              NOTE O HANDBOO VX TRANSMITTER
                      B DAV NEWKIRK

Yes th IAR transmitte desig sometimes mayb eve often 
exhibit  backwave  Assumin  maximu outpu o  W ou 
spectru analyze show i t b abou 3 d dow fro th ke 
dow output (Thi i onl abou  m o power quit  bi 
stronge tha th 10 m tha yo ar seeing.)

Th backwav occur fo on o tw o tw possibl reasons (1 
onl on stag i keyed an keyin jus on bipola transisto 
doesn' giv muc isolatio an (2 th design' buffe 
transisto (Q2 routinel oscillate (thi ma als involv 
feedbac throug th oscillato circuitry eve whe th 
oscillato transisto i turne off).

It's a tricky phenomenon, because the oscillation usually doesn't
start up until the first time the key is pressed. Then it's in there
as long as the transmitter is connected to a power supply. I've
watched this scenario on a spectrum analyzer. A clue to it is that
Q2, a 2N2222 routinely runs hot.

Radical, but most effective: Throw out the original transmitter's Q1
and Q2 circuitry (its driver and final are FB). I did this with a
sheet-metal shear; it's very effective. Replace the original trans-
mitter's Q1 and Q2 circuitry with a *three*-transistor strip modeled
after the oscillator and buffer circuitry in ZL's QRP 3-Bander. ZL's
time-sequenced keying circuitry should also be included. A builder
will have to play with attenuation between this strip and the 6-W
transmitter's 2N3866 driver so as not to overdrive the 3866. Starting
with 18 dB of atten, decrease atten in 3-dB steps until power comes
up to max. Hardwire in that attenuation.

This arrangement should provide reasonable keying. Manual TR will
still be necessary.

 don' thin th origina circuitr ca b easil fixed I has
to fe stages Yo can' eliminat th backwav (an 
interelemen Q oscillation b keyin th buffe and th driver 
b th way becaus doin s pull th oscillator ( buffe 
can' reall buf i it' turne o an of withou care. n 
experience experimente however, migh b abl t appl ZL' tim-
sequenc keyin t th -Watter' os an buffer/driver 
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