A couple of points here if I may ..
1) The narrowbanding kit sold by Communications Specialists will narrow the receiver bandwidth, but will not take into account modifications needed in the discriminator to deliver full rated audio output. Most later models use a discriminator IC that usually cannot be modified. If you get what you need by just turning the volume up higher, OK no problem... BUT... 2) Narrowband transmitters have to be designed AND FCC type accepted to work in the narrowband mode. This has to do with the overall emission envelope. Just turning down the deviation circuitry to 2.5 kHz will reduce the amount of deviation, but not the bandwidth of the emission overall. Turning down the deviation is simply not a legal option. If it isn't type accepted for Narrow Band it can't be used to transmit. There is a second caveat to turning down the deviation. since a lot of transmitters encode either digital or tone squelch injected without components (pots) allowing adjustment of the level, the transmitter will be sending those at +\- 600-800 Hz before narrowbanding. That equates to approximately 15% of the available modulation. When you narrowband, the transmitter will still be cranking out tone or digital signals that will now be at about 30% modulation. Obviously this is gonna have a horrible effect on transmitted audio quality. Any radio type accepted after February 14(?) 1997 was required to be capable of narrowband. In the case of the HT1000 for example, several versions were type accepted before, and did not include a narrowband mode while those type accepted afterward did. That is true for many radios from all manufacturers. The only tried and proven method is too 'read' each radio, and see what it can do. My experience is that most manufacturers have not been too enthusiastic in trying to compile lists model by model. I suppose I can understand that to a degree (ducking the rotten tomatoes) as they have long since discontinued support on a lot of these radios, and the task would be monumental considering the number of individual model variations /numbers for each individual series (HT1000 is the SERIES and H01RDC9AA3BN is the model number for one specific radio with a unique combination of options including frequency, band split, channels etc). In the case of the Midland ST1 radios, as I recall, the narrowband units were special order options. The basic 'normal' radio was not capable. January 1, 2011 will bring some interesting consequences. On that date it will be illegal to manufacture or import any radio with a wide band mode. There are some that say mixing w/n on the same channel will be detrimental to communications, others say it won't be a problem.. I guess we will see. Regardless, the adventure is just beginning... Bill N9SII <http://groups.yahoo.com/group/Repeater-Builder/message/88021;_ylc=X3oDMTJxb WZiOXE2BF9TAzk3MzU5NzE1BGdycElkAzEwNDE2OARncnBzcElkAzE3MDUwNjMxMDgEbXNnSWQDO DgwMjEEc2VjA2Rtc2cEc2xrA3Ztc2cEc3RpbWUDMTIzMjIyOTY3Mg--> Re: Are you ready for narrowbanding? Posted by: "[email protected]" <mailto:[email protected]?subject=%20re%3a%20are%20you%20ready%20for%20narro wbanding%3F> [email protected] <http://profiles.yahoo.com/afa5tp> afa5tp Sat Jan 17, 2009 1:50 pm (PST) Hello Group, Isn't it true that the radio must be on the "List" of type excepted units? I have a brochure for the Midland syn1 radio that says it is capable of the 12.5 kHz splits and "Narrow" dev. (2.5kHz). I was told that the Syn1 was NOT on the list of type excepted radios. What about the Moto HT-1000? Have heard that some of the later serial numbers were narrow band accepted. Is there a list from NTIA or ???? that tells which radios are going to be "Legal" to use on narrow band fxs? I guess just because you can change the I.F. filters, and knock down the deviation, some rigs just won't fly. 73's de Tim W7TRH Wa. -------------- Original message -------------- From: "Chuck Kelsey" < <mailto:wb2edv%40roadrunner.com> [email protected]> They are. I am one that says there won't be a huge flood of radios hitting the surplus market. Everything sold in the past 10 (or more) years has been narrow band capable right out of the box. Chuck WB2EDV
<<image001.png>>
