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The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: but 10 paralleled will carry 9,4 A ;-))Marco, IK1HSS ----Messaggio originale---- Da: 31-gen-2019 8.32 A: Ogg: LF: Silver mica caps... Hello Mike and Dimitris, Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.216.176.195 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (marcocadeddu[at]tin.it) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 2b323379b582abbe78ea971e119c2a1c Subject: R: LF: Silver mica caps... Content-Type: multipart/alternative; boundary="----=_Part_45925_190516.1548922005309" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_MESSAGE,RISK_FREE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false ------=_Part_45925_190516.1548922005309 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable but 10 paralleled will carry 9,4 A ;-))Marco, IK1HSS ----Messaggio originale---- Da: selberdenken@posteo.de Data: 31-gen-2019 8.32 A: Ogg: LF: Silver mica caps... Hello Mike and Dimitris, Hmmmm, ok, i admit i'm getting convinced by the idea. I just read a bit=20 at https://en.wikipedia.org/wiki/Silver_mica_capacitor Can you recommend a good source for them? I just found that one=20 https://de.rs-online.com/web/p/mica-kondensatoren-glimmerkondensatoren/8713= 189/=20 . The data sheet=20 (https://docs-emea.rs-online.com/webdocs/13e5/0900766b813e58c0.pdf)=20 tells that a 1 nF type will carry 0.94 A. So this is to small for me. 73, Stefan Am 30.01.2019 22:57, schrieb Michael WALTERS: > Hi I Still recommend hi value S/Mica crimped.Voltage ability very good to= o. They do not heat noticeably so remain stable. I found a large box of mul= tiple values and mixed as required. Used at 137 also. Mike G3JVL > > =20 >> On 30 January 2019 at 17:22 DK7FC wrote: >> >> >> Hi MF, >> >> Last night i've been at home while transmitting on the indoor loop >> again. The TX power was doubled, i.e. about 2 mW ERP, based on Rik's >> convincing calculation/estimation. >> The temperature dependency of the antenna current was much more >> expressed. I started at 70 % and moved to 100 %, then back to 70 % >> whithin less than one WSPR TX period. 100 % is equal to about 20 A >> antenna current. >> >> As mentioned, the tuning C consists out of 2.2 nF + 6.8 nF both >> WIMA-FKP-1 and a 1 nF variable capacitor. >> Yesterday, it was clearly noticable that the 6.8 nF cap becomes warmer >> than the 2.2 nF cap, although there were thermally coupled to each other= . >> >> The datasheet, >> https://www.wima.de/wp-content/uploads/media/e_WIMA_FKP_1.pdf, tells >> about the AC voltage derating curves, page 77, the 2000 VDC chart. >> But they say "Permissible AC voltage in relation to frequency at 10 =C2= =B0C >> internal temperature rise (general guide)." >> >> I interprete this chart combined with the text beside it as follows: "If >> you want to avoid a temperture rise of more than 10 =C2=B0C, due to life= -time >> of capacity-deviation considerations, then you should not apply more >> than x volts at a certain frequency" >> and NOT like "In any way you must not apply more than x volts at a >> certain frequency because otherwise the capacitor will explode and the >> whole building will burn down immediately!" >> >> Furthermore, the thermal connection of the leads to e.g. a ground layer >> will have an effect on the temperature at the working point. So, is the >> chart based on the worst-case or the best-case? >> All in all i see no risk at all to apply the full 700 V rms AC level, at >> least for smaller capacity values and if they have a good connection to >> a heat sink that pulls the heat away from the internal plates. >> >> Another thing in the resonated loop arrangement is the fact that the >> current and voltage will drop as soon as the capacitor is getting >> damaged or becomes to warm, so this is a self-regulating circuit. >> >> I've just built the arrangement shown here: >> http://www.iup.uni-heidelberg.de/schaefer_vlf/MF/MFcaps.jpg >> It also gives 9 nF, but with a better distribution and heat transfer. If >> necessary, a fan could be used to keep the temperatures down. >> >> Will be tested tonite on MF. But 20 A at 475.7 kHz and 10 nF already >> means 670 V, so i can't do much more here. >> >> 73, Stefan >> >> =20 > =20 ------=_Part_45925_190516.1548922005309 Content-Type: text/html;charset="UTF-8" Content-Transfer-Encoding: quoted-printable
but 10 paralleled will carry 9,4 A ;-))
Marco, IK1HSS

----Messaggio originale----
Da: selberdenken@posteo.de
Data: 31-gen-2= 019 8.32
A: <rsgb_lf_group@blacksheep.org>
Ogg: LF: Silver mica= caps...

