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KX3 - UHF emissions

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g0hww

KX3 - UHF emissions

Hi,

I've noticed that my pair of scanners often receive strong spurii from my KX3's
receiver, in the UHF mil air band. Whilst the spurii can be detected faintly
with no cables attached to the KX3, when I attach certain cables, the strength
of the spurii increase, most notably the I/Q cable, which causes (what passes
for) the S-meter on the scanner to fully deflect. Connecting an antenna to the
KX3 doesn't seem to have any effect.

The other day I noticed that my scanner had stopped on a locally used UHF
channel that was exactly 100 times the frequency in the 80m band that I was
listening to. Today I have noticed that listening on 7.08Mhz SSB, my scanners
stop on 389.4Mhz, which seems to be the 55th harmonic of the KX3's dial frequency.

This is affecting my AOR-8600mk2 and IC-R20. Unfortunately, I've also been
developing a hybrid spectrum sensing scanner (called Onsense), that uses a
HackRF to sample the mil air band and tune in my AOR-8600mk2 to the strongest
signal detected. I find that I am constantly having to add frequencies to
Onsense's blacklist as I tune my KX3. This isn't a good situation to be in.

I already have a ferrite on the I/Q cable, but that doesn't help. When I enable
the 8kHz shift on the KX3, the previously detected spurii goes away. Whether it
goes entirely or not, I don't know, it may just shift to another frequency that
isn't being scanned. The RX Isolation filter is enabled.

Is anyone else having similar problems? Is this normal for a KX3? Is there
anything I might try to mitigate this?

Cheers,

Darren, G0HWW

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Phil Genera

Re: KX3 - UHF emissions

If you have an early KX3, you probably need KX3BNCMDKT, a new BNC connector
assembly with some inline filtering.

See: http://www.elecraft.com/order_form_parts.htm

--
Phil

On Tue, Jun 24, 2014 at 3:00 PM, Darren Long <[hidden email]> wrote:

> Hi,
>
> I've noticed that my pair of scanners often receive strong spurii from my
> KX3's
> receiver, in the UHF mil air band. Whilst the spurii can be detected
> faintly
> with no cables attached to the KX3, when I attach certain cables, the
> strength
> of the spurii increase, most notably the I/Q cable, which causes (what
> passes
> for) the S-meter on the scanner to fully deflect. Connecting an antenna to
> the
> KX3 doesn't seem to have any effect.
>
> The other day I noticed that my scanner had stopped on a locally used UHF
> channel that was exactly 100 times the frequency in the 80m band that I was
> listening to. Today I have noticed that listening on 7.08Mhz SSB, my
> scanners
> stop on 389.4Mhz, which seems to be the 55th harmonic of the KX3's dial
> frequency.
>
> This is affecting my AOR-8600mk2 and IC-R20. Unfortunately, I've also been
> developing a hybrid spectrum sensing scanner (called Onsense), that uses a
> HackRF to sample the mil air band and tune in my AOR-8600mk2 to the
> strongest
> signal detected. I find that I am constantly having to add frequencies to
> Onsense's blacklist as I tune my KX3. This isn't a good situation to be
> in.
>
> I already have a ferrite on the I/Q cable, but that doesn't help. When I
> enable
> the 8kHz shift on the KX3, the previously detected spurii goes away.
> Whether it
> goes entirely or not, I don't know, it may just shift to another frequency
> that
> isn't being scanned. The RX Isolation filter is enabled.
>
> Is anyone else having similar problems? Is this normal for a KX3? Is there
> anything I might try to mitigate this?
>
> Cheers,
>
> Darren, G0HWW
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>

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Matt Zilmer-3

Re: KX3 - UHF emissions

In reply to this post by g0hww

You might want to enable the isolation amp in the KX3's RX. That
setting can be accessed in the MENU as RX ISO. Not sure this will
solve your problem, but it might make it a bit better. If the spurs
were radiating through the antenna, it definitely would help.

