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KX1 lower power only on 40?

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zan0416

KX1 lower power only on 40?

Finished a brand new KX1 this afternoon, with ATU and 3080 module.

Power output with 13VDC for all bands is as follows:

80 6.3 watts
40 1.7
30 4.0
20 3.0

Clearly something is amiss with 40 meters. I read somewhere to mess with the green windings of L2 on the 3080 module, but that didn't seem to do much other than make it worse. The number of windings on all the toroids have been double-checked as correct.

Anyone have any ideas where to go from here? I don't have any test equipment except for a DMM.

Thanks for any suggests you may have.

Dan, n0da

Rick Dwight

Re: KX1 lower power only on 40?

Dan,
If you tested your KX1 into a good 50 ohm dummy load, the indicated power should have been within 10 or 20% of the correct power either with the KX1 in Cal, or in Tune if you do an ATU tune.
If you tested it into a resonant 50 ohm antenna, then the reading should also be correct on that band.
If you test it into a random wire and counterpoise, then the power reading will only be approximately correct if the ATU can tune it to something like < 1.5:1 on bands you measure. If the ATU can only tune it to say an SWR of 2:1 or 3:1 or higher, then the power reading may be way off....possibly by more than 50 %.
The ATU has a very limited tuning range on 80 meters, so a resonant antenna or only very specific lengths of wire and counterpoises can be tuned. However certain lengths of wires can usually be tuned on 40, 30, and 20 meters. For example a 26 ft wire antenna with a 17 ft counterpoise laying on the ground will usually tune to well below 2:1 (typically < 1.5:1) on 40, 30, and 20 meters.
I always try and only use antennas which the ATU can tune to < 2:1 SWR, although at times I have pushed this to 3:1 without problems after about 10 years and thousands of QSO's.
My suggestion is to buy or build a 50 ohm dummy load as your first piece of test equipment.
Good Luck Rick KL7CW

Don Wilhelm-4

Re: KX1 lower power only on 40?

In reply to this post by zan0416

Dan,

With a 13.8 volt power supply and working into a good 50 ohm dummy load
(without the KXAT1 installed) you should have at least 3.0 watts on all
bands (I normally expect 3.5 watts or more). Measure with an external
wattmeter that is has known accuracy at low power - many wattmeters with
a 20/200/2000 watt range switch are inaccurate at low powers and will
typically read lower than the actual power. That is typical of analog
meters, many with digital readouts are not as bad in this respect.

While 40 and 20 meters usually have lower power output than 80 or 30
meters, yours is extremely low.
You *will* find the problem is on the Low Pass Filter board.
Check it very carefully for toroid leads that are not well tinned and
soldered. If you see any evidence of wire enamel on the solder side of
the board, that lead was not well tinned before installation and must be
re-done.
Also make certain that the green lead on L2 that routes around to the
back of the board is not contacting the red lead #4 - check both the
front and back of the board.

You may have to remove the LPF board and re-wind the toroids.

73,
Don W3FPR

On 9/23/2013 12:24 AM, zan0416 wrote:

> Finished a brand new KX1 this afternoon, with ATU and 3080 module.
>
> Power output with 13VDC for all bands is as follows:
>
> 80 6.3 watts
> 40 1.7
> 30 4.0
> 20 3.0
>
> Clearly something is amiss with 40 meters. I read somewhere to mess with
> the green windings of L2 on the 3080 module, but that didn't seem to do much
> other than make it worse. The number of windings on all the toroids have
> been double-checked as correct.
>
> Anyone have any ideas where to go from here? I don't have any test
> equipment except for a DMM.
>
> Thanks for any suggests you may have.
>
> Dan, n0da
>

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zan0416

Re: KX1 lower power only on 40?

What a wonderful source of help this group is!

Turns out the problem wasn't really a problem at all. I was loading a
long-wire antenna when doing the measurements and relying on the watt meter
provided by the KX1. As Don and Rick suggested, when I connect a 50 ohm
DL1 dummy load and use a DMM to measure the voltage across the test points
of the DL1, I see a very nice 3-4 watts on all bands (translating the
voltage on the DMM to watts using the graph provided on the DL1 manual).

Phew! I'm set to go. Thank you!

Dan, n0da

On Mon, Sep 23, 2013 at 5:09 AM, Don Wilhelm <[hidden email]> wrote:

> Dan,
>
> With a 13.8 volt power supply and working into a good 50 ohm dummy load
> (without the KXAT1 installed) you should have at least 3.0 watts on all
> bands (I normally expect 3.5 watts or more). Measure with an external
> wattmeter that is has known accuracy at low power - many wattmeters with a
> 20/200/2000 watt range switch are inaccurate at low powers and will
> typically read lower than the actual power. That is typical of analog
> meters, many with digital readouts are not as bad in this respect.
>
> While 40 and 20 meters usually have lower power output than 80 or 30
> meters, yours is extremely low.
> You *will* find the problem is on the Low Pass Filter board.
> Check it very carefully for toroid leads that are not well tinned and
> soldered. If you see any evidence of wire enamel on the solder side of the
> board, that lead was not well tinned before installation and must be
> re-done.
> Also make certain that the green lead on L2 that routes around to the back
> of the board is not contacting the red lead #4 - check both the front and
> back of the board.
>
> You may have to remove the LPF board and re-wind the toroids.
>
> 73,
> Don W3FPR
>
>
> On 9/23/2013 12:24 AM, zan0416 wrote:
>
>> Finished a brand new KX1 this afternoon, with ATU and 3080 module.
>>
>> Power output with 13VDC for all bands is as follows:
>>
>> 80 6.3 watts
>> 40 1.7
>> 30 4.0
>> 20 3.0
>>
>> Clearly something is amiss with 40 meters. I read somewhere to mess with
>> the green windings of L2 on the 3080 module, but that didn't seem to do
>> much
>> other than make it worse. The number of windings on all the toroids have
>> been double-checked as correct.
>>
>> Anyone have any ideas where to go from here? I don't have any test
>> equipment except for a DMM.
>>
>> Thanks for any suggests you may have.
>>
>> Dan, n0da
>>
>>
>