SB401 xtal Pack

[Kechkaylo Dave (ATLINKS)]

To All:

The SB-400 came with all eleven crystals (8 HFO and 3 BFO); the SB-401 just
came with the three BFO crystals as standard, mounted in three sockets under
the chassis. You had to buy the eight HFO crystals for the SB-401 for use as
a stand-alone transmitter (the crystal pack).

Yes, its true that in transceive operation, the SB-400/401 accepts all three
signals as INPUTS (BFO, LMO, HFO) from the SB-3XX series receivers. In SSB,
the LSB & USB BFO signals are derived from the receiver (both receive and
transmit). This preserves the frequency accuracy and eliminates having to
re-tune the LMO between transmit and receive SSB, due to slight differences
between the transmitter's BFO and receiver's BFO crystal. In CW, the
transmitter CW BFO crystal is always used, and in receive, the receiver uses
its USB crystal for proper BFO offset to obtain the 1000 cycle beat note. In
this way, the receiver's LMO setting will be the true transmit frequency.

One word about the LMO: There was a previous posting from a gentleman who
had a problem with no or low RF output when in transceive, presumably there
was a problem with his receiver's LMO. The only adjustment the LMO gets is
to tune the LSB shift coil slug in accordance with the manual. The LMO's
output link coil is an impedance matching transformer from the LMO's
oscillator plate circuit to the low-impedance phono jack output. Since this
output link transformer is tuned, it acts like a bandpass filter. It was
adjusted at the LMO's factory, then sealed. It does not require adjustment.

If this gentleman had an LMO output problem, I'd check the LMO signal switch
wiring, cables, and LMO power supply (LSB shift voltage). I would never
adjust anything on the LMO excepting the LSB shift slug.

Dave Kechkaylo, W8QIZ

-----Original Message-----
From: Bob Bruner WB4TAJ [mailto:RABRUNER at AOL.COM]
Sent: Tuesday, September 10, 2002 10:48 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: Re: SB401 xtal Pack


I had an SB-401/ SB-303 combination for many years. If you run the radio
with
any of the matching Heathkit receivers as a transceiver, then you only need
the CW carrier crystal in the transmitter.  It gets the USB and LSB carrier
frequencies from the receiver, as well as the HFO oscillator signal.  The
LMO
signal, is of course switch selectable between the two units.  If you are
going to run the SB-401 as a stand-alone transmitter, you must have all 11
crystals in place.  The CW xtal, plus to the two sideband crystals, plus the
8 HFO band set crystals.  The accessory xtal pack had 10 crystals in it, the
CW xtal comes with the transmitter.
73
de Bob
WB4TAJ/9

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