Search for varactor 10 ~ 1.8pf

  • Thread starter Pierre-François (f5bqp_pf
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Pierre-François (f5bqp_pf

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Hi,

I'm searching a replacement to the ZC800 varactor with the following caps
specs:
2v ===> 10pf
20v ===> 1.8pf

It's to equip a 350 ~ 500Mhz VCO (0v ~ 9v)

I've tried a BB405B but its capacity is too high at 9volt the maximum
driving voltage at its upper frequency so the max frequency is 460Mhz, not
500.

Many thanks for your help.
pf
 
"Pierre-François (f5bqp_pfm)" wrote:
Hi,

I'm searching a replacement to the ZC800 varactor with the following caps
specs:
2v ===> 10pf
20v ===> 1.8pf

It's to equip a 350 ~ 500Mhz VCO (0v ~ 9v)

I've tried a BB405B but its capacity is too high at 9volt the maximum
driving voltage at its upper frequency so the max frequency is 460Mhz, not
500.

Many thanks for your help.
pf
Click to expand...

Add a small capacitor between the varactor the the inductor to reduce
the capacitance. You could use a small trimmer capacitor to make it
easier than trying to S.I.T. Sometimes it is the only way to do a one
off repair.


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"Michael A. Terrell" <mike.terrell@earthlink.net> a écrit dans le message de
news: Ef-dnTTvHfude1fUnZ2dnUVZ_sDinZ2d@earthlink.com...
"Pierre-François (f5bqp_pfm)" wrote:

Hi,

I'm searching a replacement to the ZC800 varactor with the following caps
specs:
2v ===> 10pf
20v ===> 1.8pf

It's to equip a 350 ~ 500Mhz VCO (0v ~ 9v)

I've tried a BB405B but its capacity is too high at 9volt the maximum
driving voltage at its upper frequency so the max frequency is 460Mhz,
not
500.

Many thanks for your help.
pf


Add a small capacitor between the varactor the the inductor to reduce
the capacitance. You could use a small trimmer capacitor to make it
easier than trying to S.I.T. Sometimes it is the only way to do a one
off repair.


Hi Michael,
Click to expand...

Many thanks for the nice idea, I'll try it if I don't find a replacement.
I'll still search for a while, before I try.
I would prefer no tuning... However may be it's "Impossible Mission"...

pf


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Click to expand...
 
"Pierre-François (f5bqp_pfm)" wrote:
Michael A. Terrell wrote:

Add a small capacitor between the varactor the the inductor to reduce
the capacitance. You could use a small trimmer capacitor to make it
easier than trying to S.I.T. Sometimes it is the only way to do a one
off repair.

Hi Michael,

Many thanks for the nice idea, I'll try it if I don't find a replacement.
I'll still search for a while, before I try.
I would prefer no tuning... However may be it's "Impossible Mission"...
Click to expand...

You can use the variable, then unsolder it, measure it, and use a
fixed value capacitor if one is close enough to the measured
capacitance.

Another way is the old fashioned 'Gimmick Capacitor' which is a pair
of insulated wires that are twisted together, then trimmed with a pair
of wire cutters to get the value you need. Then there is no problem
with the value changing by accident. They were common in early
electronics, in RF circuits.


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..
As is a disk ceramic capacitor, a dremel grinding tool, and nail polish to
cover over the ground up area.


Jim



Another way is the old fashioned 'Gimmick Capacitor' which is a pair
of insulated wires that are twisted together, then trimmed with a pair
of wire cutters to get the value you need. Then there is no problem
with the value changing by accident. They were common in early
electronics, in RF circuits.
Click to expand...
 
Michael A. Terrell Inscribed thus:

"Pierre-François (f5bqp_pfm)" wrote:

Michael A. Terrell wrote:

Add a small capacitor between the varactor the the inductor to
reduce
the capacitance. You could use a small trimmer capacitor to make it
easier than trying to S.I.T. Sometimes it is the only way to do a
one off repair.

Hi Michael,

Many thanks for the nice idea, I'll try it if I don't find a
replacement. I'll still search for a while, before I try.
I would prefer no tuning... However may be it's "Impossible
Mission"...


You can use the variable, then unsolder it, measure it, and use a
fixed value capacitor if one is close enough to the measured
capacitance.

Another way is the old fashioned 'Gimmick Capacitor' which is a
pair
of insulated wires that are twisted together, then trimmed with a pair
of wire cutters to get the value you need. Then there is no problem
with the value changing by accident. They were common in early
electronics, in RF circuits.
Click to expand...
Yes I remember that trick ! A variant to get very low values was to
wind a coil on the insulation of a straight wire. One advantage of this
was that if the coil was grounded it provided a screen as well.

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Baron.
 
"RST Engineering (jw)" wrote:
.
As is a disk ceramic capacitor, a dremel grinding tool, and nail polish to
cover over the ground up area.
Click to expand...

I have plenty of wire in the shop, but don't have any nail polish.
To each his (Or her) own, I guess! The last RF equipment I built wasn't
allowed to use either method, since it was built for NASA.


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"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in
news:hsydnRtxJtKoslDUnZ2dnUVZ_gWcnZ2d@earthlink.com:

I have plenty of wire in the shop, but don't have any nail polish.
Click to expand...
None of that red anti-tamper gloop for screw heads either? Same stuff, as far
as I can tell. Smells the same (of acetone or butyl acetate), looks the same
(red, shiny). Though I doubt screw heads or finely ground disk ceramic
capacitors benefit from lanolin or whatever else the cosmetic firms see fit
to put in there.
 
Lostgallifreyan wrote:
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in
news:hsydnRtxJtKoslDUnZ2dnUVZ_gWcnZ2d@earthlink.com:

I have plenty of wire in the shop, but don't have any nail polish.

None of that red anti-tamper gloop for screw heads either? Same stuff, as far
as I can tell. Smells the same (of acetone or butyl acetate), looks the same
(red, shiny). Though I doubt screw heads or finely ground disk ceramic
capacitors benefit from lanolin or whatever else the cosmetic firms see fit
to put in there.
Click to expand...

Locktite? The last bottle dried out, years ago. I used to pick up a
few of the bottles that were too old to use in manufacturing at work,
but the newest would be close to 10 years old these days, if there are
any out in the shop. OTOH, I have over 100,000 feet of hookup & wire
wrap wire that was tossed when they dropped a couple product lines..


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"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in
news:iJGdnRNRSa0u-1DUnZ2dnUVZ_qPinZ2d@earthlink.com:

Lostgallifreyan wrote:

"Michael A. Terrell" <mike.terrell@earthlink.net> wrote in
news:hsydnRtxJtKoslDUnZ2dnUVZ_gWcnZ2d@earthlink.com:

I have plenty of wire in the shop, but don't have any nail polish.

None of that red anti-tamper gloop for screw heads either? Same stuff,
as far as I can tell. Smells the same (of acetone or butyl acetate),
looks the same (red, shiny). Though I doubt screw heads or finely
ground disk ceramic capacitors benefit from lanolin or whatever else
the cosmetic firms see fit to put in there.


Locktite? The last bottle dried out, years ago. I used to pick up a
few of the bottles that were too old to use in manufacturing at work,
but the newest would be close to 10 years old these days, if there are
any out in the shop. OTOH, I have over 100,000 feet of hookup & wire
wrap wire that was tossed when they dropped a couple product lines..
Click to expand...
Not sure what the name was. Stuff is ok though, unlike cyanoacrylate you can
keep it indefinitely just by adding some solvent. Though I think it will cure
permanently if it gets dry enough.
 
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