[NLRS] Killed my amp? Probably

[Barry Malowanchuk]

Better RF Parts or else you may get a Chinese copy

Barry VE4MA

----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj at netins.net>
To: nlrs at mailman.qth.net, "Badger Contesters" <badgercontesters at mailman.qth.net>
Sent: Thursday, September 3, 2015 2:00:06 PM
Subject: Re: [NLRS] Killed my amp? Probably



RF Parts probably also has the part.

For the future you need to attach a cable to the amp input with 1.25 dB 
loss so the 20 watts from the 897 is only 15 at the amp. That's just a 
few feet of RG-58. ARRL handbook chart shows 12 or 13 dB / 100 feet off 
the top of the graph though. So ten feet should be pretty close. And the 
driver probably is bad.

73, Jerry, K0CQ

On 9/3/2015 11:58 AM, David Palm wrote:
>
>
> OK, time to tell on myself.  I was checking out my gear last night.  222
> MHz ampflier is working fine and playing well with the transverter there.
> So good to go.
>
> On 432 it's a different story.  Here's what you get when you don't use
> stuff for a long time and forget when you have.  I connected the rig to the
> amplifier, an RF Concepts 4-110.  I had long forgotten that this amp can
> only take a max of 15 watts input.  My FT-897 puts out just over that.  So,
> I was keying the amp and getting about 80 watts out, which is actually
> rather low, especially with that much drive.  But then as I watched, the
> output just started dropping before my eyes, until I basically am getting
> little to no amplification at all.
>
> I presume that I burned out the driver stage.  The schematic says that this
> is an MRF646.
>
> Those of you who know about such things, does my diagnosis seem correct?
> And do you know of any better source to get an MRF646 than this guy, who
> has them for $20 apiece:
> http://www.ebay.com/itm/Motorola-MRF646-/281687443775?hash=item4195e1493f.
> Hopefully this will not be a big problem to swap out and be back in
> business.  If you've done such things before and have some good advice, I'd
> love to have it.
>
> Doh!
>
> 73,
>
> David  W9HQ
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