Hi Bud, all.
Lets face it the SB-220 has been the workhorse of ham radio for 30 years.
It was cheap, compact and popular.
However, the SB-220 was a modified cheapened up version of the L4 design.
Bad design concepts like floating the grids on resistors and caps was copied
into the SB-220. Even my first 3-500 amps used this flawed concept as I
copied the L4 amps myself, but later learned there were better ways.
There's a huge advantage having the PS in a separate box. It allows the
head to be more spacious and the components more rugged. It's a very easy
amplifier to service.
The only changes I recommend for the L4 is: Put a fan on the PS, ground the
grids and put a zener in the B-.
You've got a great amp.
With the SB-220 there's too much crammed into the small box. Heat is an
enemy of power. You ever seen the solder drip out of a 3-500z's pins? The
plastic ring on late 3-500's is because of SB-220's You'll not melt the
solder out of a correctly cooled L4B.
The L4 is top flight parts all the way through it. Now take that sort of
quality and build the L4's ham radio stable replacement and you've got an
Ameritron. But 2 to 3 times the price used.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Mike, K6BR
Sent: Monday, October 23, 2006 7:04 PM
To: 'W2RU - Bud Hippisley'; 'Amps'
Subject: Re: [Amps] More information for "What NOT to buy"..
What modifications did you make to get 1500 watts out, was it just a power
supply change?
Mike
Robert B. Bonner wrote:
>I think its pretty hard to beat a Drake L4B for a starter amp.
>
> it's a better quality amp
>than an SB-220 for close to the same price.
>
>
Interesting comparison. Back in the 70s I chose an SB-220 over an L-4B
because the Heath generated less TVI when driven to the same input on CW
with the same exciter (Collins 32S-3). That SB-220 is still going
strong today, even after modification to run 1500 watts output when the
rules changed.
TVI is probably not as important a consideration in these days of CATV
and satellite TV, and mine was certainly not a rigorous test, but your
comment makes me wonder what should be included or excluded when one
speaks of "quality", and what factors you used to conclude that the L-4B
is "better".
Bud, W2RU
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