Chairman’s Chat - June 2015
Wideband, Narrowband, what is this all about and what does it mean to us? Why are the committees of both CTARC and Oakdale opposed to a move to FM narrowband deviation at this time?
Firstly, a bit of background: There are 8 possible frequencies for 2 metre FM repeaters on our current wideband scheme; 145.600, 145.625, 145.650, 145.675, 145.700, 145.725, 145.750 and 145.775 MHz. If you listen around on 2 metres you will note that most of the time all of the local repeaters sit silent or perhaps one is in use. During rush hour sometimes you may find 2 or 3 repeaters being used, but not often.
Right away you can see that we are very fortunate to have so many possible repeater channels to use and we hardly make use of most of them. Some of our repeaters go for several days without any usage.
Now, what is the purpose of the narrowband concept? There are several technical reasons not to go to narrowband, including the reduction in range in weak signal conditions. The only technical reason to move to narrowband is so that you can fit twice as many repeater channels into the existing space. Instead of 8 possible repeaters you could have 16 repeaters.
Some European and a very few American cities with large and active ham populations have moved to narrowband to gain the extra channels and, for them, the move to narrowband is both necessary and sensible.
In this area you hear every week, the Western Cape Repeater Working Group (WCRWG) who maintain our repeaters are continually looking for funds to maintain our existing repeaters. Neither CTARC or Oakdale clubs can see a purpose in installing another 8 repeaters, even if we had the funds to purchase, license and maintain them.
Proponents of the move to narrowband point to the fact that turning down the deviation level on older equipment (the type most of us still use) will make it compatible with narrowband. This does make the transmitter compatible but not the receiver which will now pick up the new repeaters installed on either side of the channel you are using. And if they are not going to be installing repeaters on either side of the existing ones, then why are we moving to narrowband in the first place?
The Oakdale and CTARC Committees believe there is more to this unnecessary move to narrowband than meets the eye. Time will tell.
Additional confusion also exists around ICASA rulings. ICASA has decreed that VHF stations move to narrowband as there are more Commercial stations than there are frequencies available. This ruling makes sense for Commercial repeaters which are what the ruling was aimed at. I wish we still had our old type of radio inspectors who understood the difference between Amateur and Commercial operations and regulated them accordingly.
ICASA does not allocate what modes and channels we are to use on our 2 metre band. In fact if you check in the regulations, Annexure I which details the Amateur frequencies you will see that the law simply states that we can operate from 144 to 146 MHz all modes except Pulse or Fast Scan Television. That’s all the law says. The old Radio Inspectors knew that Amateurs were a self-regulating group that could sort themselves out as we have historically done.
The only repeater in our area that is still on wideband and therefore usable with all past and current production equipment is our 145.750 repeater. This is ably maintained by our Dave Perry ZS1SG. If you have older equipment that does not switch the transmitter and receiver between wide and narrow you will appreciate the insistence that ourselves and Oakdale have taken to keep 145.750 on wideband until there is a valid reason to need to change it to narrowband.
73
Rob / ZS1SA
CTARC Chairman
Update:
A debate on QRZ.com about Narrow-vs-Wideband FM [here].
A survey by one of the US ARES groups about Narrow-vs-Wideband FM [here],
and another [here].
A technical article about Narrow-vs-Wideband FM [here].
A Frequently Asked Questions page [here].