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We are allowed to use 300 baud on many HF bands. We are allowed to use 1200 baud on 10mFM. We can run up to 19600 baud on 6m and 2m. On 1.25m (219mhz) we can have any baud rate up to 100khz bandwidth. The top part of the 1.25m band (222 - 225) says we are limited to the bandwidth of voice emissions for whatever modulation type, so FM? On 70cm (420-450) we can do 56kbaud.
The actual frequencies we'll use for packet radio are dependent on the band plan and your neighbors. The ARRL publishes a band plan here. Their chart discusses digital modes but lays out frequencies assuming a continuing meteoric rise in FM and packet radio starting in the late 80s. For instance, there are 31 separate six meters channels designated for FM simplex channels. In practice the one frequency that is the most common, 52.525, is so rarely used that moving off that frequency (to spare the calling channel) is considered ridiculous. The two meter plan has the New OSCAR subband from 144.30 to 144.50 even though the most common packet radio frequency in the USA is on 144.39. The only mention of packet radio on the plan for 2m is that 145.01, 03, 05, 07, 09 are widely used for packet. They were back in the 90s. I don't think they are common anymore. However, in the 90s, 144.91 through 145.09, every 20 khz, were saturated across much of the country. Note that ARES claims the use of 144.99 through 145.09 throughout North Carolina!
My assumption is that if we use a frequency that is scheduled for repeater linking, or simplex (not including the national simplex frequency) that we're safe from prosecution. It behooves us to talk to the local repeater coordination agency about any link that we decide to keep on-the-air, especially if the link includes a site that is HT range of any repeaters. I think we should be concerned about showing up on somebody's repeater linking frequency, or control link frequency.
Our point to point links from house to house are very low impact compared to what repeater councils are used to regulating. TARPNs require a spread of frequencies. The repeater councils and the ARRL put packet into chunks of frequencies instead of giving us frequencies on different parts of each band. By the letter of the law, we just don't want to interfere with somebody who does have a coordination. There is enough spectrum to go around. We just have to be willing to move first if something happens. This isn't the battle on whose field we want to die on.
SERA's frequency recommendations (South East USA)
SERA's band plan page
SERA 440Mhz Frequency Use Plan from 2000
SERA 144Mhz Frequency Use Plan from 2008
Here is a another, disparate from the ARRL and SERA plans list of suggestions for point‑to‑point links, i.e. between two stations.
Keep in mind that you can, and probably should, use the same frequency somebody else is using over again.
Just be sure the other packet link is quite a bit below squelch threshold at both ends of your link, and your two transmitters are below squelch on the other link's receivers.
If they can break your squelch, they can stop you from transmitting.
Eventually other people are going to discover that we have a growing network and are gobbling up frequencies.
If we can use the same frequencies over again, we won't be accused of using up the entire band.
I can easily see that accusation being said even if we only have two low power stations with yagis and home locations on each frequency.
Some 'official' packet radio users put digipeaters in wide coverage commercial tower locations.
They'd claim the use of an entire 20khz wide channel for a thousand square miles to link two sites for one or two days a month!
Expect people to paint us with the same brush.
In this document, low profile means, under 10 miles coverage, directional if possible.
| 10 meter band | We're allowed 1200 baud on 10mFM but pay attention to the frequencies allowed for fully automatic operation.
I don't think this is a good idea. Continuous propagation changes will cause links on 10m to be unstable. | ||
| 6 meter band | 50.6↔50.8 | 7 channels-exclude .62 calling channel | 19200 baud |
| 51.12↔51.18 | digital repeater inputs - some of our equipment is here | 19200 baud | |
| 51.50↔51.60 | simplex voice - largely unused - put packet here | 19200 baud | |
| 53.90↔53.92 | repeater outputs - use 2 channels if separation needed | 19200 baud | |
| 2 meter band | 144.31 | 1 channel | up to 19200 baud |
| 144.33 | 1 channel | low profile sites only | |
| 144.35 | reserved for satellite Lilacsat-2 | ||
| 144.37↔144.49 | 6 channels | up to 19200 baud | |
| 144.91↔144.99* | 5 channels | up to 19200 baud | |
| 145.01↔145.09* | 5 channels | up to 19200 baud | |
| 145.51↔145.77* | 14 channels | up to 19200 baud | |
| 147.495 147.555 147.585 | 3 channels if separation needed | up to 19200 baud | |
| *Note: ARES in NC claims 144.99 through 145.09, and 145.51 | |||
| 1.25m band | 219↔220 | can be wide | 100khz wide max |
| 222.36↔222.44 | 5 channels | FM voice channel, no symbol rate limit | |
| 223.66↔223.78 | 6 channels | FM voice channel, no symbol rate limit | |
| 223.80↔223.88 | 5 channels | FM voice channel, no symbol rate limit | |
| 224.10↔224.98 Repeater outputs | The 220 repeater sub-band is not heavily used and repeater outputs could be co-opted for packet radio. Beware that you could interfere with users of a repeater or take interference from a repeater during band-openings. If you need to do a split to shield your own local voice access to a 220 repeater, or to enable multiple 220 links from the same site, use recommended digital frequency in the 222Mhz range paired with a repeater output in the 224Mhz range with odd split. Don't use any repeater output frequency which is in use within 120 miles and don't use any repeater input frequency. Check repeaterbook.com. See coordination note below. | ||
| 70cm band | 420.00↔430.99 avoid ATV | can be wide | allowed up to 56kbaud |
| 433.00↔434.98 avoid ATV | can be wide | allowed up to 56kbaud | |
| 439.600↔440.600 | 41 channels | use for FM channel bandwidth, but allowed up to 56kbaud | |
| 441.025↔441.075 | 3 channels | low profile use for FM channel bandwidth, but allowed up to 56kbaud | |
| 445.525↔445.600 | 4 channels | use for FM channel bandwidth, but allowed up to 56kbaud | |
| 446.025↔446.075 | 3 channels | low profile use for FM channel bandwidth, but allowed up to 56kbaud | |
ATV Channels line up with CATV channels 57 through 59 These have the following carrier and frequency range.
Note on coordination:
As I understand coordination, the FCC authorizes the ARRL to negotiate conflicts for frequency overuse, especially around repeaters and other systems with fixed input frequencies, like links and control inputs.
If the ARRL or one of its agents receives a complaint from a registered (with the ARRL or its agents) user of a frequency, they can first request the non-registered user to stop
using the frequency, and if that request is not respected, then they can file a complaint with the FCC.
This could result in license suspension for the interloper.
It behoves us to register our frequency uses with the ARRL repeater coordinating council in the area. However, the repeater coordinating council is likely to be uninterested in your request for registration if you are not following the local repeater coordinating council's recommended bandplan. Also, repeater coordinating councils may not be particularly interested in your link if it doesn't fit within their framework for repeater operations. They may also be recalcitrant about using repeater frequencies for non voice repeater operations.
Repeater coordination councils may require or at least respect membership in the council in order to request coordination.
Southeast Regional Repeater Association is here
Your mileage may vary.