telescopic antenna

wt is the minimum frequency one can detect with such available antennas ? or rather can we detect frequencies in hertz range ?

A telescopic antenna is collapsible. It is a series of small diameter tubes of 6 to 8 inches in length nested one inside the other. The antenna can be extended to its full length or retracted to a small length for storage of portability.

Radio antennas are optimally sized based upon wavelength of the frequency they are expected to "see" . Even multiples of wave length are also used for antennas to minimize there length. i.e. ( 1/2 or 1/4 wavelength)
Antenna wave length (lambda) is base on the speed (c) that a radio signal travels which is about 3x10^8 m/s (300000000 m/s) divided by the frequency (f)

lambda = c / f

Frequencies in the hertz range would have wavelengths in the 1000's of kilometers range. So any practical length antenna (2 or 3 feet in Length) would work just as well as a larger 5 to 10 foot antenna as the wavelength is so large.

2007-12-13 09:10:09 by baadshah

Test Yupiteru MVT 7300 telescopic antenna receive CW On 40m in town

It's basically a telescopic arm, with 4 cylinders. The problem is, its to be controlled electrically. I just need the interior mechanism, like the threads and such stuff by which I could build a telescopic arm, with 4 cylinders, that would move in and out of each other. Only the mechanics of it, not the electric aspects. I'd really appreciate ideas and links with sketches. Thanks.

It would help to know the dimensions of the arm when extended and retracted, what sort of loads are being imposed, but I can see two solutions, mechanical and hydraulic. The mechanical solution involves a thread on the inside of each cylinder engaging with a rotating threaded cylinder with the thread on the outside. One cylinder will then slide up and down the other. Concentric arrangements will then drive the cylinders further up the arm. The hydraulic arrangement will involve more precise machining but is much more elegant. Each cylinder is hollow, so that the exterior represents a piston and the interior the lining of a cylinder. As fluid is pumped in or out of the assembly the arm is extended or retracted.

2009-04-29 09:05:04 by Ajit S

Price: $29.95

BCN connector
Telescopic (8" collapsed, 27" extended)
For hand-held CB radios
High tensile strength

I have a portable tabletop radio with a telescopic antenna, how can I construct a simple outdoor antenna, and how does it connect to the radio

Take a piece of thin wire (22ga or 26ga from Radio Shack)....strip enough insulation off to wrap the telescopic antenna several times to HOLD the wire on it, about 5 or 6 inches will do.....

THEN find a tree or something like a ROOF and take enough wire off the <<50 foot>> or 100 Foot spool and.....

FLING IT !!

Or get somebody that can.....

You'll be getting your local radio stations in no time.....

You didn't expect Germany or Japanese radio did you?
How would you understand them anyways?

2008-06-18 01:51:28 by bfandrk

4NBF, 4NBP, 4VF, 4YBF, 6XA
2VR, 2NBR, 3PB, 3PM, 4NBL
Replacement Transmitter Antenna for the following Futaba Radios: 2L, 2NL, 2NLS, 2P
2PB, 2PKA, 2PD, 2PBKA, 2V
6XH, 6YF, 6YG, 7C series

A friend of mine says they are pushed upwards either pnuematically or hydraulically. Is he right? If not, then what is the mechanism?

They are made up of 3 or more pieces of metal shaft inside of each other. Inside that is a plastic line with teeth on it. On the bottom of the largest shaft is a motor with teeth as well. When power is applied to the motor it extends upwards and then reversed when power is taken away.

2007-09-22 16:02:10 by AL R

I have bought a telescopic antenna for my scanner. I am interested in listening to the VHF frequency 130 MHZ. I can extend my antenna upto nearly two meters, but for this frequency,what will be the optimum length of extension ?

Optimum is a quarter wavelength for a whip aerial.

Wavelength (metres) = 3 x 10^8 divided by Freq (Hz)

i.e. 3 x 10^8 div by 130 x 10^6 = 2.3 metres

A quarter wavelength for 130MHz is thus 0.577 metres.

2008-06-14 10:28:11 by Nirmala