locked Power folds back on key downs #FT8 #transmit


echris488@...
 

I wonder if anyone has ever seen this problem. Every time my WSJTX keys down the power reduces during each key down.
At the start of every key down I put out about 35 W. It diminishes linearly and by the end of each key down it’s about 6 W.
I am still making QSO’s all over the world but this power issue has me scratching my head. This does not occur on transmit with any other mode on my Icom 746.

My antenna is a hustler 5B TV. I can see it from the ground that several of the adjustments on the Antenna are out of whack and I noticed too that my Antenna match is bad is bad n 40 and 80. I will fix it, however, my antenna is at Apparent one to one match on  10, 15 and 20 meters Where it also has the same power reduction issue.

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?


Dave
 

Chris,
My first guess is that the antenna has more problems than you can see from the ground.
Usually power is being cut back from the transmitter due to high reflected power.
The 5 band trap vertical probably was not made to work on 6 meters to start with.
The traditional verticals were meant to be ground mounted with buried radials.

Dave KC3AM

On 01/16/2021 22:31, echris488@... wrote:

I wonder if anyone has ever seen this problem. Every time my WSJTX keys down the power reduces during each key down.
At the start of every key down I put out about 35 W. It diminishes linearly and by the end of each key down it’s about 6 W.
I am still making QSO’s all over the world but this power issue has me scratching my head. This does not occur on transmit with any other mode on my Icom 746.

My antenna is a hustler 5B TV. I can see it from the ground that several of the adjustments on the Antenna are out of whack and I noticed too that my Antenna match is bad is bad n 40 and 80. I will fix it, however, my antenna is at Apparent one to one match on  10, 15 and 20 meters Where it also has the same power reduction issue.

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?





--
Hams should be seen as well as heard, 73, Dave KC3AM


Tom M0LTE
 

Hi

Any radio with a protection circuit is going to fold back the power if the SWR is high, regardless of mode.

My suggestion would be to improve your antenna system to make it a better match, and probably stop operating until you’ve done so.

Have you come across the NanoVNA? It’s incredibly affordable compared to the previous generation of VNAs and I would highly recommend it for visualising what’s going on with your antenna system, and improving it.

Cheers
Tom M0LTE

On Sun, 17 Jan 2021 at 03:31, <echris488@...> wrote:

I wonder if anyone has ever seen this problem. Every time my WSJTX keys down the power reduces during each key down.
At the start of every key down I put out about 35 W. It diminishes linearly and by the end of each key down it’s about 6 W.
I am still making QSO’s all over the world but this power issue has me scratching my head. This does not occur on transmit with any other mode on my Icom 746.

My antenna is a hustler 5B TV. I can see it from the ground that several of the adjustments on the Antenna are out of whack and I noticed too that my Antenna match is bad is bad n 40 and 80. I will fix it, however, my antenna is at Apparent one to one match on  10, 15 and 20 meters Where it also has the same power reduction issue.

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?





mchenryproj <mchenryproj@...>
 

I've found anything over about 1:2.0 SWR is where it starts shutting down power, at least on mine, and I believe this is the design of it. 2 and over will cause if to go into protection.

Sean
KB8JNE

Spell checked by the NSA.

On Sun, Jan 17, 2021 at 5:22 AM, Tom M0LTE
<tom@...> wrote:




Bill Somerville
 

On 17/01/2021 03:31, echris488@... wrote:

I wonder if anyone has ever seen this problem. Every time my WSJTX keys down the power reduces during each key down.
At the start of every key down I put out about 35 W. It diminishes linearly and by the end of each key down it’s about 6 W.
I am still making QSO’s all over the world but this power issue has me scratching my head. This does not occur on transmit with any other mode on my Icom 746.

My antenna is a hustler 5B TV. I can see it from the ground that several of the adjustments on the Antenna are out of whack and I noticed too that my Antenna match is bad is bad n 40 and 80. I will fix it, however, my antenna is at Apparent one to one match on  10, 15 and 20 meters Where it also has the same power reduction issue.

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?
Hi OM,

if you have working CAT control then make sure you have checked one of the "Settings->Radio->Split Operating" options, if not then ensure you only operate with Tx audio offsets between 1500 Hz and about 2200 Hz.

Your rig may have variable PA gain due to temperature, there's no harm in driving the rig into a bit of ALC indication on transmit so long as you are sure you are not over-driving the audio input. ALC action will keep the power level more even than open loop gain with no ALC and will be far less sensitive to temperate changes and small VSWR changes.

73
Bill
G4WJS.


Gary - AG0N
 

On Jan 16, 2021, at 20:31, echris488@... wrote:

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?
The first thing you need to do is do some serious testing into a dummy load. Using all the same settings, call a long CQ into the dummy load and see if the same thing happens.

Gary - AG0N


Brian Wilde
 

I am not familiar with the Icom 746, so my suggestions will focus on the antenna.

Remember there are differences between Digital and SSB/CW, primarily in that a Digital mode has constant forward power, where SSB/CW only puts out power when driven by audio.  You can see this if you look at a power meter during transmit: on SSB/CW, it fluctuates to your speech/keyer, but on Digital it stays at whatever power level you have set your rig to.  What this does do is heat up your finals and other components, as they do not have short "rest" periods.  You will also see devices like antenna tuners give ratings in SSB/CW and Digital - notice, as an example of one tuner, that they list 125W SSB/CW but only 30W Digital, it is due to the constant, no-rest type of transmission.  You will also hear lots of operators say they have no issue with using Digital at their rig's max power, others report they have blown their finals.  It is something to pay attention to.  Bill (G4WJS) also discussed this temperature issue in another reply to your post.

