Chuck -
No, I meant uF. 0.001 uF = 1000 pF 0.01 uF = 10,000 pF
Essentially it's a bypass cap. The resistor is 1000 ohms, and the
purpose is to detune "one" half of the transformer by loading it down
while tuning the "other" half. The capacitor is to prevent sticking a
1000 ohm resistor across the _DC_ B+ that's on there. The 0.005 Drake
specified is about 10 ohms reactance at 3.5 MHz and the 0.001 is about
45 ohms, both still low in relation to the 1000 ohm resistor.
All that said, you can usually just ignore the load, and just go back
and forth between the Primary and Secondary adjustments a couple-three
times!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
Chuck Grandgent wrote:
Hey Garey,
did you mean uF or pF. Richrd is quite certain you really meant pF.
Chuck, K1OM
On Thu, Feb 25, 2010 at 2:38 PM, Garey Barrell <[email protected]
<mailto:[email protected]>> wrote:
Richard -
OK. That 0.005 cap isn't particularly critical. The 1000 ohm
resistor is the load, the cap is just to prevent shorting the DC
to ground. Any disc ceramic from 0.001 to 0.01 uF at 500V or more
would work just fine.
I wouldn't worry too much about the calibrator. As long as
someone hasn't twisted on the trimmer cap it's plenty close enough.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
Richard Palmer wrote:
Garey,
I have cleaned my eBay TR-4. Replaced two tubes, V1 &V20.
Along with tightening up the ps connector pins and probably
some other small forgotten stuff it seems to be working
nicely. Although I still have yet to make "first contact". I
thought I'd go through the complete alignment procedure to
check and adjust as necessary.
( I thought I had a source for two 0.01pF capacitors from
Allied but their web site ordering is worse than crap. I
called them and to my disbelief still more crap. So I'm still
looking for some caps to get the 0.005pf for the alignment
procedure.)
That's why I asked about calibrating the calibrator. I don't
suspect any problem... just want to check all the settings.
Richard Palmer
KB8NXO
Garey Barrell wrote:
Richard -
Do you have ANY receiver aside from your TR-4? It doesn't
have to have a BFO or be particularly stable or sensitive.
If all you have is a Broadcast Band table radio, see if
you have a commercial station on an even 100 kHz frequency
such as 700, 800, 1200, etc. It doesn't have to be local,
in fact best if it isn't too strong, and the higher the
better. Get it close to the TR-4, and possibly wrap a
turn or two of wire around the calibrator tube, bringing
the other end near the broadcast receiver antenna. Turn
on the calibrator and adjust your wire until the
calibrator signal is about the same strength as the BC
station, then adjust the calibrator until the signal is at
zero beat. Adjust as carefully as you can, if the signals
are near the same strength you'll actually be able to hear
a slow variation in amplitude when you're within a few Hz
of zero.
This is far from ideal, but BC stations are very accurate.
When you calibrate at 10 MHz, you are comparing the
100th harmonic of the calibrator to a known frequency,
whereas with a broadcast station you're only at the 10th
harmonic on a 1 MHz BC station. But plenty close enough
for our purposes.
Better still is if you can borrow a receiver that covers
10 or 15 MHz, and if you can resist adjusting the
calibrator, they stay correct for a LONG time. In fact,
unless someone has been "adjusting" it, it's probably
close enough!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
Richard Palmer wrote:
The manual says to tune to WWV ect.ect. I'm assuming
this is 10Mc. . Can I use a signal generator set to
10Mc. and accomplish the same desired result? I have
neither of these and must buy what I need to skin this
cat. Any suggestions? One caveat... it must be
inexpensive.
Thanks in advance,
Richard Palmer
KB8NXO
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