[Elecraft] KX3 RFI

[John Pierce via Elecraft]

I am trying to use a dynamic mic on a KX3 and have RFI on my output.  I am
using the KX3 as a driver to a KM3KM amplifier looking to get about 400 to
500 watts output.  I have a small pre-amp between the mike and the KX3.  I
have modified the pre-amp to ground the lines from and two the pre-amp at
the XLR input/outputs.  What frustrates me the most is that I do not have an
oscilloscope to diagnose the problem.  I have tried using toroid on all
lines, including power lines without any success.

 

Is it possible to accomplish what I am trying to do?

 

John, AD2F

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Re: [Elecraft] Kx3 rfi when power set to 0watt

[Peter Eijlander (PA0PJE)]

Hi Eben,

Welcome to "Radio-land"

If that is normal is not for me to decide but...

I actually measured the power level of my KX3 in CW with 0.0 watt as set 
level.


It varies from band to band. On 50 MHz I found -18 dBm and on the HF 
bands between -20 and -30 dBm.


On 14 MHz I found -23 dBm as carrier level and the noise over the range 
from 3 to 18 MHz -50 dBm, dropping rapidly to -80 dBm on 20 MHz and above.


-23 dBm = 0.005 mW or in "S-units" S9+50 dB. Enough to drive a sensitive 
receiver nuts in close proximity. A good dummmy load to terminate the 
KX3 is always a good idea when "dry-land swimming" the radio.


73,
Peter - PA0PJE


Op 2017-07-21 om 22:47 schreef Eben Bruyns:

I'm a new ham and this is my first radio...

So far I've managed to make contact on 80m but it leaves a lot to be desired.

While messing around I tuned a portable receiver to the same frequency
as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
receiver produced qrm every time I did this.

Is this normal?


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Re: [Elecraft] Kx3 rfi when power set to 0watt

[Dave Fugleberg]

Welcome to ham radio, Eben!
As others have said, it's pretty normal to hear your transmitter on a
receiver that's right next to it, even with the power turned way down.
About your difficult making contacts on 80m... Your antenna system (type of
antenna, height, feedline ), mode, and time of day are all going to have a
big influence. Can you elaborate on those?
On Fri, Jul 21, 2017 at 5:06 PM Fred Jensen  wrote:

> Welcome to the hobby Eben! To your question first: I'm not sure what you
> mean by "produced QRM," but if you mean audio feedback [various
> squeals], yes, I'd expect that a receiver close to the KX3 is going to
> hear it even with the power at zero.
>
> Regarding difficulty in making contact(s)on 80, what are you using for
> an antenna?  How are you feeding power to it?
>
> 73,
>
> Fred ("Skip") K6DGW
> Sparks NV USA
> Washoe County DM09dn
>
> On 7/21/2017 1:47 PM, Eben Bruyns wrote:
> > I'm a new ham and this is my first radio...
> >
> > So far I've managed to make contact on 80m but it leaves a lot to be
> desired.
> >
> > While messing around I tuned a portable receiver to the same frequency
> > as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
> > receiver produced qrm every time I did this.
> >
> > Is this normal?
> >
>
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>
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Re: [Elecraft] Kx3 rfi when power set to 0watt

[Fred Jensen]

Welcome to the hobby Eben! To your question first: I'm not sure what you 
mean by "produced QRM," but if you mean audio feedback [various 
squeals], yes, I'd expect that a receiver close to the KX3 is going to 
hear it even with the power at zero.


Regarding difficulty in making contact(s)on 80, what are you using for 
an antenna?  How are you feeding power to it?


73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 7/21/2017 1:47 PM, Eben Bruyns wrote:

I'm a new ham and this is my first radio...

So far I've managed to make contact on 80m but it leaves a lot to be desired.

While messing around I tuned a portable receiver to the same frequency
as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
receiver produced qrm every time I did this.

Is this normal?



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Re: [Elecraft] Kx3 rfi when power set to 0watt

[Don Wilhelm]

Eben,

I have not tried it, but I suspect that is normal with a receiver tuned 
to the same frequency and its antenna close to the KX3.
The KX3 is an SDR which means that it is using an internal oscillator 
tuned to the signal frequency.  That internal oscillator could be heard 
by a nearby receiver.


If you want to hear your own signal, work the KX3 into a dummy load at 
some medium power level and place the antenna for your monitoring 
receiver in whatever proximity to the dummy load that will give you an 
S-9 signal on that receiver - do not overdrive the receiver, or it may 
make 'funny noises'.


Keep trying to make contacts.  At this point in the sunspot cycle, 
propagation is poor on the higher frequency ham bands and 80 or 160 
meters are normally not very good for daytime contacts.  Try 40 meters 
during the day and early evening, and 80 meters after dark.


73,
Don W3FPR

On 7/21/2017 4:47 PM, Eben Bruyns wrote:

I'm a new ham and this is my first radio...

So far I've managed to make contact on 80m but it leaves a lot to be desired.

While messing around I tuned a portable receiver to the same frequency
as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
receiver produced qrm every time I did this.

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Re: [Elecraft] Kx3 rfi when power set to 0watt

[Lynn W. Taylor, WB6UUT]

I would expect 0 watts to be zero watts for all practical purposes.

I wouldn't be at all surprised to find out that 0 watts was very close 
to, but not exactly 0.


... and if your receiver is any good at all, picking up a signal that is 
for all practical purposes zero within 100 meters is kind of expected.


If you want to practice with the radio, get a 50 ohm dummy load.  Even 
that is likely to be heard on your other receiver.


73, and welcome to the hobby!

-- Lynn

On 7/21/2017 1:47 PM, Eben Bruyns wrote:

I'm a new ham and this is my first radio...

So far I've managed to make contact on 80m but it leaves a lot to be desired.

While messing around I tuned a portable receiver to the same frequency
as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
receiver produced qrm every time I did this.

Is this normal?


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[Elecraft] Kx3 rfi when power set to 0watt

[Eben Bruyns]

I'm a new ham and this is my first radio...

So far I've managed to make contact on 80m but it leaves a lot to be desired.

While messing around I tuned a portable receiver to the same frequency
as the kx3. I had the kx3 power set to 0 watts and keyed the mic. The
receiver produced qrm every time I did this.

Is this normal?

-- 
Regards,

Eben Bruyns
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