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converting magnum 257 to hp

romakdaddy

Member
Jul 2, 2009
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I have a blue face magnum 257 and just got a killer deal on a rfx-75 and I know the 257hp comes factory with that exact unit...my question is where are instructions to add one of these to a normal 257 radio?
 

First off I am a big Magnum fan, that said I would 90% of the time say don't waste your money and buy an external amp. Since you got the killer deal then yea, box it all up and have it done by a tech that knows what's up. It's not a DIY simple little solder this and connect that kinda mod.
 
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nothing on cb tricks or anywhere else...my next step is to take it to my radio guy but if there are instructions I can do it myself since I'm quite proficient with a soldering iron...lol the unit was only $35 shipped and brand new so I figured I couldn't pass it up.
 
$35 I don't think I'd have hesitated either. At worst you blow the crap out of it and sell it for spares and probably get your $35 back. Win win.
 
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You can normally buy them for around $39 if you're paying retail. Dealers get them for $25.

Personally, I would not pay install it installed. If you can do I yourself, and know what you're doing, then you might as well. You already spent the money. The increase in power won't be noticeable compared to the dual finals your radio currently has.

I would go with an external amp.
 
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Sorry to say I have to agree with the rest of the guys, I have owned both a 257 and a 257HP both good radios but if you get to talking a lot the RFX 75 really needs a small fan because it does get HOT. A small 100 to 150 watt amp would be a better choice to keep the heat out of the radio. Even a small RM amp would work better I think. Just my 2 cents and if you decide to do it good luck.
 
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I have one of the HP models, and only run it at about 50 watts. It does get very warm if I really ragchew. I understand you wanting to put the add on, but think you would be better off getting something like a KL-203P. Really small amp, and you'll see 100 watts easily with it on SSB. The folks at RM Italy told me it is A/B biased, too. I run one with a stock Grant XL and get nothing but great reports running it.

73,
RT307
 
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From what I have heard the rfx75 units are a lot harder to install than the larger 150 and 175 units. If you didn't buy a 257hp, I would so as others have said and either send it to a reputable tech to have it installed, or get a good amp. The 2nd choice gets my vote even though I have 3 257hp radios. I would not buy a regular 257 and do that though, run an external amp and leave the radio be, JMO. Texas star, Dave made, xforce or TNT have some decent amps, the rm Italy's are less expensive and are not built like the others I mentioned, but have heard many good things about them as long as you don't over drive them and you have a good VSWR reading. Good luck with whatever you decide.
 
well I opened the radio to have a look see since I hear the omniforce shares the same board. the whole back of the radio is one big piece of aluminum so heatsink removal is a no go...ill put it on another radio I have 2 hr2510s and a 2950 rci...they aren't pristine so I might try putting it on one of those.but theres no instructions for the 2510 so anyone got a clue if it shares a board that is covered?
 

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