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Re: [Amps] What to buy?

To: "Jim Thomson" <>, <>
Subject: Re: [Amps] What to buy?
From: "Carl" <>
Date: Sat, 5 Feb 2011 15:56:26 -0500
List-post: <">>
----- Original Message ----- 
From: "Jim Thomson" <>
To: <>
Sent: Saturday, February 05, 2011 10:08 AM
Subject: [Amps] What to buy?

From: "Carl" <>
> Sent: Friday, February 04, 2011 6:24 PM
> To: "Jim Thomson" <>; <>
> Subject: Re: [Amps] What to buy?
>> ## I have given up on torroids  for tank coils on the low bands. I have
>> found some small diam, edge
>> wound ribbon coil stock that works the best for low band work.  3/8" edge
>> wound ribbon [.072" thick]
>> is the same as .28"  tubing for current handling.   1/4" ribbon [ also
>> .072" thick]  is ample in most cases
>> and is the same as .2" OD tubing.   A friend also gave me a bunch of air
>> dux.. that uses 8 ga wire.. and the
>> wire was copper..and not the usual tinned material.  These are things of
>> beauty. I didn't know you could
>> get coil stock in 8 ga wire.
>> Jim   VE7RF
>> The NCL-2000 used one length #8 AirDux for 80-10
>> Carl
> ## The drake L4B's  use  8 ga tinned solid wire for 80+40M.  That coil
> runs stone cold on both bands.
> They used 1/4" silver plated tubing on 20-15-10m...which runs blazing hot
> on 15+10m.   One would have
> thought that on 15m...that the heat was migrate into the remainder of the
> 20-10m coil..but it doesn't. Using
> the footswitch and my finger on the 15m's hot.  Move one turn
> over into the unused part of the same coil
> and it's barely luke warm.....go figure.   These days, I use a Fluke 62 ir
> when doing heat tests.  The steel top lid on the
> L4B, too close to the 20-10m tubing coil.  With the top lid
> removed, the C1 cap has to be increased a bit.
> The torroids really save you nothing, space wise..VS airdux.  The torroids
> can be mounted closer to metal..and that's
> about it.  Torroids run way too hot, even 3 x T225-2B's, stacked.
> Jim  VE7RF

If toroids run too hot there is something too wrong with the design. Ive
been using a stack of T225-2B's for decades in adding 160M to several amps
in the old 2000W PEP INPUT and 1200W output range.

The #8 in the NCL-2000 doesnt deform the plastic even on 10M in contests. I
used to run it full bore for over 20 years, even on CW and the coil still
looks good. These days its been ressurected as part of the vintage SSB

If a T-225B is too small there are plenty of bigger ones available. Ive
stacked T-400's and 520's when I was building serious amps for folks.


%%%  Big diff between 1200 w pep out...and  1500w CCS CXR.  I looked at the
bigger T-400`s etc..and decided that If ur gonna go that big... you may as 
well use
8 ga wire coils, or tubing etc.  Esp with big tubes that typ have a low 
plate load Z.
With a low plate load Z, the tank coil values are low to begin with. Typ 
14-16 uh  used
on 160m.   The hb box`s  were big enough to handle a conventional coil, 
either edge wound
ribbon in  .375 or .5      Or .25  .375  or .5   tubing. You can get away 
with pretty small diam tubing
on 160m like .25   On the latest project.. I used 3 x coils..all at right 
angles.   .25 tubing  for 160m,
.375 tubing for 80-40m...and .5 tubing for 20-17-15m.... no 10+12m.  Zero 
heat, no surprises, and no
blow ups.  After seeing the torroids hit  226 deg C  in an Emtron DX-4.... I 
threw in the towel  on torroids.
I don`t have enough experience with em.  I have no clue how hot is too hot 
with torroids..or what is
normal or acceptable temp rise over ambient.

>From my past experience, 2 x T225-2B`s  were ok with 1200w pep out on ssb. 
>3 x are required for
1.5 kw CCS cxr out..and even then, mine ran hot.  Perhaps my winding 
technique was sub par.
Close wound airdux  weighs nothing, and had the uh required for a  160m  add 
to an existing
80-10m rf deck and runs stone cold.  3 x T225-2B`s  eat ùp 3 inchs 
in length, when stacked..
and more when you inlcude the wire.  The airdux I used was no longer than couldn`t see the
advantage of using torroids.

Jim  VE7RF

Most old regs 2000W PEP amps run just fine at 1200W out on CW, including the 
SB-220. The toroids are not the problem, its usually the PS.

Going from 1200 to 1500W for the average ham is no stretch with another 
T-225B in the stack If you want a CCS 24/7 amp then double the internal 
volume and quit whining.

One nice thing about toroids is that they take up so much less room than air 
wound and can be bolted right to an aluminum wall with a small Teflon 


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