73 Tests The
Heathkit HA-10 Linear
A I Brogd on W 4UWA/K3K M O
316 W e st Fairmount Ave nue
Sta t e College , Pe nnsylva nia
has come through again with a real
deal- where el se can you get a kilowa t t
for $230 1 The Heath IIA-10 sells for $230
in kit form or (for th e Citizens Band crowd)
$330 wired and tested. Th e kit takes about ten
hours to wire , so if you want to brag about
the time you did a j ob f or ten buck s an hour,
buy the kit and wire it yourself. A s with all
H eathk its , you need no knowledge of radio
or elect r onics-all you need is a r eaonable ability in r ea ding pla in English, and a hot solder ing i ron for where it sa ys (8) .
Th e HA-IO cir cuit is the "tried and th e
true" 8 Il A g rounded g r id cir cu it that has
been described a great numb er of times in
the vario us amateur radio publications. Thi s
particular k it uses fo ur of t he 8 U A 's in parallel to run 1000 watts PEP on sideba n d, 1000
wa t ts CW, 400 watts AM linear, or 500 watts
wit h a controlled -carrier exc ite r. A neat littl e
neutrali zing circuit is used that makes use
of a t hi r d w indi ng on the fi la ment choke for
t h e necessary fe edback.
Th e HA-10 has an untuned input circuit
t ha t matches th e 50-75 ohm output of mo st
exci ters, and a bandswitching tank circuit for
80 t hr ough 10 meters that use s a pi-section to
match 50-75 ohm loads . Any antenna outside
thi s impedance rang e should be fed through
a n antenna t u ne r. Th e in struction manual recomm ends t hat " every effor t be made to get the
SW R of t he a nten na down to less than 2 to 1."
Of cou r se, th is is no p roblem, sinc e most
modern ham s thin k it is impossibl e to "get
out" wi th an SW R high er th an 1.5 : 1, and have
th eir f eedlin es perfectly flat. Per sonally, I
wou ld rath er " get out" well than have a
pretty reading on a "vizwaa r" meter, but
some ham s prefer the pretty reading. But
I digress.
H
EATII
Condensed Speci fi cations
(
68
IJriv in-'t puw er required- 50 to 75 watt s . r epe n ding 011 freq u ency i n u sc.
Maximum power input- to OO watts P l<;P 88 B,
1000 wa tts C Wo 400 wnt t s AM (500 watt s co n t rolled ca r rier) .
Input drcuit- a p proxi ma te1y 70 oh ms, un tuned.
Oulput circuit-Pi-n et w o r k , 80 t h r o ug h 10 m et e r s .
50 to 75 o h ms.
'r u be eo m p le me n fe--Iour 811 A, t wo 861;A .
Pow er requtre mc nts-c- t t r v at', 50-60 cps , 125 0
watts ma xi mum.
Ca h i n e t si zt"- 19 lh " wide x ll .y~" h ig h x If) " deep.
Weight- 90 pou nds a c t ua l. 100 p oun d s II h ip lJ in g'.
The HA-IO's pla te power sup ply is a husk).'
full -wave r ectifier with a pair of 8(j6A's delivering nominal voltages of 1600 key-up and
1350 key-down . ( A note of exp la na t ion is in
order here . "Key-up" and "key-down" are
archaic phrases that allude to ancient times
when a mateurs u sed t elegraph keys for communications. T hese conditions are equ iva lent
to "no load" a nd "full load" respectively.} The
bias su pply delivers a stiff 4.5 volts to t h e
g rids of the 8UA's , with provision on the
rear panel for connect ing 45 to 150 volts of
cut -off bias during r eceiving period s. A cooling
fan is mounted directl y behind t h e 8UA compartment and comes on when the filaments
are turned on to in sure adequate cooling.
A single 1 rna meter is used for meteri ng,
being switched to r ead (full-scale) 200 m a
grid current, 1000 rna plate current, 2000 volts
plate voltage, and an arbitrary scale (0-1000)
relative power output. The r elative power output position is valuabl e for "on-the-nose" tuning, sin ce maximum output does not always coincide with minimum plate current. (As a note
of historica l inte r est , it should be mentioned
that th e phrase "on-the-nose" is a tribute to
one of our con tem po ra r ies in amateur radio,
a nd a great ope rator-c-Mr. K. Nose, K H 6I J .
Many s uc h phase s may be found in ham radio,
such a s t he CW oper a tors' fav orite exp ressions of "FB" and "73," referring, of course,
to the grand old man of telegraphy, Samuel
F . B. Morse, and th eir favorite magazine,
respectively.)
In add ition to t he panel meter, an adju stable
oscilloscope take-off is provided on the rear
apron of the ch assis. The inst r uction manual
g ives full details on hook-up for monitoring of
your sign a l on a scope, a wo rth-whil e feature
for proper l inear operation.
