[Amps] hf-2500

[Jeff Blaine]

They don't work very well in that implementation (the hf-2500).  A guy 
across town had the exact same failure scenario as David did.  Not quite a 
"china syndrome" but a melt-down none the less.

I think the issue with the shorted turns is overheating due to the coil's 
flux being jammed into the few turns in use.  The argument is that separate 
band-dedicated coils don't have that issue because the entire core's surface 
is used and you don't have the localized concentration of heating.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Jim W7RY
Sent: Wednesday, December 19, 2012 7:16 PM
To: Amps
Subject: Re: [Amps] hf-2500

Bill

We already had this discussion on here about a year ago. But I 'm going to
repeat it.

Alpha, Ameritron, Jerry K8RA, myself W7RY, and many others all use toroids
with shorted turns on our "L" coil in a PI-L circuit.  It works just fine.

Do you mean that a shorted turn toroid for the PI network is not good?  Or
are you making a general statement that they don't work at all in an
amplifier?


73
Jim W7RY


-----Original Message----- 
From: Bill Turner
Sent: Wednesday, December 19, 2012 12:26 PM
To: Amps
Subject: Re: [Amps] hf-2500

ORIGINAL MESSAGE:
On Wed, 19 Dec 2012 17:15:03 +0000, K1TTT wrote:

>Agreed, that is why I have modified one to do only 40-10m... removing the
>80m and 160m coils from the toroid removes the shorted turns problem and
>makes it run very nicely doing rtty on 40m.

REPLY:
As David found out, shorted turns on a toroid or any iron core coil
are a no-no unless you do some very careful design and testing, which
Command obviously did not do. Shorted turns on an air core coil are
usually no problem. A word to the wise.

73, Bill W6WRT
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