Hi
Do you have any amps you would recommend for this project?
Carl
N8CDW
----- Original Message -----
From: Will Matney <craxd@engineer.com>
Date: Friday, July 22, 2005 9:27 am
Subject: Re: [Amps] Mobile amps
> Dan,
>
> Yes, they are really the same wide-banded amps that have been
> around for years and the same as in the Motorola app notes. Most
> use the 2SC2879 transistors. The only thing is for them to be
> linear, and clean, they have to be converted to class AB1 or AB,
> an output filter should be used, and a bandswitching network added
> to the input to level the SWR across the bandspread. Generally
> these are made by the one doing the conversion as there's too many
> differences in amps to make a one-size-fits-all type of circuit.
> They generally make them using switchable pi net circuts switched
> in with relays from a rotary switch on the front of the amp. Henry
> did this on their mobile amps and is the upper board over the main
> one. These 11 meter amps dont have this. What I'm making is a good
> RF keyer, and the bias circuit to set the transistors to class AB,
> or AB1. The keying circuit they've been using on a bunch of
> different models just tie the parts together in mid air, and look
> like a rats ne
> st. Terrible construction, but the rest of the amp is usable.
> Another thing that will have to be used is an attenuated input as
> 5-20 watts will open up a set of 2SC2879's to their rated output.
> That is if the transceiver can't be cut back. However an
> attenuator is easy to build. You can buy these amps second hand
> off eBay for a good bit less than new. I may even build some new
> ones but that's a good bit in the future. For homebrewers, I can
> get the cabinets, and heatsink along with other parts they may
> need. There is also pre-punched PC boards but not etched. The
> punched holes are for the transistors. These holes can be made
> though by drilling the board first, and then cleaning up the rest
> using a spiral bit in a mini-router, or a Dremel tool with a
> router base added. The best drill to use is one of those cone
> bits. The way they've been building them is by dead bug
> construction. I prefer to use an etched board myself, but do use
> surface mount with through hole components by
> bending the leads. Those amps are too hard to repair without the
> parts mounted on the top, and unsoldered from the top. Those
> traces can be routed too if you have a steady enough hand. Hope
> this helps.
>
> Best,
>
> Will
>
>
> ----- Original Message -----
> From: "Dan Sawyer" <dansawyer@earthlink.net>
> To: "Will Matney" <craxd@engineer.com>
> Subject: Re: [Amps] Mobile amps
> Date: Fri, 22 Jul 2005 06:59:46 -0700
>
> >
> > Will,
> >
> > Is it practical to adapt these to work on 80 through 10 meters?
> >
> > Thanks,
> > Dan
> >
> > Will Matney wrote:
> >
> > > All,
> > >
> > > Some have been buying those 11 meter mobile amps and
> converting
> > > them over for amateur use. The ones which use un-etched PC
> > > boards, etc. The RF keying in these are generally rats nests
> and
> > > pretty weak circuit wise. Most dont last very long and are for
> > > use only with about 5 watts max input and have no SSB
> > > capabilities. I am now offering retrofit kits for RF keying,
> and
> > > bias control. Most are made class C only and the ones with any
> > > bias are not adjustable only using a diode clamp. I can do
> these
> > > on tie strips or on small PC boards made to mount upright on
> > > edge. The tie strips take up the less room. If any are
> interested
> > > in these, give me an e-mail. I'll be glad to help in
> converting
> > > these in any way possible.
> > >
> > > Best,
> > >
> > > Will
> > >
> > > Amateur Transformer & Supply
> > >
> > >
> > >
>
>
> --
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