73,
matt W6NIA

On Tue, 24 Jun 2014 20:00:52 +0100, you wrote:

>Hi,
>
>I've noticed that my pair of scanners often receive strong spurii from my KX3's
>receiver, in the UHF mil air band. Whilst the spurii can be detected faintly
>with no cables attached to the KX3, when I attach certain cables, the strength
>of the spurii increase, most notably the I/Q cable, which causes (what passes
>for) the S-meter on the scanner to fully deflect. Connecting an antenna to the
>KX3 doesn't seem to have any effect.
>
>The other day I noticed that my scanner had stopped on a locally used UHF
>channel that was exactly 100 times the frequency in the 80m band that I was
>listening to. Today I have noticed that listening on 7.08Mhz SSB, my scanners
>stop on 389.4Mhz, which seems to be the 55th harmonic of the KX3's dial frequency.
>
>This is affecting my AOR-8600mk2 and IC-R20. Unfortunately, I've also been
>developing a hybrid spectrum sensing scanner (called Onsense), that uses a
>HackRF to sample the mil air band and tune in my AOR-8600mk2 to the strongest
>signal detected. I find that I am constantly having to add frequencies to
>Onsense's blacklist as I tune my KX3. This isn't a good situation to be in.
>
>I already have a ferrite on the I/Q cable, but that doesn't help. When I enable
>the 8kHz shift on the KX3, the previously detected spurii goes away. Whether it
>goes entirely or not, I don't know, it may just shift to another frequency that
>isn't being scanned. The RX Isolation filter is enabled.
>
>Is anyone else having similar problems? Is this normal for a KX3? Is there
>anything I might try to mitigate this?
>
>Cheers,
>
>Darren, G0HWW
>
>
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
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Matt Zilmer, W6NIA
--
"Give me six hours to chop down a tree and I will
spend the first four sharpening the axe." -A. Lincoln
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Matt Zilmer-3

Re: KX3 - UHF emissions

In reply to this post by g0hww

N/m. Just saw that you've tried the RX ISO.

matt

On Tue, 24 Jun 2014 20:00:52 +0100, you wrote:

Jim Brown-10

Re: KX3 - UHF emissions

In reply to this post by g0hww

On 6/24/2014 12:00 PM, Darren Long wrote:
> I already have a ferrite on the I/Q cable, but that doesn't help.

The root cause of what you are experiencing is a "Pin One Problem" at
those connectors. They SHOULD be screwed down to the shielding
enclosure, but they are not. That's the definition of a Pin One Problem,
and it provides a path in and out of equipment for RFI, hum, and buzz.
And I've been banging on Wayne for nearly ten years about it.

> Is there anything I might try to mitigate this?

Ferrite cores can help, but all ferrite cores are not created equal.
Most widely used ferrites used for suppression, like Fair-Rite #31 and
#43, peak around 150 MHz, and are losing their effectiveness at 300 MHz.
We can move the resonance down by winding turns, but we can't move it
up. For that we need a different ferrite material.

For low UHF, Fair-Rite mix #61 is probably the best bet. Given the
strength of these spurs, you will likely need several on each cable. A
single turn through a typical #61 core resonates around 600 MHz. Two
turns would move the resonance down a bit, to perhaps 400 MHz, and would
double the choking impedance. Buy the longest cores you can find. See
the Fair-Rite catalog, which is online. 0461164281 is 0.25-in id., and
should hold at least two turns if the cable is fairly small.

And don't overlook the obvious -- can you move the scanner antenna
farther away from you shack?

73, Jim K9YC
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g0hww

Re: KX3 - UHF emissions

In reply to this post by g0hww

Hi Wayne and others,

Thanks for the response.

Yes, I've tried the KX3 on internal power, with no cables, of any kind,
connected, and the sproggy can be faintly heard on my AOR Rx in SSB mode just
above the noise but too weak to open the squelch on AM when not wide open.

The KX3 is in the living room on the ground floor, and the scanners are using a
discone that's about 30ft away in the loft, which is where the sproggy is
getting in.

At this signal level, I don't think there I would have any problems. However if
I connect the RS-232/USB cable to the KX3, the sproggy goes up to around S2. If
I instead connect the I/Q cable, it goes up to about S9. Connecting an external
key lifts the sproggy a little above the noise, but only by less than an
S-point. No other cables seem to have much influence, but I've not tried
anything in the Acc2 port. The I/Q output seems to be the biggest culprit by far.

The sproggy is very strong in the near field (same scanner on batteries with
whip) of the KX3, but much less so via the discone, until the I/Q cable is
connected. I'm almost always using the I/Q output from my KX3, so leaving this
disconnected isn't really an option for me. My I/Q cable has an isolation
transformer about a foot away from the KX3 as the electrons fly and a ferrite
clamped to it already.

I took one of the scanners out to my HF antenna (after reconnecting it to the
KX3), and there was no sign of the sproggy coming out that way.

It's a hellish RF environment here, it seems. The whole house is effectively a
distributed shack. The scanners cause noise in each other too, or in SDR's that
steal their antenna feeds. I am trying to minimise the 'friendly fire', as
there's not much I can do about the 'incoming' :P

Cheers,

Darren, G0HWW

On 24/06/14 21:09, Wayne Burdick wrote:

> Darren,
>
> Have you tried running the radio from its internal battery pack, with the external supply disconnected? If that were to cut the emissions, you might consider ferrite cores on the power-supply leads (or other cables).
>
> UHF/microwave emissions are a common side-effect of using really high-frequency digital MCUs, DSPs, and the like, which is becoming the norm. We use state-of-the-art multilayer PC boards, and passed all required tests. But to completely eliminate emissions of the type that can activate a sensitive receiver would require a extra pound of sheet metal (shielding), bonding wires, clips, etc. That seemed out of the scope of the product, which is suppose to be small and lightweight. Mainstream desktop radios can afford fully bonded packaging, so they have fewer emissions.
>
> Fortunately we've had very few complaints about KX3 emissions, but clearly your shack is an exception.
>
> Let me know if the power-supply leads are responsible for some of what you're observing.
>
> 73,
> Wayne
> N6KR
>
>
>
>
> On Jun 24, 2014, at 12:00 PM, Darren Long <[hidden email]> wrote:
>
>> Hi,
>>
>> I've noticed that my pair of scanners often receive strong spurii from my KX3's
>> receiver, in the UHF mil air band. Whilst the spurii can be detected faintly
>> with no cables attached to the KX3, when I attach certain cables, the strength
>> of the spurii increase, most notably the I/Q cable, which causes (what passes
>> for) the S-meter on the scanner to fully deflect. Connecting an antenna to the
>> KX3 doesn't seem to have any effect.
>>
>> The other day I noticed that my scanner had stopped on a locally used UHF
>> channel that was exactly 100 times the frequency in the 80m band that I was
>> listening to. Today I have noticed that listening on 7.08Mhz SSB, my scanners
>> stop on 389.4Mhz, which seems to be the 55th harmonic of the KX3's dial frequency.
>>
>> This is affecting my AOR-8600mk2 and IC-R20. Unfortunately, I've also been
>> developing a hybrid spectrum sensing scanner (called Onsense), that uses a
>> HackRF to sample the mil air band and tune in my AOR-8600mk2 to the strongest
>> signal detected. I find that I am constantly having to add frequencies to
>> Onsense's blacklist as I tune my KX3. This isn't a good situation to be in.
>>
>> I already have a ferrite on the I/Q cable, but that doesn't help. When I enable
>> the 8kHz shift on the KX3, the previously detected spurii goes away. Whether it
>> goes entirely or not, I don't know, it may just shift to another frequency that
>> isn't being scanned. The RX Isolation filter is enabled.
>>
>> Is anyone else having similar problems? Is this normal for a KX3? Is there
>> anything I might try to mitigate this?
>>
>> Cheers,
>>
>> Darren, G0HWW
>>
>>
>>
>> ______________________________________________________________
>> 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]
>

k6dgw

Re: KX3 - UHF emissions

I need to add to my UK <--> US dictionary:

UK=Sproggy US=Spurious emission??

