Swan 400 HF Transceiver with the 420 Full Band Frequency Control Unit & SW-117 AC Power Supply
Swan 400 HF Transceiver with the 420 Full Band Frequency Control Unit & SW-117 AC Power Supply
This Swan 400 HF Transceiver with the 420 Full band Frequency Control Unit & SW-117 AC Power Supply, is in very good condition and appears to be working okay.
I tested this rig on my bench, loading it up on 80 meters.
The transceiver put out over 200 watts and the transmit audio sounded great on both USB and LSB.
The receive sensitivity on this rig is well known to be exceptional and it did not disappoint.
It has excellent receive Sensitivity and audio from the front fired speaker.
This radio requires the 420 matching frequency control unit which is included. It is also in very good condition with a very clean front panel just as the 400 transceiver has.
Also included is the Matching SW-117 AC Power supply. It is in great shape as well.
As with most vintage gear, the 400 may benefit with an alignment or tube replacement but seems to work okay as tested. I did not test it any further. This rig has the original electrolytic capacitors and they really should be replaced before putting it into service.
I am selling this station as is, as described, for the family of a silent key.
A good Copy of the manual is included.
The shipping quote should be close depending on where your location is and I will adjust it accordingly.
I can give you the exact amount if you advise with your address.
This is a really nice example of the Swan 400 especially with the hard to find 420 frequency controller and SW-117AC power supply,
Read all about it!
The 400 series transceiver model is unique in that it is the only Swan transceiver without an internal VFO. Like
most other dual-tube PA models (other than the 600T), it requires an external power supply. An external VFO
designed for the transceiver’s 5.173-MHz IF (model 406, 410, 420) or the 405/X Crystal Controlled Oscillator
(all of which also contain the transceiver’s RF GAIN control) and an 117X type power supply are required for
operation. The amateur 400 models have features that were not included in the 350 that followed it in production,
including a sideband selection, a 100-kHz crystal calibrator, and a built-in speaker.
When the model 350 (which also uses the 5.173-MHz IF) was introduced at end of 1964, the amateur model 400
was not dropped, but continued to be produced, since Swan had a considerable investment in this model. They
finally terminated production of the amateur model 400 in 1968. Most of the units manufactured towards the
end of that production run were sold to governmental agencies such as the FAA, FCC, CHPS (California Highway
Patrol), and reportedly, even to the CIA. While production of the amateur version was terminated, the 400
model series still continued in production; it was significantly redesigned (including a 5.6-MHz IF and channelized
tuning) and marketed to both military and commercial users as the 400E/F/G/H.
The 400 was introduced in the spring of 1964 to replace the Swan 240 (tri-band), as the first 5-band SSB transceiver
offered by Swan. This design uses a 5.173-MHz intermediate frequency. Since mobile operation was on
the increase during the period, Herb felt he could meet the demands of both mobile (see Fig. 1-8) and fixed station
operation in one package. This step back to an external VFO from the internal VFO used in the earlier
mono-band and tri-band transceivers was one way of making the 400 attractive to all Hams. The use of an external
VFO permitted the transmitter to be physically separated from the transceiver in mobile installations and
circumvented the internal VFO heat related drift as all those tubes warmed-up the transceiver to its static steadystate
temperature after the first hour of operation.
The earliest version 400 retained the 240’s light gray front panel color and used the same meter surface mounting
method. Its introduction just preceded that of the 350 and it was marketed concurrently with the 350. While
both were rated at 400-W dc input PEP and used a pair of 6HF5 PA tubes, the 400 was touted as the deluxe
transceiver since it included a sideband selector, full frequency coverage with the external 420 VFO, internal
speaker, etc. The 400 sold for $395 in December 1965, but required the 420 or 406 VFO and power supply, so
the complete package, including power supply was about $600, rather pricey for the time. Even with the higher
package retail price, it was very expensive for Swan to produce due to engineering overhead and Herb’s demand
for high mechanical and electronics quality, limiting profitability. The 400 is considered by many to be the best
dollar value of anything Swan built, relative to the cost of production.
