Amps
[Top] [All Lists]

Re: [Amps] Mobile amps

To: Will Matney <craxd@engineer.com>
Subject: Re: [Amps] Mobile amps
From: n8cdw@direcway.com
Date: Fri, 22 Jul 2005 12:19:31 -0500
List-post: <mailto:amps@contesting.com>
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
> > >
> > >
> > >
> 
> 
> -- 
> ___________________________________________________________
> Sign-up for Ads Free at Mail.com
> http://promo.mail.com/adsfreejump.htm
> 
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> 

_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps

<Prev in Thread] Current Thread [Next in Thread>