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Author Topic: BitX20A - I need help.  (Read 5219 times)
KC9THA
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Posts: 3




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« on: September 07, 2012, 10:20:38 AM »

I have the bitx20a Hendricks kit together. And when i touch one of the post of the tuning knob a shortwave stastion come in. Nothing is heard after i take my finger away... What is wrong ?  And i cant tune any thing in. I hope to get some help..Kc9tha@gmail.com
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W5FYI
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Posts: 1046




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« Reply #1 on: September 07, 2012, 07:04:57 PM »

It could be a cold solder joint. I've seen it in a lot of homebrew projects--the solder job looks good, but dirt, grease, insulation, etc. sometimes prevent good connections. It's probably in the vicinity of where you put your finger when you do get signals. GL
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W4OP
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« Reply #2 on: September 07, 2012, 07:41:16 PM »

Can you hear the VFO running on a general coverage RX or see it on a freq counter?

Dale W4OP
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AD6KA
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Posts: 2238




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« Reply #3 on: September 07, 2012, 11:12:02 PM »

Can you hear the VFO running on a general coverage RX or see it on a freq counter?
Dale W4OP
Good idea.
If you don't have a frequency counter, run a
short wire from the back of your receiver to
near the top of R27. Should be in the 3000 KHz range.

Also check the soldering and winding of L7.

FYI:
The "Alignment and Tune Up" instructions
for the BITX17 (17m version) are MUCH better,
more involved, and easier to read than the
BITX20A manual. Download the BITX17 manual.
The alignment and other instructions start on page 42.
Of course you will have to change the BFO and VFO
frequencies to those of the 20m BITX.
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WB6BYU
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Posts: 13573




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« Reply #4 on: September 08, 2012, 12:18:59 AM »

From the symptoms you describe, if the rig uses a conventional tuning capacitor,
I'd guess that the shaft side of it is not properly connected to ground.  That would
cause it to oscillate too high in frequency, and when you touch the shaft your body
would add capacitance to shift the tuning.
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KC9THA
Member

Posts: 3




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« Reply #5 on: September 08, 2012, 08:01:00 AM »

i have not had the time this weekend to look at the radio. You have giving me ideas to check. I dont have the digital display hooked up yet. Thank you every one.
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KC9THA
Member

Posts: 3




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« Reply #6 on: September 10, 2012, 09:29:06 AM »

one more thing. On r-66 if i turn it to the right all the way,full on , its like a vibrating sound.   and no current on c-16 right side. C-14  and C-18 do nothing. Bad solder spot some where? 
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AD6KA
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Posts: 2238




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« Reply #7 on: September 21, 2012, 12:20:45 AM »

one more thing. On r-66 if i turn it to the right all the way,full on , its like a vibrating sound.   and no current on c-16 right side. C-14  and C-18 do nothing. Bad solder spot some where? 

"Vibrating sound" out of the BITX or your big rig?
R66 and C65 control the Balanced Modulator.
They should be alternately adjusted while transmitting with
NO audio input. Then listen for that signal on your
"big rig" and adjust for minimum received RF signal.

I would solve the receive problem first.
If neither C14 nor C18 do anything I would check
ALL the solder connections in that area (The RCV and
XMIT RF Filter Circuit). especially check the solder connections
from the wires to boards for toroid inductors L4 and L6.
If you don't get all the insulation off of the enameled wire
there is often no, or a poor, connection. You can try reheating
these inductor wire connection. But if the enamel is still on
the wire as it goes into or out of the solder connection,
there is probably no connection. If the enamel wire looks like
it is sitting in a pool of solder, with no solder wicking up the
sides of the wire, that is a bad sign.

Quote
From the symptoms you describe, if the rig uses a conventional tuning capacitor, I'd guess that the shaft side of it is not properly connected to ground.


The BITX uses an off board Polyvaricon for tuning, whose center lead is
to Ground. I would check to make sure this is well connected.
In the kit is a white plastic spacer and screw to extend the
center "control" of the Polyvaricon, which is a short metal
affair. I would get that extension and a knob on there to
cancel out any effects from touching metal in an RF circuit.

(And when you get the BITX working get rid of that damn
cheap one turn Polyvaricon and do the Varicap Ten Turn Pot
Tuning Mod. It will save you a world of headaches and uses
about 5 parts.
The mod is described on KC0WOX's site
and many others.

MOST OF ALL:
I would check out ALL of Lonnie's(KC0WOX) BITX20A
Assembly and Troubleshooting videos:
http://golddredgervideo.com/kc0wox/bitx20a.htm

73 and Good Luck!
The BITX20A is a spiffy rig when you get it going! Ken  AD6KA
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AB3LD
Member

Posts: 3




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« Reply #8 on: October 30, 2012, 06:31:15 PM »

Did you install the correct resistor at R21?  It should be 1K ohms, but there is a mistake in the assembly manual on the Hendricks website that gives the color code for 100 ohms instead (brown black brown).  This made my receiver deaf!  Once the 1K was installed it worked fine.
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