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Author Topic: Power out increases until the load cap is 100 % meshed  (Read 13552 times)
W8JX
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Posts: 13268




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« Reply #15 on: February 02, 2018, 07:53:30 AM »

It means you aren't driving the amp hard enough when tuning.

Not so sure as he is getting 1200 watts out at current drive level.
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM4AH
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Posts: 955




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« Reply #16 on: February 02, 2018, 07:54:35 AM »

That will be the simplest thing to try. The tuning is such that the Load Cap on 75 has little dramatic effect. I mean you can find a peak output, but 1/4 turn in either direction won't make 50 watts out difference. Matter of fact on 40 you can unmesh the cap from 0 up to 20 on the dial and won't lose 50 watts. Running about 75 watts drive and 1200 or so out.

Try swapping both, placing 80m 750 pf on 40m and 40m 500 pf cap on 80.


Well, I can drive it with 200 watts if necessary and try what QE says.

I can swap them easy enough, famous last words.
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AF6LJ
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Posts: 582




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« Reply #17 on: February 02, 2018, 08:31:14 AM »

That will be the simplest thing to try. The tuning is such that the Load Cap on 75 has little dramatic effect. I mean you can find a peak output, but 1/4 turn in either direction won't make 50 watts out difference. Matter of fact on 40 you can unmesh the cap from 0 up to 20 on the dial and won't lose 50 watts. Running about 75 watts drive and 1200 or so out.

Try swapping both, placing 80m 750 pf on 40m and 40m 500 pf cap on 80.


Well, I can drive it with 200 watts if necessary and try what QE says.

I can swap them easy enough, famous last words.
Have you checked the input VSWR to make sure the transmitter is seeing a more, or less fifty ohm load??
That will cause the same thing to happen.
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Take Care
Sue,
AF6LJ

Don't Kalifornicate My Life
N3QE
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Posts: 5587




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« Reply #18 on: February 02, 2018, 08:59:13 AM »

It means you aren't driving the amp hard enough when tuning.

Not so sure as he is getting 1200 watts out at current drive level.

Just because he's getting 1200 Watts PEP out under voice modulation, doesn't mean he has really tuned the amp up, especially the load control.

I was ham for 40 years before I really learned the foibles of "tuning up" using voice modulation and how this often results in a non-optimal position on the load knob.
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W8JX
Member

Posts: 13268




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« Reply #19 on: February 02, 2018, 09:46:33 AM »

It means you aren't driving the amp hard enough when tuning.

Not so sure as he is getting 1200 watts out at current drive level.

Just because he's getting 1200 Watts PEP out under voice modulation, doesn't mean he has really tuned the amp up, especially the load control.

I was ham for 40 years before I really learned the foibles of "tuning up" using voice modulation and how this often results in a non-optimal position on the load knob.


A carrier/steady tone is best for tuning but depending how you use you voice tuning it can be done that way too in a pinch. 
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM4AH
Member

Posts: 955




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« Reply #20 on: February 02, 2018, 11:11:47 AM »

It means you aren't driving the amp hard enough when tuning.

Not so sure as he is getting 1200 watts out at current drive level.

Just because he's getting 1200 Watts PEP out under voice modulation, doesn't mean he has really tuned the amp up, especially the load control.

I was ham for 40 years before I really learned the foibles of "tuning up" using voice modulation and how this often results in a non-optimal position on the load knob.


A carrier/steady tone is best for tuning but depending how you use you voice tuning it can be done that way too in a pinch. 


Actually I'm using a pulser or pecker . Not sure I want to use a higher duty cycle until I figure out a little more about what is going on.
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KM4AH
Member

Posts: 955




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« Reply #21 on: February 02, 2018, 11:13:14 AM »

That will be the simplest thing to try. The tuning is such that the Load Cap on 75 has little dramatic effect. I mean you can find a peak output, but 1/4 turn in either direction won't make 50 watts out difference. Matter of fact on 40 you can unmesh the cap from 0 up to 20 on the dial and won't lose 50 watts. Running about 75 watts drive and 1200 or so out.

Try swapping both, placing 80m 750 pf on 40m and 40m 500 pf cap on 80.


Well, I can drive it with 200 watts if necessary and try what QE says.

I can swap them easy enough, famous last words.
Have you checked the input VSWR to make sure the transmitter is seeing a more, or less fifty ohm load??
That will cause the same thing to happen.

I will. Just finished putting a floor pan in my 81 F150. Worn out right now.
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W1QJ
Member

Posts: 2966




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« Reply #22 on: February 02, 2018, 03:19:32 PM »

What model amp?

It is an Amp Supply LK500NTB  No Tune that has been converted to a standard tune.  The workmanship is beautiful, but something is a little off on 40 .

Increase value of capacitor in 40m circuit 20% or so.

What capacitor are you talking about?Huh?
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W8JX
Member

Posts: 13268




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« Reply #23 on: February 02, 2018, 04:00:16 PM »

What model amp?

It is an Amp Supply LK500NTB  No Tune that has been converted to a standard tune.  The workmanship is beautiful, but something is a little off on 40 .

Increase value of capacitor in 40m circuit 20% or so.

What capacitor are you talking about?Huh?

Its explained in thread
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM4AH
Member

Posts: 955




Ignore
« Reply #24 on: February 02, 2018, 04:51:04 PM »

What model amp?

It is an Amp Supply LK500NTB  No Tune that has been converted to a standard tune.  The workmanship is beautiful, but something is a little off on 40 .

Increase value of capacitor in 40m circuit 20% or so.

What capacitor are you talking about?Huh?

Its explained in thread


OK JX .   I swapped the 40 meter 500PF with the 75 meter 750PF and now it loads at about 39 instead of 0  on 40 meters. 75 loads about the same.

You can only creep up drive a few watts at a time because if it is even slightly out of tune something starts chattering. Not sure what that is all about. Seems to be 60 cycle whatever it is.

As long as it is in tune seems to play OK

Incidentally, tuning with a pulser and RTTY tunes at exactly the same place.
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W1QJ
Member

Posts: 2966




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« Reply #25 on: February 02, 2018, 07:14:25 PM »

That amp with a proper load cap does not need any padding on 40 meters.  It obviously has the wrong load cap when someone made the conversion.
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KM4AH
Member

Posts: 955




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« Reply #26 on: February 02, 2018, 11:44:03 PM »

That amp with a proper load cap does not need any padding on 40 meters.  It obviously has the wrong load cap when someone made the conversion.

I don't doubt it. But, he did the project for free for a friend. Didn't charge for parts, shipping, or anything. Looking a gift horse in the mouth sort of thing I suppose.
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W1QJ
Member

Posts: 2966




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« Reply #27 on: February 03, 2018, 01:59:17 AM »

All right then fine but if you are called upon to make repairs why not do it right?  The correct load cap is about $35.  Cheap is dear.  You get what you pay for. 
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KM4AH
Member

Posts: 955




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« Reply #28 on: February 03, 2018, 05:18:01 AM »

All right then fine but if you are called upon to make repairs why not do it right?  The correct load cap is about $35.  Cheap is dear.  You get what you pay for. 

Well, If it can be explained to me why it will play one bit better with the correct loading cap than it will having to add another pad for 40 meters maybe I will.
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W1BR
Member

Posts: 4189




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« Reply #29 on: February 03, 2018, 06:27:58 AM »

All right then fine but if you are called upon to make repairs why not do it right?  The correct load cap is about $35.  Cheap is dear.  You get what you pay for. 

Well, If it can be explained to me why it will play one bit better with the correct loading cap than it will having to add another pad for 40 meters maybe I will.


It will increase the tuning and impedance matching range.
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