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Power Control

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Mike K4PI

Power Control

Just finished installing the DSP board after the return from Aptos and then
loading the latest program updates. I know when turning the power control
there is a known dead spot between 8 and 13 watts which I hope them can
correct soon, but I noticed that there is an increase in the receive gain at
this point. When I turn the Power knob from 8 to 13 in receive mode the
receive gain jumps up 1 S unit almost like the preamp was turned on. I
tried different setting of the preamp and the ATT but the gain wll always
increase 1 S unit over whatever the S meter is reading when the power level
indication moves from 8 to 13 watts.. I am looking at it on 6 M and have
not tried it on other bands but wondered if anyone else notices this?
Nothing I can't live with..

Regarding the dead spot 8-13 watts, I use a solid state amp and I can run
either down around 400 watts or I can run up near 1 Kw but not in between
due to the dead spot.

73 Mike K4PI

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Joe Subich, W4TV-4

Re: Power Control

> I know when turning the power control there is a known dead spot
> between 8 and 13 watts

That only happens on Six Meters and is documented in the manual.

> When I turn the Power knob from 8 to 13 in receive mode the
> receive gain jumps up 1 S unit almost like the preamp was turned on.
> I tried different setting of the preamp and the ATT but the gain wll
> always increase 1 S unit over whatever the S meter is reading when
> the power level indication moves from 8 to 13 watts..

I do not see that here. It sounds like you may have some issue in
the KPA3 bypass switching (bad bypass contacts in K1 on the KPA3IO
board?). Were you changing power across the "dead spot" in transmit?

> Regarding the dead spot 8-13 watts, I use a solid state amp and I
> can run either down around 400 watts or I can run up near 1 Kw but
> not in between due to the dead spot.

If 13 watts drive gives you 1 KW output, why not install a 6 dB
attenuator on the input (between the TR relay and the amplifier)
of the amplifier? That would allow you run between 250 and 1000 W
as the drive was varied from 13 to 53 watts. Even better, a 9 dB
attenuator would give you a range of 120 to 1000 W.

73,

... Joe, W4TV

On 8/14/2010 11:05 AM, k4pi wrote:

> Just finished installing the DSP board after the return from Aptos and then
> loading the latest program updates. I know when turning the power control
> there is a known dead spot between 8 and 13 watts which I hope them can
> correct soon, but I noticed that there is an increase in the receive gain at
> this point. When I turn the Power knob from 8 to 13 in receive mode the
> receive gain jumps up 1 S unit almost like the preamp was turned on. I
> tried different setting of the preamp and the ATT but the gain wll always
> increase 1 S unit over whatever the S meter is reading when the power level
> indication moves from 8 to 13 watts.. I am looking at it on 6 M and have
> not tried it on other bands but wondered if anyone else notices this?
> Nothing I can't live with..
>
> Regarding the dead spot 8-13 watts, I use a solid state amp and I can run
> either down around 400 watts or I can run up near 1 Kw but not in between
> due to the dead spot.
>
> 73 Mike K4PI
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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DAVID M. Elliott

Re: Power Control

In reply to this post by Mike K4PI

For what it is worth, mine (1740) does the same thing on 6 meters. For example, I can't set the power to 10 watts on 6. The same does not happen on 80 meters.
I also notice that the receive gain is lower in the dead band between 8 and 13 watts.

73 de W6BK

On Aug 14, 2010, at 8:05 AM, k4pi wrote: