Thanks Larry,
You are making my simple mind spin.

Seriously though, I am truly appreciative of your advice in this and
all matters. What you say about backstay aerials makes sense and I
shall do as you suggest. What I would really like, as do most others,
is long range voice comms. If anything reasonable helps in any way, I
will do it. There is nothing quite so annoying as to not be able to
receive an interpretable weather fax because of poor reception.

I'll add the ground from my stays. By the way, I neglected to tell
that I have a painted box section wooden mast, deck stepped. Forestay,
backstays and capshrouds are electrically connected due to their
attachment at the head of the mast. There is an aluminium sailtrack
which has no connection. Should this be a factor for consideration?

My specific area of small expertise over the past few years has been
packet data and such as better compression algorithms, up and down
linking to comms satellites, and the problem of latency or delay in
resending packets - solved by a really neat way of transmitting two
packet streams, with a slight delay on the second. If one packet
address is missing or denatured in some way, "it" merely grabs its
copy from the second incoming stream without having to ask the
originator for a resend and the consequent latency or time delays
whilst waiting - speeds it up no end. Probably been invented before
somewhere else but that sort of thing happens all the time. The
tracking system can track all of our active patrol boats as well as
Indonesia's ( and give postion, direction, speed and a lot of other
data in sub minute real time as well as sending and receiving text
messages and orders. If we needed to, we could add engine revs,
temperature and a lot of other really uinnecessary stuff.

Even though mobile phones are just glorified two channel radios, So
far as radio propagation (and most of the rest of it) has failed to
lodge in my brain successfully.

Thanks again for being so helpful and for freely disseminating your
experienced advice to those such as me whom you will probably never
meet.

cheers
Peter

On Fri, 27 Apr 2007 16:33:31 +0000, Larry wrote:

Peter Hendra wrote in
:

Oh, and what is an optimum length and diameter - covered in plastic or
bare? - I know, only a project manager would want precision such as
this.

Thanks for all of this Larry. I shall follow your advice.



Optimum length would be 5% longer than 1/4 wavelength of the frequency
you are operating on. 1/4 wavelength in meters is 75.7/frequency in Mhz.

So, if we are on 6 Mhz, for instance, we get 75.7/6 x 1.05 = 13.2 meters.

But, because the radiating element ISN'T a proper length and we are using
a tuner, just make it LONG and the tuner will tune out the reactance and
match it up...

--------------------------------------------------

On another issue you have brought up, you said you had two backstays in
parallel, one with insulators that is the antenna and one that is not and
is solidly connected to the mast, right??

If this is so, in close proximity to the radiating element, that second
backstay is simply absorbing a major part of your radiation from the real
antenna, greatly reducing your actual field strength at some remote
receiver. We can't stop induced, out of phase, RF currents in any of the
rigging, but you can reduce it, greatly, giving you a nicely stronger
signal.

If these backstays are as I think, please consider putting insulators at
equal distance in BOTH backstays,not just one. Then, run a jumper
between upper end of the bottom insulators, effectively paralleling them.
Feed the tuner into the CENTER of this jumper, which can also be two
equal-length wires from the HV output of the tuner to the two insulator
feedpoints. The effect of doing this is a radiator that is MUCH greater
in "virtual diameter", both radiating IN PHASE, which aids their field
strength. Instead of the second backstay absorbing the signal, it will
create more signal, in phase. If your tuner is below them, you can
either make a T to feed the two backstays or just Y them out of the
tuner, itself, with EQUAL LENGTH conductors to preserve their phase
relationship.

Larry