varicap diode testing?

M

mynick

Guest
Hi
if you test an OK varicap diode with analog reistance meter what are
you supposed to get?Does it get hot/warm in battery powered
transmitter (if not than the element suspected to be a varactor and
mounted to stick a little bit out of the transmitter box, could be
an ic diode although it could not transmit trough walls, could it?)
 
On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglomont@yahoo.com>
wrote:

if you test an OK varicap diode with analog reistance meter what are
you supposed to get?
Click to expand...
A varicap is just an ordinary diode. When reverse biased, it acts as
a capacitor which varies with the applied reverse bias. It never
conducts current in the forward direction. Never... Ever...

Does it get hot/warm in battery powered
transmitter
Click to expand...
No.

(if not than the element suspected to be a varactor and
mounted to stick a little bit out of the transmitter box, could be
an ic diode although it could not transmit trough walls, could it?)
Click to expand...
I have no idea. Perhaps it would be helpful if you would disclose:
1. What are you trying to accomplish?
2. What are you working on? (Make and model)?
3. What have you done so far and what happen?

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Oct 18, 9:37 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:

if you test an OK  varicapdiode with analog reistance meter what  are
you supposed to get?

Avaricapis just an ordinary diode.  When reverse biased, it acts as
a capacitor which varies with the applied reverse bias.  It never
conducts current in the forward direction.  Never... Ever...

Does it get hot/warm in battery powered
transmitter

No.

(if not  than the element suspected  to be a varactor and
mounted to stick a little bit out of the transmitter  box,  could be
an ic diode although it could not transmit trough walls, could it?)

I have no idea.  Perhaps it would be helpful if you would disclose:
1.  What are you trying to accomplish?
2.  What are you working on?  (Make and model)?
3.  What have you done so far and what happen?

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Click to expand...
Thanks for reply
this is a photo of the outdoor part of the wireless thermometer that
stopped working
http://img517.imageshack.us/img517/7053/img00331n.jpg
checked discrete elements ok but no bias voltage at (varicap?)diode-
that, kind of
a transparent element, seen up front close to battery contacts having
resistance in both directions od 6Kohms,
any ideas?
 
On Wed, 20 Oct 2010 19:18:25 -0700 (PDT), mynick <anglomont@yahoo.com>
wrote:

On Oct 18, 9:37 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:

if you test an OK  varicapdiode with analog reistance meter what  are
you supposed to get?

Avaricapis just an ordinary diode.  When reverse biased, it acts as
a capacitor which varies with the applied reverse bias.  It never
conducts current in the forward direction.  Never... Ever...

Does it get hot/warm in battery powered
transmitter

No.

(if not  than the element suspected  to be a varactor and
mounted to stick a little bit out of the transmitter  box,  could be
an ic diode although it could not transmit trough walls, could it?)

I have no idea.  Perhaps it would be helpful if you would disclose:
1.  What are you trying to accomplish?
2.  What are you working on?  (Make and model)?
3.  What have you done so far and what happen?
Click to expand...

this is a photo of the outdoor part of the wireless thermometer that
stopped working
http://img517.imageshack.us/img517/7053/img00331n.jpg
Click to expand...
Blurrrrrrry useless photo. Try again, this time with the camera set
to macro, and without the drastic tilt angle, which requires too much
depth of field.

checked discrete elements ok but no bias voltage at (varicap?)diode-
that, kind of
a transparent element, seen up front close to battery contacts having
resistance in both directions od 6Kohms,
any ideas?
Click to expand...
Nope. See my 3 questions.

I've had far too much entertainment with wireless weather stations.
They don't seem to fail, but they do drift off frequency, or lose
power output due to moisture absorption in the PCB. I cheat and use a
spectrum analyzer to look at what it's sending. To the best of my
knowledge, most such remote thermometers do not use a varicap.
However, the humidity sensor is a polyimide or polystyrene capacitor,
with no case. The capacitor changes value as the dielectric absorbs
moisture and swells.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Oct 20, 7:18 pm, mynick <anglom...@yahoo.com> wrote:
On Oct 18, 9:37 am, Jeff Liebermann <je...@cruzio.com> wrote:





On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:

if you test an OK  varicapdiode with analog reistance meter what  are
you supposed to get?

Avaricapis just an ordinary diode.  When reverse biased, it acts as
a capacitor which varies with the applied reverse bias.  It never
conducts current in the forward direction.  Never... Ever...

Does it get hot/warm in battery powered
transmitter

No.

(if not  than the element suspected  to be a varactor and
mounted to stick a little bit out of the transmitter  box,  could be
an ic diode although it could not transmit trough walls, could it?)

I have no idea.  Perhaps it would be helpful if you would disclose:
1.  What are you trying to accomplish?
2.  What are you working on?  (Make and model)?
3.  What have you done so far and what happen?

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Thanks for reply
this is a photo of the outdoor part of the wireless thermometer that
stopped workinghttp://img517.imageshack.us/img517/7053/img00331n.jpg
checked discrete elements ok but no bias voltage at (varicap?)diode-
that, kind of
a transparent element, seen up front close to battery contacts having
resistance in both directions od 6Kohms,
any ideas?
Click to expand...
You expect anybody to get even the faintest idea of what that
'picture' is? You DID replace the batteries on both the transmitter
and receiver, right?

