Elecraft › [K2]

K2 MDS numbers off

Classic

List

Threaded

6 messages Options

Brian - N5BCN

K2 MDS numbers off

Hi all,

I attempted to calculate my K2's (S/N 6800) receiver sensitivity using an XG2, but I'm getting numbers way off from what are listed in the XG2 instruction sheet.

Using a Fluke 117 multimeter, I'm measuring S+N = 0.132 Vrms and N = 0.034 Vrms, which I calculate MDS = -119 dBm. I'm probing the external speaker leads (I can't figure out how to get a reading from the headphone or ext speaker jacks). I'm using the set up parameters recommended by the XG2 instruction sheet: AGC Off, RF Gain maxed, Att Off, Preamp On, filter 500 Hz, etc.

The K2 appears to be performing normally except for strange CAL S LO/HI behavior. Apparently, there might be a problem with the K2's receive sensitivity which is causing problems with the CAL S LO/HI.

Any suggestions would be most appreciated!!!

N5BCN - Brian

Don Wilhelm-4

Re: K2 MDS numbers off

Brian,

Your K2 seems to be somewhat deaf based on your MDS measurements.
I would recommend that you do the steps in the K2 manual under Receiver
Signal Tracing to identify the failing stage. Once the failure point is
identified, we can offer additional assistance.

73,
Don W3FPR

On 1/5/2011 8:10 PM, Brian - N5BCN wrote:

> Hi all,
>
> I attempted to calculate my K2's (S/N 6800) receiver sensitivity using an
> XG2, but I'm getting numbers way off from what are listed in the XG2
> instruction sheet.
>
> Using a Fluke 117 multimeter, I'm measuring S+N = 0.132 Vrms and N = 0.034
> Vrms, which I calculate MDS = -119 dBm. I'm probing the external speaker
> leads (I can't figure out how to get a reading from the headphone or ext
> speaker jacks). I'm using the set up parameters recommended by the XG2
> instruction sheet: AGC Off, RF Gain maxed, Att Off, Preamp On, filter 500
> Hz, etc.
>

______________________________________________________________
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

Peter, DL2FI

Re: K2 MDS numbers off

In reply to this post by Brian - N5BCN

Brian,

Over the years I had about 3-4 K2 on my workbench being so deaf. All of them
had T7 on the RF board installed reversed. Check T7 if the green winding (5
turns) really is soldered to the solder lugs numbered 1 and 2. If you
reverse this transformer, you will miss about 20 dB gain.
73 de Peter, DL2FI

> -----Ursprüngliche Nachricht-----
> Von: [hidden email] [mailto:elecraft-
> [hidden email]] Im Auftrag von Brian - N5BCN
> Gesendet: Donnerstag, 6. Januar 2011 02:11
> An: [hidden email]
> Betreff: [Elecraft] K2 MDS numbers off
>
>
> Hi all,
>
> I attempted to calculate my K2's (S/N 6800) receiver sensitivity using
> an
> XG2, but I'm getting numbers way off from what are listed in the XG2
> instruction sheet.
>
> Using a Fluke 117 multimeter, I'm measuring S+N = 0.132 Vrms and N =
> 0.034
> Vrms, which I calculate MDS = -119 dBm. I'm probing the external
> speaker
> leads (I can't figure out how to get a reading from the headphone or
> ext
> speaker jacks). I'm using the set up parameters recommended by the XG2
> instruction sheet: AGC Off, RF Gain maxed, Att Off, Preamp On, filter
> 500
> Hz, etc.
>
> The K2 appears to be performing normally except for strange CAL S LO/HI
> behavior. Apparently, there might be a problem with the K2's receive
> sensitivity which is causing problems with the CAL S LO/HI.
>
> Any suggestions would be most appreciated!!!
>
> N5BCN - Brian
>
> -----
> K2 #6800 KSB2 KAT2 KIO2 KNB2
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-
> MDS-numbers-off-tp5894232p5894232.html
> Sent from the [K2] mailing list archive at Nabble.com.
> ______________________________________________________________
> 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

Brian - N5BCN

Re: K2 MDS numbers off

Peter,

Thanks for the suggestion: T7 checked out ok with proper orientation and proper number of turns. Another post mentioned checking RFC11, so I'm checking that next.

Does anyone have a suggestion about a simple test oscillator/rf signal generator kit to purchase to perform the signal tracing? Buying a dedicated signal generator is beyond me financially, and building the test oscillator in Appendix E may be beyond me technically (I'm not very good at homebrewing).

I've researched wb6dhw's kits, but his website states that he is out of parts until at least Jan 17, and it appears that his kits are sold as group buys only.

Does Elecraft sell all the parts necessary to build the test oscillator?

Thanks again for your help!

N5BCN - Brian

Brian - N5BCN

Re: K2 MDS numbers off

Many people have suggested using the XG2 as a signal source for signal tracing.

My understanding from reading a previous post was that the 50 uV output of the XG2 was too low to perform signal tracing on the receiver circuitry (however, it's adequate for the transmitter circuitry).

I'd love to use the XG2 because I already have one. Can anyone confirm that they have signal traced the receiver circuitry using the XG2 as the signal source?

Thanks everybody?

N5BCN - Brian

Don Wilhelm-4

Re: K2 MDS numbers off

Brian,

The XG2 will not work for that purpose at all, the signal level is too
small, and the noise pickup on a 'scope probe will likely be larger than
the signal.

The generator shown in the K2 manual is dirt simple, and does not have
to be carefully assembled. I built one Manhatten style on a small piece
of PC board. The crystal can be any within the tuning range of the K2,
but 40 meters or 30 meters is preferred.
If you have to, just punch some holes in a piece of cardboard to support
the components and solder the leads on the other side - not much
critical as long as you get the correct leads connected together.

73,
Don W3FPR

On 1/6/2011 2:59 PM, Brian - N5BCN wrote:

> Many people have suggested using the XG2 as a signal source for signal
> tracing.
>
> My understanding from reading a previous post was that the 50 uV output of
> the XG2 was too low to perform signal tracing on the receiver circuitry
> (however, it's adequate for the transmitter circuitry).
>
> I'd love to use the XG2 because I already have one. Can anyone confirm that
> they have signal traced the receiver circuitry using the XG2 as the signal
> source?
>
> Thanks everybody?
>
> N5BCN - Brian
>
> -----
> K2 #6800 KSB2 KAT2 KIO2 KNB2