[Yaesu] NB question mod for Yaesu!!!!

[Chris Boone]

If only that were true.....In my 40+ years of lowband FM and 6FM operation, that is not true...ignition noise and electrical as well as lightning ionization of the air can cause static noise on FM voice radios (in fact DB Products used to advise wrapping lowband antennas with tape to keep such static from building up...even on grounded antennas!)...ALL Lowband FM commercial radios had NB options....GE was the first (W5VPQ, George Munsch, designed it..he was an expert in noise reduction and was a consultant for the Navy on eliminating noise in radio systems...he was a good friend and a technical leader of the TX VHF FM Society for years when it WAS a technical leader...he became a SK a few years back)...

Motorola used the name Extender to trademark it, but the Extender in the Micor was crap...often would go into oscillation and blanket the main channel; no matter what freq it was tuned to..At the power company I worked at (GSU, now owned by Entergy) our 48MHz radios all had the NBs in them except for some of the base stations when I started...some of them had 50-100uV eff sensitivity...when I swapped them with NB rcvrs that we got from Calif Hi Patrol, the rcvrs went down to less than 5uV eff sensitivity. During one thunderstorm, I stood in front of the Micor base and saw its limiter go full scale after a lightning strike miles away..the mobile being received went away in the local spkr..yet a GE Mstr II mobile with its NB sitting outside heard the mobile just fine..we eventually got rid of the MICOR bases! I ran a GE Delta in my van with and without the NB option..without it, the ignition noise from ANY vehicle, not just my Chevy van, and anytime I drove under a noisy power line tore up the rcvr..with it, the noise was totally gone....IF they did not need a NB, why were they offered? Midland and all other LB makers pretty much make the NB standard these days.

BTW GE offered the NB in their VHF Hiband MII/EXECII as well....I had a 2m rptr site that could have used it..on the bench the rptr heard 0.2uV...at the site, it was well over 10uV effective....needless to say, the rcvr range sucked...a move to a new site suddenly allowed 1/2watt talkies get in where 30w mobiles did not. YET a 220 rcvr on the same noisy site heard fine...an IFR tied to the antenna showed the noise floor dropped around 190MHz.

The idea of limiters taking out noise sounds good on paper...in real life, that is not the case. Noise Blankers on FM are needed...those that did not buy them did not realize what they missed (especially on COLD dry days which are the worst!)


Chris
WB5ITT

-----Original Message-----
>From: Glen Zook <gzook at yahoo.com>
>Sent: Jul 9, 2014 1:18 PM
>To: Chris Boone <cboone at earthlink.net>, "yaesu at mailman.qth.net" <yaesu at mailman.qth.net>
>Subject: Re: [Yaesu] NB question mod for Yaesu!!!!
>
>In general, noise is AM in nature and the limiter circuits in FM receivers are designed to take out any AM components of the signal.  As such, except when the noise is extremely strong, there is no need for any noise blankers in an FM signal.
>
>Motorola had, as an option on low band FM equipment (29.7 MHz to 50 MHz), what they called an "Extender".  This was a type of noise blanker that sampled the signal fairly near to the desired frequency.  However, most end users did not need the "Extender" and relatively few units were equipped with "Extenders".  During the going on 10-years that I owned the Motorola reconditioned center for the south-central United States, Only about 5-percent of the low band units shipped had "Extenders".
> 
>Glen, K9STH
>
>
>Website:  http://k9sth.com