[Elecraft] KX3 - UHF emissions

[Dave]

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: <elecraft at mailman.qth.net>; "Wayne Burdick" <n6kr at elecraft.com>;
> <jim at audiosystemsgroup.com>
> 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.
>>
>