My own amp is a LK-500ZC which isnt much different than a SB-220. Bought
it new in 1986 and VSWR hasnt hurt it yet.
Carl
KM1H
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: <amps@contesting.com>
Sent: Wednesday, April 22, 2009 5:39 PM
Subject: Re: [Amps] High SWR
> Jeff, there's a huge difference between being conservative - a good
> thing, usually - and forgoing significant benefit because of a
> misconception. I love my SB-220 too, and I try very hard not to do
> dumb things like operating it into no load, but SWR, per se, is not
> something to worry yourself about, so long as the amplifier can match
> the load.
>
> 73, Pete N4ZR
>
> At 05:21 PM 4/22/2009, Jeff Carter wrote:
>>I have had others tell me I can get away with it, too. At the center
>>of the issue, the problem isn't engineering, it's cowardice.
>>
>>See, I built this amp from the metal up, and it's probably the coolest
>>ham-related thing I ever built. I regularly build things for work,
>>and I can even do surface mount component work if I have to do so, but
>>this old SB-220 is special to me.
>>
>>If the cost of keeping well within the lines of operation is missed
>>contacts, then I guess I'm just going to miss them. I don't really
>>care about talking to anybody anyway, but I do care about this
>>amplifier.
>>
>>It's probably a little bit psychotic, but I was really, really proud
>>of this thing when I got it finished, and unless the coming Global
>>Depression forces me to sell it for food money, I'll still have it
>>when I die.
>>
>>Then my kids can sell it for $5 on eBay, not understanding that their
>>Dad built it by hand, piece-by-piece, or even understanding for sure
>>what it is.
>>
>>Jeff/KD4RBG
>>
>>
>>---- Original message ----
>> >Date: Wed, 22 Apr 2009 16:54:53 -0400
>> >From: Pete Smith <n4zr@contesting.com>
>> >Subject: Re: [Amps] High SWR was SB-1000 tuning question
>> >To: amps@contesting.com
>> >
>> >You are missing out on a lot by limiting yourself this way, because
>> >the SB-220 is a great active antenna tuner. I routinely use mine on
>> >antennas cut for the low end of 80M up in what used to be called the
>> >DX window at 3790-3800 KHz. The indicated SWR is over 3 to 1 but so
>> >long as the amplifier finds an output peak somewhere in the Load
>> >capacitor range I just go with it. My best antenna is 1:1 at one
>> >point in 15 meters, but everything else ranges from a low of 1.2 to
>> >a
>> >low of 1.5, depending on band - as for the high end of the range on
>> >those bands .... don't even ask.
>> >
>> >I think your math only tells part of the story. According to TLW,
>> >the ARRL's transmission line calculator, for 100 feet of RG-213 into
>> >a 100 ohm resistive load at 3.5 MHz, SWR at the transmitter end is
>> >1.88 (less than 2 because of line loss), the total loss is .43 dB,
>> >and the additional loss due to SWR is .066 dB. Losses are higher at
>> >higher frequencies, of course, but still in roughly the same
>> >proportions.
>> >
>> >The idea about large amounts of reflected power coming back down
>> >from
>> >a high SWR and causing problems was debunked here years
>> >ago. Open-wire transmission lines are routinely run at very high
>> >SWRs. So long as they can be matched to your transmitter, that is
>> >not a problem.
>> >
>> >73, Pete N4ZR
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|