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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