The rf sect ion of th e HA-10 is placed along
the front half of th e chassis, with the power
su pply com pone nts along t he r ear half. The
rf section is provided w it h a full sh ield around
it. This, plu s t he added shieldin g of the cabinet
itse lf, does an excellent job of sh iel ding which
a id s in TV I r eduction. The packaging job on
the H A-I O is very n ice, with th e whole linear
weighing in at 90 pounds and taking up less
than two cubic f eet. Indeed, this is a far cry
from the 75 meter phone kilowatts of ten years
ago, which w ere built in seven-foot r elay racks
a nd requ ired a dozen hu sky men to move
73 MAGAZINE
around.
from the meter reading. The efficiency a s
shown in Table 1 is called "indicated effiThe instruction manual gives full information on operation of the linear, including deciency," s ince part of the H T-32A output will
scr ipt io n of pads to be u sed if yo u r exciter
appear in the \ Va r r ior output. It would have
runs more than 100 watts output, or if the
required far more time than was available
linear is to be u sed for ext ens ive AM operafor measurements, to measure the actual effition . The II A-I O is designed for use with the
ciency , so the figures are labeled apparent
common 50 to 100 watt exciters, but may be
efficie ncy and the h eck with it.
run at reduced input with less than 50 watts.
T he apparent efficiency on all bands is 50 70
A statement appears in the manual sa ying
or better, so thi s is fair efficiency. There are
som e purists in the crowd who b)' now are
t hat "the H A -I O should not be u sed to amplify
A l\1 signals in excess of 100 watts, a s a worth.
sc r ea m ing , " I can get 75 % efficiency with a
while increa se in power will not be realized."
class C sta ge !" True, hut let us mull this over
I a d m ire H eath 's honest y in mak ing t his statea bi t. Assume we ha ve two one-K w a mplifier s ,
ment, si nce t here a r e m an y of ou r f ellow
one of whic h is 50 % efficient, the other, 75 % .
amateurs today who do no t rea lize th at t he
So one pu ts out 500 wa tts, an d the ot her, 750.
S-un it sca le is not lineal', but requi res a four
So what? T his is only I lh db, or a qua r t er of
times power boos t to read one S u n it h igher. a n S un it . If you are so bad off that t his quarter of an S u nit will kill you-take up stamp
But nowadays, the kilowatt is a status symbol,
a nd a lot of the f ellows will run the H A-I O collecting. W or ry in g about that last db is
behin d their Apaches, DX-I OO's and Viki ng II 's somewha t aki n to the fellow who worked for
with t he only indica t ion of the power increase
month s in finding compass directions from
being the increased electric bill each month.
his location to any point in the world-within
Speaking of electric power, the HA- I O manual one half of one degree. Then he used these
mentions no less than three times that wiring figures to aim hi s four element beam-s-you
know, the one with a beamwidth of 15 degrees.
to th e outlet feeding the HA-IO 115 vac input
should be no smaller than # 14. This advice
It should be pointed out to owners and prosshould be heeded, si nce the Wa r- r -i or- draws over
pective owners of the Wa r -r-ior or any other
10 amps u nder full load.
linear amplifier that the FCC defines input
power with grounded grid amplifiers to be the
The front-panel controls include ba nd switch,
input to a ll st ag es su p ply ing power to the
tun ing , loading, met er switch, relative power
a nte nna. T h is mea ns that the input power with
sens itivity, fi lament switc h a nd plate switch.
the combi nation used in the tests mentioned
Also on the fro n t pa nel are the meter an d the
above , according to F CC defi nition, would be
two king-size pilot lam ps. Across the rea r
the s um of th e inpu t power to th e HT- 32A a nd
ap ron of t he H A-I O a re t he following connections: rf in pu t , rf output, g rou nd lug, AC
that of t he Wa rrlo r. A nd thi s su m shoul d not
input, b ias ter mina ls, sco pe out put, and scope exceed 1000 watts. The 1000 watts was exceeded duri ng the efficiency tests , but t his was
ampli t ude a djustment.
\V3JZF, now in Flor ida awaiting his new
into a d ummy loa d , so it was OK . But be
"four" call, was ki nd enough to allow his Wa r - careful not to exceed the li mit when you're
on th e a ir, else a friendly FCC representative
rior to be used in some efficiency measurements. Table 1 shows the results of this effort. might catch you at it some day.
The Wa r r ior was driven by an H T-32A exAll in all, the W a r- r ior is a very attractive,
lightweight (considering), and compact packciter, and the output was fed to a 50 ohm
dummy load. T he rf voltage wa s mea sured at age that is well worth the asking price. In
the load with a Hewlett- Packa rd model 410B fact, if you will check catalog prices of comparable components, you will see that it would
VTVM. In put was adjusted to 700 rna indicated plate current on all bands except 10 be difficult to copy the Wa r -r-ior for $230. And
meters, where the HT-32A could only drive the an added fe ature a s far a s economy goes is
Wa r- r -i o r- to 660 rna plate current. As noted in
t hat the 8IlA final tubes may be bought on
the su r plus market for as little as $3.65 each .
the inst ruction man ua l, 30 rna of bleeder CUI' rent is included in t he current indica ted on the
This heats hav ing to buy a $35 tube in case
of a fail ure .
. .. K3K MO
pla te meter, 8 0 t his amou nt wa s discounted
Fre!luency
(lie)
Plate
Current
Plate
Vo ra ge
tput •
°f
(r volt s)
Pow er
Input
670
1350
165
905
170
670
13 90
930
670
1460
162
980
670
1450
156
970
1420
670
1 58
895
·Output measured ac r oss a 50 ohm dum my load .
3900
7250
14330
21300
28900
MAY 19b2
Pow er
Output
54 5
580
525
490
500
Ap.parent
Efflci ency
60 %
62%
54 %
51%
56%
b9