On Tue, 14 May 2002, Jim wrote:

>   "A simple monopole needs more careful matching
>    and tuning than a dipole"
>
>Practical experience in the real world will not
>bear this out ... ever seen or used the classical
>Motorola 19" whip on 2 Meters? No matching network,
>mates up directly to RG-58 50 Ohm coaxial cable and
>deleivers reasonable preformance for the simplicity
>and size ...

We are talking UHF and microwave here, low power, no voltage or power
margin on the Tx, very poor noise figure on Rx (relative to what is
possible), high noise background from FCC compliant (pun intended) nearby
office computing equipment.  Matching is everything. Tuning improves the
noise margin on Rx and the useful in-band power (a little) on Tx. I don't
have to tell you this. A legal 433MHz 1mW transmitter at 5V had better be
matched *perfectly* to a *tuned* whip to be heard at 30 feet by a
similarly prepared receiver. This is NOT the case in 99% of the cases (see
millions of usenet postings - also on this list - from people who are
disappointed by the range obtained), because the ground plane/shield/box
whatever is not appropriate or because of nearby wires and metal objects,
even if the layout, and antenna are perfect (you wish).  Remember that
this is not twinax in the lab or on some high end navy ship stuff or the
best dreamland manufacturer figures obtained in an anechoic chamber and
rounded up or down, as appropriate.

>   "A vertical 5/4 lambda will outclass it"
>
>You *might* be alluding to a "5/8 wavelength antenna" - and
>you would be closer to corect ...

Yes, that's right. Whew, I'm posting after midnight again ...

>  "a lambda/4 whip probably costs them 6dB in transmitted power"
>
>Again, practical experience will not quite bear this out ...

This one I HAVE to insist on. Believe me, real life sucks, engineering
wise, 99.999% of the time. I know because I make my living out of
engineer's mistakes ;-) ;-). They are sort of, paying my salary, you see ?

I'll stop now. I state based on my experience that by adding a tiny load
coil (1 turn 4mm dia) and/or a 0.8pF-6pF trimmer at a whip at both Tx and
Rx you can up the range by at most 30% in many cases (at 433MHz).

Peter

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