[Elecraft] K3 Sub Receiver Problems

[Matt Zilmer]

Hi Dave,

To some extent, my sub-RX experience duplicated yours.  After a lot of
experimentation, I determined that the sub's antenna has a number of
differences from the main antenna.  This is the purpose (in the case
of diversity reception) anyway: To reduce fading effects.  For SO2V
ops, having such differences may not be desirable - because you want
to use each receiver in a similar way listening to signals on and off
your main's frequency.

I can only use my sub's antenna on 60, 40, and 30m because it's a full
length 40m 1/4-wave vertical.  The main antenna is a doublet cut long
for 80m.  There is a world of difference between these two antennas.
On bands where the vertical isn't even close to resonance, it doesn't
work very well.  Not too much of a surprise when one thinks about it.

I mostly use the subRX for diversity reception.  This is quite a
different use case than SO2V.  For SO2V, you might want to use a subRX
antenna similar to your main RX.  Of course, you'd probably need to
separate them a fair distance.

One suggestion for you is to check the sensitivity of each receiver,
independently of the other and not considering antennas.  This should
be reassuring to you, that the subRX isn't deaf -and- that most
differences you hear are due to antennas being different.  Using one
of Elecraft's XG (XG2 or XG3) signal generators might of value to you.
The XG2 is a kit but it's inexpensive and kinda fun to assemble (easy
enough as well).  The XG2 uses fixed frequencies on 80, 40, and 20m.
The XG3 is a lot more flexible -programmable from a PC- and it comes
already assembled.

I used a regular HP signal generator to measure MDS on each receiver.
I found that they both meet the rated senstivity spec, and are matched
within 1 or 2 dB of each other.  You could do the same with one of the
XG signal generators.

Not everyone has a lab full of test equipment around the shack.  The
XG devices can help make up for this.  

Just a suggestion.  

73,
matt W6NIA

On Wed, 02 Jan 2013 21:27:12 -0800 (PST), you wrote:

>I tried to work the recent 10 meter contest using SO2V but I found that weaker 
>signals were virtually uncopyable when using the sub receiver.  The main 
>receiver appears to be working correctly.
> 
>The sub receiver appears to have problems:
> 
>I have noticed that the PRE does nothing when pressed after pressing the SUB and 
>then pressing the BSET button.  Pressing the PRE on the main receiver, I see a 
>one or two S unit increase on the meter as well as hearing an increase in 
>noise.  I see no increase on the S meter and hear no noise increase when 
>activating the PRE on the sub receiver.
> 
>I have had a constant S9 noise on the 75 meter DX window since our light snow 
>the other night.  On a clear frequency I notice that the sub receiver only shows 
>S6 on the meter.  I did use the RX ANT button to switch to Main from Aux to 
>eliminate differences in receive antennas.  I also physically swapped the 
>antennas in the back to verify the difference in sensitivity.  I used a PL259 to 
>BNC adapter to make the swap.
> 
>I also noticed that the sub receiver audio and S meter goes completely dead when 
>I engage the ATT using BSET on the sub receiver.
> 
>I successfully ran the RF gain cal but I do not have a calibrated source.  
>Without the calibrated source, the procedure only uses factory default values.
> 
>I am not sure if this is related but occasionally I have been getting the 
>following error:
> 
>E 040AA8  err dse
> 
>Anyone know what the error code means?
> 
>73,
> 
>Dave KG0US
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