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KPA-500 from Orlando

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Jack Brindle

Re: KPA-500 from Orlando

Another way is to add series diodes between the driver and the
amplifier. You will want to have pullups on the amplifier side.

Accidental powering is a major, but for the most part unrecognized,
problem with low-power equipment when one is not powered. We have to
provide isolation circuits to keep power from one system from
accidentally activating another. In your case it is the XCVR power
powering the amp's MCU. Microprocessors require amazingly small
amounts of power these days, and will quite readily power themselves
through their I/O pins, although it actually may end up destroying the
processor.

In your case, since the band data is one-way, adding the isolation
diodes on the amplifier side actually provides a good solution. Use a
schottky diode,like a 1N5711 for good results. And don't forget the
pullups on the amplifier side of the diodes.

Jack Brindle, W6FB

On Feb 15, 2011, at 4:47 PM, Phil & Debbie Salas wrote:

> "Wayne, I have my THP HL-2.5kfx, is there a way to control both via
> the K3?
> I would
> like to select the device to use based on conditions without going
> through a
> lot of switching. Bill K9YEQ"
>
> Unless the design has been changed recently, either the HL1.5 or the
> HL2.5
> (or maybe both - I can't remember) load down the band data lines
> when the
> amp is turned off. If you have a stiff enough band data source
> (like a TTL
> driver), you can actually partially power-up the processor in the
> THP amp
> via the band data inputs when the amp is off. So you may have to
> switch the
> band data lines between the KPA500 and the THP amp. Or use band
> data for
> the THP amp, and the KPA500 RF sense for KPA500 band changing (the
> KPA500 RF
> sense works VERY well).
>
> Phil - AD5X
>
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Phil Salas

Re: KPA-500 from Orlando

"Another way is to add series diodes between the driver and the amplifier.
You will want to have pullups on the amplifier side.... Jack Brindle, W6FB"

This is a good solution. The HL2.5 has internal pull-up resistors so you
would just need the series diodes in the interface cable (anode towards the
HL2.5 amp). The HL2.5 uses a DB15 connector, so it would be easy to add the
diodes inside the mating connector. The HL1.5 does NOT have internal
pull-up resistors. So if this idea is used with the HL1.5, pull-up
resistors must be added inside the amp or in the interface cable with a
means of connecting to a pull-up voltage source. The HL1.5 uses a
240-degree 5-pin DIN, so there is not much room inside that connector.

Phil - AD5X

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Dave Perry N4QS

Re: KPA-500 from Orlando

In reply to this post by Bill K9YEQ

I have been thinking about a similar scenario in switching between two amps
when the new KPA500 comes available. In my case I would like to use the
KPA500 most of the time and only revert to my vintage Drake L7 amp in the
rare instances when I really need 1.3 KW. I am wondering if I can run the
KPA500 at 500 W through the bypass circuit of the L7 if the L7 is off or in
standby status. The L7 manual doesn't mention any power limitations for the
bypass circuit. It certainly handles 100 W with no problem. Does anyone
have any thoughts on this? Otherwise, I guess I will have to come up with
some type of a DTDP switching scheme to switch the K3 and antennas between
the two amps. Another option would be to buy another K3 and go SO2R.

Dave, N4QS

----- Original Message -----
From: "Bill K9YEQ" <[hidden email]>
To: <[hidden email]>
Cc: "'Elecraft'" <[hidden email]>
Sent: Tuesday, February 15, 2011 5:37 PM
Subject: Re: [Elecraft] KPA-500 from Orlando

> Don,
>
> Thank you for your input. I would also want band switching to work with
> both. I know if I shut off the 2.5KFX it is bypassed. The issue is to
> control both, with one or the other shut off. I operate lots with the 2.5
> shut off. I also have the P3, which shouldn't be an issue, I would think.
> I need to get the KPA-500 soon so the other half doesn't notice too much
> change and before she retires. Have been loading up the shack if you
> know
> what I mean. :-)
>
> Also, I have not resolved the KX-1 question yet, so when I get time will
> try one more time and if not successful will send to you. I am not about
> to
> retire, so am so busy I have trouble keeping up with all the great
> Elecraft
> stuff that I keep adding just so I have it. I even miss updates unless I
> am
> a beta tester. If I get the beta it avoid so much of the watching the
> list.
> Most beta's are perfect.
>
> Bill
> K9YEQ
>
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Tuesday, February 15, 2011 5:26 PM
> To: Bill K9YEQ
> Cc: Elecraft
> Subject: Re: [Elecraft] KPA-500 from Orlando
>
> Bill,
>
> I don't know how many lines you have connected between the THP and the K3,
> but the simplistic view would be to use a relay to switch the RF input
> between the two amplifiers and also place the non-selected one in Standby.
> Of course that simplistic solution would require that both amplifiers have
> an input signal line to place the amp into standby remotely - many do not,
> but modern amplifiers should IMHO. Older amplifiers typically have only a
> front panel switch.
>
> 73,
> Don W3FPR
>
> On 2/15/2011 6:15 PM, Bill K9YEQ wrote:
>> Wayne,
>>
>> I have my THP HL-2.5kfx, is there a way to control both via the K3? I
>> would like to select the device to use based on conditions without
>> going through a lot of switching.
>>
>> Bill
>> K9YEQ
>>
>
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