Hello Mike and Dimitris,

Hmmmm, ok, i admit i'm gett= ing convinced by the idea. I just read a bit
at https://en.wikipedia.or= g/wiki/Silver_mica_capacitor
Can you recommend a good source for them?I just found that one
https://de.rs-online.com/web/p/mica-kondensator= en-glimmerkondensatoren/8713189/
. The data sheet
(https://docs-eme= a.rs-online.com/webdocs/13e5/0900766b813e58c0.pdf)
tells that a 1 nF ty= pe will carry 0.94 A. So this is to small for me.

73, Stefan

=




Am 30.01.2019 22:57, schrieb Michael WALTERS:
> H= i I Still recommend hi value S/Mica crimped.Voltage ability very good too. = They do not heat noticeably so remain stable. I found a large box of multip= le values and mixed as required. Used at 137 also.   Mike G3JVL>
>   
>> On 30 January 2019 at 17:22 D= K7FC<selberdenken@posteo.de>  wrote:
>>
>>
= >> Hi MF,
>>
>> Last night i've been at home while = transmitting on the indoor loop
>> again. The TX power was doubled= , i.e. about 2 mW ERP, based on Rik's
>> convincing calculation/es= timation.
>> The temperature dependency of the antenna current was= much more
>> expressed. I started at 70 % and moved to 100 %, the= n back to 70 %
>> whithin less than one WSPR TX period. 100 % is e= qual to about 20 A
>> antenna current.
>>
>> As = mentioned, the tuning C consists out of 2.2 nF + 6.8 nF both
>> WI= MA-FKP-1 and a 1 nF variable capacitor.
>> Yesterday, it was clear= ly noticable that the 6.8 nF cap becomes warmer
>> than the 2.2 nF= cap, although there were thermally coupled to each other.
>>
&= gt;> The datasheet,
>> https://www.wima.de/wp-content/uploads/m= edia/e_WIMA_FKP_1.pdf, tells
>> about the AC voltage derating curv= es, page 77, the 2000 VDC chart.
>> But they say "Permissible AC v= oltage in relation to frequency at 10 =C2=B0C
>> internal temperat= ure rise (general guide)."
>>
>> I interprete this chart = combined with the text beside it as follows: "If
>> you want to av= oid a temperture rise of more than 10 =C2=B0C, due to life-time
>>= of capacity-deviation considerations, then you should not apply more
&g= t;> than x volts at a certain frequency"
>> and NOT like "In an= y way you must not apply more than x volts at a
>> certain frequen= cy because otherwise the capacitor will explode and the
>> whole b= uilding will burn down immediately!"
>>
>> Furthermore, t= he thermal connection of the leads to e.g. a ground layer
>> will = have an effect on the temperature at the working point. So, is the
>&= gt; chart based on the worst-case or the best-case?
>> All in all = i see no risk at all to apply the full 700 V rms AC level, at
>> l= east for smaller capacity values and if they have a good connection to
&= gt;> a heat sink that pulls the heat away from the internal plates.
&= gt;>
>> Another thing in the resonated loop arrangement is the = fact that the
>> current and voltage will drop as soon as the capa= citor is getting
>> damaged or becomes to warm, so this is a self-= regulating circuit.
>>
>> I've just built the arrangement= shown here:
>> http://www.iup.uni-heidelberg.de/schaefer_vlf/MF/M= Fcaps.jpg
>> It also gives 9 nF, but with a better distribution an= d heat transfer. If
>> necessary, a fan could be used to keep the = temperatures down.
>>
>> Will be tested tonite on MF. But= 20 A at 475.7 kHz and 10 nF already
>> means 670 V, so i can't do= much more here.
>>
>> 73, Stefan
>>
>>=      
>   



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