My HF station consists of an FT-1000D and Alpha 87A. Having recently
replaced an 80/40 trap dipole which blew down a few gales ago, I noticed
that even on the dipole's frequency of lowest VSWR and with the 87A
carefully tuned and loaded into it, the 'HI SWR' lamp in the 1KD flashes
merrily in time with the keying on both bands. The VSWR indicated by the
1KD's metering under these conditions is about 3:1.
The dipole was tuned up with an MFJ-269 and displays VSWRs of about 1.3:1 at
resonance on both bands. The 1KD's auto ATU has no problem at all matching
the dipole at any in-band frequency. The Alpha 87A appears to have no
difficulty with the dipole at or near resonance. The 1KD's auto ATU will
easily remove the mismatch if switched in when the amplifier is being
driven, but Alpha/Power emphasises in the manual that automatic ATUs must
not be used in conjunction with the 87A (it's not clear why).
I suspect this is something trivial and silly, like the length of the feeder
between the 1KD and the 87A, but has anyone had a similar problem?
--
John Nelson
Crew Green Consulting Ltd
www.crew-green.com
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