Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF

Hello,
you might add a "Huff and Puff" stabiliser.
It is a very good and simple system to lock a vfo in 10Hz or larger steps.
The original is made by PA0KSB.
Just google and read..
Johan PE1AEQ

"Steven Fritts" schreef in bericht
...
Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF

Steven Fritts wrote:
Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF
The problem is, for the most part, lack of proper temperature
compensation. Sure, the voltage regulation isn't that great, but it's
not the main problem.

Looking at the diagram for the VFO you can see the tuned circuit
components. You can add a negative temperature coefficient capacitor to
the circuit to compensate for the (usually) positive coefficients of the
parts.

I did this successfully in a Viking Valiant. I reduced the drift from
about 10kHz or more on 10 meters to about 1kHz. One thing I did was
move a hot resistor out of the VFO compartment to reduce the amount of
temperature rise of the critical parts.

You can also leave the unit on, at least the VFO, at all times so the
temperature will be more stable.

73, Bob K6DDX

Steven Fritts wrote:
Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF
Ah yes the famous 3-drifty. I wonder if they had a temp compensation
adjustment. Consists of one positive and one negative coeficient fixed
cap of the same value, each one tied to one side of a differencial
trimmer cap, the other side of each cap tied to the tuned circuit.
You then adjust the variable trimmer for the least drift.

Bob,

can you tell me what part of the circuit needs the negative cof cap
and what value you think would be best?

Thank you for the help!!

Steve


On Wed, 16 Nov 2005 01:08:20 GMT, Bob wrote:

Steven Fritts wrote:
Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF
The problem is, for the most part, lack of proper temperature
compensation. Sure, the voltage regulation isn't that great, but it's
not the main problem.

Looking at the diagram for the VFO you can see the tuned circuit
components. You can add a negative temperature coefficient capacitor to
the circuit to compensate for the (usually) positive coefficients of the
parts.

I did this successfully in a Viking Valiant. I reduced the drift from
about 10kHz or more on 10 meters to about 1kHz. One thing I did was
move a hot resistor out of the VFO compartment to reduce the amount of
temperature rise of the critical parts.

You can also leave the unit on, at least the VFO, at all times so the
temperature will be more stable.

73, Bob K6DDX

Steven Fritts wrote:
Bob,

can you tell me what part of the circuit needs the negative cof cap
and what value you think would be best?

Thank you for the help!!

Steve


On Wed, 16 Nov 2005 01:08:20 GMT, Bob wrote:


Steven Fritts wrote:

Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF

The problem is, for the most part, lack of proper temperature
compensation. Sure, the voltage regulation isn't that great, but it's
not the main problem.

Looking at the diagram for the VFO you can see the tuned circuit
components. You can add a negative temperature coefficient capacitor to
the circuit to compensate for the (usually) positive coefficients of the
parts.

I did this successfully in a Viking Valiant. I reduced the drift from
about 10kHz or more on 10 meters to about 1kHz. One thing I did was
move a hot resistor out of the VFO compartment to reduce the amount of
temperature rise of the critical parts.

You can also leave the unit on, at least the VFO, at all times so the
temperature will be more stable.

73, Bob K6DDX


Steve,

I don't have the circuit diagram so I can't advise. But across the
inductor is the first place I would try. Of course you will have to
reduce any other capacitors by that amount so that the circuit will
resonate at the same frequency as before.

As someone suggested, a differential arrangement will work but it's a
bit tricky. I'd prefer to substitute various values until I hit one
that is close enough.

Bob

On Wed, 16 Nov 2005 17:00:57 GMT, Bob wrote:

As someone suggested, a differential arrangement will work but it's a
bit tricky. I'd prefer to substitute various values until I hit one
that is close enough.

It can be hard to get a differential capacitor these days.

One alternative could be to add a varactor (and a series capacitor)
into the resonant circuit and vary the varactor control voltage
according to the temperature. A suitable NTC or PTC in the voltage
divider feeding the varactor could be used.

Paul OH3LWR

Hi Steven,

Please read the Swan and Siltronix Radio "care and feeding"
information found on my Swan and Siltronix Radio web page.

www.radiowrench.com/siltronix

The drift fix should start off with a good cleaning and
conditioning using the information I describe in the pages.

Don't crack open the vfo box until you've read my information
and asked a few more people for help.

The radio probably hasn't run in a while... it might need
new filter caps in various places. The contacts all need to
be cleaned really well and restored using the proper chemicals
and lubricants.

