[Amps] QRO Technologies HF2000 plate choke, cont.

[hzp_electronics at juno.com]

Here is some food for thought.  In both my SB-220 and my HL-2200, I added a 10 ohm 10 watt resistor directly below the stock RFC and prior to the bypass capacitor to ground.  Its purpose is to protect the power supply from plate to grid shorts.  It seems that this resistance may have 'reduced' resonances in the RFC circuit by accident.  If someone is doing some measurements, you might check what a 10 ohm resistor in series with the RFC does to the resonances.  
   73
.... Bill K3HZP


---------- Original Message ----------
From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
To: amps at contesting.com
Subject: [Amps] QRO Technologies HF2000 plate choke, cont.
Date: Sun, 14 Nov 2021 14:07:18 -0800

Date: Fri, 12 Nov 2021 11:45:57 -0800
From: Jim Brown <jim at audiosystemsgroup.com>
To: amps at contesting.com
Subject: Re: [Amps] <
Message-ID:
        <95d62c19-7d9e-f068-5fda-28d08e167c73 at audiosystemsgroup.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

On 11/8/2021 4:18 PM, jim.thom jim.thom at telus.net wrote:
> I have heard of at least 5  of the ameritron chokes blowing up in the last
> 7 months....and they were  ALL  on  17m band... go figure.

<MFJ has never been known for their quality control, regardless of which
<of their brand names are involved.

<73, Jim K9YC

##  The ameritron choke is supposed to series resonate at 11.6 mhz...and
also  27.1 mhz.  225 uh, 4 kv, and 1.5 amp.   17m band is the last place it
should blow up, wtf ?

##  W8JI makes a more precise version, looks identical.  However, it's
rated for  245 uh,  and series resonates at 11.7 mhz...and  16.3 mhz...per
his CTR website.  He may have stated the 16.3 mhz resonance incorrectly.

##  2 more blow ups with the ameritron choke last week.... again on 17m.....
  go figure.

##  The  RF choke from  RF parts, ameritron, MFJ catalog  and alpha  are
all identical..and all come from  mfj.

##  I bought 2 x of these chokes from RF parts a while back, and measured
225 uh and  224 uh.  I will have to test em for series resonances...using
the original  JI test method.  Dead simple..and works.

##  Stuffing the  MFJ choke into a L4B  would be a snug fit.... with not a
lot of clearance between top of choke..and  top steel lid... like  7/16".

##  I measured the OEM drake choke in the  80-10m L4B.  It's  154 uh...and
doesn't seem to resonate anywhere.   It works on all 3 x warc bands  +
11m.  This was all into a dummy load.   It's gotta resonate  somewhere.

Jim  VE7RF
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