| Author |
Message |
    
Galileo
| | Posted on Wednesday, June 19, 2002 - 11:54 am: | 
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Please help, using a MFJ antenna analyzer my KL300P is showing a 6 swr, and 20 ohms, my antenna on the other hand is showing 1.4 swr, and 51 ohms..I am using 2-2 foot rg58 jumpers between the radio, the amp, and my dosey meter and 50 foot of LRM400 to the antenna....Any help would be appreciated.....Thanks, Tom Shaw |
Marconi
| | Posted on Wednesday, June 19, 2002 - 1:57 pm: |
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Hey Tom, I guess you are taking the coax off the radio and pluging it into the MFJ, right? Of course you are seeing the system match to the antenna this way. Not a very good report, is it.
I have written a piece for the topic SWR that Taz started, but that thread got so disjointed due to some unintentional mis-direction that I just quit. Maybe I will post it anyway. Your rig is working fine, regardless, believe me when I tell you that. If you decide to get technical you will find that this business is very forgiving, but you can't tread too far away and still slide by.
We all need a lot of help with understanding the dynamics involved with line technology when using an amp. I am digging through some old notes to see if I have already addressed this issue. If I find them I will post.
In the mean time if you have a GOOD dummy load, start doing some checking, using various lengths of coax as we talked about the other day. Use your MFJ and the notations in their manual for 1/4 & 1/2 tuned lines. You mention only the impedance and the SWR when describing your MFJ test as noted above. You need to begin to concentrate on frequency, and the reactance (X value) as this is very releveat to matching for a balanced thru-put to the antenna. A GOOD dummy load means one that is non-reactive and show what it should over a pretty good bandwidth.
The MFJ manual is not a Dick-Jane-Spot reader either. It can be difficult.
Good luck with your new meter, I will get back to you soon.
Marconi |
Galileo
| | Posted on Wednesday, June 19, 2002 - 1:18 pm: |
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Does this amp have to have anything done to it to work propely on 11 meters, it was purchased from Coppers..Thanks |
Ss8541
| | Posted on Wednesday, June 19, 2002 - 8:14 pm: |
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one quesion here, is the mfj causing the 300p's relay to close?? i have never seen one even have enough output to close the relay on any amp. even if it is closing the relay, there isn't enough input to the rf trans for them to work properly(which if it is class c they won't be 'active' at all with this low of an input). this in return will show a bad swr due to the very very low input.
there is a way to test an amp's input/output match/swr with an mfj, but this requires replacing the amps base and collector with resistors to gnd. you also have to know what impedance the base and collector is at during 'proper' operation/drive level for this to work. |
Galileo
| | Posted on Wednesday, June 19, 2002 - 4:53 pm: |
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Hey Marconi,
Its not my meter, but a friends..All test were done at 27.305, which I believe is channel 30..I also did a graph for the antenna, like you suggested..I will try some different lenghts of coax..I just was not expecting the high swr, I was thinking that the input should be around 50 ohms...Also with this unit I seem to have alot of splatter,and bleedover, which I did not have with the KL200, or the KL40...No other changes have been made to the radio...1.5 watt drive swinging to about 5 or 6 watts...As always thanks for your input.....Tom Shaw |
Galileo
| | Posted on Thursday, June 20, 2002 - 7:11 pm: |
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Good point Ss8541, I hadnt thought of that..Marconi told me the same thing....You guys never cease to amaze me...Thanks....Tom Shaw |
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