A 4:1 i wouldn't get really excited about with a tube type amp, a solid
state amp thats a whole other story. Just make sure you have a good rf
ground for the amp! I put in a ground rod throught the basement floor
behind the shack wall, about a 2ft distance from the amp, radio, and tuner.
I don't have any RF problems in the shack like some have reported when
running one of these older amps.
I have heard that before about the Cushcraft verticals, perhaps that's just
normal for them then they way they are made.
I set my Alpha Delta to 3860 as that's where we have our MN and SD net's.
If i venture off too far then i have to touch it up with the tuner a bit.
The SA-2040 is a nice legal limit tuner but it only covers 80-10 so i have
to bypass it for 160, but then i use a different antenna for 160 most of the
time anyway and the amp, SB-200, doesn't cover 160 either so they both get
bypassed by a antenna switch.
The SA-2060 covers 160-10 and has some added features such as a meter and
antenna switch, nice tuner if you can get your hands on one. Even the
2040's average around $200-$300 for a nice to mint condition one.
Of course you could build a tuner too, been there done that! It's not that
hard if you can scrounge some good parts for it. I built one with parts
from surplus sales of nebraska, one part at a time as i could afford it.
That would handle legal limit when it was done, sold it to another guy and
then when i bought the amp i wanted a tuner again so i found this 2040
cheap.
73,
Scott
----- Original Message -----
From: "Jeff Carter" <amps@hidden-valley.com>
To: <amps@contesting.com>
Sent: Monday, March 02, 2009 7:07 PM
Subject: Re: [Amps] SB-220 and load mismatching...
Right, I've got a Cushcraft R7 which fits your requirement of a
multiband vertical, but it's extremely narrowbanded. I rebuilt this
antenna a couple of years ago, partially for this purpose, but both
the documentation from the factory and my antenna analyzer say that it
never gets 1:1 anywhere regardless of what you do, and the SWR rapidly
climbs away from reality on either side of where you set the trap.
What I'm saying is that even with a multiband antenna, the SWR
situation eventually rears its ugly head.
I've got two or three tuners, none of which will do legal limit.
Something else to buy...lol
Somebody pointed out that I was facing 4:1 out on the edges of 80m
since I'd cut the dipole for 3800, and that's right, of course.
Whenever I wanted to work down between 3500 and 3600, I'd just been
turning the amp off out of paranoia. It's good to hear that I
shouldn't have to worry about that.
What I'm hearing is that the SB-220 should accept a VSWR of 4:1 or
better at the 500-800 watts at which I usually run it. Is that the
consensus?
Jeff/KD4RBG
---- Original message ----
>Date: Mon, 2 Mar 2009 17:55:32 -0600
>From: KBØNLY <kb0nly@mchsi.com>
>Subject: Re: [Amps] SB-220 and load mismatching...
>To: <amps@hidden-valley.com>
>
>Do your amp a favor, if you can't put up a mutliband vertical or dipole get
>a tuner after the amp. I run an old heathkit SA-2040 2kw roller inductor
>tuner. Sure, that means the tuner is taking the heat, but I would rather
>arc or burn up a tuner instead of a spendy part in a amp. Consider the
>cost
>of a tuner compared to a cost of a new set of tubes or load cap, its cheap
>insurance.
>
>Scott KBØNLY
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