Re: LF: Re: 8kHz of spectrum ERRATA

[M0FMT <m0fmt@yahoo.co.uk>]

 Sorry divide my 10

 

".......for a QSOs in the worst case about 850kcs away or if its CW I would.............."

 

Should read......................>>>

 

".......for a QSOs in the worst case about 85kcs away or if its CW I would.............."

73 es GL Pete M0FMT IO91UX47VN

From: M0FMT <m0fmt@yahoo.co.uk>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Sent: Thursday, 3 November 2011, 11:27
Subject: Re: LF: Re: 8kHz of spectrum

 

Hi Mal its not the same. We are talking about a maximum of 3kcs separation but more likely to be only one to half a kcs. The IF selectivity can sort that OK but what it can't do is stop front end being flattened by the proximity of a station running hi power. On every other band HF of 600m we can achieve relatively wide separation. In other words if a station is desensing my RX on 160 I can go and move and look for a QSOs in the worst case about 85kcs away or if its CW I would just have to give up like 600m. But even then on 160 its not too bad largely because of antenna selectivity which you don't get on 600m owing to the narrowness of the band. Its not so much the power alone its proximity and power and the narrowness of the frequency separation.

My guess is you don't have any competition on 600m because I have never heard a station on the band within your QRA square so maybe you don't understand the phenomenon.

 

Anyway I am working on it over a period of time but at the moment 600m is a dead-loss around here because I flatten ADSL in a big way even with mico power. The effect is not temporary because the exchange DSLAM sees 500kcs as noise and shuts the data rate down to a level that seems to require human intervention at the exchange to reinstate the miserly 1.2mbs that BT laughingly call Broadband.

 

Any way thanks for the prompt I'll try some more ..... just thought, if you look at the PSK31 screen dumps I attached in another mailing yesterday you will see the effect just 50Watts RF out probably between 1/4 to 1/2 W radiated does to my RX sensitivity from 6 miles away over fairly flat terrain.
I think it would mess your RX up as well.

 

73 es GL Pete M0FMT IO91UX47VN

From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb_lf_group@blacksheep.org
Sent: Thursday, 3 November 2011, 1:19
Subject: Re: LF: Re: 8kHz of spectrum

Pete

We all manage on 160 metres where the same criteria applies. You just need selectivity and expertise.

Some operators get nervous when Watts are mentioned and prefer uWatts.

You must be having a hard time with the Mega Watt commercial stations adjacent to the amateur bands, how do you cope ?

mal/g3kev

 

----- Original Message -----

From: M0FMT

To: rsgb_lf_group@blacksheep.org

Sent: Wednesday, November 02, 2011 11:16 PM

Subject: Re: LF: Re: 8kHz of spectrum

Hi all

In my humble opinion high power only goes with wide band width because ground wave on these medium frequencies travels. So I welcome the lower power suggestion (assuming anybody sticks to it) with the narrow band width proposal. And don't jump on me about front end selectivity  because I think it is insurmountable even by "Real" Amateurs.

73 es GL Pete M0FMT IO91UX47VN

From: James Moritz <james.moritz@btopenworld.com>
To: rsgb_lf_group@blacksheep.org
Sent: Wednesday, 2 November 2011, 22:58
Subject: LF: Re: 8kHz of spectrum

Dear LF Group,

Well, I think this is a positive development - the only minor disappointment is the reduction in maximum ERP to about 3W.

As for the choice of frequency, the maritime people have a plan for a sort of  "super Navtex" using OFDM modulation with a bandwidth of 10kHz centred on 500kHz. It may be that this is just a pipe dream, and/or a way to justify continued primary user status at 500kHz. But if it ever does come into existence, it will certainly be using vastly higher powers than amateur stations, and the noise sidebands will extend well beyond the actual signal bandwidth due to "spectral re-growth" in the TX PA. So it will be good to have a significant difference in frequency between ourselves and the noisy things. I expect all those REAL amateurs will manage to reduce their TX frequency by 5 percent somehow ;-)

Cheers, Jim Moritz
73 de M0BMU