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 6/24/2014 3:57 PM, Darren Long wrote:

> Yes, I've tried the KX3 on internal power, with no cables, of any kind,
> connected, and the sproggy can be faintly heard on my AOR Rx in SSB mode just
> above the noise but too weak to open the squelch on AM when not wide open.

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g0hww

Re: KX3 - UHF emissions

In reply to this post by Jim Brown-10

Hi Jim,

Thanks for the informative response. I dug up a fairly hefty blue torroid that
a colleague gave me some time ago when I was lamenting about a different RFI
problem and managed to get about 8 turns on it. That has made quite an
improvement, 2 or 3 s-points at least. I also discovered that if I grasp the
left side end-plate handle (I have SideKX end-plates fitted now, but the problem
predates their installation) the spurii drops down to a mere S1. I'm not sure
what this means yet, though.

I'll investigate the ferrite appraoch further.

Cheers,

Darren

On 24/06/14 22:14, Jim Brown wrote:

> On 6/24/2014 12:00 PM, Darren Long wrote:
>> I already have a ferrite on the I/Q cable, but that doesn't help.
>
> The root cause of what you are experiencing is a "Pin One Problem" at those
> connectors. They SHOULD be screwed down to the shielding enclosure, but they are
> not. That's the definition of a Pin One Problem, and it provides a path in and
> out of equipment for RFI, hum, and buzz. And I've been banging on Wayne for
> nearly ten years about it.
>
>> Is there anything I might try to mitigate this?
>
> Ferrite cores can help, but all ferrite cores are not created equal. Most
> widely used ferrites used for suppression, like Fair-Rite #31 and #43, peak
> around 150 MHz, and are losing their effectiveness at 300 MHz. We can move the
> resonance down by winding turns, but we can't move it up. For that we need a
> different ferrite material.
>
> For low UHF, Fair-Rite mix #61 is probably the best bet. Given the strength of
> these spurs, you will likely need several on each cable. A single turn through a
> typical #61 core resonates around 600 MHz. Two turns would move the resonance
> down a bit, to perhaps 400 MHz, and would double the choking impedance. Buy the
> longest cores you can find. See the Fair-Rite catalog, which is online.
> 0461164281 is 0.25-in id., and should hold at least two turns if the cable is
> fairly small.
>
> And don't overlook the obvious -- can you move the scanner antenna farther away
> from you shack?
>
> 73, Jim K9YC
> ______________________________________________________________
> 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]

JHRichards

Re: KX3 - UHF emissions

In reply to this post by k6dgw

On 6/24/2014 7:48 PM, Fred Jensen wrote:
> I need to add to my UK <--> US dictionary:
>
> UK=Sproggy US=Spurious emission??

________________________________________________
spoggy

Sparrow (bird): Spoggies are the most common birds in the
residential areas of Broken Hill. Compare spagger, sprag, sproggy.

I suspect he means "birdie" ... i.e., as you guess.

More probably from "Down Under" ... more than the UK...

==================== K8JHR =====================

;;\
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g0hww

Re: KX3 - UHF emissions

Well, I've always thought of sproggies as spurious emissions, i.e. external to
the source, whereas I've thought of birdies as internal interference, perhaps
like tinitus.

Googling finds the following (typed up, not copied, as the source is a scan)
from "A Dictionary of Slang and Unconventional English", by Eric Partridge:

sprog,n .... <other unrelated defs> ... 'According to the Home Office, a graver
problem than politcal flak are the "spurious emissions" (known in the trade as
"sprogs"), which interfere with emergency services' (New Society article on
pirate radio stations, 19 May 1983, p. 252).

