| Author |
Message |
    
Lucassheehan
Junior Member
Username: Lucassheehan
Post Number: 13
Registered: 4-2008
| | Posted on Wednesday, May 21, 2008 - 3:08 pm: | 
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I was hoping someone could help me understand more of whats going on technically in the situation described below.
My SWR when testing is good, I have everything setup nicely and really have no problems. Things work great but I am curious on a back swing I get when modulating in the SWR meter reading. Mind you the backswing is ONLY on the SWR movement, power and mod swing nicely up where I expect. I don't think there is anything wrong but want to understand it better.
Radio <-> Amp <-> Meters <-> Antenna
Radio = Galaxy DX2517 (also saw this with 148GTL)
AMP = RM 300P
Meters = Libra 631
Antenna = A99 + GP
SWR when calibrated and measured is reading between 1.3:1 and 1.8:1, depending on power settings of radio and/or amp at dead key. When modulating the SWR back swings 0.2~0.3 units. What causes or could cause this? Again there is no back swing on the power or mod movements just the swr.
Thanks!
Lucas
Lucas "Mad Hatter" Sheehan
lucassheehan@gmail.com
CEF#0987
AM-27.165/27.265 2M-146.840
PDX, Oregon
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1861
Advanced Member
Username: 1861
Post Number: 725
Registered: 2-2004
| | Posted on Wednesday, May 21, 2008 - 4:02 pm: |
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PROBABLY HARMONICS |
Starface
Senior Member
Username: Starface
Post Number: 1934
Registered: 1-2005
| | Posted on Thursday, May 22, 2008 - 8:42 am: |
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does this also happen with the amp off?
George
CEF#Ø476
KI4NBE Amateur Extra
HAM#Ø181
CVC#ØØ14
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Bruce
Senior Member
Username: Bruce
Post Number: 4722
Registered: 9-2003
| | Posted on Thursday, May 22, 2008 - 12:04 pm: |
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RM 300P only use about 2 watts for full output how many are you using to drive it? I agree with 1861 if you are using over 3 watts harmonics are going to go through the roof.
On 6 since 66
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1861
Advanced Member
Username: 1861
Post Number: 726
Registered: 2-2004
| | Posted on Thursday, May 22, 2008 - 2:07 pm: |
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i used a kl 300p one time , swr was horrible , put in a good LP filter and fixed it right up |
Lucassheehan
Junior Member
Username: Lucassheehan
Post Number: 14
Registered: 4-2008
| | Posted on Friday, May 23, 2008 - 8:36 pm: |
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Hrm I was finding that I needed 2.5 to 3 watts to get full output though I rarely ran it on full. I like to hold to some degree of responsible band usage, just enough to get the job done. I was running 1.5 - 2 and still saw the same thing. I was also seeing the effect though much less dramatic run barefoot both at 2watts and turning the radio s up to about 6watts. I have since upgraded to a BLA300 and its gone. (really nice unit btw, great for its price!) One a side note I discovered I had some nasty interference from a light in the room and have fixed that I havent tested the 300P since then. I'll give it a try with out the RF bleed from the lighting and let you all know. Thanks for all the reponses.
CHeers,
Lucas
Lucas "Mad Hatter" Sheehan
lucassheehan@gmail.com
CEF#0987
AM-27.165/27.265 2M-146.840
PDX, Oregon
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Starface
Senior Member
Username: Starface
Post Number: 1936
Registered: 1-2005
| | Posted on Saturday, May 24, 2008 - 1:56 am: |
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hope all goes well
George
CEF#Ø476
KI4NBE Amateur Extra
HAM#Ø181
CVC#ØØ14
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