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K1 Receiver Issues

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rhsanborn

K1 Receiver Issues

I am completely new to amateur radio, the K1 is my first xcvr, and I
don't even have my license yet.

I have recently completed the assembly of my K1 and I'm not able to pick
anything up on the receiver. I worked with someone on the #hamradio
channel at irc.freenode.net, and hopefully we've narrowed some things
down. I will attempt to explain what we've looked at so far with my
butchered lack of understanding.

I've tested all the toroids for continuity and they all check out, and
I've also gone through the and filter baord portions of the voltage
tables, and those check out as well.

With some quick and dirty signal tracing (30ft of wire with a probe on
the end), I tried inputing rf into various points in the circuit. I got
responses at the following points, all on the rf board:

U2 Pin 1
C38
X4, the leg connected to C38

I didn't get any response at the following points on the rf board:

C39
X1-X4 (except for X4 mentioned above)

Checked the voltages on D6-8 and they are all installed and working
properly.

Any ideas where I should look next?

Randall H. Sanborn
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rhsanborn

Re: K1 Receiver Issues

Is there any way that I can use one of the programs that turn the PC sound card into a signal generator to inject some amount of noise into the radio at various points for testing? I'm not confident in my very rudimentary antenna, and while I understand that the sound card can't output at a receivable freq, perhaps it can cause some noise that I can hear on the phones... ?

Any ideas?

Randall

-------------- Original message ----------------------
From: "Randall H. Sanborn" <[hidden email]>

> I am completely new to amateur radio, the K1 is my first xcvr, and I
> don't even have my license yet.
>
> I have recently completed the assembly of my K1 and I'm not able to pick
> anything up on the receiver. I worked with someone on the #hamradio
> channel at irc.freenode.net, and hopefully we've narrowed some things
> down. I will attempt to explain what we've looked at so far with my
> butchered lack of understanding.
>
> I've tested all the toroids for continuity and they all check out, and
> I've also gone through the and filter baord portions of the voltage
> tables, and those check out as well.
>
> With some quick and dirty signal tracing (30ft of wire with a probe on
> the end), I tried inputing rf into various points in the circuit. I got
> responses at the following points, all on the rf board:
>
> U2 Pin 1
> C38
> X4, the leg connected to C38
>
> I didn't get any response at the following points on the rf board:
>
> C39
> X1-X4 (except for X4 mentioned above)
>
> Checked the voltages on D6-8 and they are all installed and working
> properly.
>
> Any ideas where I should look next?
>
> Randall H. Sanborn
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

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Post to: [hidden email]
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rhsanborn

Re: K1 Receiver Issues

In reply to this post by rhsanborn

The best antenna I have is a piece of wire about 30ft long with a 100pF cap on the end as mentioned in the article. I tried U1 pin 1, and get nothing. I suppose that would indicate a problem...but I'm not sure where.

Not much point in going backward, because anything behind that will certainly be stopped there.

Any ideas?

Randall

-------------- Original message ----------------------
From: Tom Hammond <[hidden email]>

> Randall:
>
> >At best Ive been getting some quiet popping noises...I occasionally
> >heard some hums, but I think that is some bleed-in from my work
> >area, and not quite so much to do with something coming in from the antenna.
> >
> >I put the bottom cover back on to try and isolate it from the table
> >and any frequencies coming through it, and the hum is gone, and I
> >cant hear anything now. I think all the antenna was doing was
> >bleeding out that errant signal.
>
> It was probably providing a VERY small amount of signal which was
> able to sneak thru
> the product detector and into the AF Amp.
>
> >Perhaps its time to introduce myself to some local hams and see if I
> >can't get some help, and perhaps a signal gen.
>
> It NEVER hurts to get to know your 'locals'... sometimes you'll find
> someone who is very
> knowledgeable and quite willing to help a newbie.
>
> However... FIRST try using the techniques (and test points) in my
> article. You first want to try to confirm that everything from the
> Receive Mixer on thru the AF Amp is working. So try injecting an
> off-the-air signal, even if it's only 40M noise, at U1 pin 1. IF you
> hear noise in the speaker, then go to pin 1 of T1, and then to pins 8
> & 3 (in that order) of K1.
>
> Each time you CAN hear a signal, as long as it's relatively the same
> (or higher) level as that which you heard from a prior injection
> point, there's a good chance that things are still OK to that point.
> You want to work your way from the INSIDE of the circuit out toward
> the ANT input. If you find an injection point where the signal really
> drops (or completely disappears) THAT's where you want to try to find
> out why... the loss should be between THAT point and the last known good point.
>
> This is quick and easy to do and may save you having to find someone
> locally for help... though it's STILL good to get to know the locals.
>
> 73,
>
> Tom N0SS
>

Don Wilhelm-4

Re: K1 Receiver Issues

In reply to this post by rhsanborn

Randall,

Is this a K1 with the 2 band board or with the 4 band board?

The Pre-mixer and the bandpass filter must be tuned before you will hear
much of anything.

Since you have no strong signal source (like another transceiver that
you can operate into a dummy load) to help you tune the Pre-mixer and
the bandpass, things are a bit more difficult.

I would suggest that you start by constructing an RF probe to help you
adjust the Pre-mixer. There is a schematic for an RF probe in the
Troubleshooting section of the K1 manual. If you choose to do it that
way, I can give you some pointers about how to go about preliminary
adjustments (that procedure is not in the manual) - so let me know if
you have an RF probe available or have built one and we can continue.

It is normal to have a significant dropoff in signal level between the
input to the product detector and the remainder of the filter crystals
because the filter itself is restricting the RF fed through it to the
center frequency of the filter - that fact is not present at the filter
output (C38 to X4 junction) because there the product detector can
respond to the full RF spectrum input rather than just the 4913 kHz
slice of the spectrum.

73,
Don W3FPR

Randall H. Sanborn wrote:

> I am completely new to amateur radio, the K1 is my first xcvr, and I
> don't even have my license yet.
>
> I have recently completed the assembly of my K1 and I'm not able to
> pick anything up on the receiver. I worked with someone on the
> #hamradio channel at irc.freenode.net, and hopefully we've narrowed
> some things down. I will attempt to explain what we've looked at so
> far with my butchered lack of understanding.
>
> I've tested all the toroids for continuity and they all check out, and
> I've also gone through the and filter baord portions of the voltage
> tables, and those check out as well.
>
> With some quick and dirty signal tracing (30ft of wire with a probe on
> the end), I tried inputing rf into various points in the circuit. I
> got responses at the following points, all on the rf board:
>
> U2 Pin 1
> C38
> X4, the leg connected to C38
>
> I didn't get any response at the following points on the rf board:
>
> C39
> X1-X4 (except for X4 mentioned above)
>
> Checked the voltages on D6-8 and they are all installed and working
> properly.
>
> Any ideas where I should look next?
>
> Randall H. Sanborn
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>