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K3 Sub Receiver Problems

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KGØUS

K3 Sub Receiver Problems

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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Barry Simpson

Fwd: K3 Sub Receiver Problems

---------- Forwarded message ----------
From: Barry Simpson <[hidden email]>
Date: 3 January 2013 09:04
Subject: Re: [Elecraft] K3 Sub Receiver Problems
To: DR <[hidden email]>

Hi Dave

You need to engage B Set before pressing any of the other functions. This
will enable you to turn on the sub receiver pre amp as from your
description, it is turned off.

I cannot imagine what the attenuator issue is unless you are mistakenly
pressing the RX ANT button. That would have the effect that you describe
but on both the main and sub receivers if you have no antenna on the
receive antenna connector.

In summary, press and hold the B Set button and B Set will appear on the
readout. I think that you will then find that Pre Amp, ATT and other sub
receiver functions work normally until B Set is disengaged.

73

Barry VK2BJ

On 3 January 2013 05:27, DR <[hidden email]> 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
> ______________________________________________________________
> 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
>

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Matt Zilmer

Re: K3 Sub Receiver Problems

In reply to this post by KGØUS

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
>______________________________________________________________
>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

KGØUS

Re: K3 Sub Receiver Problems

I am confident that I am operating the sub receiver properly. I have also compared the main receiver and sub assembly with the sub receiver approximately 3 S units or 18 dBs down from the main receiver.

Engaging the ATT attenuator on the sub receiver drives the signal, no matter how strong, down to nothing on the S meter and inaudible in the speaker.

Engaging or disengaging the PRE preamp on the sub receiver has no effect on noise or signal level.

I think that the sub receiver has taken some damage from my recent SO2V and diversity operations while running high power.

I recently located and downloaded the K3 schematics from the Elecraft web site. The sub receiver schematic is located on pages 53 and 54 of the drawing package.

The upper left corner of the schematic on page 54 contains the 10 dB attenuator consisting of R37 (100 Ohms), R43 (68 Ohms), and R45 (100 Ohms). I removed the KRX3 sub receiver PCB with my static pad and wrist strap. Using my DVM R43 and R37 are both “open” while R45 is practically “open” measuring over 400 K Ohms. This pretty much explains my problem with the sub assembly attenuator circuit.

Any ideas as to what else I can check using my DVM while I have the PCB out to troubleshoot the preamp problem along with the 18 dB down sensitivity problem? Will a standard diode check work on the PIN diodes D3 and D4 on the input and output of the preamp circuit?

Thanks,
Dave KG0US

ON4YVO

Re: K3 Sub Receiver Problems

This post was updated on .

My sub receiver is not sensitive either. Signals are very weak on strong signals on the main receiver. Difference is 9 S-points.

That's why I took the effort to measure the resistors. R43 is 51 Ohm, R37 and R45 are both 63 Ohm. These are on the other side of K10. Of course these measurements are influenced by the circuit.

These resistors are only in use when the attenuator is switched on. Otherwise they are bypassed by the relay.

I plan to make some cables so I can measure the board while connected to the receiver and being fed by a HF generator.

KGØUS

Re: K3 Sub Receiver Problems

This post was updated on .

"That's why I took the effort to measure the resistors. R43 is 51 Ohm, R37 and R45 are both 63 Ohm."

From what you measured above, I can tell you that your R43, R37, and R45 resistors are all good.

Please take a closer look at the schematic. When you measure R43, you are actually measuring R43 in parallel with R37 and R45 in series. This would be 68 || (100 + 100) = 50.74 Ohms.

When you measure R37 or R45, you are actually measuring 100 || (68 + 100) = 62.68 Ohms.

I plan to make a few more measurements this weekend and was hoping for some guidance from the experts. I have been getting the cold shoulder here.

I will make a few more measurements here but I have limited resources at home. I have unlimited resources at work but I am not allowed to work on home equipment.

I have four choices:
1.) Try to fix it myself but I will need to ask a friend if I can use his surface mount solder station.
2.) Remove it, or do nothing and live with it.
3.) Buy another subreceiver kit for $600.
4.) Send it in for repair.

Good luck,

Dave KG0US

Guy, K2AV

Re: K3 Sub Receiver Problems

You need to call Elecraft Tech Support on this problem before you go
further. They don't live on the reflector. Someone knowledgeable can walk
you through a series of steps to isolate what is going on. There are too
many possibilities to work this efficiently over email.

Do not go soldering things until you have called Elecraft. It could easily
be something you misread in the manual, or a misconception about how it
works with the components you have. Or it can be an improperly seated tiny
plug on those coax leads. Everyone has done that. There is a certain
"feel" to it when it is really seated.

Frankly 9 S units usually means that something is not connected at all. 9
S units down means all you are hearing is capacitive coupling. BOTH the
cable connections AND the state of the RX hold button must match. But
there is a pile of possibilities.

Call Elecraft and have them walk you through.

73, Guy.

On Thu, Jan 10, 2013 at 11:32 PM, KGØUS <[hidden email]> wrote:

>
>
> "That's why I took the effort to measure the resistors. R43 is 51 Ohm, R37
> and R45 are both 63 Ohm."
>
> From what you measured above, I can tell you that your R43, R37, and R45
> resistors are all good.
>
> Please take a closer look at the schematic. When you measure R43, you are
> actually measuring R43 in parallel with R37 and R45 in series. This would
> be 68 || (100 + 100) = 50.74 Ohms.
>
> When you measure R37 or R45, you are actually measuring 100 || (68 + 100) =
> 62.68 Ohms.
>
> I plan to make a few more measurements this weekend and was hoping for some
> guidance from the experts. I have been getting the cold shoulder here.
>
> I will make a few more measurements here but I have limited resources at
> home. I have unlimited resources at work but I am not allowed to work on
> home equipment.
>
> I have four choices:
> 1.) Try to fix it myself but I will need to ask a friend if I can use his
> surface mount solder station.
> 2.) Do nothing, remove it, or live with it.
> 3.) By another subreceiver kit for $600.
> 4.) Send it in for repair.
>
> Good luck,
>
> Dave KG0US
>
>
>
>
>
> --
> View this message in context:
> http://elecraft.365791.n2.nabble.com/K3-Sub-Receiver-Problems-tp7568116p7568540.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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Eric Swartz - WA6HHQ

Re: K3 Sub Receiver Problems

Administrator

Or email [hidden email]

73,

Eric
---
www.elecraft.com

On 1/11/2013 10:09 AM, Guy Olinger K2AV wrote:
> You need to call Elecraft Tech Support on this problem before you go
> further. They don't live on the reflector.

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ON4YVO

Re: K3 Sub Receiver Problems

This post was updated on .

In reply to this post by Guy, K2AV

I got the sub receiver fixed. The previous owner had the filter inserted the wrong way. By this the signal pins are shorted to ground by the filter.

I discovered this by measuring on the connectors of the filters. On the selected filter the signal pins carry 5 volt DC. The DC is blocked by capacitors on the filter circuit.

When having few resources, you can swap the NB and mixer print and also change coaxes to swap main and sub receiver.