On to your antenna: I also have the 5BTV (added the 30m kit to make it a 6BTV), love it, works well for me.  Two items to consider:

Point #1: what do you mean "you can see from the ground that several adjustments are out of whack"?  Obviously, if not assembled correctly, it will cause issues.  If this was mounted in a different place and moved to a new home (like I just did), it is well worth the time to go through the setup again, as many things can affect it.

Point #2: When you say you "know" you have a 1:1 match on 10/15/20, and a terrible match on 40/80, how did you get those measurements?  Is that measured with an analyzer direct to the antenna, or is that the result of employing a tuner (external or internal to the Icom - I'm assuming it has one)?  
  • Using an analyzer of some sort (like a RigExpert or MFJ-259, or a NanoVNA like Tom M0LTE mentioned in his post) will give you the truest picture of how your antenna is performing.  The assembly instructions suggest you use it afterwards at the base of the antenna to give you a reasonable ballpark of your antenna, allowing you to keep making adjustments.  Your next step (IMO) is to go back to your rig and hook the analyzer in right there, so you are now measuring the entire pathway and any components (switches, chokes, ground/arrestors, etc) in the path that is between your rig and antenna.  You will likely see different numbers than from the antenna base measurement, they may be better or worse, but they may also be small enough to make no difference.  You will have to see what you get and decide if further antenna adjustments are needed.
  • If using a tuner to get a match, your antenna may need more work than you think.  An external tuner is WAY more forgiving than a rig's internal tuner, and can show you a good match even if the antenna is way out of line (some can tune 5:1 or 6:1 and make you think you are fine).  An internal tuner is not as powerful, most seem to be good up to about 3:1 (again, depends on the rig, this is just my experience).  So, you may think you have a good match on 10/15/20, but those aren't that hard to tune (the antenna is way more forgiving with its assembly at those frequencies due to their shorter lengths to the traps), but you may be way off of resonance.  40 will get trickier, and 80 is really dependent upon the length you cut the whip to (refer to the chart in the instruction manual) - even an external tuner will struggle with too far from the cut frequency (though I have had reasonable luck with it).
  • Finally, remember that a tuner just fools your rig into thinking the antenna is fine and delivering full power (at whatever level you set).  If the antenna is way out of alignment, you will still get lots of reflected power back.  So the rig "sees" a good match (from the tuner), starts high, sees power coming back towards it, lowers its output, still sees reflected power, lowers it output, still sees reflected power, and on and on ...  
Anyway, just my thoughts.  Spend the time with the antenna to make sure it is good and eliminate that from your checklist of items.

Good luck!

73,

Brian, N2OWD



On Sat, Jan 16, 2021 at 10:31 PM <echris488@...> wrote:

I wonder if anyone has ever seen this problem. Every time my WSJTX keys down the power reduces during each key down.
At the start of every key down I put out about 35 W. It diminishes linearly and by the end of each key down it’s about 6 W.
I am still making QSO’s all over the world but this power issue has me scratching my head. This does not occur on transmit with any other mode on my Icom 746.

My antenna is a hustler 5B TV. I can see it from the ground that several of the adjustments on the Antenna are out of whack and I noticed too that my Antenna match is bad is bad n 40 and 80. I will fix it, however, my antenna is at Apparent one to one match on  10, 15 and 20 meters Where it also has the same power reduction issue.

Could this all be from my out of tune 40 and 80 part of the antenna or do I have some other issue?



echris488@...
 

Thanks Dave good info.


echris488@...
 

Thanks Tom I will get an analyzer and check it.


echris488@...
 

Thank you for the advice of Sean!


echris488@...
 

Thank your Bill!! I’m going to digest everything you wrote. Also My split setting is set on “fake it”...


echris488@...
 

I will get a dummy load thank you very much for your time!!


echris488@...
 

Brian, thank you so much for taking the time to list all of that information. I will do exactly as you had suggested I think you are probably correct. I will report back with the answer.


Mark Pope <mpope@...>
 

Check if you are using the heavier power cable from the power supply to the radio

Had the same problem when going up beyond 50 watts and the power would bounce the radio and restart 

Hope that helps 




Osiyo!
Laissez les bons temps rouler 
Mark Pope
-.- -.. ..... .... ..- ...



On Jan 17, 2021, at 18:35, echris488@... wrote:

Thanks Tom I will get an analyzer and check it.



JP Tucson, AZ
 

Most 100 Watt rigs run 20-25A, so 
10 gauge wiring is recommended - as is stated also in many rig manuals.  

73 - John - N7GHZ


On Sun, Jan 17, 2021, 6:22 PM Mark Pope <mpope@...> wrote:
Check if you are using the heavier power cable from the power supply to the radio

Had the same problem when going up beyond 50 watts and the power would bounce the radio and restart 

Hope that helps 




Osiyo!
Laissez les bons temps rouler 
Mark Pope
-.- -.. ..... .... ..- ...



On Jan 17, 2021, at 18:35, echris488@... wrote:

Thanks Tom I will get an analyzer and check it.






mchenryproj <mchenryproj@...>
 

We all want you to succeed.  You’ll figure it out and be on the air in no time.  Be sure to let us know what you find too.

 

Sean

KB8JNE

 

Pushing quantum packets and wavelets your direction since the invention of the Internet.

 

From: echris488@...
Sent: Sunday, January 17, 2021 6:59 PM
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Power folds back on key downs #FT8 #transmit

 

Thank you for the advice of Sean!

 


Jim
 

Good evening everyone... I have another possibility that I didnt see mentioned.  ALC overshoot.  I noticed this in one of my older radios some time ago (an ic821) luckily I didnt have to fix the problem .. the radio died beforehand.. 

JIm K3YBN