APRS 70 cm

[KK4IFN]

Good morning everyone!! Quick question.

I know the US aprs frequency is 144.390 MHz , but is there a 70 cm aprs frequency? If so, is it a dedicated frequency in the US or does it vary by location? Furthermore, is there any 70 cm aprs use in Tennessee or the Knoxville area?

Thanks everyone and 73's.


Andrew L.
KK4IFN

Sent from my iPhone using Tapatalk 2

[fineshot1]

Originally Posted by KK4IFN

Good morning everyone!! Quick question.

I know the US aprs frequency is 144.390 MHz , but is there a 70 cm aprs frequency? If so, is it a dedicated frequency in the US or does it vary by location? Furthermore, is there any 70 cm aprs use in Tennessee or the Knoxville area?

Thanks everyone and 73's.


Andrew L.
KK4IFN

Sent from my iPhone using Tapatalk 2

Most of the APRS I know of on 70cm is backbone links between nodes
and i think they are mostly on 441 Mhz but this does vary depending on
the area.

[KK4IFN]

Alright! Thanks! I've been trying to research online and from what I have gathered there is no dedicated 70 cm frequency for aprs, like the 2 meter 144.390 MHz.

Although I did find a UHF proposal written by Bob Bruninga, WB4APR, proposing the use of 445.925 MHz for aprs use. From the sounds of it, at present time it is only a theory and has not been developed.

I have noticed on aprs.fi that some of the stations show "Callsign using 70 cm". That is actually what first sparked my thoughts wondering if aprs was used on the UHF side.

Thanks again and 73's.





Andrew L.
KK4IFN

Sent from my iPhone using Tapatalk 2

[W9BU]

Originally Posted by fineshot1

Most of the APRS I know of on 70cm is backbone links between nodes...

Can you tell me where in the country you have seen APRS "nodes" linked together on 70cm?

The fixed infrastructure in APRS consists of digipeaters and I-gates. In my experience, the term "node" is not typically used with regard to APRS. Digipeaters are "store and forward" repeaters that re-transmit the APRS data that they receive. Both receive and transmit are typically on 144.390 MHz (in the U.S.). I-gates just receive on 144.390 MHz and then inject the APRS data they receive into the APRS-IS database. Reverse I-gates gate some APRS data, typically just APRS messages for local users, from the APRS-IS database to the local APRS frequency, again, 144.390 MHz.

Since APRS is a real-time information system, there's not much need for "node" linking. The position reports, objects, or weather data that I might be transmitting is useful to APRS stations in my local area, but not all that useful to stations outside my area. And, as long as there's an I-gate in my area, the information I'm transmitting is available on the Internet.

Perhaps you are thinking of packet radio, of which APRS is a subset, where switched nodes gate traffic from the local packet frequency to a backbone frequency.

To the OP, if you want to take advantage of the local APRS infrastructure, i.e. digipeaters and I-gates, you will want to use the frequency that is being used in your area. For most of the U.S., that's 144.390 MHz. In some special circumstances, for example, a search and rescue event where the users are fairly localized and you don't need to use the existing digipeaters, using another frequency is an advantage because you can pick a frequency that's less congested than 144.390 MHz.

[fineshot1]

Originally Posted by W9RXR

Perhaps you are thinking of packet radio, of which APRS is a subset, where switched nodes gate traffic from the local packet frequency to a backbone frequency.

You are correct, yes I said it incorrectly. I meant the packet radio nodes before APRS came into being.

Thanks for correcting me.

[KZ9G]

I ran a digipeater on 444.925 for almost six months and did not have a single packet except what I was generating. Took it down after that. I plan on moving it to a high profile location and see if there are any others using it now. In some areas this really needs to be considered. Traffic saturation is pretty bad in some metro areas. Put local traffic on the uhf frequency and have local info pushed to both frequencies. Gate whatever is on the uhf to vhf once or twice an hour.

[LtDoc]

I'm not aware of any widely accepted 70 cm frequency for APRS. There can certainly be 'locally' accepted 70 cm frequencies for it, but that's a 'local' thing. If using 70 cm works out the best for APRS for some reason then use it. Naturally, you should check for prior use of that frequency. The 'accepted' frequencies for APRS are just that, 'accepted', not 'formalized', or a 'hard-n-fast' rule by any means.
Have fun.
- 'Doc

[autovon]

I seem to remember reading the Kansas City has some type of UHF network. If there were some UHF digipeaters or igates near me, I would use those. I like to keep my dual band radio on VHF most of the time, so having the APRS side on UHF would make sense to me. Plus it would be fun to experiment with.

[kc4jgc]

There are no APRS UHF freqs that I know of amywhere in SERA territory, which Tennessee is a part of. There is an ALTERNATE 2m freq, 144.99 (note this is a standard 600khz offset), which is intended for mobiles/portables to transmit. Digipeaters listening on .99 would repeat signals heard on that freq on .39. This allows the mobiles/portables to be heard more reliably on .39 without collisions from other digis and fixed stations.

As far as I know, this is only being used in the large metro areas like DC/Baltimore where .39 is all but saturated.