146-147 MHz

The place to discuss reduced bandwidth fast scan amateur television on 70cms and below
g6jyb
Posts: 24
Joined: Thu May 09, 2013 12:57 pm

146-147 MHz

Post by g6jyb » Tue Oct 14, 2014 12:23 am

Greetings

On Friday Oct-10, Ofcom's statement confirmed the release of 146-147MHz on a temporary NoV basis

On Sunday, Oct-12, the RSGB Convention had a presentation on '146-147 MHz A New Frontier for Amateur Innovation'

Links and Slides are here:-

http://rsgb.org/main/operating/band-pla ... m-release/

The plan is the NoVs should appear around here at then end of October:-

http://rsgb.org/main/operating/licensin ... plication/

By then the various new IARU-R1 DATV recommendations should also be available - that apply to across the VHF/UHF/Microwave bands (inc this one)

regards

Murray G6JYB

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: 146-147 MHz

Post by G4GUO » Wed Oct 15, 2014 7:40 am

Currently I am rushing to get a narrowband system up and running.
I have just added a low bandwidth channel mode to the DATV-Express software
although I need to add extra digital filtering so it is clean enough (close in)
for 146 MHz.

On the receive side it looks as if www.sdrplay.com may be able to help us.
Their SDR is based on Mirics developed chips (the one used in the frontend
of the funcubePro+ SDR) which were designed for a SDR based TV receiver.
Consequently they have PC based DVB-T demodulator software that works with
their device and the API they supply will allow the narrow bandwidths we need.

So things are looking rosy I just need to build a small highly linear PA and some
filters for the band.

- Charles G4GUO

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: 146-147 MHz

Post by G4GUO » Wed Oct 22, 2014 10:35 am

I contacted Mirics to see if they still sold their MSi3101 evaluation board and they do not.
Due to the small market for this Narrowband Application while they were very encouraging
we are too small for them to work with and they referred me to sdrplay.com

Devices based on the Mirics chipset seem no longer to be available but here is a list of
old devices that use this chip http://sdr.mirics.com/forum/archive/ind ... ead-3.html
those that like to hunt for things on eBay might be interested.

The sdrplay avenue still needs investigating but in the meantime I am trying to use a RTL
dongle instead which is better than nothing. I have almost finished implementing a DVB-T
demodulator in C (this has been done by others already but I like a challenge).

I had hoped to use 500 KHz channel spaced DVB-T but it is proving a challenge to keep the
out of band noise to -60 dB so I am now looking at using 437.5 KHz channel spaced DVB-T
but in a 500 KHz channel. By choosing this channel size we get a sample rate requirement
of 500 KHz, although for my implementation I will use a multiple of that. 500 KHz is the
lowest rate the sdrplay devices support btw.

I will report again when my modem software achieves first lock but as has been said before people
should write up what they are doing even if it turns out to be a spectacular failure.

IF I manage to get it to work I plan to release the source code as a C library and as a GStreamer
object. I have done all the smart maths and it should now be an issue of getting it to work in the
real world.

On another note for transmit I am going to be using a modified version of the DATV-Express software,
a standard DATV-Express board and a GH Engineering based 60 watt PA, by running it at only 5 watts
output there should be little noticeable spectral regrowth, I will report on my findings later.

- Charles G4GUO

G3VZV
Posts: 21
Joined: Mon Feb 25, 2008 12:38 am

Re: 146-147 MHz

Post by G3VZV » Wed Oct 29, 2014 5:51 pm

There is a new FAQ page available on the RSGB website - this gives useful guidance about how we should be using this "new" band!
http://rsgb.org/main/files/2014/03/146-147MHz_FAQ.pdf

G4GUO
Posts: 625
Joined: Tue Feb 16, 2010 12:51 pm

Re: 146-147 MHz

Post by G4GUO » Sat Dec 20, 2014 9:31 pm

Here are some initial tests using DATV-Express on 146.5 Mhz at a symbol rate of 333KS/s
http://www.g4guo.blogspot.co.uk/

I am hoping we will have some further news in the next few days about a real QSO .....

- Charles

g6jyb
Posts: 24
Joined: Thu May 09, 2013 12:57 pm

Re: 146-147 MHz

Post by g6jyb » Wed Oct 12, 2016 10:57 pm

For info, I have added a pdf of the 146 update from RadCOm Oct-2016 here:-

http://rsgb.org/main/operating/band-pla ... m-release/

regards

Murray G6JYB

G4EWJ
Posts: 711
Joined: Wed Feb 17, 2010 10:11 am

Re: 146-147 MHz

Post by G4EWJ » Thu Oct 13, 2016 10:48 am

The NOVs expire at the end of this month. Are they going to be renewed?

Brian

g6jyb
Posts: 24
Joined: Thu May 09, 2013 12:57 pm

Re: 146-147 MHz

Post by g6jyb » Fri Oct 14, 2016 6:29 pm

G4EWJ wrote:The NOVs expire at the end of this month. Are they going to be renewed?

Brian

HQ is working on it !
(and 71)

Murray

g6jyb
Posts: 24
Joined: Thu May 09, 2013 12:57 pm

Re: 146-147 MHz

Post by g6jyb » Fri Oct 28, 2016 1:33 pm

Just in time, another years worth of 146-7 is available - you can renew now:-

http://rsgb.org/main/blog/news/gb2rs/he ... z-nov-now/

My thanks for various presentational efforts which were used to impress Ofcom on recent progress

Murray

G4EWJ
Posts: 711
Joined: Wed Feb 17, 2010 10:11 am

Re: 146-147 MHz

Post by G4EWJ » Fri Oct 28, 2016 9:50 pm

Bravo!

Brian

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