Topics

k3 receiver issues


Lou Kolb
 

Greetings all,

For ten years now, I have thoroughly enjoyed owning and using K3-100
SN-4290. Along the way, I've upgraded the synth board (only one
receiver) and added the general coverage filter. Things have worked
flawlessly until recently I'm hearing what sounds like a loose
connection somewhere in the receive path. signals and atmospheric
noise are jumping up and down, as if something is not making proper or
consistent contact. This happens regardless of what antenna is
connected. I'm saying "receive signal path", because, by all accounts,
my transmitted signal is rock solid. Other than normal QSB, no one is
hearing the slightest variation on it's strength but the signal I'm
receiving is varying wildly and randomly. The base audio noise in the
rig does not seem to change at all, just signals from the outside. I'm
also hearing some broadcast images that come and go as the signals
vary. any suggestions on which boards I should clean or reseat would
be appreciated. I've never had my hands inside the radio and I'm just
a bit timid. Lou WA3MIX


David G3YYD
 

Lou

If you are hearing harmonics and or intermodulation products of broadcast signals then the most probable cause is a corroded connection in your antenna or coax feeder.

When you transmit the signal amplitude is so large that it overcomes the corrosion. 

73 David G3YYD 

On 12 May 2020 22:20, Lou Kolb <loukolb@...> wrote:

Greetings all,

For ten years now, I have thoroughly enjoyed owning and using K3-100
SN-4290. Along the way, I've upgraded the synth board (only one
receiver) and added the general coverage filter. Things have worked
flawlessly until recently I'm hearing what sounds like a loose
connection somewhere in the receive path. signals and atmospheric
noise are jumping up and down, as if something is not making proper or
consistent contact. This happens regardless of what antenna is
connected. I'm saying "receive signal path", because, by all accounts,
my transmitted signal is rock solid. Other than normal QSB, no one is
hearing the slightest variation on it's strength but the signal I'm
receiving is varying wildly and randomly. The base audio noise in the
rig does not seem to change at all, just signals from the outside. I'm
also hearing some broadcast images that come and go as the signals
vary. any suggestions on which boards I should clean or reseat would
be appreciated. I've never had my hands inside the radio and I'm just
a bit timid. Lou WA3MIX





 

Lou,

I had something like that not long ago. It was a corroded coax connection outside my house. RX was OK for a while after a short transmit but problem was still there after a few minutes.
So check that first before digging into the K3.

73
Arie PA3A
K3 #12xx


Dave Cole
 

I also had an incident like that, a friend was getting AM stations everywhere on 80, so was I at my home, 700 feet from his home...

Turns out it was a corroded guy wire... The guy was corroding at the point where it was connected to the guy anchor. Years ago he had buried it in his garden, and it had corroded.

We located it, fixed it, and it never happened again... Moral of the story: It might not be just coax.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/13/20 2:17 AM, Arie Kleingeld PA3A wrote:
Lou,
I had something like that not long ago. It was a corroded coax connection outside my house. RX was OK for a while after a short transmit but problem was still there after a few minutes.
So check that first before digging into the K3.
73
Arie PA3A
K3 #12xx


Lou Kolb
 

Thanks, guys, for all the suggestions. I have two antennas here, a
G5RV and a vertical for 2 and 440. The problem is present no matter
which antenna is inline. Both instalations are only a month old, both
using the Andrew equivalent to LMR400 with new, well protected
connectors. That's why I suspect the radio, but I'll look into
everything. Lou WA3MIX

On 5/13/20, Dave Cole <dave@...> wrote:
I also had an incident like that, a friend was getting AM stations
everywhere on 80, so was I at my home, 700 feet from his home...

Turns out it was a corroded guy wire... The guy was corroding at the
point where it was connected to the guy anchor. Years ago he had buried
it in his garden, and it had corroded.

We located it, fixed it, and it never happened again... Moral of the
story: It might not be just coax.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources

On 5/13/20 2:17 AM, Arie Kleingeld PA3A wrote:
Lou,

I had something like that not long ago. It was a corroded coax
connection outside my house. RX was OK for a while after a short
transmit but problem was still there after a few minutes.
So check that first before digging into the K3.

73
Arie PA3A
K3 #12xx







 

OK, if not the antenna installation...

On another occasion I traced a problem like this to the connections of the KAT3  antenna tuner.
Took the KAT3 out, cleaned all connectorpins of the KAT3 and the connectors in the RF path.
Problem gone.

Arie PA3A


Op 13-5-2020 om 13:17 schreef Lou Kolb:

Thanks, guys, for all the suggestions. I have two antennas here, a
G5RV and a vertical for 2 and 440. The problem is present no matter
which antenna is inline. Both instalations are only a month old, both
using the Andrew equivalent to LMR400 with new, well protected
connectors. That's why I suspect the radio, but I'll look into
everything. Lou WA3MIX


Drew Vonada-Smith K3PA
 

Lou,

Easy test.  If you kick in an attentuator and the interference goes down about the same as signals, they problem is before the atten..outside the radio.  If the interference drops drastically with some atten, its likely overload within the RX.

73,

Drew K3PA


Keith_WE6R
 

Check the tightness of the center of the SO-239 Antenna socket. You can re-tension it with a sharp pin. Some of the older ones need it. (compare with ant 2 if you have a ATU).
If you have a P3, and the signals stay strong on it, but you loose them on the K3, we suspect the KREF3 board pin oxidation. Change them to gold or pull and re-seat or treat them. 
We may start doing gold pin swap on this board on all repairs but have not come to a decisive conclusion. 
Keith WE6R, Elecraft K3 Tech.