Perhaps sprogii is the appropriate plural :)

Cheers,

Darren, G0HWW

On 25/06/14 01:27, K8JHR wrote:

>
>
> On 6/24/2014 7:48 PM, Fred Jensen wrote:
>> I need to add to my UK <--> US dictionary:
>>
>> UK=Sproggy US=Spurious emission??
>
>
>
> ________________________________________________
> spoggy
>
> Sparrow (bird): Spoggies are the most common birds in the residential areas
> of Broken Hill. Compare spagger, sprag, sproggy.
>
> I suspect he means "birdie" ... i.e., as you guess.
>
>
> More probably from "Down Under" ... more than the UK...
>
> ==================== K8JHR =====================
>
>
>
>
>
> ;;\
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> 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]

Jim Brown-10

Re: KX3 - UHF emissions

On 6/24/2014 5:44 PM, Darren Long wrote:
> According to the Home Office, a graver
> problem than politcal flak are the "spurious emissions" (known in the trade as
> "sprogs"), which interfere with emergency services' (New Society article on
> pirate radio stations, 19 May 1983, p. 252).

You guys across the pond sure do talk funny sometimes. :)

73, Jim K9YC
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k6dgw

Re: KX3 - UHF emissions

In reply to this post by k6dgw

OK Darren, I just try to keep up with all my comrades, separated as we
are by a common language. Thanks

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 6/24/2014 4:58 PM, Darren Long wrote:
> Indeed. Some people over here call their kids "sprogs" too. I'm not sure if
> that relates to the spurious emissions as well, though.
>
> Darren, G0HWW

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Fred Townsend-2

Re: KX3 - UHF emissions

In reply to this post by g0hww

Yes, they should learn to speak English. :)
73
Fred, AE6QL

-----Original Message-----

>From: Jim Brown <[hidden email]>
>Sent: Jun 24, 2014 6:39 PM
>To: [hidden email]
>Subject: Re: [Elecraft] KX3 - UHF emissions
>
>On 6/24/2014 5:44 PM, Darren Long wrote:
>> According to the Home Office, a graver
>> problem than politcal flak are the "spurious emissions" (known in the trade as
>> "sprogs"), which interfere with emergency services' (New Society article on
>> pirate radio stations, 19 May 1983, p. 252).
>
>You guys across the pond sure do talk funny sometimes. :)
>
>73, Jim K9YC
>______________________________________________________________
>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
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>Message delivered to [hidden email]

Stewart@twinwood

Re: KX3 - UHF emissions

In reply to this post by g0hww

In the UK the term "Sprogs" has been applied to offspring.

Possibly, because some of the electronic definitions apply...

:-)

73
Stewart G3RXQ

On Wed, 25 Jun 2014 01:44:28 +0100, Darren Long wrote:
On Wed, 25 Jun 2014 01:44:28 +0100, Darren Long wrote:
> Well, I've always thought of sproggies as spurious emissions, i.e. external to
> the source, whereas I've thought of birdies as internal interference, perhaps
> like tinitus.
>
> Googling finds the following (typed up, not copied, as the source is a scan)
> from "A Dictionary of Slang and Unconventional English", by Eric Partridge:
>
> sprog,n .... <other unrelated defs> ... 'According to the Home Office, a
graver

> problem than politcal flak are the "spurious emissions" (known in the trade as
> "sprogs"), which interfere with emergency services' (New Society article on
> pirate radio stations, 19 May 1983, p. 252).
>
> Perhaps sprogii is the appropriate plural :)
>
> Cheers,
>
> Darren, G0HWW
>
>
> On 25/06/14 01:27, K8JHR wrote:
>>
>>
>> On 6/24/2014 7:48 PM, Fred Jensen wrote:
>>> I need to add to my UK <--> US dictionary:
>>>
>>> UK=Sproggy US=Spurious emission??
>>
>>
>> ________________________________________________
>> spoggy
>>
>> Sparrow (bird): Spoggies are the most common birds in the residential

areas

>> of Broken Hill. Compare spagger, sprag, sproggy.
>>
>> I suspect he means "birdie" ... i.e., as you guess.
>>
>>
>> More probably from "Down Under" ... more than the UK...
>>
>> ==================== K8JHR =====================
>>
>>
>> ;;\
>> ______________________________________________________________
>> 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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Dave-5

Re: KX3 - UHF emissions

In reply to this post by g0hww

I can back Darren up on this, sprogs and sproggies are common slang words
used in Amateur Radio and the Radio/TV industries in the UK to mean
spurrious emissions.

