Icom_AH-2_review_1987.pdf

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1、D . TheICOM AH-2 HFMobileAntennaSystem BYlEWMCCOY,WllCP Hereisthe tuner with theweatherprooftopremoved. TheCOM AH-2 is acomplete digitally controlled,HF,all-band antenna system. If that soundslike a mouthful,it is! Basic- ally, the AH2 is an automatically tuned antenna system thatcovers 3.5 MHz thro

2、ugh the 10 meter band (and with any antenna longerthantzmeters.it willcov er160also). There are se.eral piecesof equipment in the system, including an antenna, which is a9footwhip. Theantenna sys- tem is designed tobeused with either the ICOM 735,745,or751.Thecontroller unit is attached to the trans

3、ceiver used, and it in turn is connectedvtacables to the re- motely mountedtunerunit(at thebase,or end of the antenna). Thetunerunit is completelyweatherproofed and sealed. AsI foundIrommytests, the AH-2 has an extremelywidematching range. It is designed for the9loot whip, but I tested the systemona

4、 widevariety of antennas (including open-wire feed, balanced-fed dipole,butmore onthat in a moment), Be- fore mounting it in amobile setup, first tested it inmy home stationso that Icould try a.ariety of antennas. The AH-2 has a controller unit that is connectedtothe transceiver. Thecon- troller uni

5、t ismountedtothe side of the transceiver and connections are made from the radio.An RFcable from the con- troller is connected to thetransceiver. along with four conductorcables. Fig. 1 is a circuit diagram of the tuner unit, and as can be seen, it is acomplex circuit exceptfor the actual antenna ma

6、tching portion. ha.e also included a block diagram of the controller, fig.2,to pro.idemore information.Theactualtun- er is essentially an extremelywide-range pi network. Here is basicallyhowthesys- tem works. When the TUNE buttonon thecon- trollerunit is pushed. thetransmitter comeson(atvery lowpowe

7、rbecause the controller alsocontrolstheALC line in the transcelver).This small amount of power *TechnicalEditor,CO.200IdahoSt., Silver City,NM88067 42COAprI11887 is fedtothe tuner unit, and both thetor- ward and reflected.oltagesareanalyzed .lathe ratherextenstvecomputerctrcutt- ry.Very rapidly, a s

8、eries of small relays (21) areacti.atedanddeactivated.al- ways seekingthegreatest range orlevet offorwardtoreflectedvoltages. When the voltage ratio attains alevetof 1.5to1 or less, the unit considersthecircuit matched and shutsdown.Nowget this: This whole procedure is usuallyaccom- plished in 1 or

9、2 seconds! The secret of the system, to me at least, is that the ICOM engineerscorrectly realized that an$WAof 1.5to1, for allpracticalpur- poses, is just as good as 1to1. andbe- lieve me, it is. The 1.5to1 ratio ismuch. much easiertoobtain, and of course quicker. The unit is designed towork into en

10、d- fedwires having a single outputterminal. However, likemanyamateurs,Jhave an overwhelmingcuriosityaboutTrans- matches andtuners, havingbuiltand de- scribed somanyover the years.So, de- cidedtohookupthe AH-2 to feed bal- ancedlines (open-wire or Twinlead types of feeders). I hookedupatoroidal balan

11、c- ing transformer such as Ihaveused in the Ultimate Transmatchandothersto the single-ended AH-2 output andchassis ground, lea.ing me with balanced output on theotherside of the transformer. Next, I connected open-wire feeders s.yYouS.WIIIn CO , , s , ,. - .,. . . _. . -. . - .,. . .- e . , , ; I -

12、. - , - I a ! , , ! , I , . , , ;, -Ii !. - : I , , . ,.-, .,. lto , . .,. .- , i I i , - , - . ,!, ,. I I:q! ! ,._- I ioo- . ,. -, 1111 1 i ,. - I I I. I 0 ; r ,., Iill , , , . , ,rmm,.I it,.!. , . i i I , , , -,. l ._. I I -. ; I I I i , - , -: , , . . , i.l. , . ,. - ,-.- I I ., I-. , I I .- tUB

13、flm . . .-s s ;: ID _. .,. .,n . . o . . J!J .,. JB ,. . . ,.n .r ,.,.-l,t:o Ii.n_ - .,. . ,. . . . -li . I I . jF . ., . . . . - ,. I. ,. . -10: ,. - 1 , ,. i I . I Fig.1-Circuit diagramofthe AH2 luner unit. Aprt11987 co - 43 frommylarge (150loot)center-fedanten-. natothe transformer. I then starte