Over a 3½-year period, 1,150 units were built. There were three versions of the 400, with the earliest using four
discrete crystals (plus one shunt crystal) in the IF filter (3,000-Hz IF bandwidth), rather than the hermetically
sealed 8 crystal, 2,700-Hz bandwidth unit used in later versions (after mid 1965). It received a facelift in late
1965, with the front panel being refinished in two-tone light gray. Along with the 350 and 400 models, the
LOAD control has 10 positions, versus the 7-position switch used in later models (350C, 500C, etc.).
The were a few hundred model 400s of the last version made at the end of the production run, but only about 100
schematics, however that later schematic is nearly identical to the initial version of the model 500 transceiver
(less the VFO). The schematics for the first two versions have no identification (date or letter), while the last has
a date affixed. Model 400 units with serial numbers B19.. & B20.. use the later schematic, which also shows, in
addition to the date, an encapsulated crystal filter instead of the five individual crystal filter design. The later
schematic also shows a border around the 12-pin Cinch-Jones connection, whereas the earlier schematic does
not. On the earliest versions, the design applied full power during tune-up; on version three this was changed to
protect the PA tubes from damage by switching a resistor into the screen grid circuit when in the TUNE mode,
which decreases the screen voltage and hence the maximum dc input power.
A common problem on early model 400 production units (and the 350) is sagging of the PI output stage air-core
coil (on the top and to one side) due to melting of the plastic reinforcement turn separators/supports.
VFO Options. For mobile operation with the 400, Swan offered the partial frequency-band coverage (most of
the audio portions of each band) external 406 VFO (matching panel, but approximately ½ the height of and
less length than the 400) with an extended length interface cable, which permitted the transceiver to be placed
anywhere in the vehicle, even the trunk. The full-coverage external 420 VFO (height and style match that of
the 400), which has 20-frequency ranges (200-kHz per range), was offered primarily for fixed station operation.
A replacement VFO was developed in mid-1965, the 410, which is also full coverage but band switching
is considerably simplified (and production costs reduced) as it has only eight frequency range selections.
When the inventory stock of 420 VFOs was depleted, Swan 400 owners had to buy either the 410 or 406B.
The 405/X Crystal Controlled Oscillator was also available for net or other fixed-channel type applications.
Standby Switch. This model (along with the 240) employed an inter-connected STBY (standby) mode switch
and an ON-OFF switch on the audio gain potentiometer to control power distribution within the transceiver.
The manual’s discussion and switch labeling suggests that only the filament voltages are present when the ONOFF
switch is ON and the mode switch is in STBY – this is not true, as all power supply voltages are present
within the transceiver chassis. The STBY switch merely interrupts the MV (~+275 V) within the transceiver.
The rationale behind this arrangement was to keep the filaments warm for quick operation. Since in standby
the MV is unloaded it will rise to a higher than normal operating voltage value. This system was discarded beginning
with Swan 350 and on all later models.
5,175-kHz and 13-MHz Filter Trap Alignment Comments. These two traps are used as part of the receiver
RF amplifier input circuit. There are no alignment instructions in the 400 manual for the 13-MHz trap adjustment.
However, the model 350, which contains a similar circuit, does provide the following information on
alignment: “Tune the VFO to 14,325 kHz, insert a RF signal into the antenna at 13,000 kHz, and tune the RF
generator for a beat signal in the speaker. Adjust L603 and L604 for minimum beat signal.”
5,175-kHz Trap. Alignment instructions for the 5,175-kHz trap require the adjustment of L602. Unfortunately,
the chassis labeling of that coil and the 13-MHz coils (L603/L604) is a bit confusing. The two 13-
MHz trap coils are mounted on the bottom of the chassis and the 5.175-MHz IF trap is mounted on the top.
13 MHz Trap. The 13-MHz trap system uses a pair of LC tuned circuits. The parallel combination of
L604 and C606 is really the trap for 13 MHz; it is in series with the incoming signal and grid of the RF amplifier
and has a high impedance, which significantly attenuates any signal in that frequency region. Even
though that trap is good, a little residual signal voltage still gets by to the grid because it needs to be sort of
a broadband and doesn’t focus in on a very narrow frequency segment about 13 MHz. Therefore, the second
resonant circuit made up of L603 and C605 is included in the circuit. It’s not really a trap at 13-MHz,
but at that frequency it functions as a low impedance signal path that channels any residual 13-MHz signals
reaching the grid of the RF amplifier (V6) to ground