Rss- bandwidth setting question

[Johnx]

In programming a Visar, I'm unclear as to bandwidth settings:
if I program a channel such as 467.1234, does this mean it's 12.5 spacing? (As opposed to 467.1230- whereas the last digit is a zero? And if so, will the rss automatically recognize it as 12.5 spacing? Or do I have to change it manually? My radio works fine, but the audio always seems "scratchy" and I'm wondering if I programmed it correctly. Thanks.

[escomm]

No, channel bandwidth is completely independent of whether or not you're using a splinter frequency with a 2.5KHz channel step. These are two separate concepts and should not be conflated.

[wa6ylb]

In programming a Visar, I'm unclear as to bandwidth settings:
if I program a channel such as 467.1234, does this mean it's 12.5 spacing? (As opposed to 467.1230- whereas the last digit is a zero? And if so, will the rss automatically recognize it as 12.5 spacing? Or do I have to change it manually? My radio works fine, but the audio always seems "scratchy" and I'm wondering if I programmed it correctly. Thanks.

The answer: Almost. Radios tyically only synthesize on channels that are divisable by .005 (5 Khz) or .00625 (6.25 Khz). This allows them to select all the traditional channels plus the splinter channels between those traditional channels. This doesn't apply for the eventual "Narrow - Narrow" band channels.

There are splinter RF channels, the ones which have four numbers after the decimal point, such as .2875. In the VHF band, channels were originally on 30 KHz spacing, with "splinter" channels every 15 KHz between these. On UHF, the regular channel split was 25 KHz, with 12.5 KHz splinter channels typically used in low power stations. (I.E. .2875 vs .2750)

Don't get these confused with deviation setting per channel in the radio, requardless of the actual RF frequency. The 25/30KHz setting is the typical 5 KC deviation (wideband), with 20Khz band with = 4 KC deviation, and 12.5Khz channel bandwidth is what we call 2.5 Khz deviation or the new buzz word for "narrowband". The 12.5KHz bandwidth is a summation of the amount of deviation (+-2.5 KHz plus the highest frequency (typically +-3 Khz) plus a small guard band around that. Add it all up and its around 12.5 KHz of bandwidth.(25 KHz for wideband)
You can have a narrow band deviation on a regular band plan channel (traditional channels like .850) or on a splinter channel, such as .8625.
The FCC typically limits the splinter channels to be narrow band, as operating them in wide band would certainly cause a problem to the traditional channels. When you look at the frequency list, in part 90, there usually is (or had been many years ago), a stipulation saying you could only use the splinter channels
in very low power mode with wideband deviation. Each channel may have has its own stipulations, so I refer to Part 90 for more examples.

This is the reason the bands are converting over to narrowband modulation. You couldn't live on a splinter channel well, if there was a wide band user on the traditional channel next to you, as the actual bandwidths overlayed each other (the wideband user hammers the narrowband user on an splinter channel). If all the users select narrowband deviation, its a much easier proposition being on a splinter channel next to a traditional channel (distance between users on channels 12.5 KHz from you helps here too).

[Johnx]

Ah, I think I understand more clearly now, none of my current freqs are "splinter" channels thus far, and my deviation is set at 25/30. So I think I'm good to go. Thanks for the education. J.

[wa6ylb]

Ah, I think I understand more clearly now, none of my current freqs are "splinter" channels thus far, and my deviation is set at 25/30. So I think I'm good to go. Thanks for the education. J.

Not quite. The setting for deviation is seperate from the RF channel being programmed. On newer radios, the setting of deviation is on a per channel basis.
While some MFG's may try to be tricky and cause the deviation to be set to narrow if a splinter channel is programmed into the radio, don't count on it. Check.
B.

[Johnx]

Ah, I think I understand more clearly now, none of my current freqs are "splinter" channels thus far, and my deviation is set at 25/30. So I think I'm good to go. Thanks for the education. J.

Not quite. The setting for deviation is seperate from the RF channel being programmed. On newer radios, the setting of deviation is on a per channel basis.
While some MFG's may try to be tricky and cause the deviation to be set to narrow if a splinter channel is programmed into the radio, don't count on it. Check.
B.[/quote
Is this a per channel setting? Or radio wide? (on Ht1000/Visar)
Thanks.

[wa6ylb]

Ah, I think I understand more clearly now, none of my current freqs are "splinter" channels thus far, and my deviation is set at 25/30. So I think I'm good to go. Thanks for the education. J.

Not quite. The setting for deviation is seperate from the RF channel being programmed. On newer radios, the setting of deviation is on a per channel basis.
While some MFG's may try to be tricky and cause the deviation to be set to narrow if a splinter channel is programmed into the radio, don't count on it. Check.
B.[/quote
Is this a per channel setting? Or radio wide? (on Ht1000/Visar)
Thanks.

It should be per channel. I'll have to go pull an visar / ht1000 archive to tell you where. Look for channel options while in each channel's entry page.
B.

[Johnx]

Thank you in advance