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+---- Thread: Comms: Where are we now? (/showthread.php?tid=5428)
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Comms: Where are we now? - Lightspeed - 26 June 2013
To get an up to date indication of the SUK group's coms capability, please could you respond to this latest poll?
BTW this poll is anonymous.
RE: Comms: Where are we now? - Jonas - 26 June 2013
I wonder if folks have backup power source(s) to power their comms if the grid goes down?
RE: Comms: Where are we now? - Lightspeed - 26 June 2013
(26 June 2013, 16:40)Jonas Wrote: I wonder if folks have backup power source(s) to power their comms if the grid goes down?
We haven't discussed this in depth Jonas, but for sure a number of us have this covered.
Thanks for the reminder.
RE: Comms: Where are we now? - Grumpy Grandpa - 27 June 2013
I would have contributed to this poll but couldn't find a tickbox for - 'haven't got them, haven't planned them and haven't even thought about it yet'!
RE: Comms: Where are we now? - Lightspeed - 27 June 2013
(27 June 2013, 07:53)Grumpy Grandpa Wrote: I would have contributed to this poll but couldn't find a tickbox for - 'haven't got them, haven't planned them and haven't even thought about it yet'!
RE: Comms: Where are we now? - BeardyMan - 27 June 2013
Just need NVIS set up now, but that stuff called money keeps getting in the way...
RE: Comms: Where are we now? - Tarrel - 27 June 2013
(27 June 2013, 08:03)BeardyMan Wrote: Just need NVIS set up now, but that stuff called money keeps getting in the way...
Doesn't have to be expensive. For a base station, fabricate a home-made half-wave dipole and mount it around 2-3 metres above the ground. Connect to radio with balanced feeder, or via a Balun and coax. Or, use a simple long wire, again mounted close to ground, and connect to radio via an antenna tuner. It is the closeness to the ground that makes it NVIS.
For mobile, take a long whip, attach it to vehicle near the front using a gutter mount or similar. Bend it back towards the rear of the vehicle and tie it down with an insulated rope, so you have an arc-shaped antenna. Vehicle body takes the place of the ground.
HTH
RE: Comms: Where are we now? - Lightspeed - 28 June 2013
(27 June 2013, 08:03)BeardyMan Wrote: Just need NVIS set up now, but that stuff called money keeps getting in the way...
Hi BM
Tarrel's advice on antennas is spot on.
Daylight NVIS is generally recommended on the 7MHz band and night time on 3.5Mhz band.
There was a plan for the Ham members on this forum to start NVIS transmissions and to then give a report back on what techniques and frequencies have been found to be most effective. I will re-launch that idea in a short while. The idea is to give best advice on what systems are viable in real world conditions.
Interestingly, over the last month or so propagation in UK has supported very short range (NVIS?) communications UK wide on the 14Mhz band. On several occasions this has also happened on the CB band as well.
RE: Comms: Where are we now? - Highlander - 28 June 2013
(27 June 2013, 23:16)Tarrel Wrote: Or, use a simple long wire, again mounted close to ground, and connect to radio via an antenna tuner. It is the closeness to the ground that makes it NVIS.
I was lead to believe that to have the antenna too close to the ground would not give good results, because of the fluctuation of the wetness in the ground
RE: Comms: Where are we now? - Tarrel - 28 June 2013
(28 June 2013, 09:38)Highlander Wrote:(27 June 2013, 23:16)Tarrel Wrote: Or, use a simple long wire, again mounted close to ground, and connect to radio via an antenna tuner. It is the closeness to the ground that makes it NVIS.
I was lead to believe that to have the antenna too close to the ground would not give good results, because of the fluctuation of the wetness in the ground
If that's a problem, you could bury a layer of chicken wire or similar in the ground beneath the antenna, to provide a more reliable earth. Opinions vary about how low to the ground an NVIS antenna needs to be. General view seems to be around 1/8 wavelength or less.