<<This I dont understand as the same amount of DC current will still flow
through the windings of the RF transformer if the DC is fed to its center
tap like in all designs. Or are you speaking of connecting a choke to each
collector where only RF would be handled by the transformer? >>
Yeah that's what it means...you got it... the collectors are fed via a choke
that is bifilar wound with a center tap for the DC+, while the RF
transformer is cap coupled (DC blocked). Check Helge Granberg's later
designs... they were all done this way because he recognized the problem.
Sincerely,
Dr. William J. Schmidt, II K9HZ
Trustee of the North American QRO - Central Division Club - K9ZC
Email: bill@wjschmidt.com
WebPage: www.wjschmidt.com
"If computers get too powerful, we can organize them into a committee; that
will do them in." -- Bradley's Bromide
----- Original Message -----
From: "Will Matney" <craxd1@ezwv.com>
To: <amps@contesting.com>
Sent: Thursday, March 31, 2005 10:46 PM
Subject: Re: [Amps] Solid state amps
> See below,
>
> *********** REPLY SEPARATOR ***********
>
> On 3/31/05 at 7:39 PM Dr. William J. Schmidt, II wrote:
>
>>Of course you realize that running the DC through the transformer is
>>disadvantageous because it creates a strong "B" field in the core which
>>can
>>drastically reduce the dynamic response of the DC/RF transformer.
>
> I take it "B field" meaning the maximum flux density or Bmax? Once Bmax is
> reached, the waveform becomes distorted anything over this maximum flux
> density. The permeability drops off sharply here too. The trick is to
> design the core so it wont saturate at maximum power.
>
>>With an
>>outboard choke, both parts can be smaller in size... and keep the RF
>>transformer from saturating (reduce non-linearities and less distortion
>>because of it!).
>
> This I dont understand as the same amount of DC current will still flow
> through the windings of the RF transformer if the DC is fed to its center
> tap like in all designs. Or are you speaking of connecting a choke to each
> collector where only RF would be handled by the transformer? Youv'e lost
> me here on the explanation.
>
>>
>>Most of us use another core as a DC choke... and AC couple the RF
>>transformer... and there are better materials to use...
>
>
> Actually, I think Palomar and others recommend 61 material in place of 43
> for 2-30 MHz. For iron powder, color red is the one most used. I know in
> the Motorola texts, Helge recommended a minimum permeability of around
> 800-900 if I recall, but 61 is way lower. When maximum power is used, the
> 43 will heat up quicker than the 61 or what I was told by Palomar. Once
> you fully saturate ferrite and heat it to a certain point, the core is
> ruined and has to be replaced. Something about the heat destroys its
> properties.
>
>>
>>
>>Sincerely,
>>
>>Dr. William J. Schmidt, II K9HZ
>>Trustee of the North American QRO - Central Division Club - K9ZC
>>
>>Email: bill@wjschmidt.com
>>WebPage: www.wjschmidt.com
>>
>>"If computers get too powerful, we can organize them into a committee;
>>that
>>will do them in." -- Bradley's Bromide
>>
>>
>>----- Original Message -----
>>From: "Carcia, Francis A HS" <francis.carcia@hs.utc.com>
>>To: "Amps (E-mail)" <amps@contesting.com>
>>Sent: Thursday, March 31, 2005 3:09 PM
>>Subject: [Amps] Solid state amps
>>
>>
>>> Hi all,
>>> I've collected parts to do 9 push pull MRF150 stages and someday maybe I
>>> will assemble. The boards will
>>> be modified ENI surplus. I found ENI transformers don't work well below
>>> 7
>>> MHz. and the typical type 43
>>> sleeve doesn't work well below 3 MHz. I found it takes 2 sleeves in
>>series
>>> to get minimum primary inductance
>>> on 160 meters. These are the .875 inch O.D. sleeves. I wonder if anyone
>>> has
>>> also noticed this on 160 M.
>>> I have also seen this with CCI kits. I plan to run DC through the
>>> transformer because I found it forces a better
>>> balance with MRF429 bipolars. Frank, WA1GFZ
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
> Best,
>
> Will
>
> Amateur Transformer & Supply
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
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