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Need narrow band explaination

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Old 02-09-2005, 11:08 PM
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dyna_mo
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Default Need narrow band explaination

Hi

As I was about to trash some older radios, I was standing above the garbage can and just couldnt seem to let go. I was wondering if there was any hope for my first radio when I came uop with the following.

It appears there must have been 3 phases of RC equipment ..Wide band (80Khz),
Mid Band(40 Khz), and now Narrow band (20 Khz). In the 80s, when they went to channel numbers instead of colored flags, they sold radios on even frequencies...at that time I was on ch 40 and flew concurrently with others on channel 38 and/or 42 (40Khz between channels).

In the process, I came up with the following questions.

1)I am courious if my transmitter IS or could be "narrowband" ?? The practical ways I know to tighten the bandwidth would be to add another tuned circuit or to use higher Q components in the tuning circuit. With the AMA gold sticker shops charging $15-20 for a gold sticker, I can imagine they are adding circuitry or replacing RF coils.

2) Are transmitters that were sold NEW on numbered frequencies actually Illegal to use by the FCC?? If so what section/part??

3) Since the gold sticker program only references AMA and RC/MA is the FCC even involved?
Please note: The AMA guideline for acceptable use of frequencies ( sect 1.1) states the
guidelines are "voluntary" and in section (1.2) they use the wording " it is urged that all......"

Thanks for any insite

T
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Old 02-10-2005, 12:14 PM
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Default RE: Need narrow band explaination

R/C transmitters were either wide-band or narrow-band. There was no "mid-band". During the phase-in, the suggested-use channels in the upper-half of the band were initially spaced 40 KHz apart so that wide-band equipment could be used on the new channels.

Some older equipment can be modified to comply with narrow-band specifications, but you'd have to check with your R/C system's manufacturer or authorized service center. Please be aware that many field modifications may not actually be legal because the FCC regulations require that a permissive change be issued by them before such modifications are legal. Many older R/C transmitters do not have such certification. Only the manufacturer can obtain the permissive change.

Modifications are legal only if the frequency tolerance is within the 0.002% demanded in the technical regulations. Many older transmitters will not meet this standard.

The relevant regulations for R/C transmitter specifications can be found in CFR 47 Part 95.

The "Gold Sticker" program was implemented by the AMA and R/CMA (R/C Manufacturer's Association) to help modelers identify which transmitters complied with the narrow-band specifications. After the mid-90's, the program was dropped because wide-band equipment became illegal to use after 1998. Because only narrow-band equipment is allowed to be used, the sticker program was no longer relevant.
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Old 02-11-2005, 12:12 PM
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dyna_mo
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Default RE: Need narrow band explaination

Thanks, I didnt see that the first time i looked.

The exact number is CFR47 part 93.623 section c. It states after march 1 1998 all 72 Mhz transmitters must maintain within a frequency tolerance of 0.002%max (~14.4k).

T
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