Topics

Powering off on TX


Lance Homer
 

It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


David Milligan
 

Your DC Power input powers to low 13.8 V Or it will shut off and reset every time


David P Milligan
N4URR 


On Apr 24, 2020, at 15:16, Lance Homer <k7lqh@...> wrote:

It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


Joe
 

On 4/24/2020 3:16 PM, Lance Homer wrote:
What's the best troubleshooting path?
The first thing I would look for is voltage sag on the DC power line when you key the radio. The easiest and best way to test for this is to look at the voltage at the connector for the external tuner. Pins 3&4 (farthest from the "V" end) should have the 13.8VDC (or thereabout) and should not drop very much when you key the radio at 50 watts.

This is the best test for DC power because it tells you what voltage is really getting inside the radio. This tests your power supply, power cable (including any connectors and fuses) and even the connector on the back of the radio. And, you don't even have to open the radio!

Let us know what you find.

73, Joe, K1ike


Chuck Scott
 

Lance:

First thing to do is to put a dummy load on the radio. I suspect that will work.

Next put a dummy load at the antenna. I also suspect that will work.

Then connect your antenna. Of course this is still going to give you trouble.

An antenna in an attic is often a trouble-maker. Even though the SWR is fine, there can still be common-mode currents on the transmission line and other stray RF issues. The G5RV is also a trouble-maker in this regard in that you have radiation not only from the dipole portion but also from the twin-lead portion and it's difficult to get the entire antenna separated far enough from wiring in the house and the rest of the feed-line headed toward the radio.

You should also note that there is no such thing as an RF ground for that kind of an installation in particular, but also in general. Even if you had ground wires to somewhere, those would also pick up energy and either conduct it to places you don't want it or re-radiate it where it can cause more trouble due to the proximity to the antenna.

In your situation, I suggest at least one good common-mode choke at the point where the transmission line connects to the antenna. Next, review the direction the transmission line is taking as it runs away from the immediate area of the antenna. Try to keep it perpendicular to the antenna and away from the twin-lead section of the antenna.

Since there will likely still be significant near-field coupling adding common-mode current to your transmission line, you might need to add common-mode chokes at various locations on the transmission line, including near the radio, to discourage this. It may also help to put chokes on the mic, power, and any other connections to the radio and on your power supply.

Lastly, don't be surprised that it would work initially and then have problems later. It might be that the cables, radio, and you have moved to a different position or that you operate on a frequency you haven't used before. The better you isolate the transmission line and radio from the near-field of the antenna, the better you'll be.

And of course there's another final comment. Wiring in your house, particularly that runs through the attic, will also conspire to convolute any possibility of you being completely free of stray RF. These are the things you live with when you have an antenna in the attic or elsewhere inside the house. You can also have the same problems with antennas outside that in in close proximity to the house.

Having said all that, I've used dipole antennas in an attic and even Slinky antennas tacked to a wall with good results. I hope you have the same.

Chuck - N8DNX


On 4/24/2020 3:16 PM, Lance Homer wrote:
It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  

_._,_._,_


don ---------
 

REMEMBER   Rf  can  cause  meters  to READ Hi  or  low  on  DC  voltages  while  transmitting 

Meter  or  digital  meters both are effected 

KA7qqv Don Alameda  CA

On April 24, 2020 at 12:39 PM Joe < k1ike_mail@... > wrote:


On 4/24/2020 3:16 PM, Lance Homer wrote:
What's the best troubleshooting path?
The first thing I would look for is voltage sag on the DC power line
when you key the radio. The easiest and best way to test for this is to
look at the voltage at the connector for the external tuner. Pins 3&4
(farthest from the "V" end) should have the 13.8VDC (or thereabout) and
should not drop very much when you key the radio at 50 watts.

This is the best test for DC power because it tells you what voltage is
really getting inside the radio. This tests your power supply, power
cable (including any connectors and fuses) and even the connector on the
back of the radio. And, you don't even have to open the radio!

Let us know what you find.

73, Joe, K1ike


don ---------
 

If  issue  dose  not happen on a  dummy load 

Issue is  RF related   

Did you try  with face plate on the  Radio ?
not  extended  from  radio body

Ka7qqv
Don Weber 
Alameda CA

On April 24, 2020 at 12:30 PM David Milligan <1proinv@...> wrote:

Your DC Power input powers to low 13.8 V Or it will shut off and reset every time


David P Milligan
N4URR 


On Apr 24, 2020, at 15:16, Lance Homer <k7lqh@...> wrote:

It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


 


don ---------
 

Great  Comments 

And  thoughts 

KA7qqv

On April 24, 2020 at 12:56 PM Chuck Scott <cscott@...> wrote:

Lance:

First thing to do is to put a dummy load on the radio. I suspect that will work.

