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Palomar 600 Elite: How Many Input Watts Are Too Much?

moleculo said:
The key on an amp like this is to not overdrive the first stage, in this case a MRF454. With that transistor, you're looking at like a 2 watt carrier, or maybe even 1.5 watts. From there, about 16 watts will probably make it do all it should do and still be clean. You might be able to push it a little bit more than that, but I wouldn't think you'd want to go much more. Those type of amps were really intended to be used with very stock radios with the carrier reduced a bit.
Click to expand...

You see - this is my very concern.
I'm new to working on radio equipment and I thought that this Cobra 148 might be too 'hot' for the input of this amp. I set up a Cobra 29 LTD for him with a 3 watt dead key and a 10 watt swing last week as a backup radio. I will need to lower the dead key lower on the 29 and the same for the 148.

The amp is very powerful and in our South Bay Area of CA, it walks the dog! Locally, that is.
But I am trying to make his station better than it is, and I'm applying all that I am learning to make it so. As my learning continues, I am starting to make some pocket change already from a few locals working on their stuff. There is NO ONE in the Bay Area that works on radios any more - not commercially anyway.

What is the BEST way to lower the deadkey on a 148? I know how to do it for a 29; any sugesstions welcome!
Thanks!
 
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you're wasting your time. your friend has a class c pos and you're NOT working on a LINEAR amplifier. until you correct the bias and get rid of the 455 driver you might as well be beating your head against the wall. if you're seeing more than .4 - .5V of base-emitter bias on those 3749's you're screwed, you'll NEVER see the proper peak-to-carrier power levels (4:1) at the output.

"The MRF455 is the driver; so what would be the peak amount of input watts for this unit?"

60-80W out from a 455 is too much drive for 4XSRF3749's. pay attention to the power output vs. power input graphs.

http://www.firecommunications.com/trdbase/mrf455rev0.pdf
http://www.firecommunications.com/trdbase/srf3749.pdf

(see MRF454)
http://www.firecommunications.com/trdbase/mrf454rev1.pdf

by altering and expanding the peak-to-carrier levels you're simply butchering the transmitter so you can use THE WRONG CLASS OF AMPLIFIER. how stupid is that?
 
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Now you have a better idea of what I meant by "realistically" speaking . Now you just want to make that amp work the best your going to get with what you have to work with and that has already been noted. Some times the truth can feel like a slap in the face.

This is very simlar to the Texas Star 667 having a driver transistor :headbang and why I've heard it so many times that one was better off going with the 500 model of that amplifier and achiving better and cleaner numbers.

So basically because of the driver in the unit , just drop the watts down to 1 on either radio , Your Dosy is all you have to work with ? So be it . Set as close to 100% modulation on both and leave it at that. I'd go with about 12 or so watts on SSB .

The amp was not made perfect from the get go , but it will work for you all the same. Your just trying to get the best out of a not so perfect situation to begin with.
 
I expected all of that, as far as that info goes - anyway.
I just wasn't sure about the character of the amp - thanks all.
I'll have to contact the owner and tell him to bring his radios over so I can lower the dead key to 1-1 1/2 watt and check the modulation swing.
I guess a swing kit for the 148 (to make it responsive) will have to be done, as well as turning down the dead key.
It's like you said S.K, It IS what I have to work with...

Don't like my Dosy?
Aw c'mon; it sure isn't a Bird. But it is still a long way from a Radio Shack/Micronta!
 
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Me ? I have absolutely no problem with your Dosy. A lot could be said about the Bird 43P as well. I just meant , if that's all you have to work with , so be it.
 
why not just use your dosey behind the 600 and set the radio to make the amp deadkey 80ish and swing 320ish ?
 
No SK, I was speaking to BootyMon. Sorry; I should have specified who I was addressing.
BootyMon:
Like FreeCell pointed out; the MRF455 would need to be changed out to a MRF454 to be able to get the 'swing' and 'linearity' of the 4:1 dead Key/swing watts. I've got both radios (Cobra 29 LTD & 148 GTL) re-set at 1 1/2 watt dead key and swinging to 10-11 watts.

Deadkey with the Palomar is now 165 watts, and swings to 325 on the low side. Not bad, sounds pretty impressive! Actually - it might not be the 'best amp' in the world or optimally set up, but the owner sounds better than he did yesterday.
SO, thanks to all - for all of the input on this thread...
 
i never mentioned your dosey . i run an astatic my self , same quality and accuracy level . neither is a bird but either is good enough for my purposes .
just wanted to clarify . is all good and im glad yall are happy with the amp .
 
Just got one of these...blown finals!

Hey folks, new member, nice to be here. I have enjoyed talking with many of you fine folks from up here in western Canada over the years.

I have replaced finals a few times...all with success. The 4 SRF4739's in one of these same old Palomar 600's i have recently had dumped on me are toast, so out they come. The only finals I seem to be able to get are mrf454's. About 5 watts lower a piece. Will the unit get much drop in performance? Any hints, and tips, and guidance in replacing these pills would be greatly appreciated as I try to replace the magic blue smoke into this old girl! I put this post here, as it might be of use for this particular unit in regards to drive/output/repair.
 
srf3749 is popular with the palomar and boomer amps they use them in small linears also 250bommer uses the same pill try to use something that is comp if you change it may take a dump fast
 
I know this is an older post, but has anyone tested one of these old boomer 600's on ssb, I can pic one up but don't know if its worth it
 
Boomer amplifiers are one slight step above junk for the most part. They are class C with auto SSB delay. The only way I would pick one up is if it was clean, functioned 100%, and was priced right.
 

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