[Amps] New Alpha 8410 photos + Video

[Paul Christensen]

That's just a bit more than 10% of maximum delivered power and cabinet 
ventilation openings should provide ample convection.  Take for example the 
AT4K ATU.  Into a 1:1 resistive 50-ohm load on 40m, loss is 32% (1.67dB) as 
measured by the ARRL.  That's not some extreme load -- and it's just one 
example from the manufacturer's C-L-C tuners.

The same tuner also shows high loss on the low bands under conditions of low 
load Z.  That's an indication of insufficient output C for the job.  Classic 
C-L-C tuner loss is primarily attributed to marginal coil Q across the 
operating spectrum, poor cabinet layout around the coil, and insufficient 
output C with low Z loads.  In order for the high loss to occur on 40m into 
a 50-ohm load, there's some quirk in the AT4K design that the manufacturer 
has decided to address with a cooling fan rather than attacking the root 
cause in the design phase.

Paul, W9AC

----- Original Message ----- 
From: "Paul Playford" <paul at w8aef.com>
To: "'Paul Christensen'" <w9ac at arrl.net>; <dezrat1242 at yahoo.com>; 
<amps at contesting.com>
Sent: Wednesday, March 09, 2011 12:08 PM
Subject: RE: [Amps] New Alpha 8410 photos + Video


>I have designed and built a 20m 1.5 Kw bandpass filter that has .4 dB
> insertion loss.
>
> After 30 seconds at 1.5 Kw it gets HOT!
>
> .4 dB loss from 1.5 Kw is 165 watts.  When was the last time you grabbed a
> 165 watt light bulb after it has been on for 30 seconds?
>
> Time to install a cooling fan.
>
> de Paul, W8AEF
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Paul Christensen
> Sent: Wednesday, March 09, 2011 9:36 AM
> To: dezrat1242 at yahoo.com; amps at contesting.com
> Subject: Re: [Amps] New Alpha 8410 photos + Video
>
> True, but I'm referring to their past ATU designs with cooling fans.
>
> Paul, W9AC
>
>