[chbot] A couple of interesting radio projects

[Robin Gilks]

> NPR looks like a V interesting project. Wonder how we justify 400kHz
> band occupancy on 432MHz - an open ID (callsign) is required for one thing
>
> I took some interest in the Si4463 a while ago - but using 100bps
>
> -Mark
>
> On 20/06/2020 12:24 AM, ceo at andygardner.com wrote:
>>
>> New Packet Radio...
>>
>> https://hackaday.io/project/164092-npr-new-packet-radio/discussion-146914
>>
>> Lora based emergency radio network...
>>
>> https://disaster.radio
>>
>>

Reminds me of the 23cm project from PE1JPD (I think) in the late 90's.

This is about the time I was very active with data modems on 70cm, 2m & 4m
running full duplex 9k6 links across the home counties in the south if
England (as well as 2k4 and 1k2 local links). I've recently given away all
the 9k6 modems, the 70cm Storno 5000 series radios etc as there is next to
no packet here and certainly not a 44 subnet IP network running faster
than 1k2 :( The 20 4 port TNCs I also brought from the UK went about 12
years ago!

The 9k6 modem used the original AVR CPU and was developed by Andy/g4xyw
and myself (I added the async interface, TX FIR and the 2k4 AFSK).

I can remember even 20 years ago having long discussions about the need
for CWID on data equipment despite the loss of bandwidth. Just as well I
implemented it as we had a node on a hill just outside Amersham on a cell
tower where the 20 harmonic of the receiver crystal was making its way
into the transmit chain and could be heard with a hand-held in the east of
London (Canary Wharf 50 miles away) on a frequency that was 2 MHz away
from what the unattended operation license allowed. Cross mod allowed the
CWID to be heard and the station (i.e. one of the groups nodes)
identified. Quick mods followed!

70cm in the UK used to allow wide bandwidth TV (405 line) transmission but
after 9/11 the defense ministry that shared the 70cm band basically shut
down most activity (no new licenses were issued). Not sure of the history
of the band here.

-- 
Robin Gilks zl3rob/g8ecj