The unit probably has a lot of moisture build up. When I
rebuild radios... a temp cycle and moisture bake out are
always part of the process.

Email me through the web page or through the yahoo groups
I frequent if you have more questions. You really don't
need the added vfo box mods if you're patient with the proper
rebuild.

cheers,
skipp

www.radiowrench.com/sonic
www.radiowrench.com/siltronix

: Steven Fritts wrote:
: Hello All,
: I picked up a really nice working Swan 350 at a hamfest this past
: weekend. I bought it for nostalgic reasons as it was the kind of rig
: my dad bought for me in 1965. I need info on how to fix the infamous
: "Swan drift problem". Anyone have any websites I can go to get mods
: for this rig including the drift fix?
: Any help will be appreciated!

: Steve W4SEF

To go Skipp one step better... After you've read his info, also stop
by and check out the Swan Tech website at
http://www.angelfire.com/ny2/hamradio/index.html. Stu (K4BOV) knows
his stuff when it comes to Swans, he's even added the 160 meter band
to his Swan 350. At the URL noted there's a link to "ask the tech."
If anybody knows how to cure the Swan drift phenomenon, it's Stu.



On Wed, 7 Dec 2005 00:15:23 +0000 (UTC), Skipp is a Swan and Siltronix
Radio Guy was heard to say:

Hi Steven,

Please read the Swan and Siltronix Radio "care and feeding"
information found on my Swan and Siltronix Radio web page.

www.radiowrench.com/siltronix

The drift fix should start off with a good cleaning and
conditioning using the information I describe in the pages.

Don't crack open the vfo box until you've read my information
and asked a few more people for help.

The radio probably hasn't run in a while... it might need
new filter caps in various places. The contacts all need to
be cleaned really well and restored using the proper chemicals
and lubricants.

The unit probably has a lot of moisture build up. When I
rebuild radios... a temp cycle and moisture bake out are
always part of the process.

Email me through the web page or through the yahoo groups
I frequent if you have more questions. You really don't
need the added vfo box mods if you're patient with the proper
rebuild.

cheers,
skipp

www.radiowrench.com/sonic
www.radiowrench.com/siltronix

: Steven Fritts wrote:
: Hello All,
: I picked up a really nice working Swan 350 at a hamfest this past
: weekend. I bought it for nostalgic reasons as it was the kind of rig
: my dad bought for me in 1965. I need info on how to fix the infamous
: "Swan drift problem". Anyone have any websites I can go to get mods
: for this rig including the drift fix?
: Any help will be appreciated!

: Steve W4SEF
Raymond Sirois Sr. KU2S
SysOp: The Lost Chord BBS
http://www.geocities.com/SiliconValley/Park/9257
telnet://thelostchord.dns2go.com:6023

"Bob" wrote in message
news:8Evef.21536$5R4.8753@trnddc06...
Steven Fritts wrote:
Hello All,
I picked up a really nice working Swan 350 at a hamfest this past
weekend. I bought it for nostalgic reasons as it was the kind of rig
my dad bought for me in 1965. I need info on how to fix the infamous
"Swan drift problem". Anyone have any websites I can go to get mods
for this rig including the drift fix?
Any help will be appreciated!

Steve W4SEF
The problem is, for the most part, lack of proper temperature
compensation. Sure, the voltage regulation isn't that great, but it's not
the main problem.

Looking at the diagram for the VFO you can see the tuned circuit
components. You can add a negative temperature coefficient capacitor to
the circuit to compensate for the (usually) positive coefficients of the
parts.

I did this successfully in a Viking Valiant. I reduced the drift from
about 10kHz or more on 10 meters to about 1kHz. One thing I did was move
a hot resistor out of the VFO compartment to reduce the amount of
temperature rise of the critical parts.

You can also leave the unit on, at least the VFO, at all times so the
temperature will be more stable.

73, Bob K6DDX


While most tube rigs will drift *some*, I found that turning on my Swan
700CX about 30-45 minutes before using it did a LOT to reduce drift. I
think, too, that newer hams, not being familiar with the old tube rigs, are
more critical than those of us who are familiar with them. I hear people
putting down Swans ("I HATE them old Swans cuz they drift"), but it isn't
all *that* bad! I mean, just think, what did we DO back in the glowing
tube days, right? If it had been THAT bad, we'd not been able to function.
Sure---Swans drift and have a reputation for it, but I owned 3 of them and
never had THAT much trouble. I HAVE had worse!

73

Jerry