Mostly OT: TS-820

[Tom Skinner]

Hello group,

I'm not sure where else to ask this question. I can't seem to get anything
but an answering machine at the Kenwood Amateur Radio Tech support Center.

While waiting for a new K2, I would like to get on the air (after a
considerable absence) with an old (but very good) TS-820S. The problem is -
too much interference with the computer and TV at rated output. Since the
neighbors are pretty close, I probably would interfere there as well.  I
have done short tests at qrp levels with no interference.

However:  Is it advisable to reduce the drive to qrp levels (for longer than
short tests) without damage to the 6146 finals?

Thanks,

Tom, K0PXL

 



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[Rick Hampton-2]

Hi, Tom.

Tom Skinner wrote:

> Hello group,
>
> I'm not sure where else to ask this question. I can't seem to get anything but
> an answering machine at the Kenwood Amateur Radio Tech support Center.
>
> While waiting for a new K2, I would like to get on the air (after a
> considerable absence) with an old (but very good) TS-820S. The problem is -
> too much interference with the computer and TV at rated output. Since the
> neighbors are pretty close, I probably would interfere there as well.  I have
> done short tests at qrp levels with no interference.
>
> However:  Is it advisable to reduce the drive to qrp levels (for longer than
> short tests) without damage to the 6146 finals?
>
> Thanks,
>
> Tom, K0PXL

I'm someone else who uses an '820s (bought mine brand new in '76!), if only
occasionally now.

Yes, you can run QRP mode by simply turning down the "carrier" control knob
without any problems.  That's what I used to do before I could afford a
dedicated QRP rig.

Have fun.

73.

Rick, WD8KEL

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[Don Wilhelm-3]

Tom,

I don't know about the TS-820S, but if the finals are run in linear mode for
both CW and SSB, you can safely reduce the drive without hurting anything.
If your TS-820 has a drive control, I would think it would be safe to use it
to reduce the drive.

OTOH, (just as a cautionary note) a few manufacturers used to run the finals
in class AB for SSB, but changed the bias to class C self-bias techniques
for CW (mainly to obtain greater output power in CW - but this was usually
only true for ancient boat anchors).  Some class C stages use the drive
power itself to develop the grid bias (using rectification using the grid to
cathode junction) - these designs will have runaway plate current if the
drive is removed or substantially reduced.  If you have fixed bias on the
grids for both modes, it is very likely safe to reduce the drive level.



73,
Don W3FPR

> -----Original Message-----
>
> Hello group,
>
> I'm not sure where else to ask this question. I can't seem to get anything
> but an answering machine at the Kenwood Amateur Radio Tech support Center.
>
> While waiting for a new K2, I would like to get on the air (after a
> considerable absence) with an old (but very good) TS-820S. The
> problem is -
> too much interference with the computer and TV at rated output. Since the
> neighbors are pretty close, I probably would interfere there as well.  I
> have done short tests at qrp levels with no interference.
>
> However:  Is it advisable to reduce the drive to qrp levels (for
> longer than
> short tests) without damage to the 6146 finals?
>
> Thanks,
>
> Tom, K0PXL
>

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[Geoffrey Mackenzie-Kennedy-2]

Hello Tom,

Having spent countless hours in the company of members of the 6146 family,
from their conception, please be assured that even with zero RF signal drive
a 6146B will be undamaged provided that 1) Supply voltages are within
specified limits 2) "Real" DC bias is used for the control grid (Grid 1) 3)
Dissipation limits are not exceeded - in major part controlled by Grid 1
bias and 4) The circuit is stable and also free of parasitics. Grid 1 should
be RF loaded, as it will be in the transmitter. In other words the same
rules that apply to most tubes.

I do not know the Final's circuitry of the TS-820S, but I would guess that
it is two 6146s in parallel biased somewhere between AB1 and AB2. So the
caution about parasitics is relevant, but if that was a problem, it should
have shown up before when adjusting the output tank. I also assume that
there is a real" DC bias supply.

So have some fun! Good hunting!

73,
Geoff.
GM4ESD

----- Original Message -----
From: "Tom Skinner" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, February 26, 2005 1:53 PM
Subject: [Elecraft] Mostly OT: TS-820


> Hello group,
>
> I'm not sure where else to ask this question. I can't seem to get anything
> but an answering machine at the Kenwood Amateur Radio Tech support Center.
>
> While waiting for a new K2, I would like to get on the air (after a
> considerable absence) with an old (but very good) TS-820S. The problem
is -
> too much interference with the computer and TV at rated output. Since the
> neighbors are pretty close, I probably would interfere there as well.  I
> have done short tests at qrp levels with no interference.
>
> However:  Is it advisable to reduce the drive to qrp levels (for longer
than
> short tests) without damage to the 6146 finals?
>
> Thanks,
>
> Tom, K0PXL
>

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