K3: Noise Reduction (NR) in FM Mode
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Yesterday I discovered by accident (or stupidity) that if you have Noise Reduction engaged and you go to FM mode, you do not receive any intelligible signals. You can tell that there is a signal, but you cannot make it out. I realize that there is no earthy reason to use NR in FM. But, if you have NR engaged on another mode and go to FM, you will be sorry. So, perhaps on the "we will get to it someday list" there could be a firmware change to disallow noise reduction in the FM mode? It wouldn't hurt . . . 73, John, WA6L |
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Hi John
When I worked for Motorola, both their and GE's top of the line two-way FM mobile radios did include noise blankers for the mobile environment. They worked quite well for their intended use. 73, Bob N6WG ----- Original Message ----- From: "WA6L" <[hidden email]> To: <[hidden email]> Sent: Thursday, June 05, 2008 7:34 AM Subject: [Elecraft] K3: Noise Reduction (NR) in FM Mode > > > Yesterday I discovered by accident (or stupidity) that if you have Noise > Reduction engaged and you go to FM mode, you do not receive any intelligible > signals. You can tell that there is a signal, but you cannot make it out. > > I realize that there is no earthy reason to use NR in FM. But, if you have > NR engaged on another mode and go to FM, you will be sorry. > > So, perhaps on the "we will get to it someday list" there could be a > firmware change to disallow noise reduction in the FM mode? It wouldn't > hurt . . . > > 73, > > John, WA6L > > > -- > View this message in context: http://www.nabble.com/K3%3A--Noise-Reduction-%28NR%29-in-FM-Mode-tp17671258p17671258.html > Sent from the Elecraft mailing list archive at Nabble.com. > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3: Noise Reduction (NR) in FM Mode
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The Motorola and GE 2-way mobile radios with noise blankers
were just that ... noise blankers ... that worked in the IF chain and "blanked" (turned off) the IF's for the duration of a noise pulse. They were primarily found in "low band" (30 - 50 mHz) radios and were aimed at ignition noise. The NB's were options and not installed in every radio. 73! Ken Kopp - K0PP (Retired career 2-way radio tech) _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by n6wg
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Re: K3: Noise Reduction (NR) in FM Mode
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At least with the Motorola Syntor X, they used a separate and very
simple receiver to pick out impulse noise and used this secondary RX detector output to poke holes in the main RX audio. They called it an Extender and I believe it was only included with the low-band Syntor X. It is described as a Noise Blanker. I have one of these LB Syntor X's in mobile use, but have never found a situation where the Extender was needed (or a way to real-world test it!). Turning the Extender on or off has no apparent effect on receive sensitivity however. I've watched the blanking pulse train from the Extender outpt to the blanking circuit on the main RX - the pulses are present, but can't really be heard in the main. Shamless Plug: my little company makes agile controllers for the Moto Syntor and Syntor X radios. This is the only reason I know this fairly useless bit of trivia. 73, matt, W6NIA On Thu, 05 Jun 2008 20:44:27 -0700, you wrote: >Aaargh! I meant to say we used high level I.F. limiters so no AM would get >to the detector. That included noise. > >So "blankers" were never needed. > >Maybe Motorola didn't use good limiters. > >Now to see if I can pry my foot out of my mouth... > >Ron AC7AC > >-----Original Message----- >??? > >I worked on FM gear in the land mobile business as a service rep and >salesman and we *never* used a noise blanker. A limiting I.F. amplifier was >a basic part of the receiver design since the detector does not respond to >amplitude modulation at all, including noise. > >Noise does not modulate the frequency. > >Maybe Motorola didn't use good FM detectors. Some simple types of "FM >detectors" respond to both AM and FM. > >Come to think of it maybe that's why I outsold Motorola in our market area >with E.F. Johnson land mobile FM gear <G>. > >Ron AC7AC > > >-----Original Message----- > >Hi John >When I worked for Motorola, both their and GE's top of the line two-way FM >mobile radios did include noise blankers for the mobile environment. They >worked quite well for their intended use. 73, Bob N6WG > >_ > >_______________________________________________ >Elecraft mailing list >Post to: [hidden email] >You must be a subscriber to post to the list. >Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > >Help: http://mailman.qth.net/subscribers.htm >Elecraft web page: http://www.elecraft.com Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by AC7AC
That could be, Ron.
