In message , Helmut Wabnig
writes
On Sat, 21 Apr 2012 20:23:04 -0700, Jeff Liebermann
wrote:

gain. However, I'm not in the mood for building yet another
mechanical marvel, and will probably use the discone.


discones are fine, but like to pick up static.

Any more than any other vertical antenna (or even ANY antenna)?
--
Ian

On Sun, 22 Apr 2012 10:34:23 +0200, Helmut Wabnig [email protected] ---
-.dotat wrote:

On Sat, 21 Apr 2012 20:23:04 -0700, Jeff Liebermann
wrote:

gain. However, I'm not in the mood for building yet another
mechanical marvel, and will probably use the discone.

discones are fine, but like to pick up static.
w.

Static electricity or radio static noise? Static electricity should
not be a problem as the PCR1000 probably has a 100K resistor across
the antenna connector. This is standard on most radios. If not, I
can easily add one to bleed off any excess charge.

At VHF frequencies, any generated radio static should not be a
problem. The building is high enough that it might end up inside a
thunder cloud, where precipitation static might cause trouble.
Besides, there's not enough dielectric material on the discone to
build up much of a charge. If the humidity is low enough and the wind
speed high enough to create arcing, I'll have much bigger problems
than to deal with than a little static noise.

However, there may be another problem. We try to use grounded and low
impedance antennas on mountaintop sites in order to reduce induced
currents from nearby lightning hits. Both my proposed antennas are
ungrounded and/or fairly high impedance. Oh-oh.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Jeff Liebermann" wrote in message
...
On Sat, 21 Apr 2012 22:59:10 -0700, "Sal" wrote:

Nothing small is going to be broadbanded. Roy, W7EL, a contributor here,
offered his wisdom on antennas and it's been echoed by others, I'm sure.

Small
Broadband Pick any two.
Efficient

Words to live by.
"Sal"

Thats a good rule of thumb. However, this is a receive only antenna,
which does not need to be perfectly matched and can be fairly
inefficient and low gain.

Yup. As long as what you're giving up has a worthwhile advantage to
something else, go for it.

"Jeff Liebermann" wrote in message
...

snip

... However, what I was hoping for was some manner of
fairly short antenna (about 3-6 meters), with a fixed LC network that
yields a fair approximation of 50 ohms. 2-30MHz, without tuning. I've
been playing with such a matching network in 4NEC2, but getting
nowhere. Surely, such a thing exists.

I can address that but, alas, not with encouragement.

When I was working, my domain included Navy shipboard antennas, including
broadbanded HF transmit antennas, fed by banks of four or eight couplers
through 50-ohm Heliax. (Yes, I know your application is receive-only.
Please stick around.)

When a ship had the usual three antennas, they covered the range of 2-6,
4-12 and 10-30. At each one's feed point, a fixed, passive matching network
using two, three or four reactive components brought the antenna inside the
3:1 circle on a Smith chart. (We didn't adjust them, we just periodically
inspected and tested them. Why, Ye-es-s-s, we usually found loose, missing
or corroded hardware on the mast. Why do you think we climbed up there?)

I mention this because the Navy tried to get better by doing HF transmit
using only two broadbanded antennas (2-9 and 8-30) but had to relax the spec
to a 4:1 SWR. It worked on a few ships, but the radiomen often encountered
freqs that were difficult or impossible to tune, so they'd revert to a whip
antenna with a base coupler, like the Harris RF-601.

A good passive matching network for 2-30 seems unlikely. The Navy would
have bought them by now if "surely such a thing exists."

"Sal"