| Author |
Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 377
Registered: 4-2006
| | Posted on Thursday, May 17, 2007 - 12:38 pm: | 
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OK, in me attempt to eliminate noise, I went ahead and bonded my vans front hood to the rest of the frame of the van. I sanded all paint away, made really good contacts with the bolts, etc... But now I cannot tune my SWR's below 1.7 no matter what. If I raise the hood, the SWR's do go down to about 1.4. Weird. I thought bonding the hood would help. What is going on here? |
Dale
Advanced Member
Username: Dale
Post Number: 866
Registered: 12-2002
| | Posted on Thursday, May 17, 2007 - 8:25 pm: |
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sounds like your ground wire/stap is acting as
part of the radating antenna something like that.
is it 1.7 all thru the 11meter band?if so do you
have access to a mfj anylzer to check out of 11 meter band?
dale/a.k.a.hotrod
cef426
cvc#64
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Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 378
Registered: 4-2006
| | Posted on Thursday, May 17, 2007 - 9:17 pm: |
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Yes. 1.7 throughout. Channel 40 and channel 1 are 1.7. If I make the antenna longer, channel 1 stays at 1.7, but channel 40 goes higher on the SWR. And vice versa. In other words, 1.7 is the lowerst point I can get it to before it starts going back up. at 26.815, same thing (Well almost). Could the fact that the hood is so far away from the roof, that the antenna is looking to reflect off of both the roof and the hood? I know sounds weird. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3734
Registered: 7-2004
| | Posted on Friday, May 18, 2007 - 5:12 pm: |
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try going farther in & out with stinger to see if you are not resonant at 27.205. may be getting false reading of 1.7:1. |
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 379
Registered: 4-2006
| | Posted on Saturday, May 19, 2007 - 1:03 am: |
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I don't have the MFJ meter though. I tried moving both ways with the stinger. Eventualy going to both extremes, BUT it seems to tail off at 1.7 before it starts to rise again. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3737
Registered: 7-2004
| | Posted on Saturday, May 19, 2007 - 9:42 am: |
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see if it goes back down by removing the hood (extreme, yes, but....). then, try 'adjusting' the coils. spread THEM apart a bit, tighten them up, make sure the delrin spacer is centered inside the coils. in response to dale's suggestion, do you or anyone nearby, have an 'export' radio that goes much above & below your radio-to check swr there.
did you change ANYTHING else before you first noticed higher SWR? even different coax, length, routing, ground to amp, antenna, etc.... |
Hotwire
Senior Member
Username: Hotwire
Post Number: 2218
Registered: 1-2005
| | Posted on Saturday, May 19, 2007 - 6:34 pm: |
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What was the antenna SWR before you grounded the hood? Maybe ground the hood a different way? Only use no more than a foot or so of ground strap/braid?
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Dale
Advanced Member
Username: Dale
Post Number: 869
Registered: 12-2002
| | Posted on Saturday, May 19, 2007 - 7:42 pm: |
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i thought maybe his ground strap was radating
but not sure if thats it now?
dale/a.k.a.hotrod
cef426
cvc#64
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Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 380
Registered: 4-2006
| | Posted on Saturday, May 19, 2007 - 7:48 pm: |
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The SWR used to be about 1.2. Almost 1.1.1 on some channels. The ground wire I used is about 10 inches. It is 4 gauge monster wire. Stranded. Really good stuff. Matter of fact, it is the same wire I used to go from the amp to the fused panel I made which then in turn got powered by zero gauge cable. |
Tech237
Moderator
Username: Tech237
Post Number: 788
Registered: 4-2004
| | Posted on Sunday, May 20, 2007 - 8:46 am: |
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Use a flat strap for grounding. It is possible that the 1.7:1 you are now reading is correct and the earlier one was being thrown out by the ungrounded hood.
Simon
Tech237
KD7IEB
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Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 381
Registered: 4-2006
| | Posted on Sunday, May 20, 2007 - 5:36 pm: |
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Interesting. Will try the flat ground starp. I would think though that even with the wire I have now, I would be able to tune less than 1.7. Then again, you never know I guess. |
Tech237
Moderator
Username: Tech237
Post Number: 790
Registered: 4-2004
| | Posted on Sunday, May 20, 2007 - 7:21 pm: |
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I am not saying that you should not be able to, just that, that may be the more accurate reading. I would not be too concerned if you cannot get it much lower as you still have a very small loss at that level.
Simon
Tech237
KD7IEB
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Wildrat
Senior Member
Username: Wildrat
Post Number: 1308
Registered: 12-2003
| | Posted on Monday, June 25, 2007 - 9:48 am: |
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Have you grounded the body and engine to the frame?
I have also had a problem one time where the meter was giving a false reading till I touched it and the reading went down, so I ground my meter now.
Just an idea.
WILDRAT
Mark
27.285MHZ
CEF674
CVC029
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