I remember when GE had it in their radio, and we didn't, it soon showed up so we could compete in bids. I imagine the bid process drove that more than any actual need :-) 73, Bob N6WG ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> To: <[hidden email]> Sent: Thursday, June 05, 2008 8:12 PM Subject: RE: [Elecraft] K3: Noise Reduction (NR) in FM Mode > > ??? > > I worked on FM gear in the land mobile business as a service rep and > salesman and we *never* used a noise blanker. A limiting I.F. amplifier was > a basic part of the receiver design since the detector does not respond to > amplitude modulation at all, including noise. > > Noise does not modulate the frequency. > > Maybe Motorola didn't use good FM detectors. Some simple types of "FM > detectors" respond to both AM and FM. > > Come to think of it maybe that's why I outsold Motorola in our market area > with E.F. Johnson land mobile FM gear <G>. > > Ron AC7AC > > > -----Original Message----- > > Hi John > When I worked for Motorola, both their and GE's top of the line two-way FM > mobile radios did include noise blankers for the mobile environment. They > worked quite well for their intended use. 73, Bob N6WG > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3: Noise Reduction (NR) in FM Mode
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In reply to this post by Matt Zilmer
If I remember correctly it was Collins who first came up with the idea of
using a simple secondary 'noise receiver' to blank the main receiver in HF SSB mobile installations using the KWM -1 and / or KWM-2A transceivers. The secondary 'noise' receiver was tuned to a frequency above 30 MHz and had its own small whip antenna. The FM receivers in our old RCA 'Carphone' series of VHF Land Mobile rigs used hard limiting before the discriminator to get rid of impulse noise and other AM gremlins. A modified version of the Collins system provides very effective noise blanking when used in a receiver covering the ham bands. Usually the noise receiver which provides the blanking pulses is tuned to a frequency clear of signals just outside of the band in use so that the main receiver is not blanked by strong unwanted in-band signals, which can be a problem with blankers driven by in-band noise especially during contests. One name given to this arrangement many years ago is the 'Evasive Noise Blanker'. Further improvement in overall receiver performance can be gained by removing the noise blanking gate, which is usually in the main receiver's signal path ahead of the IF filter(s), and use the blanking pulses from the noise receiver to turn the LO injection to the first mixer on and off - quite easy to do if any 'logic' is used in the LO system. The next improvement is aimed at dealing with storm static! Sorry to have drifted off subject! 73, Geoff GM4ESD. Matt Zilmer <[hidden email]> wrote on Friday, June 06, 2008 at 6:24 AM > At least with the Motorola Syntor X, they used a separate and very > simple receiver to pick out impulse noise and used this secondary RX > detector output to poke holes in the main RX audio. They called it an > Extender and I believe it was only included with the low-band Syntor > X. It is described as a Noise Blanker. _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: K3: Noise Reduction (NR) in FM Mode
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In reply to this post by AC7AC
On Jun 5, 2008, at 8:44 PM, Ron D'Eau Claire wrote: > Aaargh! I meant to say we used high level I.F. limiters so no AM > would get > to the detector. That included noise. Right. If you use a discriminator there was amplitude sensitivity in the detector so limiters stages were used in the IF before the discriminator. A ratio detector compensated for signal amplitude and didn't require a dedicated limiter stage. PLL-based detectors were also immune to amplitude variations. I worked my way through my last year in high-school working for an outfit that provided commercial two-way radio systems. (I did a *bunch* of installations in police cars.) We sold EF Johnson too. I hated those radios because the crystal ovens kept failing. Fixing them was not considered high on the list of fun jobs so guess who got to fix all the damned crystal ovens? :-) We did Motorola too. The Motorola stuff was just better built. We always felt that Motorola was the best, GE next, and EF Johnson was what you got when you couldn't afford anything better. I know that when I was building repeaters I preferred Motorola or GE RF decks. > So "blankers" were never needed. > > Maybe Motorola didn't use good limiters. > > Now to see if I can pry my foot out of my mouth... Hey, you've been around linear radios for too long. It could happen to anyone. :-) -- 73 de Brian, WB6RQN Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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