G˛
 
On Sat, 23 Oct 2010 21:09:41 -0700 (PDT), mynick <anglomont@yahoo.com>
wrote:

On Oct 20, 10:32 pm, Jeff Liebermann <je...@cruzio.com> wrote:
On Wed, 20 Oct 2010 19:18:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:



On Oct 18, 9:37 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:

if you test an OK  varicapdiode with analog reistance meter what  are
you supposed to get?

Avaricapis just an ordinary diode.  When reverse biased, it acts as
a capacitor which varies with the applied reverse bias.  It never
conducts current in the forward direction.  Never... Ever...

Does it get hot/warm in battery powered
transmitter

No.

(if not  than the element suspected  to be a varactor and
mounted to stick a little bit out of the transmitter  box,  could be
an ic diode although it could not transmit trough walls, could it?)

I have no idea.  Perhaps it would be helpful if you would disclose:
1.  What are you trying to accomplish?
2.  What are you working on?  (Make and model)?
3.  What have you done so far and what happen?
this is a photo of the outdoor part of the wireless thermometer that
stopped working
http://img517.imageshack.us/img517/7053/img00331n.jpg

Blurrrrrrry useless photo.   Try again, this time with the camera set
to macro, and without the drastic tilt angle, which requires too much
depth of field.

checked discrete elements ok but no bias voltage at (varicap?)diode-
that, kind of
a transparent element, seen up front close to battery contacts having
resistance in both directions od 6Kohms,
any ideas?

Nope.  See my 3 questions.  

I've had far too much entertainment with wireless weather stations.
They don't seem to fail, but they do drift off frequency, or lose
power output due to moisture absorption in the PCB.  I cheat and use a
spectrum analyzer to look at what it's sending.  To the best of my
knowledge, most such remote thermometers do not use avaricap.
However, the humidity sensor is a polyimide or polystyrene capacitor,
with no case.  The capacitor changes value as the dielectric absorbs
moisture and swells.


thanks
the 'varicap' mentioned then might be a temp sensor(no humidity)
as for frequency (589M says on the box)drift adjusting the screw near
top of pic1 did not help
Click to expand...
It's not a varicap. The thermometer element is either a thermistor,
or a semiconductor, such as an LM335:
<http://www.national.com/mpf/LM/LM335.html>
There are also thermometer chips that have the sensor inside:
<http://para.maxim-ic.com/en/results.mvp?fam=temp_sens>

I wonder where is the antenna input
please se
http://img233.imageshack.us/img233/9038/img00333.jpg
http://img6.imageshack.us/img6/9894/img00336q.jpg
Click to expand...
The previous photo was blurry. These two are both blurry and too
small. Looks like you're using a Blackbery 8100 camera phone. Few
camera phones take decent closeup photos. Try using a real digital
camera with a "macro" setting.

See my 3 questions.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On Oct 20, 10:32 pm, Jeff Liebermann <je...@cruzio.com> wrote:
On Wed, 20 Oct 2010 19:18:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:



On Oct 18, 9:37 am, Jeff Liebermann <je...@cruzio.com> wrote:
On Mon, 18 Oct 2010 06:41:25 -0700 (PDT), mynick <anglom...@yahoo.com
wrote:

if you test an OK  varicapdiode with analog reistance meter what  are
you supposed to get?

Avaricapis just an ordinary diode.  When reverse biased, it acts as
a capacitor which varies with the applied reverse bias.  It never
conducts current in the forward direction.  Never... Ever...

Does it get hot/warm in battery powered
transmitter

No.

(if not  than the element suspected  to be a varactor and
mounted to stick a little bit out of the transmitter  box,  could be
an ic diode although it could not transmit trough walls, could it?)

I have no idea.  Perhaps it would be helpful if you would disclose:
1.  What are you trying to accomplish?
2.  What are you working on?  (Make and model)?
3.  What have you done so far and what happen?
this is a photo of the outdoor part of the wireless thermometer that
stopped working
http://img517.imageshack.us/img517/7053/img00331n.jpg

Blurrrrrrry useless photo.   Try again, this time with the camera set
to macro, and without the drastic tilt angle, which requires too much
depth of field.

checked discrete elements ok but no bias voltage at (varicap?)diode-
that, kind of
a transparent element, seen up front close to battery contacts having
resistance in both directions od 6Kohms,
any ideas?

Nope.  See my 3 questions.  

I've had far too much entertainment with wireless weather stations.
They don't seem to fail, but they do drift off frequency, or lose
power output due to moisture absorption in the PCB.  I cheat and use a
spectrum analyzer to look at what it's sending.  To the best of my
knowledge, most such remote thermometers do not use avaricap.
However, the humidity sensor is a polyimide or polystyrene capacitor,
with no case.  The capacitor changes value as the dielectric absorbs
moisture and swells.

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Click to expand...
thanks
the 'varicap' mentioned then might be a temp sensor(no humidity)
as for frequency (589M says on the box)drift adjusting the screw near
top of pic1 did not help
I wonder where is the antenna input
please se
http://img233.imageshack.us/img233/9038/img00333.jpg
http://img6.imageshack.us/img6/9894/img00336q.jpg
 
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