[Central-Electronics] 160 meter operation

[Jim Candela]

Tom,

     Your best bet is to look for a 600L CE amplifier. These are a good 
match for the 10B/20A exciter. The 600L requires only 3-10 watts drive, so 
even with your 20A, overdriving the 600L is likely if your not careful, 
especially on 160-80M where the 20A puts out the most drive. I see pictures 
all the time of a 600L teamed with a 100V or 200V, but I have NEVER heard 
these stations on the air. Using a 100w exciter with an AMP that can be 
driven to full output with as little as 3 watts is the perfect recipe for 
severe overload, and distortion. The 20A/600L combo is more appropriate.

     Another alternative is to QRO your 20A. I have done that to two rigs 
now, where I can get considerable more RF power from the 20A. The sacrifice 
is the upper bands (10-15, and to an extent 20m) become unusable or 
unstable. Since you want 160M primarily, then the QRO option of the 20A is 
even more desirable. Outputs up to 60w pep are obtainable with different 
output tubes, and higher B+

   I like the other post too with a Home Brew linear amplifier. This might 
be the best option for many.

    Realize that higher power on the 20A brings with it some undesirable 
results. As your VFO drifts, as your carrier suppression drifts, and as your 
sideband rejection might not be the best, more people will notice. I 
countered these two issues by stabilizing my VFO better, and beefing up the 
20A R-C audio phase shift network such that SB suppression is better up to ~ 
5 Khz audio. Still, and lows below 200-300Hz will come through on both 
sidebands. The Flex guys with pan adapters were quick to point that out to 
me since my QRO 20A looks different to them than the usual signal. This is 
because I was on 80m LSB where my lower audio frequencies up to a few 
hundred HZ where not reduced on the USB. I was clean at the upper audio 
frequencies however.

Here is one Flex guy recording me when I was on the 3870  Boat Anchor net:

http://pages.prodigy.net/jcandela/20A_MP3/

I was running ~ 65w PEP RF with my 20A into an 8877 based amplifier, and 
about 1500w pep RF out. The Flex guy used 7 Khz BW to get me all in. That 
means I was about -6.8Khz LSB, and about + 200hz USB. :-)

I can describe the QRO mods, and all the other stuff if anyone is 
interested. I did cover all of that years ago on this reflector. The 
archives of this forum contain many posts on these topics.

Jim
WD5JKO





----- Original Message ----- 
From: "Tom Elmore" <tom at telmore.com>
To: <central-electronics at mailman.qth.net>
Sent: Thursday, November 25, 2010 11:54 PM
Subject: [Central-Electronics] 160 meter operation


>
>
> I am thinking about building a 160m linear for my CE-20 and was wondering 
> if
> anyone has suggestions as such. My CE-20 puts out almost 20 watts stock. 
> Any
> current crop of linear amps capable of 160 able to be driven by only 20
> watts?
>
>
>
>
>
>
>
>
>
> Thank You
>
>
>
> Tom Elmore
>
> Anchorage, Alaska
>
>
>
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