[ARC5] [Milsurplus] 6AQ5 Tank

[jmfranke]

John,

Yes, you are correct about the coil. I was working the capacitance issue and 
arrived at the same number as you for the capacitor. And, having changed the 
capacitance by a factor of 6 the coil inductance would have to increase by a 
factor of 6 for resonance. Working on maintaining the same reactance values 
for the coil and/or the capacitor should and does bring us both to the same 
point. Ignoring any change in resistive elements, Q would be maintained by 
maintaining the same reactance values as the frequency is changed.

John  WA4WDL

--------------------------------------------------
From: "J. Forster" <jfor at quik.com>
Sent: Wednesday, July 20, 2011 7:04 PM
To: "David Stinson" <arc5 at ix.netcom.com>
Cc: "ARC-5 List" <arc5 at mailman.qth.net>; <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] 6AQ5 Tank

>> Ok all you smart people-
>> I'm looking at a 6AQ5 Pierce crystal oscillator/tripler
>> with a plate tank circuit which outputs at 24 MC.
>> The plate tank capacitor is 40 pFd.
>> The capacitive reactance at 24 MC is only 166 ohms.
>
> You have to multiply by the Q. If the Q=100, it will look like 16.6K
>
>> This seems low for a tube tank.  Output capac.
>> of 6AQ5  is 6 pFd,  so that doesn't change the picture much.
>
> Agreed.
>
>> I was looking at changing the tank to output at 3.9 MC,
>> but if Xc = 166 ohms is correct, the tank cap
>> at 3.9 MC would be 6.7 uFd.  That can't be right.
>
> Let's see:
>
> The frequency scales as the SQ. RT. of LC
>
> 24 MHz / 3.9 MHz = about 6, so the C needs to be 6*6 *40 pF = 6*240 = 1440
> pF.
>
> This is probably still too large. I'd increase the number of turns on the
> coil by about 6 and the C to about 240 pF.
>
> Best,
>
> -John
>
> ================
>
>
>
>
>
>
>
>> What's up with this?
>>
>>
>> ______________________________________________________________
>> Milsurplus mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Milsurplus at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>