So, at a typical Microwave Roundtable you might hear someone say "Look at
the sproggies on that!" when connecting the output of an oscillator or
amplifier to a spectrum analyser.

It can also mean a small child or baby, as in "I see she has brought her
sprogs with her" it was also used in the RAF as a description of a new
recruit, possibly putting 'frog spawn' into one word, as the recruit was
often said to be 'as green as a frog' as they didn't know much.

What frequencies are these emissions on specifically? As I'll get out my
portable spectrum analyser and go and look for them on my KX3 if I know
where to look.

Dave (G0DJA)

----- Original Message -----
From: "Darren Long" <[hidden email]>
To: "K8JHR" <[hidden email]>; <[hidden email]>
Sent: Wednesday, June 25, 2014 12:44 AM
Subject: Re: [Elecraft] KX3 - UHF emissions

> Well, I've always thought of sproggies as spurious emissions, i.e.
> external to
> the source, whereas I've thought of birdies as internal interference,
> perhaps
> like tinitus.

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g0hww

Re: KX3 - UHF emissions

Hi Dave,

Well, the only time that I've specifically investigated one of these spurs, was
with my KX3 tuned to 7.080Mhz. The only reason why I've followed up on this one
is that I've cleared the backlog of other things to do and figured that I'd try
and nail this problem now. I've had the scanners stop on UHF channels whilst
operating on most HF bands with the KX3.

I noticed the spur (from 7.08MHz) on 389.4MHz, which is a frequency used at RAF
Marham. A related spur can be found at 141.6Mhz too. It would be interested to
see if you can find anything. I've used my USRP with a whip in the near field
to monitor a wider swath of spectrum and can see the spur from 7.08MHz drop down
by 160KHz to 141.440Mhz and down by 440kHz to 388.96kHz when I enable the 8kHz
shift in the KX3.

I watched 8MHz of spectrum and knobulated (there's another one for the
dictionary) the KX3's VFO and followed the sprog as it traversed the plot. I
slewed the KX3's VFO down to 60m and at some points could see a pair of spurs
tracking the VFO.

Anyway, I've ordered about £30 of type 61 ferrite which should arrive tomorrow,
so I'll see if that gets results.

Cheers,

Darren, G0HWW

On 25/06/14 15:07, Dave wrote:

> I can back Darren up on this, sprogs and sproggies are common slang words used
> in Amateur Radio and the Radio/TV industries in the UK to mean spurrious emissions.
>
> So, at a typical Microwave Roundtable you might hear someone say "Look at the
> sproggies on that!" when connecting the output of an oscillator or amplifier to
> a spectrum analyser.
>
> It can also mean a small child or baby, as in "I see she has brought her sprogs
> with her" it was also used in the RAF as a description of a new recruit,
> possibly putting 'frog spawn' into one word, as the recruit was often said to be
> 'as green as a frog' as they didn't know much.
>
> What frequencies are these emissions on specifically? As I'll get out my
> portable spectrum analyser and go and look for them on my KX3 if I know where to
> look.
>
> Dave (G0DJA)
>
>
> ----- Original Message ----- From: "Darren Long" <[hidden email]>
> To: "K8JHR" <[hidden email]>; <[hidden email]>
> Sent: Wednesday, June 25, 2014 12:44 AM
> Subject: Re: [Elecraft] KX3 - UHF emissions
>
>
>> Well, I've always thought of sproggies as spurious emissions, i.e. external to
>> the source, whereas I've thought of birdies as internal interference, perhaps
>> like tinitus.
>
> ______________________________________________________________
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DaveL G3TJP

Re: KX3 - UHF emissions

In reply to this post by g0hww

I'd very much like to see a response from Elecraft on this one; perhaps they
are running some tests of their own? If proven, maybe some sort of hardware
solution is needed.

