[Elecraft] K3 Two amplifiers 1 key line

[Joe Subich, W4TV]

Correction ... Paul's call is WD7S (that's what I get for 
writing e-mail after 10 hours of working on manuals). 

73, 

   ... Joe, W4TV 
 

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Joe 
> Subich, W4TV
> Sent: Friday, July 04, 2008 3:26 AM
> To: w3fpr at arrl.net; 'Lee (WW2DX)'
> Cc: 'Elecraft Reflector'
> Subject: RE: [Elecraft] K3 Two amplifiers 1 key line
> 
> 
> 
> All the work has already been done by Paul, WD7D.  See "Improved 
> Amplifier Interfacing for the Yaesu Mark V FT-1000MP"  QST, 
> September 2004, page 51.  The only change necessary to Paul's 
> circuit is to add a pair of pull-up resistors ... he even has 
> (had?) circuit boards for the project.     
> 
> The circuit will switch PTT and Inhibit lines between HF and 
> six meter amplifiers based on partial decoding of the Band 
> data lines.  
> 
> Note: partial decoding will not work if you have any transverters 
> on the K3 and are using the band data outputs for switching them. 
> 
> 73, 
> 
>    ... Joe, W4TV 
>  
> 
> 
> 
> 
> > -----Original Message-----
> > From: elecraft-bounces at mailman.qth.net
> > [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don Wilhelm
> > Sent: Thursday, July 03, 2008 5:48 PM
> > To: Lee (WW2DX)
> > Cc: Elecraft Reflector
> > Subject: Re: [Elecraft] K3 Two amplifiers 1 key line
> > 
> > 
> > Lee,
> > 
> > You should be able to provide control lines for HexFETs or 
> some other
> > kind of switch with just a little bit of logic and the 
> > signals from the 
> > ACC connector.
> > 
> > Look at the Band Data outputs - the only time *both* Band3
> > and Band1 are 
> > at a high impedance state is on 6 meters.  A NAND gate (with pullup 
> > resistors on the inputs) will give you a LOW output on 6 
> > meters and HIGH 
> > on all other bands - call this 'partial band decode'.
> > Now add an inverter to the KEYOUT-LP signal (another pullup 
> > resistor is 
> > needed at its input) and feed its output to one input each 
> of 2 more 
> > NAND gates - the 'partial band decode' NAND gate output feeds the 
> > remaining input of one of these NAND gates and that one will 
> > have a low 
> > output when HF is selected *and* Keyout is active.
> > Invert the output of the 'partial band decode' and feed the 
> inverted 
> > output to the input of the other NAND gate that you connected the 
> > inverted Keyout signal to - that NAND will have a LOW output when 6 
> > meters is selected *and* keyout is active.
> > I don't know how much voltage and current your amps PTT 
> > inputs require, 
> > so I leave the final keying of the amps up to you.  A pair of 
> > the K2 Amp 
> > Keying Circuit on the Elecraft website or one of Tom 
> Hammond's K2 Amp 
> > Keying kits can be driven by the circuit I described and be 
> > used to key 
> > your amplifiers.  A 74AC00 dip and a 74AC04 will do this task 
> > with one 
> > NAND gate and 4 inverters to spare - it takes longer to describe in 
> > words than to draw it.
> > 
> > To be safe, I would not consider letting the RF path
> > determine which amp 
> > transmits - if you ever find the ANT1/ANT2 selection changed (by an 
> > inadvertent button tap), you could send RF to the wrong 
> amp.  You may 
> > not be able to simply run the KEYOUT to both amplifiers - 
> > that will only 
> > work if both amplifiers have the same voltage on their PTT IN lines 
> > (measure with your DMM with the amplifier on and nothing 
> connected to 
> > the PTT IN jack).
> > 
> > 73,
> > Don W3FPR
> > 
> > Lee (WW2DX) wrote:
> > > I have a HF amp on ANT1 and (soon to be) 6M amp on ANT2. ANT2 is 
> > > dedicated 6M antenna.
> > >
> > > Has anyone come up with a way to PTT each amp when on
> > desired band? Is
> > > it possible to just hook both AMPS to the same PTT key 
> line so both
> > > amps  Key at the same time but the RF path would then take over?
> > >
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