BATC Forum

The latest from the IARU studies are available here: https://www.iaru-r1.org/2022/23cm-band- ... tu-r-wp4c/

The scale of the problem for the amateur services is becoming clear. For example, the studies predict that even a 10W 23cm band station could cause interference to RNSS receivers at up to 30km on the antenna main beam heading. Although the level of amateur activity and the density of users is quite low (compared to other more popular bands) the issue remains that from a regulatory perspective the amateur services are required to not cause harmful interference to RNSS services.

Although this may sound bad news, I do know from talking to Barry G4SJH that everything possible is being done to preserve the amateur allocation, although it may not be in its current form. Also, the UK is fortunate in having the band extension from 1300 - 1325 MHz where all our TV repeater outputs are.

73
Noel G8GTZ

Will they be shutting down all the radar stations in and adjacent to 23/24cms band

The Belgian radar can wipe the band out at times on the east coast in Essex …especially if there is a bit of enhancement

Radars are a primary user, like radio navigation satellites. Primary users will need to sort out any interference between them on an equal footing. Amateur radio is a secondary service and should not cause interference to primary users. If it does, it will have to stop doing so. The easiest way to achieve that is to turn it off, but this is a 9.1 agenda item for WRC23, so should not result in any regulatory changes. What it is likely to mean in practice are restrictions to licences to ensure interference isn't harmful.

I don't tend to follow WP5A but had a look at the preliminary draft CPM text that has appeared as a draft output, and points to the new recommendation M.[AS.GUIDANCE], which will provide guidelines in order to harmful interference to RNSS receivers in future.

The initial draft of the recommendation is a sea of grey, green and yellow highlighting (i.e. not agreed) but seems to be moving towards proposing power limits in segments of the band that coincide with satellite navigation signals. I expect it will be worked on next week.

The various proposals range from power limits of 5mW to 100W for narrow band modes. For broadband modes like ATV the proposals range from complete exclusion to 100W. There are also proposals for the amateur satellite service, which is earth to space, that would severely limit earth station EIRP.

The May meeting is not done yet, there are sessions all next week and curiously the ITU are not having time off for the Platinum Jubilee. I will try and remember to look up the latest texts.

Mike

>Radars are a primary user, like radio navigation satellites. Primary users will need to sort out any interference between them on an equal footing.

Er - NO!!
The Radio Regs give absolute clear super-primary priority to the radars - and that unfortunately meant that the GNSS signals are inherently weaker and wider bandwidth receivers than they need have been - with rather unfortunate consequence that a primary 'weak signal' service is attempting to claim protection for its inadequate receiver and waveform design. Meanwhile Climate change will require more 23cm radars in any case as many folk are already experiencing down the East Coast.

We are of course secondary, but that is no excuse for sub-standard GNSS-Rx. Interestingly CEPT WGFM this week has a presentation on GPS jamming - (non of which is amateur), showing the scale and location of the real culprits in adjacent bands:
https://www.cept.org/Documents/wg-fm/70 ... 5_gnss-rfi

The 23cm situation will be a key one in IARU Interim Meeting (C5-VHF-Micorwave committee) later in June, where RSGB has is prepared to propose a full analogue ATV shutdown in this band as part of the changes needed to mitigate and replan the band below 1300 (as the UK section at 1300-1350 is largely out of scope).

73

Murray G6JYB

Er - yes. I didn't say anything about how primary users sort out interference but they do so on an equal footing, as in they at least have something to stand on, just some are more equal than others, depending on what it says is whatever footnotes / sharing criteria apply. Secondary users have no such footings.

I agree on the receiver side. It sets a dangerous precedent that will impact all secondary users if it goes through.

Mike

The latest update from the IARU is available - please do take a look at it and start to understand the possible implications for 23cms so it does not come as a surprise in 2024 when there are changes made to your license by Ofcom.

I think it is safe to say this is probably not the time to invest much money in more 23cms wideband FM equipment.

https://www.iaru.org/wp-content/uploads ... ne2022.pdf

We should all be very grateful to Barry G4SJH and other members of the IARU team who as volunteers have put in a lot of hours to try and win compromises on behalf of the amateur community worldwide and without them, this would have been a whole lot worse....

73
Noel