Can watch VietFace and VTV4 but not others Viet's channels

[phhumike]

all of these vietnamese channels are on Galaxy 19 at 97 West

On my TV I can watch chanel “VietFace” and “VTV4″
(setup: tp10, 11966,22k,h) strength 82, quality 98
do you know why I cannot see these chanels little saigon tv, saigon tivi, vbs tv, vnbc tv
(setup: tp11,11929,22k,v) strength 85, quality 36 (little saigon, saigon tivi)
(setup: tp12,12022,22k,v) strength 85,quality 39 (vbs tv, vnbc tv)
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Hardware I have:
Receiver : BEC DB-6600+ MPEG-2 Free To Air FTA Satellite Receiver and one lnb
BEC DB-6600+ DB 6600 MPEG-2 DVB SatelliteTV TVRO FTA Receiver
1 lnb: digital ku lnbf, lo: 10.750ghz, input: 11.7-12.2ghz, gain: 55db typ, nf: 0.6db

Configuration:
type: normal
lbn type: non-univ
lnb freq. 1: 5150
lnb freq. 2: 10750
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Is because my receiver is old (7 years) or need new lnb?
or do I need two lnb?