From: "Carl" <km1h@jeremy.mv.com>
> Sent: Friday, February 04, 2011 6:24 PM
> To: "Jim Thomson" <jim.thom@telus.net>; <amps@contesting.com>
> 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 tap...it'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, IMO..is 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
station.
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.
Carl
%%% 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 ...works 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
that..so couldn`t see the
advantage of using torroids.
Jim VE7RF
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