Data transmission on 30 meters with PX3 problem

[Gwen Patton]

This happens very rarely for me EXCEPT for 30 meters. Then it happens so
much, it makes data modes (CW, RTTY, PSK) useless. I'm using a wired USB
keyboard connected to the PX3. If I'm on 30 meters, and I use the ATU to
match the antenna, transmitting any data mode causes extra, spurious
characters to be added onto the end of the keyboard input buffer. In some
circumstances, it starts appending additional messages stored in message
slots mapped to function keys.

Usually it's just a few characters -- a couple of numbers, a few alphas --
that get transmitted at the end of my transmission. In less frequent cases,
the transmission doesn't stop, as new characters are being shoved into the
keyboard buffer faster than they can be transmitted. Pressing backspace to
erase these characters works very seldom, though it can help, marginally.
In very rare cases, it seems scan codes for function keys are getting
shoved into the keyboard buffer, which appends those message slot contents
to the end. I usually wind up hitting ESC to stop the transmission, because
it's running wild.

RF power isn't a determinant. I can run power down to less than a watt and
it still happens. I tried wrapping a big ferrite toroid (T200-2) with the
keyboard cable just before the PX3 keyboard port, but it doesn't appear to
help.

I've searched for solutions online and in both the PX3 and KX3 manuals. The
antenna is a half-length "W3EDP Jr."  end-fed antenna with an LDG RU-4:1
unun, run from my front porch to a tree, about 15' up at the porch end, and
about 25' up at the far end.

This is the antenna I'm using:
https://thewakesileave.wordpress.com/2016/08/15/a-42-portable-multiband-hf-antenna-with-no-wire-on-the-ground-the-w3edp-jr/

Has anyone else had this problem, or can you suggest something I might set
differently in a menu option? I've gone through about everything I can
think of, including changing the position of the coax, the aforementioned
choke on the keyboard cable, et. al., but can't figure out what's causing
this. It acts like RF getting into the keyboard. I'll try a different
keyboard while I wait for any suggestions, but other than that, I'm stuck.
Being a member of 30MDG, I'd sort of like to be able to operate on 30!

73,
Gwen NG3P

--

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Jenny Everywhere's Infinite: Quark Time
http://quarktime.net
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[Gary K9GS]

Hi Gwen,
Still sounds like RF getting in somewhere.  That kind of antenna is guaranteed to bring common mode current into the shack.
If you have a dummy load I would connect it directly to the output of the radio and see if the problem still occurs.


73,
Gary K9GS
-------- Original message --------From: Gwen Patton <[hidden email]> Date: 9/1/18  10:00 PM  (GMT-06:00) To: [hidden email] Subject: [Elecraft] Data transmission on 30 meters with PX3 problem
This happens very rarely for me EXCEPT for 30 meters. Then it happens so
much, it makes data modes (CW, RTTY, PSK) useless. I'm using a wired USB
keyboard connected to the PX3. If I'm on 30 meters, and I use the ATU to
match the antenna, transmitting any data mode causes extra, spurious
characters to be added onto the end of the keyboard input buffer. In some
circumstances, it starts appending additional messages stored in message
slots mapped to function keys.

Usually it's just a few characters -- a couple of numbers, a few alphas --
that get transmitted at the end of my transmission. In less frequent cases,
the transmission doesn't stop, as new characters are being shoved into the
keyboard buffer faster than they can be transmitted. Pressing backspace to
erase these characters works very seldom, though it can help, marginally.
In very rare cases, it seems scan codes for function keys are getting
shoved into the keyboard buffer, which appends those message slot contents
to the end. I usually wind up hitting ESC to stop the transmission, because
it's running wild.

RF power isn't a determinant. I can run power down to less than a watt and
it still happens. I tried wrapping a big ferrite toroid (T200-2) with the
keyboard cable just before the PX3 keyboard port, but it doesn't appear to
help.

I've searched for solutions online and in both the PX3 and KX3 manuals. The
antenna is a half-length "W3EDP Jr."  end-fed antenna with an LDG RU-4:1
unun, run from my front porch to a tree, about 15' up at the porch end, and
about 25' up at the far end.

This is the antenna I'm using:
https://thewakesileave.wordpress.com/2016/08/15/a-42-portable-multiband-hf-antenna-with-no-wire-on-the-ground-the-w3edp-jr/

Has anyone else had this problem, or can you suggest something I might set
differently in a menu option? I've gone through about everything I can
think of, including changing the position of the coax, the aforementioned
choke on the keyboard cable, et. al., but can't figure out what's causing
this. It acts like RF getting into the keyboard. I'll try a different
keyboard while I wait for any suggestions, but other than that, I'm stuck.
Being a member of 30MDG, I'd sort of like to be able to operate on 30!

