Den 13-10-2015 kl. 19:31 skrev Scott, Christopher:
Hi all,
First question: when I try to subscribe to the digest, I get an "access forbid
den" error message ?
But my question relates to swr mismatch protection. My project is a 2 x Blf188
XR 1200 watt amp, 80/40/20, for ssb service. I've ordered a 4z4rb board, and g
ot my two Fets for 129 euros each from [1]www.pcs-electronics.com. I spent $1
90 on a 0.75" x 6" x 12" copper heat spreader, and it will be mated to a large
aluminum forced air heat sink. As much as I hate to do it, it seems that solde
ring the fets in is best to keep case temps reasonable. That makes one doubly
worried about blowing the fets.
They brag about 65:1 swr survivability, but this is pulsed. Clearly a post LPF
reflectometer ref sample is necessary to shut it down with a poor match, say a
bove 2:1. But I see another pitfall; the switched LPFs being set to the wrong b
and.
So, is the best solution adding another reflectometer after the output transfor
mer and prior to the filter to protect against that? With an expected third ha
rmonic being 10-12 dB down at this point, the threshold might need to be high,
like 5:1 ...
Chris Scott
W4NEQ
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Chris,
If you want to see what it can survive in real life, take a look here:
[4]http://www.frenning.dk/OZ1PIF_HOMEPAGE/LDMOS_SSPA.html
Scroll down towards the end of the article....
--
Vy 73 de OZ1PIF/5Q2M, Peter
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** If it sounds too good to be true -- **
** it is! **
** If it sounds about right -- make **
** sure you can afford to be wrong! **
** **
** -- Robert Heinlein: **
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email: peter(no-spam [5]filler)@frenning.dk
[6]http://www.frenning.dk/oz1pif.htm
Ph. +45 4619 3239/ +45 2332 9464
Snailmail:
Peter Frenning
Ternevej 23
DK-4130 Viby Sj.
Denmark
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References
1. http://www.pcs-electronics.com/
2. mailto:Amps@contesting.com
3. http://lists.contesting.com/mailman/listinfo/amps
4. http://www.frenning.dk/OZ1PIF_HOMEPAGE/LDMOS_SSPA.html
5. mailto:filler)@frenning.dk
6. http://www.frenning.dk/oz1pif.htm
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