The succinct math is this: Going from wide to narrow makes for a 6dB reduction in SNR due to half deviation of the transmitter, but around a 3dB gain in SNR at the receiver, due to narrower RX filter bandwidth. This equates to around 3dB less overall SNR. Other factors come into play, but the overall range will be somewhat less on narrow vs wide. Whether or not it makes a substantial difference depends on the original coverage. But it's never better.
Here in the UK, we have been narrow-FM for 20+ years now. Sadly this does still be above the ability of many to deal with. Especially those who grupm about a repeater clipping them as the repeater filtration is super tight. 70cm went the same last year but it just slipped in quietly. Ofcom (our version of the FCC) do not dictate how we use the bands, it is the RSGB who "advise" the best use of the bands based on IARU and ITU regulation. When people do work N-FM it all fits nicely and does NOT degrade audio if both sides of the QSO are N-FM.
Is this based on actual real life voice audio with constantly changing frequencies and deviation or a 1 kHz test tone that never changes at 2.5 kHz (or 5 kHz) deviation that never changes?
Neither. It's just "best case" math. There is no instance where narrow band deviation is equal to or better than wide band deviation, all things remaining comparable. If narrow was somehow better, why wouldn't we just continue to reduce deviation to 2, 1.5, 1 or .5KHz deviation? Why stop at 2.5?
What appears to be happening out there is a gradual transition from Repeaters and Links to Hotspots and finally loading Apps like Echolink, Droidstar and Peanut onto Smartphone for convenience. Change is the only Constant but this Change might not appeal to some or many. KH6/G3SEA
The question "is WHY?" In most areas of the US analog repeaters are dead and are dropping off the air one-by-one. Day to day, the band is an empty wasteland. It's going to take more than NBFM to bring them back. It will take something like packet or auto-patches once were to give hams a reason to get back on 2-meter FM.
Sorry, I think, & here's my blunt 2 cents worth, its a stupid idea, Why do we need or want this ?? to cram more unused radios on the air. NO NO and furthermore NO
There are too many repeaters with zero traffic. A lot of waste. I was a bag carrying tech in the later 60s early 70s land mobile in the NYC region. Did a lot of part 90 wide to narrow refits, often reminding the users the older radios despite new filters and retune will not work as well as before. We weren't wrong then but that was 15Khz deviation to 5khz shift. A lot of the radios that did't or could not be narrowed ended up in Amateur hands where it was cheap and worked. Now we have a far larger number of radio that are 5khz deviation and cannot be changed (tx deviate reset and narrower RX filters). They will perform poorly and there are far more than back in the early 70s. Worse, many are cheap enough (low quality) that even with current spacing they are crap. FYI de-sensing is a very common receiver failure on decent radios and china has not done much to help that. That and the desire for wide tuning range that negates narrow filters in the front end. I didn't mention nor have others what about the 6M FM, few repeaters and many unused. Some of that was because of CH2 TV (analog days) being an interference source. Shame too as most provide very good coverage. So first get rid of repeaters that are simply there (allocated but dead), and unused, or worse unusable (many due to terrible sites, low or obscured). There are few active ( more than 1 qso per day) repeaters in the eastern New England region and more than a few inactive. That suggests wasted space. 222 and 440 also has that though 222 is mostly unused. As to planning overlapped repeaters have proven a source of interference PL or not when on the same frequency. Planning should if anything provide best possible coverage of a region across multiple channels as modern radios are frequency agile and not rock bound (crystals) for at least the last 30 plus years. Over 50 years of radio... lot of good ideas badly implemented or worse wrong choice of frequencies. It needs work.
I would suggest DMR via Brandmeister group of 1500+ talk groups and 2 TG's per repeater. Audio is great at 12.5kHz. DMR mode to repeaters or simplex is far superior at 4X the range with lower power, better penetration, better battery life, less heat and very intelligible with compander, versus FM. Utilizing one talk group with many DMR repeaters to access from anywhere in the world is far superior to old technology. I too started in 1967 on FM now age 72, it is time to utilize today's superior technology and take a different path. Try an Anytone 878 dual band, dual mode FM & DMR, with 500K ham location & name storage, GPS, Sat auto doppler shift xmit and receive in real time, APRS in digital and FM and fast talk group access to anyplace in the world full quieting and can just utilize a rubber duck with direct call access or text to another ham or group. Doubling and noisy FM signals are a thing of the past. Personally I would convert many under utilized FM repeaters to DMR very cost effectively and give new life to utilization of the repeaters in case you wondered where all the hams went from FM to DMR.
WHy not forget FM entirely and go with translators and SSB on 2M. The entire point of a repeater is to make use of the mtn top tower to get more range. SSB is 3khz of BW . CW and psk is even less. 73 Pete ve3hoh/w3
No. There are no overcrowding problems. The 2m band is completely empty and the repeaters are totally unused. I think there is some mistake here. Wrong time period? Have you listened to the radio since 1982? It makes no difference anywhere whether you use narrow or wide. The band is empty.
