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K3 P3 Spurious signals

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k6dgw

K3 P3 Spurious signals

K3 [#642] w/P3 in FixTune mode [cursor moves, ends of screen are fixed].
K3 has the resistor mod to increase the 8 MHz IF output. I see them
on CW, I haven't tried SSB.

I've got a pair of weak, steady spurious signals ~14.5 KHz above and
below the VFO A cursor. They tune with the VFO [i.e. I can never tune
to them] With a noise floor around -135dBm, they run about -115 dBm. I
see them only on 10m, however my noise floor is in the -120 to -115dBm
range on other bands and they may be there and I just can't see them.

With no antenna, the signals appear to be each bracketed by two very
weak bands of noise about 2 KHz wide, about 3 KHz above and below each
signal. They only show up on the waterfall [I use a monochrome WF].

The K3 and P3 appear to be working just fine and I only notice them
because when I tune VFO A, I end up with faint slanting traces on the
WF. Anyone have an explanation?

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org

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Peter Lambert

Re: K3 P3 Spurious signals

Hello Fred,

I see a very similar thing on my IC-7700. Different frequency spacings but
pretty much as you described.

They're visible on the band scope but that's it. I can't detect any I'll
effect from them. They're so far down to be of no consequence. I write
them off as images in the DSP processing that produces the bandscope and
appreciate that absolutely nothing is perfect.

73's Peter VK4JD

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Fred Jensen
Sent: Tuesday, 19 February 2013 6:42 AM
To: Elecraft Reflector
Subject: [Elecraft] K3 P3 Spurious signals

K3 [#642] w/P3 in FixTune mode [cursor moves, ends of screen are fixed].
K3 has the resistor mod to increase the 8 MHz IF output. I see them on
CW, I haven't tried SSB.

I've got a pair of weak, steady spurious signals ~14.5 KHz above and below
the VFO A cursor. They tune with the VFO [i.e. I can never tune to them]
With a noise floor around -135dBm, they run about -115 dBm. I see them only
on 10m, however my noise floor is in the -120 to -115dBm range on other
bands and they may be there and I just can't see them.

With no antenna, the signals appear to be each bracketed by two very weak
bands of noise about 2 KHz wide, about 3 KHz above and below each signal.
They only show up on the waterfall [I use a monochrome WF].

The K3 and P3 appear to be working just fine and I only notice them because
when I tune VFO A, I end up with faint slanting traces on the WF. Anyone
have an explanation?

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org

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gm3sek

Re: K3 P3 Spurious signals

On 18/02/2013 20:57, Peter Lambert wrote:

> Hello Fred,
>
> I see a very similar thing on my IC-7700. Different frequency spacings but
> pretty much as you described.
>
> They're visible on the band scope but that's it. I can't detect any I'll
> effect from them. They're so far down to be of no consequence. I write
> them off as images in the DSP processing that produces the bandscope and
> appreciate that absolutely nothing is perfect.
>
> 73's Peter VK4JD
>

Fred, Peter: have you replaced the Elecraft supplied BNC-BNC cable?

I had very similar problems because the cable shield was improperly
crimped at both ends. A BNC cable from the junk box cured the problem
almost completely.

--

73 from Ian GM3SEK

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Fred Jensen
> Sent: Tuesday, 19 February 2013 6:42 AM
> To: Elecraft Reflector
> Subject: [Elecraft] K3 P3 Spurious signals
>
> K3 [#642] w/P3 in FixTune mode [cursor moves, ends of screen are fixed].
> K3 has the resistor mod to increase the 8 MHz IF output. I see them on
> CW, I haven't tried SSB.
>
> I've got a pair of weak, steady spurious signals ~14.5 KHz above and below
> the VFO A cursor. They tune with the VFO [i.e. I can never tune to them]
> With a noise floor around -135dBm, they run about -115 dBm. I see them only
> on 10m, however my noise floor is in the -120 to -115dBm range on other
> bands and they may be there and I just can't see them.
>
> With no antenna, the signals appear to be each bracketed by two very weak
> bands of noise about 2 KHz wide, about 3 KHz above and below each signal.
> They only show up on the waterfall [I use a monochrome WF].
>
> The K3 and P3 appear to be working just fine and I only notice them because
> when I tune VFO A, I end up with faint slanting traces on the WF. Anyone
> have an explanation?
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2013 Cal QSO Party 5-6 Oct 2013

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Dave Van Wallaghen

Re: K3 P3 Spurious signals

Fred and I discussed this problem off line a couple of weeks ago as I
have the same thing here. I did wiggle and re-seat my BNC cable but did
not try another one.

I will try that first thing in the morning when I get home as I found
wiggling the cable did alter it a bit.

Thanks Ian,
Dave W8FGU

On 02/18/2013 05:19 PM, Ian White wrote:
> Fred, Peter: have you replaced the Elecraft supplied BNC-BNC cable?
>
> I had very similar problems because the cable shield was improperly
> crimped at both ends. A BNC cable from the junk box cured the problem
> almost completely.
>
>
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Dave Van Wallaghen

Re: K3 P3 Spurious signals

Tried another BNC cable I had here and it knocked the problem down
appreciably. Without an antenna connected (well, a 6' piece of RG8) I
can barely see them on 40m - they are non existent now on 10m. With my
antenna connected, I can't see them at all anymore - well below the
noise level I have here.

The cable I tried has connectors that fit much tighter (no wiggling at
all) than the Elecraft supplied cable. So I'm not sure if it is the
connectors or a bad crimp as others have suggested.

I may tear my P3 down at some point to look at the case grounding and
clean them up. This may help even further if there is a grounding problem.

73,
Dave W8FGU

On 02/18/2013 06:23 PM, Dave Van Wallaghen wrote:

> Fred and I discussed this problem off line a couple of weeks ago as I
> have the same thing here. I did wiggle and re-seat my BNC cable but did
> not try another one.
>
> I will try that first thing in the morning when I get home as I found
> wiggling the cable did alter it a bit.
>
> Thanks Ian,
> Dave W8FGU
>
>
>
> On 02/18/2013 05:19 PM, Ian White wrote:
>> Fred, Peter: have you replaced the Elecraft supplied BNC-BNC cable?
>>
>> I had very similar problems because the cable shield was improperly
>> crimped at both ends. A BNC cable from the junk box cured the problem
>> almost completely.
>>
>>
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>