Arthur Pozner wrote:

Well said. But, even my older radios did not have a drift of such a
magnitude, especially the really fine tube sets!
Again, Tecsun/eton/Grundig should have corrected the temperature drift
problem by now. How many of them did they make so far? The serial
number on mine is S35031039210...

I expect many analog radios to drift, but the portables are usually a
good bit worse than the bigger radios..
IE: if I had a constant drifting of 30-60 kc, even after warmup, I would
probably get out a gun and shoot the radio. Of course, for AM use, that
much drift can be usable, except you might need to fine tune some...For
SSB use, that much drift is terrible. As an example, once warmed up, the
drift in my TS-830 using the internal l/c VFO will be about 30-40 cycles
with the average temp change of the a/c unit cycling off and on. With
the external PLL VFO, there is no drift. Another example...My all tube
drake R4...Once warmed up, again the drift is in cycles, not kc's...Only
the initial warmup might you see drift in the kc's, but that lasts only
the first few minutes. You'd never hear the difference on AM once warm.
But on SSB, it's possible you might have to tweak the tuning about once
a day or so to stay exactly on freq.. Depends on the temp changes in the
room to a degree...
I've never seen a lower cost portable that didn't have some noticable
drift...To avoid drift, you gotta cough the change for a higher quality
radio...Just the way it goes...Even some of the higher end radios can
drift some, but the amount is so small, most people would never notice
it. Say fer instance my icom-706mk2g...In the house, I'll never notice
any real drift. But if I took the radio in the car, and had it at 20
degrees on a cold day and cold car, and then fired up the car, and had
the warm heater blowing directly on the radio, then yes, I might notice
some drift until it is stable in temp. I've had this happen before with
my older icom-730...I've never had the chance to test this with the 706
yet, but I suspect it would move a bit...I don't have the optional
hi-stab xtal in it...But in the house, even with the a/c cycling, it's
stable. And yes, the 706 is not exactly a cheap radio...I don't know the
price of the mentioned portable, but you could probably buy two, three
or more of them for the price of the 706...When it comes to drift,
readout accuracy, etc, you get what you pay for...MK
--
http://web.wt.net/~nm5k

Arthur Pozner wrote:
Drake used to carry a modification kit to cure
that problem,but it was not very serious-1 to 2 Khz in the most extreme
cases. I can live with that. Nobody is perfect.

Some are pretty close though...My Kenwood TS-830 using the external PLL
VFO-230 is ultra stable. I mean, you could tune in a ssb station and
listen for MONTHS at a time, and not hear drift. There is also no warmup
drift on that VFO. But the internal L/C VFO in that radio does move a
bit with temp changes. But!, it's VERY linear...If you can keep the temp
stable, the radio will be also. Pretty much the same for my IC-706, as
long as it's in the house, or any fairly stable temp, you won't notice
any drift. You are right about one thing...The drift is thermal, not
mechanical. All l/c type VFO's are prone. The better ones use temp
compensating caps to increase stability. MK
--
http://web.wt.net/~nm5k

What kind of variable capacitor is used for the main tuning? I found the
one in the Panasonic RF-2800/2900 was the cause for most of it's
drifting. Does the S-350 have a tuned front-end?


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"Arthur Pozner" wrote in message
...
Yes, that is what I have. An updated S350 . But, despite being
plugged in at all times to to 120VAC outlet it still drifts enormously.
I keep a record of frequency displayed over an extended period (several
weeks) versus approximate ambient temperature.Tuning dial is
untouched. At one point it went down a full ... 59 KHz(!!!) from the
original setting. Again,this is
NOT a mechanical drift and is definetely NOT normal. I have a tube
based Grundig type 4570U/stereo table receiver. Though it doesn't posess
a digital frequency readout ,it dosn't seem to drift anywhere near like
a brand spanking S350 does.
BTW both of my Drakes, the R-7 and TR-7 seem to have a relatively
'innocent drift' due to humidity changes ,not temperature variations
affecting the VFO. Drake used to carry a modification kit to cure
that problem,but it was not very serious-1 to 2 Khz in the most extreme
cases. I can live with that. Nobody is perfect.


You can't really compare a $100 portable like the S350 to radios like
Drakes, and others that people mention in this thread.
Pete

Arthur Pozner wrote:
Have used it for about 3 months now. Seems like a good
sounding and well thought out portable .
However, why does it drift down in frequency as the temperature
increases? As a test, I had it set to a station in the 21 MHz broadcast
band and to my horror seen frequency set go down...30 to 60 KHz as if
something was moving it ! What kind of gremlin did Tecsun,the OEM, plant
in it? Why it is not modified; as far as I know this is has been a
problem since its inception- nearly two years ago!!

well, we are new to this whole shortwave thing, having bought a
grundig s350 at a garage sale and a little spool antenna thing from
radio shack. there is certainly some noticable drift with ours,
seemingly more towards the beginning of a listening session than at the
end. we figure its part of the experience and don't really find it that
annoying.

Conan Ford wrote:


Here's an idea: use a digital frequency counter circuit, like the S-350 has,
but have a circuit that reads the value, and if it drifts without the user
touching the knob (you could tell by capacitance on the knob) have it correct
itself. You'd have to have a small motor drive to turn the mechanism.
Perhaps you could then have the lower-noise sound of an analog radio with the
non-drifting benefits of digitally tuned radios. Or, have an entirely analog
radio, except have a digital circuit to activate a motor and turn a variable
capacitor inside the radio.

Seems it would be easier to just use a Oak Hill DDR box, or whatever
with the older rig. You would have to have one heck of a slow bandspread
to be able to accurately have a motor tune the radio. Would be easy to
overshoot, etc..Their box can be used on many types of radios..You can
have analog radios that don't drift enough to notice. My Drake R4
"1965-serial #0058" is all tubes, and totally analog, and it doesn't
drift enough to worry about in the real world. The only real plus to
adding the DDR to it, would be the readout. The old drake 4 line was
pretty stable for it's time, and had the advantage of having the same
drift rate, etc, no matter what the freq. It's still quite usable even
today, even on picky SSB, or even digi stuff. Same as the Collins, that
used the similar circuit. Actually, I think Drake more copied Collins,
than the other way around. Drake used to work at Collins the way I hear
it...Then started his own company. My drake T4XB transmitter VFO is even
more stable than the tube version in the R4. It uses solid state parts
for the vfo, instead of the 6AU6 in the R4. When I run the pair, I tend
to use the xmtr vfo...MK

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