Next put a dummy load at the antenna. I also suspect that will work.

Then connect your antenna. Of course this is still going to give you trouble.

An antenna in an attic is often a trouble-maker. Even though the SWR is fine, there can still be common-mode currents on the transmission line and other stray RF issues. The G5RV is also a trouble-maker in this regard in that you have radiation not only from the dipole portion but also from the twin-lead portion and it's difficult to get the entire antenna separated far enough from wiring in the house and the rest of the feed-line headed toward the radio.

You should also note that there is no such thing as an RF ground for that kind of an installation in particular, but also in general. Even if you had ground wires to somewhere, those would also pick up energy and either conduct it to places you don't want it or re-radiate it where it can cause more trouble due to the proximity to the antenna.

In your situation, I suggest at least one good common-mode choke at the point where the transmission line connects to the antenna. Next, review the direction the transmission line is taking as it runs away from the immediate area of the antenna. Try to keep it perpendicular to the antenna and away from the twin-lead section of the antenna.

Since there will likely still be significant near-field coupling adding common-mode current to your transmission line, you might need to add common-mode chokes at various locations on the transmission line, including near the radio, to discourage this. It may also help to put chokes on the mic, power, and any other connections to the radio and on your power supply.

Lastly, don't be surprised that it would work initially and then have problems later. It might be that the cables, radio, and you have moved to a different position or that you operate on a frequency you haven't used before. The better you isolate the transmission line and radio from the near-field of the antenna, the better you'll be.

And of course there's another final comment. Wiring in your house, particularly that runs through the attic, will also conspire to convolute any possibility of you being completely free of stray RF. These are the things you live with when you have an antenna in the attic or elsewhere inside the house. You can also have the same problems with antennas outside that in in close proximity to the house.

Having said all that, I've used dipole antennas in an attic and even Slinky antennas tacked to a wall with good results. I hope you have the same.

Chuck - N8DNX


On 4/24/2020 3:16 PM, Lance Homer wrote:
It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


 


James KB7TBT
 

Change the inline fuses and/or clean them up and reseat.



On 4/24/20 12:16 PM, Lance Homer wrote:
It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


Lance Homer
 

Yes, it was a power issue.  Voltage was dropping across ISOPWR on high TX power.  

73,
Lance Homer / K7LQH


Lance Homer
 

Yes, it was a power issue.  Voltage was dropping across ISOPWR on high TX power.  

73,
Lance Homer / K7LQH


don ---------
 

I had  bad  crimps on the  fuses  I  cleaned and  then Soldered the  original crimp connection 

Issue  resolved    on  decreased  power on  my 7000.

On April 24, 2020 at 2:08 PM James KB7TBT <kb7tbt@...> wrote:

Change the inline fuses and/or clean them up and reseat.



On 4/24/20 12:16 PM, Lance Homer wrote:
It has been a few years since using my rig, but quarantining is making me want to get back to the hobby.  I powered up the rig today and I'm having issues with the machine powering off when transmitting above 50W.  I've got an AT-7000.  On the antenna side the SWR is about 4 on the 40M freq. but radio is seeing 1.4 on the other side of AT-7000.    (Used Rigexpert)

When I check SWR via the 7000 directly, it doesn't show any SWR issues on tuned frequency but will shut off with power about 50W.  Moving it to an untuned frequency it does properly show SWR being high.

Antenna is G5RV JR in the attic.  Same one I had before and didn't have issues with powering off before.  

Rig and tuner aren't RF grounded (nor were they when it worked before).  

Balun in the attic.  No ferrite chokes.

What's the best troubleshooting path?  


 


Othmar S.
 

Lance, I think the only thing you have to do is cleaning the fuses,
many many more had this "issue", me included...
Take out the fuses and clean the contacts. Put hem in and out
a few times and then check the power again.
99% sure that the problem is solved this way.
Much better would be to swap the fuses and holders with
gold plated parts of car-HIFI.

Good luck !
73, Othmar, OE1SOW


Geoff
 

Hi Lance,

Make sure your power supply is not shutting down due to it being incapable of supplying the required current the radio needs when operating above 50 watts. If you operate on hf  in fm mode the  current can be in excess of 20 amps. Could be your power supply current limiting is kicking in.

Cheers
Geoff
VK3ZGW



On Sat, 25 Apr. 2020, 09:14 Othmar S., <oe1sow@...> wrote:
Lance, I think the only thing you have to do is cleaning the fuses,
many many more had this "issue", me included...
Take out the fuses and clean the contacts. Put hem in and out
a few times and then check the power again.
99% sure that the problem is solved this way.
Much better would be to swap the fuses and holders with
gold plated parts of car-HIFI.

Good luck !
73, Othmar, OE1SOW