It would be a pity for the technical problem to be lost beneath a debate on
slang terms.

73 Dave G3TJP

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wayne burdick

Re: KX3 - UHF emissions

Administrator

"Dave Lankshear" <[hidden email]> wrote:

> I'd very much like to see a response from Elecraft on this one....

Hi Dave,

It may be possible to further reduce emissions, and we'll post if we have any new information. Some external cable treatments were suggested to the original poster by the world's leading authority on such issues. We added a 60-MHz low-pass filter right at the KX3's output early on, though the current issue isn't related to the antenna jack.

A word on design compromises: The KX3 is a very small all-band/all-mode radio with a high degree of integration, intended for lightweight field use. To hit our size/weight/cost targets, we chose to use miniature PCB-mount connectors where practical, and did not go overboard on internal or external shielding. We did use state-of-the-art multi-layer PCB design techniques, which provides a significant shielding effect for RF paths. As a result, the KX3 passed all required tests, and very few of the thousands of KX3 owners have had any issue with emissions.

That said, if solutions to specific problems become practical, we will test and document them and make components available.

73,
Wayne
N6KR

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g0hww

Re: KX3 - UHF emissions

Hi,

The #61 ferrite torroids and snap-ons arrived today. I've confirmed that the
sproggies I'm receiving in my other radios aren't being picked up in the near
field of my KX3 by relocating the entirely disconnected KX3 to the other end of
(my admittedly small, terraced) house, and the strength of the spurii remain
roughly the same. I've also taken the KX3 upstairs to within 8ft of the discone
in the loft and have seen the strength of the same specific sproggy increase by
about 20dB.

My I/Q cable assembly includes a short adapter with a 2.5mm plug and in-line
3.5mm socket, followed by an inline stereo line-isolator and then on to to the
extension cable to the PC (all other connections being with 3.5mm TRS other than
the one on the rig).

The torroids I bought are Fair-Rite 5961001201, I got 5. I am able to get 2
turns around the torroid with the short 2.5/3.5mm adapter, which when straight
is about 6 inches long.

Without nothing connected to the KX3, I'm seeing the spur on 389.4MHz at about
-68dB, as observed on my USRP using my loft discone. The noise floor is about -80dB.

Plugging in the adapter without the 2 turn choke boosts the receive signal to
about -46dB.

Plugging in the adapter with the 2 turn choke puts the spur at about -65dB,
about 20dB improvement than without the choke (how much the bunching of the
cable into a small bundle contributes to this I don't know).

After connecting up the full compliment of cables and liberally scattering the
remaining 4 #61 torroids and 6 snap-ons around the rest of the KX3's own
personal rats-nest, the spur is at about -61dB, around 20dB over the noise floor
in the USRP (sampling at 125kHz).

This is a decent improvement, over the same setup without the benefit of the #61
ferrite, but I think there's still some way to go before satisfaction is achieved.

Also, it should be remembered that this is just a spot check on a single
frequency. I have good reason to suspect that there are other sproggies related
to this fundamental, and then a vast range of other fundamentals to consider,
all equally likely to generate some cruft in undesirable places. I have no idea
yet how effective the ferrite is at taming the full spectrum of unwanted
emissions. I will have time to investigate further over the coming weekend.

If there was a way to nail this inside the KX3 box, I would be very grateful.

I've often thought that an optical SPDIF interface for the I/Q output would have
made sense.

