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Author Topic: Tuning Ameritron AL-811  (Read 4009 times)
AC4R
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Posts: 18




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« on: October 13, 2006, 05:45:42 AM »

One thing I have noticed is the final tune doesn't end up near the suggested pre set numbers. I just bought my first amp an AL-811. I have read all of the tuning suggestions on this forum and need some feedback from you seasoned AL-811 users.

Heres is one I am doing. First off I am using a Kenwood TS-520D to drive the amp, and run the ARB 704 between the amp and the rig. I do not have the ALC hooked up from the interface to the amp. I start off tuning with 20 watts of drive and usually end up with 35 W of drive to produce 400 watts.
 I tune the load and plate controls using a watt meter for max power out, then crank in a little more load to reduce the grid current. After tuning at 20 watts drive I crank it up to 35 watts.From the posts I have read this seems to be what most are saying
 .On 3940 Mhz with 35 w drive the load is set on 1.2, plate 4.0 , an IP on 440, and grid current of 80 for 400 watts out.  On 7235 MHz with the same drive the load is 4.3, plate 7.2, with an IP of 450, and a grid current of 70 for 400 watts out. What say you ? Do these numbers look right, am I tuning the amp correctly. Your feedback is welcome.

TKS
73
AA4FH
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WB2WIK
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Posts: 20633




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« Reply #1 on: October 13, 2006, 09:32:54 AM »

The numbers in the book are based on tuning at MAX output power, which is ~600W and requires about 65W drive, and into a 50 Ohm dummy load.

Change the drive power, which will change the output power, and change the load, and of course your final settings will not agree with the published ones.  The published numbers are STARTING points for tuning, and really only applicable when running full drive/full power.

Never tune up with only 35W drive as the "final setting,"  with a TS-520S if you ever intend to use it on SSB.

The reason is: The amp will suffer and produce more distortion (IMD) than if you had tuned at full power.  And the reason for that is there's no way to turn the output power down in the SSB mode using a TS-520S.

The objective is to ALWAYS make your final tuning adjustments at the "most drive power" your transceiver can produce, so when you switch to SSB it will be properly tuned to accommodate peaks that high.

If you use only CW, where the TS-520S does have an output level adjustment, and want to ALWAYS run at reduced power (35W drive, or 400W output, or whatever), then it's okay to tune up at that level.

WB2WIK/6
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WD8PTB
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Posts: 670




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« Reply #2 on: October 13, 2006, 09:54:11 AM »

How to tune an amp is a sure way to get disagreement among hams. The only thing two hams will agree on is that the third ham is wrong.
    Diferent readings are normal for several reasons:
1. Your antenna is probably not exactly 50 ohms resistive. Even a 1.2:1 swr will effect your settings for max output.
2. Someone who wrote the manual picked those numbers. There will be minor variations of new units because of construction details and part tolerance.
3. The amp settings change slightly depending on the drive level. Someone loading to 550 mills will probably end up with different numbers than someone loading to 400 mills.
  As long as you have a reasonable SWR, resonable power out,plate, and grid current you are probebly doing it correct. Don WD8PTB
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KB9CRY
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Posts: 4283


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« Reply #3 on: October 13, 2006, 11:02:03 AM »

Do these numbers look right,
The numbers are only starting points.  They will change depending on the real impedance of the connected antenna system, etc.  The number you end up are the numbers you should have.  Also, when redoing things later, normally you'll be close to these numbers and any large differences would be a sign to check things out because something has changed.

am I tuning the amp correctly.
Your feedback is welcome.

You're following the right procedure but....

Are you tuning into a dummy load or live on the air?
Know that if on the air, you could be making QRM.

Always, always tune the amp for full output with full drive and then back down on your rig's knobs to achieve the power level you desire.  Steve described why you need to do this.

Phil
 

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AC4R
Member

Posts: 18




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« Reply #4 on: October 13, 2006, 03:40:20 PM »

My mistake I said TS520, it should have been a TS-570D. senior moment I guess as i owned a TS520 years ago. I am using a  TS570D to drive the amp going inot a Palstar At1km tuner. I tune the ant. flat using the tuner and 100 W drive from the 570D before I begin to tune the amp.
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WB9SFM
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Posts: 5




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« Reply #5 on: October 15, 2006, 12:10:40 PM »

You did not list whether or not you have the manual for the Amp. Here are staring points for the Ameritron 811 Amp. Make sure you check SWR close to 1.1 to 1 if you can tune that (i.e antenna tuner of direct tuning of the antenna).
MHZ ----      Plate  ----            Load    
_________________________
1.80  - -   - -1 1/2  ----          6 1/2
1.90  ----     3  ----              7 1/2
3.50 ----      5  ----              2
3.7  ----      6  ----              3
4.0  ----      6 1/2  ----          5 1/2
7.0 ----       8 ----               3
7.3----        8 ----               3 1/2
10.1 ----      7 1/2 ----           0
14.0 ----      9  ----              3
18.1 ----      9 ----              2 1/2
21.0 ----      9 1/2  ----          4
24.9 ----     9 1/2----            4 1/2
28.5 ----      9 1/2 ----           5

Again, these are starting point setting by Ameritron (from the manual). I hope this helps you.  
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WB9SFM
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Posts: 5




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« Reply #6 on: October 15, 2006, 12:29:26 PM »

That 1st listing is for a Aameritron 811 H amp. Please go the following link for the Ameritron 811 amp. Sorry for the listing earlier.

Here the Link:http://www.ameritron.com/man/pdf/AL-811.pdf
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WB9SFM
Member

Posts: 5




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« Reply #7 on: October 15, 2006, 12:30:03 PM »

That 1st listing is for a Ameritron 811 H amp. Please go the following link for the Ameritron 811 amp. Sorry for the listing earlier.

Here the Link:http://www.ameritron.com/man/pdf/AL-811.pdf
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