[Scanner] "Waterfowl" antennas
Harry Marnell
[email protected]
Sat, 15 Jun 2002 18:20:26 -0700
For folks more inclined to take the simplest route with most-familiar =
units of measurement, another "formula" for determining the length of a =
half-wave is to divide 5616 by the frequency in MHz, which gives you the =
approximate halfwave length in inches... e.g.
for 150 Mhz: 5616 / 150 =3D 37.44"
for 42 Mhz: 5616 / 42 =3D 133.71" (a definite problem with a =
handheld!)
for 460 Mhz 5616 / 460 =3D 12.21"
for 850 Mhz 5616 / 850 =3D 6.61"
for 900 Mhz 5616 / 900 =3D 6.24" =20
Quarter-wavelength antennas would be exactly half those lengths, of =
course [or 2808/MHz - F (in)]
Harry Marnell
http://www.snowcrest.net/marnells/kma367.htm <~~ LAPD Communications =
History
----- Original Message -----=20
From: "Edmund F Leavitt" <[email protected]>
To: <[email protected]>
Sent: Saturday, June 15, 2002 17:46
Subject: [Scanner] "Waterfowl" antennas
>=20
> On Sat, 15 Jun 2002 17:46:18 -0500 "Mike Urich" <[email protected]> =
writes:
> > From: "anthony costa" <[email protected]>
> >=20
> > I have a radio shack pro 91.I listen mainly around the 800-900 mhz=20
> > freq,I
> > now use a telescopic antenna in the retracted position.6" in=20
> > height.the
> > signal's are in and out.Now on the vhf freq's it has great=20
> > sensitivity,But i
> > listen mainly on 800 mhz.any good ht antenna's for this band??
> >=20
> >=20
> ****************************************************************
> c. A half wave antenna is generally able to perform well,
> independent of a ground plane, making it desirable for use on hand =
held
> devices. (Another place this comes in handy is for mounting on
> fiberglass roofs of travel trailers and the like.) Typical designs
> include end fed coil matched "whips", and at higher frequencies, =
center
> fed "coaxial" or "sleeve" antennas. =20
>=20
> [As an aside: If you've ever wonder how long is a half wave antenna, =
the
> math is simple...divide 150 by the frequency in MHz and you have the
> approximate length of a half wavelength IN METERS. If you are more
> comfortable with inches, you can approximate by multiplying meters =
times
> 39. eg. 150/900 MHz =3D 0.16 meters or about 6 1/2 inches.
>=20
> That says that if you are looking for a half wave antenna, expect it =
to
> be about one meter long for 150 MHz, 0.3 meters or 30 centimeters =
long
> at 450 MHz, around 18 centimeters for Cellular/Trunked freqs, and =
around
> 16 centimeters for 900 MHz.]
> Recommendations:=20
> a. If you are receiving the stations in your area well with
> whatever you presently use, be happy...invest your money in the stock
> market. If you need better, buy better.=20
> b. If you use the factory rubber duck a lot, recognize that =
it
> is designed to work fairly well in the 153 MHz range. Consider =
buying
> one(s) designed specifically for the frequency ranges you like. Same
> comment applies for mobile antennas. With either, it's probably
> reasonable to ignore the difference between a cellular (824-896 MHz)
> antenna, an "800" (806-866 MHz) antenna, and a "900" (865-965 MHz)
> antenna. The profusion of cellphones probably makes mobile cell =
antennas
> the easiest to find and the cheapest to afford.=20
> c. Want to play around to see just how foul that fowl =
antenna
> is? Find a weak station in the 860 part of the band using your =
factory
> rubber duck antenna. Listen with the squelch open or just barely =
closed.
> Cut a paper clip to 3 3/4 inches in length (approximating a 1/4
> wavelength antenna at 860 MHz). Make sure there are no jagged ends on
> the paper clip that could damage the radio's BNC contacts. While
> monitoring a weak conversation, carefully replace the duck with the =
paper
> clip, by inserting the end of the clip into the center contacts of the
> BNC connector. Let go of the paper clip. Also, be certain not to =
change
> the radio's position when you switch back and forth. If the duck =
works
> consistently as well or better, keep it.=20
>=20
> If the 1/4 wavelength paper clip works consistently better, I would
> consider shopping for a UHF antenna. Splurge on a half wave 800 MHz
> rubber duck. It will probably be worth the bucks. Does this =
procedure
> sound too simple and too crude to be meaningful? It is not. I'd be
> interested to hear from a few users how their factory ducks stand up
> against the 1/4 clip.=20
> ***************************************************************
> Edmund Leavitt Ph: 253 582-5034 =
=20
> =20
> Ham/MARS/SHARES: KA7UKN / AFA5AH / KPS654 =20
> Lakewood, WA N 47=BA 09' W122=BA 31'
> _______________________________________________
> Scanner mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/scanner
>=20
--- StripMime Report -- processed MIME parts ---
multipart/alternative
text/plain (text body -- kept)
text/html
The reason this message is shown is because the post was in HTML
or had an attachment. Attachments are not allowed.
Please post in Plain-Text only.---