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Author Topic: Tuning a linear into a dummy load  (Read 5365 times)
KM3F
Member

Posts: 509




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« Reply #15 on: March 22, 2013, 01:53:15 PM »

A point that nobody seems to pay attention to.
You hear a tune up by the tone.
That station is 'not' on  or zero beat to your frequency.
Why, he is either up or down frequency but within the 'passband' of your receiver and causes more QRM than if it were right on 'zero beat' to your frequency. It make be laugh to hear comments about tuning the tuner-upper will never hear.
Said another way, moving up or down 'less' than 4000  to tune will cause QRM to the intended frequency.
When you tune, move 5 or more and then you may still cause QRM to some other QSO for the same reason.
Tuning an amplifer: Are you gong to tune directly into a load for a tank match to 50 ohms?
Then return to the Tuner and tune again for it's best setting?
That's two actions.
Everybody wants to see a flat match when 99% of the time it's not necessary unless your antenna system is so bad with common mode feedback that it causes audio problems. If so, fix the antenna and understand what your doing with all this..
Good luck.
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KC4MOP
Member

Posts: 743




Ignore
« Reply #16 on: March 23, 2013, 12:06:15 PM »

A point that nobody seems to pay attention to.
You hear a tune up by the tone.
That station is 'not' on  or zero beat to your frequency.
Why, he is either up or down frequency but within the 'passband' of your receiver and causes more QRM than if it were right on 'zero beat' to your frequency. It make be laugh to hear comments about tuning the tuner-upper will never hear.
Said another way, moving up or down 'less' than 4000  to tune will cause QRM to the intended frequency.
When you tune, move 5 or more and then you may still cause QRM to some other QSO for the same reason.
Tuning an amplifer: Are you gong to tune directly into a load for a tank match to 50 ohms?
Then return to the Tuner and tune again for it's best setting?
That's two actions.
Everybody wants to see a flat match when 99% of the time it's not necessary unless your antenna system is so bad with common mode feedback that it causes audio problems. If so, fix the antenna and understand what your doing with all this..
Good luck.
Really a pretty good idea to reduce the deafening tone of tuner-upper. Zero-beat and quickly make adjustments.
I'm gonna try that from now on.
TNX
Fred
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KH2G
Member

Posts: 306




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« Reply #17 on: March 30, 2013, 01:12:35 PM »

Regarding the dummy load rating. Let us not forget the difference between PEP and AVG DC INPUT. 1500W PEP is not 1500 W out of the amp except on peaks which are of short duration. Peak Envelope Power  is not Average Power .A KW Dummy load will handle 1500 W PEP with no problem unless you stay key down for extended period. The Heath Canteena was Rated under AVG DC INPUT Smiley
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N4CR
Member

Posts: 1672




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« Reply #18 on: April 01, 2013, 04:11:47 PM »

Regarding the dummy load rating. Let us not forget the difference between PEP and AVG DC INPUT. 1500W PEP is not 1500 W out of the amp except on peaks which are of short duration. Peak Envelope Power  is not Average Power .A KW Dummy load will handle 1500 W PEP with no problem unless you stay key down for extended period. The Heath Canteena was Rated under AVG DC INPUT Smiley

This is a thread about tuning an amp into a dummy load. Nobody tunes an amp with voice input.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
KD0UN
Member

Posts: 58




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« Reply #19 on: April 03, 2013, 04:13:21 PM »

Real world:   Initial settings obtained on a dead band.  In the future return to logged settings and tune for max with a series of dits. 5-10 seconds on a clear freq.
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WB5PGX
Member

Posts: 13




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« Reply #20 on: April 04, 2013, 04:12:25 AM »

So, are you saying it is ok with an amp to just tune into the dummy load and then switch to the antenna and transmit without tweaking as long as the antenna is fairly resonant?
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NO2A
Member

Posts: 800




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« Reply #21 on: April 04, 2013, 07:43:28 PM »

I would retweak the plate cap just to be sure. It only takes a second and will give you piece of mind.
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W9KDX
Member

Posts: 770




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« Reply #22 on: April 06, 2013, 04:49:49 PM »

Thanks again for all the feedback.  As it takes me just seconds to do the complete tune up and most here agree that you need to re-tune on the real antenna, it kind of makes no sense to waste time on a dummy load.
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Sam
W9KDX
NA0AA
Member

Posts: 1042




Ignore
« Reply #23 on: April 08, 2013, 07:57:21 PM »

Since I'm using a tuner into a 160 meter loop, I always have to tune the tuner first - and what I have found with my AL-80B is that provided I'm close to 1:1 on the tuner, I can use my pre-set numbers and get so close as to not worry - these pre-sets all developed with dummy load and some on-air testing with dead bands. 

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