Tuesday, March 22, 2011

Changing the 30m bandplan

I have never had a JT65A contact on 30m. This is surprising. The 30m band is the most popular band for the WSPR mode which has demonstrated that it provides good propagation 24 hours a day. The trouble is that there is nowhere for JT65A to operate. The JT65-HF software frequency menu offers two choices for VFO frequencies: 10.139MHz and 10.147MHz. But the former will cause interference to WSPR and have you fighting it out with a phalanx of PSK signals and the latter conflicts with the frequencies used by APRS packet and other digital networks.

To those who wonder why you can't just find a clear frequency and operate I would point out that this doesn't work with weak signal digital modes. Not only will users of other modes not know you're there and call on top of you, but the DX you hope to work won't be able to find you either. So it's important to have a frequency of operation that has a good chance of being clear, where other users know to listen.

From recent discussions it appears that the two previously mentioned 30m frequencies were chosen in a desire to find a place to operate that fits in with the IARU Region 1 and Region 3 bandplans. In the USA (which is Region 2) narrow band digital modes can use 10.130-10.140MHz but in the rest of the world the area up to 10.140MHz is allocated to CW.

I have long believed (and have probably written before in this blog) that it is absurd to have different bandplans and different rules for different parts of the world because radio waves don't stop at national boundaries. I suspect that the allocation of just 10kHz for digital modes was made back in 1979 when the 30m was first allocated to amateurs, when the only digital mode was RTTY. Since then, and especially in the last ten years or so, there has been an explosion in the number of digital mode users (due to the increasing use of computers) as well as a proliferation of different digital modes. It is time the band plans were updated to reflect that.

I think the bandplan for 30m in the rest of the world should be brought into line with that in the USA. I have nothing against the CW mode but if 30kHz is enough for US amateurs to get by with then the rest of the world can also manage with 30kHz.

6 comments:

Paul - PC4T said...

Hi Julian, there not much JT65 activity on 30 meter, and you gave the reasons why. So I almost never work JT65A on 30 meter. The band is too small for it. My favourite JT65A bands are 20 meter, 80 meter and sometimes 15 meter. 73 Paul

Casey Bahr said...

Is the situation similar for 17 and 12 meters?

73,
Casey, TI2/NA7U

Julian said...

No. There's a bit more space, less usage (due to propagation) and there appears to be no permanent occupancy by networks and other unattended stations.

Paddy said...

Julian stick with it just worked VK3AMA on 10.138 this seems to be the choice freq for jt65 HF. What a wonderful program W6CQZ has created

SV9OFO said...
This comment has been removed by the author.
SV9OFO said...

Hi Julian.

There is no "legal bind" to the bandplan description, but that it is actually a "Gentlemens agreement".

In Greece, Law allows use of a given amateur spectrum allocation in any way users see fit, provided they do not cause intentional interference to each other, or to other primary users of the given allocation.

So, if a chunk of spectrum is available, i.e. not in use by other users, it is free for use even for 3k wide modes, like SSB!

Thus the "Gentlemens agreement" description of the IARU bandplan.

Is is defined as such by radio amateurs because it is extremely difficult (and even vaporizes versatility if you succeed in doing it) to try to embed a spectrum map in every ITU member state Law.

ITU member states telecommunication bureaus want versatility regarding their planning of spectrum usage and they wouldn't accept proposals for stict definitions like planning on "per KHZ" basis.

If you check with the actual ITU bandplan you will find that restrictions in spectrum usage are so complicated and densely interleaved regarding member states requirements that it is impossible for us hams to develop and implement any band planning other than nation-wise.


If there is no way of establishing 2-way communication but using negative SNR tolerant modes, there is no actual "requirement" before their use, but verifying that by using them you are not causing harmful interference to other users.

Technology lapses ahead and we amaterus owe to ourselves to pioneer. If there is a certain "gentlemens agreement" that needs revisioning, that need won't actually establish to our (the very "parts of the agreement") minds unless it is proven on the field first.
And to prove that the need is actual and well defined, we need to be able to experiment first.
If we hadn't been so far, we would still be stuck to CW and AM. Evolution and experimentation is the base on which most ITU member states laws regarding amateur radio are based anyway, to even stop amateur society from declining itself technological evolution.


73 de SV9OFO John
(p.s. sorry, had to fix some typos, me no native english user, hihi).