On Sun, 24 Aug 2003 10:23:36 +1200, Fred wrote:

Thanks Barry and others for your informative replies. When I talked
about security, I meant being able to find someone to talk to if you got
lost or fell down a cliff etc. If you have a CB set with you and you are
lost in dense bush, at least searchers can listen out for your signal if
they know the frequencies you are likely to use. In circumstances like
this, where no cell phone signal is available (and this often happens in
the bush believe me) a CB radio could be really useful in an emergency.

A UHF CB would be just as useless as a cellular phone in such a case.

If you're that worried, carry a locator beacon. That's what they're
designed for and satellites have the advantage of looking damned near
straight down, so terrain is irrelevant.

Oh BTW, always take an unwanted CD with you and learn to use it as a
signal mirror, they work great, BUT DO NOT TAKE A MICRO$OFT one, you
know how insecure their stuff is !

If you're going to take half a helioscope, you should make sure you know
how to use and aim it. the hole in the middle is there for a reason on the
old-style ones, as was the matchstick thingie with the loop on the end. It
makes aiming trivial, even if you can't see the light hitting the far
target.

Hint, look through the hole, hold a stick at arms length, line up the end
of the stick on the target, then aim the sunspot so the hole is
surrounding the end of the stick. You have pinpoint illumination and no
shaking is required. If someone's looking in your direction, you'll get
their attention fast.

This works at distances in excess of 50km. I've used it to setup antennas
- it's a good idea to confirm you're aiming at the right remote hilltop...

Practice helps....

On Sun, 24 Aug 2003 01:11:12 +0000, "Uncle StoatWarbler"
wrote:


If you're that worried, carry a locator beacon. That's what they're
designed for and satellites have the advantage of looking damned near
straight down, so terrain is irrelevant.

That's not a bad idea, they are quite cheap nowadays, at least for the
1/2 freq ones. Be aware though, that around 90+ % of all alerts are
false. And the satellites can only locate you within quite a large
sphere. Then it's down to the SAR air and ground teams. A signal
mirror and loud whistle will help them locate you much more easily.

The 406MHz COSPAS/SARSAT ones are much more accurate, typically about
200-300metres just from a satellite fix, but they are also much more
expensive. Depends on how much you are worth!


If you're going to take half a helioscope, you should make sure you know
how to use and aim it. the hole in the middle is there for a reason on the
old-style ones, as was the matchstick thingie with the loop on the end. It
makes aiming trivial, even if you can't see the light hitting the far
target.

With a CD. I just hold my thumb at arms length over the target, then
sight through the CD hole, and get the reflection onto my thumb, hence
the target. Works great, and it seems like they are custom made for
signal mirrors.

On Sun, 24 Aug 2003 19:35:16 +1200, Barry Lennox wrote:

The 406MHz COSPAS/SARSAT ones are much more accurate, typically about
200-300metres just from a satellite fix, but they are also much more
expensive. Depends on how much you are worth!

It won't be long before the new generation combines a gps fix with the
distress squawk.

With a CD. I just hold my thumb at arms length over the target, then
sight through the CD hole, and get the reflection onto my thumb, hence
the target. Works great, and it seems like they are custom made for
signal mirrors.

The problem with using your thumb is that your hand will obscure more of
the reflection than a stick will.

On Mon, 25 Aug 2003 00:26:46 +0000, "Uncle StoatWarbler"
wrote:

On Sun, 24 Aug 2003 19:35:16 +1200, Barry Lennox wrote:

The 406MHz COSPAS/SARSAT ones are much more accurate, typically about
200-300metres just from a satellite fix, but they are also much more
expensive. Depends on how much you are worth!

It won't be long before the new generation combines a gps fix with the
distress squawk.

They already exist right now, and have done for about 6 years, but
they are expensive, and that won't come down too much. The problem is
the 121.5/243 MHz ones cannot support embeddded data, and
COSPAS/SARSAT plans to stop monitoring these freqs in 2006 (I think,
maybe 2008) because of this limitation and the VERY high rate of false
alarms, over 90% in most countries, inc NZ.

The 406 MHz ones certainly support embedded data, but you pay a lot
for them. The big cost driver is the very stable oscillator required,
plus the many thousands required for certification.