Cheers, 73

Darren, G0HWW

On 26/06/14 19:07, Wayne Burdick wrote:

> "Dave Lankshear" <[hidden email]> wrote:
>
>> I'd very much like to see a response from Elecraft on this one....
>
> Hi Dave,
>
> It may be possible to further reduce emissions, and we'll post if we have any new information. Some external cable treatments were suggested to the original poster by the world's leading authority on such issues. We added a 60-MHz low-pass filter right at the KX3's output early on, though the current issue isn't related to the antenna jack.
>
> A word on design compromises: The KX3 is a very small all-band/all-mode radio with a high degree of integration, intended for lightweight field use. To hit our size/weight/cost targets, we chose to use miniature PCB-mount connectors where practical, and did not go overboard on internal or external shielding. We did use state-of-the-art multi-layer PCB design techniques, which provides a significant shielding effect for RF paths. As a result, the KX3 passed all required tests, and very few of the thousands of KX3 owners have had any issue with emissions.
>
> That said, if solutions to specific problems become practical, we will test and document them and make components available.
>
> 73,
> Wayne
> N6KR
>
> ______________________________________________________________
> 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]
>

Dave-5

Re: KX3 - UHF emissions

In reply to this post by g0hww

As this message doesn't appear to be on the forum, I guess the attachments
were the problem, so I'm reposting the original and I've put the attachments
into my dropbox at

https://dl.dropboxusercontent.com/u/65397105/KX3%20Test%2027-06-2014%201002.jpg

Which is with my KX3 switched off and

https://dl.dropboxusercontent.com/u/65397105/KX3%20Test%2027-06-2014%201005.jpg

Which is with my KX3 switched on and set to 7.080MHz USB.

Dave (G0DJA)

----- Original Message -----
Sent: Friday, June 27, 2014 9:43 AM
Subject: Re: [Elecraft] KX3 - UHF emissions

> I've just done a couple of tests using an RF Explorer portable spectrum
> analyser set to monitor between 15MHz and 614MHz. I can 'zoom in' if
> necessary but kept it wide in the first case to have an overview of as
> wide
> a frequency range as possible. The antenna is the "Ngoya NA-773
> 144/430MHz"
> whip antenna supplied with the analyser with the whip fully retracted.The
> analyser and fitted antenna are about 15cm (6inches) away from the KX3.
>
> My KX3 has leads plugged into the RX I/Q socket, the Phones socket, the
> ACC1
> socket and a 13.8V supply to the 9-15V DC socket. No cable connected to
> the
> ACC2 socket. None of the leads have any RF beads on them, that I can see
> anyway. The DC, ACC1 and RX I/Q leads are the ones suplied by Elecraft.
>
> If the screenshots get taken off before they get onto the reflector, I'll
> put them in a dropbox folder and will post a link.
>
> The 1st screenshot shows the situation with the KX3 switched off, date
> stamped 27-06-2014 1002. With the KX3 swiched off I see a steady signal at
> 389.999MHz (-83dBm) and, as the red line shows, there's an occasional
> signal
> at 143.571MHz (-78.5dBm). There's also another occasional signal at
> 422.142MHz (-78.5dBm).
>
> The second screen shot is with the KX3 switched on, date stamped
> 27-06-2014
> 1005, frequency set to 7.080Mhz USB. With the KX3 on I am seeing a rise
> in
> the noise floor at a whole range of frequencies, but no specific single
> frequency spike, other than the ones that I see with the KX3 switched off
> of
> course, as yet.
>
> I'll set the analyser to monitor just the VHF/UHF spectrum next and see if
> I
> can track any specific carriers down.
>
> Dave (G0DJA)
>
> ----- Original Message -----
> From: "Darren Long"
> To: <[hidden email]>; "Wayne Burdick" <[hidden email]>;
> <[hidden email]>
> Sent: Thursday, June 26, 2014 11:30 PM
> Subject: Re: [Elecraft] KX3 - UHF emissions
>
>
>> My I/Q cable assembly includes a short adapter with a 2.5mm plug and
>> in-line
>> 3.5mm socket, followed by an inline stereo line-isolator and then on to
>> to
>> the
>> extension cable to the PC (all other connections being with 3.5mm TRS
>> other than
>> the one on the rig).
>
>> Without nothing connected to the KX3, I'm seeing the spur on 389.4MHz at
>> about
>> -68dB, as observed on my USRP using my loft discone. The noise floor is
>> about -80dB.
>>
>> Plugging in the adapter without the 2 turn choke boosts the receive
>> signal
>> to
>> about -46dB.
>>
>