AT-271/PRC Fishing Pole Antenna
NSN 5820-00-242-4967OE-505
© Brooke Clarke 2004
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| AT-271A |
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| AT-271A |
In W.W. II the BC-1000 used the AN-130 & AN-131 "Fishing Pole" type antennas, later the Korean conflict PRC-8, PRC-9 and PRC-10 Squad Radios used the AT-271 "Fishing Pole" antenna. Then the AT-271 was used on the PRC-25 and PRC-77 Squad Radios and also on the PRC-104 HF radio. A number of commercial radios also use the AT-271.
The construction is the same as is used for sectional fishing poles. Each of the 7 hollow tubular metal sections has a plug one one end and a socket on the other end. All the sections are connected by a string made of either a cloth or metal cord. At the bottom of the base element there's a spring inside the tube to tension the cord. This way all the elements are kept in order when they are disconnected from each other and are held together when assembled into a 113.5" (2.88 meter) meter long antenna. When an 8" long base is added the overall length is 121.5" (3.09 meters). When disassembled the package is only 17 inches long. 7 sections times 17 inches is 119 inches, but the plug ends go into the socket ends so the overall length is shorter than 119". There are some web pages that erroneously give the length as 7.5 Feet.
The AB-591 Antenna Base has a male 3/8-24 thread which is the same as is used on most ham radio and CB antennas. The base also has a center pin that actuates the antenna switch in the PRC-25 or PRC-77 radio to switch from the BNC 50 Ohm output to the whip antenna. (My Tape Whip Adapter will accept the AB-591 and screw into a standard ham or CB spring base for stationary applications.) Some sort of spring base is needed when this antenna is used because the hollow antenna elements will "fold" if too much force is applied to them.
Fabric cord & Stainless Steel
spring.
Since the spring is at the bottom of the lowest antenna element you want to avoid jamming it's operation. This means that when assembling the antenna you start with the lowest section and when taking down the antenna you start with the top section. This way the spring is not trying to pull the string around joints the are open.
AB-129/PR
This is the 8" long base used with the PRC-8, PRC-9, PRC-10 and PRC-104.
It has a female 3/8-24 thread to accept the AT-271 and a male 3/8-24 thread to go into the radio. This is a spring base, not a gooseneck base. It is straight, but will bend when force is applied to it. If I try to bend it and use strong force it bends maybe 20 degrees.
AB-591/PRC-25
The PRC-25 was designed to use two different antennas.
The AT-892 is a 1 meter long tape measure type antenna that's used with the "Part/Of AT-892" (p/o AT-892) gooseneck base. This is for shorter range communications.
For longer range communications the AT-271 antenna is used with the 8" long AB-591 spring base. The PRC-25 (and the PRC-77) need to change antenna matching for the short or long antennas and so the threads on the radio are 5/16-24 to prevent the AT-271 from being connected directly to the radio. This way when the AB-591 which has a "finger" below the 5/16-24 threads is installed a switch is actuated selecting the antenna matching circuitry for the long AT-271. When the 1 meter tape antenna is installed the switch is not activated and the match is for the short antenna.
AB-1135/PRC Ground Mount
AB-1135/PRC is an angle iron stake that can be driven into the ground and will hold the AB-591 + AT-271 Antenna. The mounting block that accepts the AB-591 looks just like the antenna block on the PRC-25 or PRC-77 and has a right angle BNC(f) connector on it's bottom side.
These new in government wrap are being sold by Jim Wiliams & Sons Surplus on eBay as "Military Radio PRC-25/77 Antenna Ground Mount". The AT-892 + flex base is about 1 meter long and will be near 50 Ohms at 75 MHz. The AT-271 + AB-591 is about 3 meters long and will be near 50 Ohms at 25 MHz.
4 Sep. 2003 - By opening a joint and folding the top sections of the AT-271 down beside the lower sections and tying them together you can make a number of different lengths of whip antenna. Using this method you can easily match the AT-271 to the frequency of operation.
Experimentation is needed here using the 4395A as a network analyzer to see what bandwidths are possible for each of the above configurations. Then a range of frequencies could be given for each one.
# Sections connected
Len in.
Freq. Mhz
7
120
25
6
104
28
5
88
33
4
72
41
3
56
53
2
40
74
1
24
123
Tape Whip Adapter
This adapter has a female 5/16-24 thread to accept the bottom AB-591 threads and has a male 3/8-24 thread to go into a standard ham or CB antenna base, thus allowing the use of the AT-271 with the protection of the AB-591 spring base.
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