Attached are copies of path profiles from Avon Valley to Roleystone,
kindly done by Milan VK6KTV using the Radio Mobile software.(WARG
members may recall William VK6KWT demonstrating this at a previous
meeting, last year).
The plots may not be 100% accurate (Milan asked me for the key info,
some of the figures I gave him are a bit rubbery, eg: antenna heights
on the Roleystone mast) but provide an interesting picture. The key
conclusion being that a Roleystone-Avon link is feasible, but it is no
picnic – the path loss doesn’t leave much fade margin at all.
According to the plots, a UHF link would need lots of antenna gain,
eg: stacked/bayed yagis, and possibly a low noise preamplifier. A 2m
link has a better path, but would require more complex filtering at
the Avon Valley end to prevent the repeater TX blocking the news RX.
(Click images to view full size)
I am putting this on the email list to allow some consideration/
discussion prior to the meeting tomorrow (or today…depending on when
you read this..)
My thoughts would be that the results are encouraging enough to
proceced with future experiments on a link path, but we should
expect some effort will be required to engineer a good solution.
I suggest a good first step would be to find & prepare a length of
LDF-450 cable (we have stocks of s/hand at Hillview) with suitable
connectors, ready to install to the VK6RAV mast at the same time the
problem antenna is changed, etc. Once the feeder is in place &
suitably weatherproofed a variety of antenna/RX system combinations
can be tried to see what works. Of course if a trial link antenna is
ready to go at the same time as the feeder, all the better. However,
if not I would still prioritise the feeder installation in the short
term – it’s a much simpler matter to climb a tower & swap antennas on
an existing feeder than to also have to run the feeder from scratch.
One other point I should make is that due to existing commitments I am
unlikely to have time in the near future to devote to much of the work
for this project. I suspect many of WARG’s techo “usual suspects” are
So, calling all hitherto non-techo WARG members, whether old-timers,
newcomers &/or newly licensed: over to you, were you thinking of
volunteering for a WARG project? Could this be the one? Come to the
meeting, discuss it further, put your hand up to be part of the team.
Us techos are not going to drop you in it – any questions you want
answered, any support you want, we will be there to guide the way. But
us small group of usual suspects can’t do all of the work by
ourselves. We need you to join us. Don’t think it all looks too hard.
(As I keep telling everyone: if I can do it, it can’t be that hard).
Sometimes it will be hard, but it is not impossible and you will learn
heaps. As you learn your confidence will grow, and at the end of the
day have the satisfaction of knowing you are helping develop our
repeater network & keep it running.
See you at the meeting!
BR & 73,
42 total views