I want to pay attention that
UHF antennas for mountain climbing has the own specificity. So,
antennas having the gain more the 6-9-Db-dB
are not necessary in mountains at big height (from 3000 meters
and is higher), as well as you do not need mast for the antennas.
Also I prefer not knock- down antenna design.
This antenna was developed specially for high-mountainous
trip proceeding from my previous experience. At the first place
I stand following characteristics: gain, weight, reliability.
The antenna is optimized of the maxima forward gain. The design
is made not knock- down that is
very conveniently as the antenna is always ready to operation. You can hold
the antenna by its tail and direct the antenna to your correspondent
1 shows the design of the antenna. The boom
is made of an ebonite rod of 412-mm length and of 8-mm diameter.
Antenna elements are made of a copper wire of 2- mm (#12 AWG)
diameter. 50 Ohms coaxial cable is soldered to antenna vibrator
without any symmetrical and matching devices. The coaxial cable
goes along the boom and get out from the antenna tail. Antenna
elements are fastened to the boom by epoxies. The antenna can
place above or inside a tourist backpack.
The coaxial cable has length of 50-mm.
The place of the soldering of the coaxial cable to the vibrator
must be protected from the weather. Antenna has weight of 150
gramm. 150gramm, real gain of 6-7 dB above half-wave dipole. SWR
is: at 433-MHz =1.8:1, at 435-MHz =1.4:1, at 438-MHz=1:1, at 440-MHz=1.5:1
( it as measured by device 'SWR-121').
I recommend to use the antenna with low-power UHF radio (10-mWtts)
for a range 433-434 MHz. I have 30- 50 kms of distance (at direct
vision) using the antenna with such station. Also I recommend
to use the antenna with usual UHF radios, be
sure, you easy will skip more than 100-kms!