's basically useless on their products. Galaxy's "GNF" was another Galactic Noise Failure.
Thanks for the ClrSpkr tips. Had already used toroids on leads. The others look like good ideas to follow up.
Great link. Thanks Comes in at exact right moment.
With a DSP Speaker after a CB or Export, one can do much the same thing. Literally drive right up to, “a voice that crieth in the wilderness”, and underline it by RF Gain/Squelch/Filtration adjustments, then sometimes radio & speaker volume control. So well that the real surprise — the OTHER voice (radio) — is now legible.
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That RF gain knob is quite capable when you know how to use it.
I made this a while ago but still fits the topic. Sorry the audio is low..