Gift to

t u re st a b ilizes. If the
display is so lid, you can try
advanc ing t he drive slight ly
until instability is noted.
Yo u then ca n back it off
slightly.
All tests on th e air sho uld
be conducted with a statio n
w h ic h wi ll pr o v id e an
hon est v id eo repor t. Some
fell ows a re so e nt hused by
seeing a TV signa l they will
give ra ve review s eve n if
the y have to ro ll their eyes
to kee p up with the picture.
Avoid suc h a statio n! You
are now in business at th e
10-Watt level. Note that in
t ran smi t you w ill ge t a n ice
cle ar pi cture on yo ur i-f
cha nne l-very nice fo r use
as a viewf inder!
High Power. At 10 Watts
peak o ut p u t, the MMT
432/28 tran sver ter will dr ive
a va rie ty of li n ear
am p li f iers to Quite re specta
b le power o u t p u ts . A
n u m b e r of d iffe rent
am p lifiers are in use w ith
our ATV grou p. WB8jXF
and I run 4CX250s in VHF
Handb ook cav ities. With a
2-kV plate supply, the tra nsve
rt er w ill drive su ch an
amp lifie r to close to 500
Wa tt s peak input-provided
you supply p lenty of air !
tv\y own c av ity is ru n w ith
on ly 800 V o n the p la te a nd
loafs along a t a bout 160
Wa tts peak inpu t.
Seve ral othe r sta t ions a re
using 2C39 cavities from
com merc ial FM eq ui pment
(Motor o la and GEl, running
t hem in AB1 wit h excell e nt
resu lts. In grounded grid
service, th ese amplifie rs
will supply 25-30 Watts of
a v erage pow er o u t p u t
when operated off an o ld
tran sceive r po wer supply.
The K2RIW and so me of th e
newer 432 power am plif iers
sho u ld do equa lly we ll. O ne
a pproach which has no t
been used in our area inv
o lv es usi ng one of t he
lineari zed so lid -sta te po we r
a m plifiers. The co st o f suc h
a mp lifie rs a nd the ir high
c urre nt su ppli es ma kes a
tu be-type pow e r a m plifier
far mo re a ppeal ing. Do lla r
Photo F. Jim WBBYSC run ning about 10 Watts a verage power ou tput using a 2C39 cavity
final. Most of our ATV group (six operators as of the las t net) are located ea st and south of
Lansing, but l im is in Grand Ledge, M ich igan, off to the west o f Lansing. This is about a
1O-mi/e pa th to m y Q TH, and despite th e fac t that bo th o f our antennas are just mounted
at rooftop heigh t, the use of sensitive cr ystal-contro lled converters at the receiving end
provides a perfectly usable p icture. l im does his share w ith careful tra nsmitt er setup and
good lighting - both fa cto rs wh ich make a big d if ference over an extended path.
fo r do lla r, yo u probably ca n
do far better with a tubetype
c irc uit.
Fig. 3 can be used as a
.~f7 E N N A
T ,J,
..,
TIRA
~REL AY L .....
gu ide in hoo k ing up such an
a m p l if ie r. Se v e ra l differences
from the l o w ­
power syste m exis t that are
CHANNEL
TRANS VE RTE R 2 O R 3
DRI VER
'" " "
'"
eaz
OUTPUT ,NPUT I'O W E ~ cur
i>OW£R l- ..H 'y' fl-
"
1'21/DCPOwE:, .
wort h co mment. First, you
w ill ha v e t o provid e a
sepa rate re cei ve input for
the transverter. The BNC
Til RECE IIiER
Fig. 3. System interconnections when using the transverter with an external po wer
amp lifi er. In additi o n to the amplifier, you will need an antenna change-ove r rela y and an
addi tional set of contacts on the T-R switc h to co ntrol the rela y. You also wi ll have to
con nect the receive-converter input to the 432 input jack as noted in the text and your
tran sverte r manual. Depend ing up on your amp lifier and power supply, you ca n run 500
W atts or more peak input with such a s ystem.
0
o 0 0 0 0
I II
,j ('"
TIRB
73 Magazine · Octo ber, 1980 65