73,
Gwen NG3P

--

-+-+-+-+-
Jenny Everywhere's Infinite: Quark Time
http://quarktime.net
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[Don Wilhelm]

Gwen,

First of all, a T200-2 is an iron core toroid, not ferrite, and is not
likely to prevent much RF noise coupling.  Any ferrite core will have an
FTxxx diameter designation with two digits after the hyphen.

That W3EDP antenna is a strong suspect, as is any off-center fed antenna
or end fed antenna.  They can produce large amounts of RF in the shack.
Install a GOOD current mode choke near the antenna feedpoint.  One of
the best is a stack of 4 or 5 FT240-31 with the coax wound for 4 or 5
turns through the center.  That should be placed close to the antenna
end of the coax - exception, an end-fed antenna may need to use a part
of the coax as a counterpoise (which is why a minimum length of coax is
specified for them) - put the choke that minimum length away from the
antenna.

73,
Don W3FPR

On 9/1/2018 11:00 PM, Gwen Patton wrote:
> This happens very rarely for me EXCEPT for 30 meters. Then it happens so
> much, it makes data modes (CW, RTTY, PSK) useless. I'm using a wired USB
> keyboard connected to the PX3. If I'm on 30 meters, and I use the ATU to
> match the antenna, transmitting any data mode causes extra, spurious
> characters to be added onto the end of the keyboard input buffer. In some
> circumstances, it starts appending additional messages stored in message
> slots mapped to function keys.
>
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[John Oppenheimer]

On 09/02/2018 07:56 AM, Don Wilhelm wrote:
> That W3EDP antenna is a strong suspect, as is any off-center fed antenna
> or end fed antenna.  They can produce large amounts of RF in the shack.

Hi Gwen,

Don is correct. The W3EDP with a large choke Balun, as pictured, between
the Unun and KX3 is an OCF Doublet with a resonant frequency of 11 MHz.
It is rather difficult, if not impossible, to isolate a dipole end
impedance using a choke Balun. The KX3, being at the high impedance
point on 30 meters, will experience a rather high RF voltage.

A way to determine if the rig is part of the antenna is to use what I
call a "touch test." Observe SWR while transmitting, if touching the KX3
antenna BNC jack causes the SWR to change, then the KX3 is part of the
antenna. At the extreme, the touch results with a RF burn. I have
experience RF burn at 15 watts.

John KN5L
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[Martin]

You might want to add a common mode choke.
Look here :

http://www.dg0sa.de/balun1zu4kleinptfe.pdf

It is in german, but the pictures show how easy it is to do. First, the
choke is shown.
The second core is the 4:1 transformer which you already have.
FT 140-43 cores will do. For higher power, use FT 240-43.
Connect : TRX->choke->Transformer->antenna.


--

73, Martin

Ohne CW ist es nur CB...
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[Jim Brown-10]

On 9/2/2018 7:39 AM, Martin wrote:
> FT 140-43 cores will do. For higher power, use FT 240-43.

#43 material is only good above about 10 MHz.

73, Jim K9YC

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[Bob Nielsen-4]

Back in my early days as a ham (1950s), I inadvertently discovered that
the metal housing of a D104 microphone was very effective in performing
such a touch test.

Bob, N7XY


On 9/2/18 7:19 AM, John Oppenheimer wrote:

> On 09/02/2018 07:56 AM, Don Wilhelm wrote:
>> That W3EDP antenna is a strong suspect, as is any off-center fed antenna
>> or end fed antenna.  They can produce large amounts of RF in the shack.
> Hi Gwen,
>
> Don is correct. The W3EDP with a large choke Balun, as pictured, between
> the Unun and KX3 is an OCF Doublet with a resonant frequency of 11 MHz.
> It is rather difficult, if not impossible, to isolate a dipole end
> impedance using a choke Balun. The KX3, being at the high impedance
> point on 30 meters, will experience a rather high RF voltage.
>
> A way to determine if the rig is part of the antenna is to use what I
> call a "touch test." Observe SWR while transmitting, if touching the KX3
> antenna BNC jack causes the SWR to change, then the KX3 is part of the
> antenna. At the extreme, the touch results with a RF burn. I have
> experience RF burn at 15 watts.
>
> John KN5L
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

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