14、d on r- 160metersandprogressedcleardownto , A.,. 10 meters. covering all bands (at bolh .-., . ,. if - ,. ends). I can saythatwithout reservation . I ,. . the AH2matchedto lessthan1.5 to 1on . ,., 1 all these frequencies-andon each oneJ as last as you can say one one-thou- ._.-. _.J.-I _. of -, f-Io

15、:=z: c,.,. ,. ,.c lime of 2 1 0 4 seconds. Also, the specs . ., 0 - . saythattheluner hasover250,000possl- _. .-, eoMe,.,. eret-Ocombinations (and Iamsureit 1 does).II A 9 foot stainlesswhipandmounting . l-r- - . system isprovided formobile,marine.or - _., RV work. Imountedthewhipontopofmy Ti 21 foo

16、ttrailerandtestedthesetupon80 . _. through 10.Thewhiphas no loadingcalls 0., .,. 0$AGOI.oc lengthsmatchedandworked. lSC1OI ThepowerratingoftheAH-2 is 120 . .c. walls. There is no reasonwhytheunit L. ,0 B could notbeusedwithothertypesof120 N .c,.0_ n_ - Jr+ POCKET SIZED ISOOMHZ ,_. FREQUENCV COUNTER

17、8Ul.T. TESTED.AJJ AAOVTQ-GOt ,- ONLY$49.95Prepaid 1. .o I : w Io,I HANDHELD 11300 MHZ c,. FREOUENCV COUNTER BNCINPUTCONNECTOR Fig.3-Block diagramofthe controller. ONLY119.95 waltrigs.However.andthis isveryimpor-isusedtoconnectthe rigandcontroller PICK UP THOSe WEAK tantowhateverrig is usedtheremustb

18、eatothetunerunit.Additionally, acoaxline SIGNALS FULLV systemsetupsimilarto ICOMsin thatis neededfromthecontrollertothetuner. ENCLOSED PA19E HAS 5200 MHZ RANGE.whentheTUNEbuttononthecontroller isFifteenfeet is adequate for most mobile POWERSUPflV OPTION pushed,thelevelofthetransmitterisinstallations

19、,butJcanseemanycasesin ATJ)CHARGE WITH ThISPREAMPliFIERdroppedto10wallsorless(5 to10watts).whichanamateurwouldmountthetuner ONLY$24.95Prepaid (seefig.3.blockdiagramofthecontrolleratgreaterdistances. Anytypeofon- w-._.h.r.; -AutomaticControlline.)Therearetwocuctorcablecouldbeusedaslong asthe LEOsonth

20、efrontofthecontroller.onegroundandhot leads (12.5 volts)willhan- PA-2OEPAE-AMP for TUNEconditionsandtheotherfordie 2amperes, becausethatIs the maxi- FULLvENCLOSED WITH A OCIOOOMHZTHROUGHoperation. In TUNEagreenmumpowerratingofthetuner. RANGE AND POWER. LED lightswhenthe tuner unit is matchedOverthey

21、earshave hadmanyre- SVPflY OfTION andreadytouse. A red LED lights whilequestsforthedesignofatrulyautomatic ONLY$34.95Prepaid tuning is inprogress.andredTUNE)andtunerthatcanbeusedremotely.After us- Wlthou1c-.Slt.r.; yellow(THROUGH) LEOs lightwhentheIngtheAH2.particularlywiththetuned Speo;llyDI.adIo_c

22、wdel0ll_,*,5 tunerisunabletoachieveamatch.JfeedersystemwhereI had complete DIGITREXELECTRONICS mightaddthatIneverencounteredthismatching.Iwouldstronglyendorseit. condition. but IassumeIt is possible withTheAH-2 lists at $495 without the whip division of NCIwest Coast:someextremelyhigh orlow reactive

23、antennaand $625withthe whip and 10073 North MaryannCall Ray Lukas loads. The THROUGH LED lights whenwhip-mountinghardware.TheAH-2 Is Norttlville, MI 48167605-497-2397 thetunerisbypassedandtheantennaismanufacturedbyICOManddistributed _-.coor,_ _OI_.CODIHOJNEP,nJ_fed directly.byICOMAmerica,Inc.2380116th Ave. CIRClEONONREADER SERVICE CARD A15foot (5meter)e-corductorcableNE, Bellevue.WA98004.Iij 44coAprll1987 Say YousawItIn CO