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I built a hot Cobra 29 for a local boy and he blew it up...

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mr_fx

Sr. Member
Oct 8, 2011
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Kansas City
I built a hot Cobra 29 for a local boy and he blew it up...

I built it a few days ago, gave it to him last night

it was punching out a solid 48 watts pep on the swing...

I took a trip out to his 'station' and the antenna was some old 2 piece fiberglass jobbie with really flakey fiberglass... the coax were spliced in at least 3 places and the end that connected to the radio was suspect as well...

well I checked the SWRs and they where around 3.1-3.2... keep in mind Mosfets do not like high SWRs

I told him I can not warranty a radio hooked up to such a messed up antenna system... he said, "well it has been working just fine for about 6 or 7 years on this old royce !"

I said that did not surprise me, I bet the royce is running 4 or 5 watts peak... and it uses old school transistors...

well not the radio is not making the same amount of power it did when I sent it to him... it's only making about 15 PEP on the swing...

I fully explained to him that this is a HOT Rod Cobra 29 and that the antenna needs to be in check or it will blow... further more I told him that I can not warranty a radio that is hooked up to a high swr antenna...

what do you guys think?
 

Wondering...

Is your "Hot Rod" modification better than that guy on Ebay that does those "Flame Thrower" mods?
 
m42duster said:
Is your "Hot Rod" modification better than that guy on Ebay that does those "Flame Thrower" mods?
Click to expand...

I doubt it, similar I would guess... I can not say for sure I just know that it works, I know little to nothing about the 'flame thrower'

but I can tell you the Cobra 29s respond very well to mosfets, esp if you pick the correct companion parts... it really is all in the companion parts
 
GLR said:
No you weren't or you would have helped him fix his problems before he trashed his "hot rod Cobra"
Click to expand...

interesting... I gave him his radio last night... asked him about his antenna setup... THEN he and I agree that I would come by and make sure his SWRs where ok BEFORE he hooked up his radio... I had NO idea he was going to install the radio and yack on it all night and all morning before I got there...

in the future don;t pass judgement when you only have a limited understanding of what is going on :)
 
Offer to test it on your bench. It may come back up to specs, because his coax is messed up, giving high SWRs. Personally, I would not hook up a radio of any kind, with such high SWRs.
 
mr_fx said:
interesting... I gave him his radio last night... asked him about his antenna setup... THEN he and I agree that I would come by and make sure his SWRs where ok BEFORE he hooked up his radio... I had NO idea he was going to install the radio and yack on it all night and all morning before I got there...

in the future don;t pass judgement when you only have a limited understanding of what is going on :)
Click to expand...

Kinda like putting candy on the table and telling the little boy to wait until he's had his supper.
 
m42duster said:
Is your "Hot Rod" modification better than that guy on Ebay that does those "Flame Thrower" mods?
Click to expand...

I thought the Flame Thrower was a hamburger available at the local Dairy Queen? :confused1: :wink:

Wrench said:
Offer to test it on your bench. It may come back up to specs, because his coax is messed up, giving high SWRs. Personally, I would not hook up a radio of any kind, with such high SWRs.
Click to expand...

Agreed. If his antenna system is as screwed up as it sounds it would definitely impact the number on the watt meter.
 
Wrench said:
Offer to test it on your bench. It may come back up to specs, because his coax is messed up, giving high SWRs. Personally, I would not hook up a radio of any kind, with such high SWRs.
Click to expand...

I told him I would not transmit n that antenna system... we tested it in my buddies truck... 10k predator... and a 'nice' mag mount... 1.3 swr
 
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