Search for varactor 10 ~ 1.8pf

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

Reply to
Pierre-François (f5bqp_pfm)
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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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Reply to
Michael A. Terrell

"Michael A. Terrell" a écrit dans le message de news: Ef-dnTTvHfude1fUnZ2dnUVZ snipped-for-privacy@earthlink.com...

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"...

pf

Reply to
Pierre-François (f5bqp_pfm)

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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Reply to
Michael A. Terrell

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

Jim

Reply to
RST Engineering (jw)

Michael A. Terrell Inscribed thus:

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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Reply to
Baron

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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Reply to
Michael A. Terrell

"Michael A. Terrell" wrote in news:hsydnRtxJtKoslDUnZ2dnUVZ snipped-for-privacy@earthlink.com:

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.

Reply to
Lostgallifreyan

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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Reply to
Michael A. Terrell

"Michael A. Terrell" wrote in news:iJGdnRNRSa0u-1DUnZ2dnUVZ snipped-for-privacy@earthlink.com:

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.

Reply to
Lostgallifreyan

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