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Message |
    
Showtime
New member
Username: Showtime
Post Number: 9
Registered: 2-2007
| | Posted on Sunday, April 08, 2007 - 6:16 pm: | 
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here is the problem im haveing .. the ant. is a laser 400 the coax is lmr 400 gamma m are 10.000w when i get the swr down on the flat side the last strap that holds the gamma rod to the element is right up net to the capacitor..the big white insulator .... will this hurt anything??? when i had the 213 on there they both tuned fine 1.1 or 1.2 why is that??? thanks for any help... showtime in ga.. |
Tech833
Moderator
Username: Tech833
Post Number: 1650
Registered: 8-2002
| | Posted on Monday, April 09, 2007 - 11:01 am: |
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No problem on the cap. As for a difference in tuning from one coax to another... Hmmm... Was one of the coax runs (new or old) damaged in any way? I would be highly suspicious.
Although, it it not at all uncommon when changing from high-loss to low-loss coax, that SWR can climb and bandwidth be reduced. This is because the low loss cable can appear to reflect more, when actually, it is losing less power both directions. |
Dale
Advanced Member
Username: Dale
Post Number: 735
Registered: 12-2002
| | Posted on Monday, April 09, 2007 - 11:03 am: |
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well all i know is the lmr400 is much better quality.i got lmr400 hooked to my imax2k.when i switch from rg8 to lmr400 my swrs went up slighty but still only about a 1.2.was told that
being the lmr-400 had less loss that it had more accurate swr then the 213
dale/a.k.a.hotrod
cef426
cvc#64
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Marconi
Advanced Member
Username: Marconi
Post Number: 690
Registered: 11-2001
| | Posted on Monday, April 09, 2007 - 4:30 pm: |
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I would check the coax using a good dummy load and see what the thru put and SWR is. |
Showtime
Junior Member
Username: Showtime
Post Number: 10
Registered: 2-2007
| | Posted on Monday, April 09, 2007 - 7:07 pm: |
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the 213 was about 1 1/2 yrs old.. the lmr is brand new!!! with 259s on one end and the other is hard wired i put a copper braid around the shield and solder it to the shield and drilled it to the boom.... dont think that has any thing to do with it.... is there a nother way???? thanks for the help guys...i got the last strap right up next to the cap .and it was going down but i cant slide the strap any futher!!! |
Marconi
Advanced Member
Username: Marconi
Post Number: 691
Registered: 11-2001
| | Posted on Monday, April 09, 2007 - 7:55 pm: |
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That sure doesn't sound right to me Showtime. These two coaxes may react a little differently, but I wouldn't think it would be as much as you note. Since the coax is new, I would check it for thru-put as noted above. I have purchased long runs 50'+ and have found impedance bumps where the manufacture mended two pieces of coax together. If this is what you have you might be able to feel the bump in the coax if you check it. These bumps are probably not all that uncommon and are done for convience in making 500' spools.
Also, the pigtail you made to connect to the antenna is supposed to be kept very short. Sounds like you may have a problem there also, but not sure. How long is the pigtail from where the center and shield seperate to the end? |
Showtime
Junior Member
Username: Showtime
Post Number: 11
Registered: 2-2007
| | Posted on Monday, April 09, 2007 - 9:40 pm: |
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maybe a foot with the pigT...i got the antenna about a foot off the ground and on V i got a1.2 on H 1.4 but the strap is touching the cap lol when they go do u think they will come down? if not thats kinda difeating the purpose do u think? |
Showtime
Junior Member
Username: Showtime
Post Number: 12
Registered: 2-2007
| | Posted on Monday, April 09, 2007 - 9:42 pm: |
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need someone i can contact lol not to good at this typing lol
Moderator Note!
You can contact other Copper Forum Members by clicking on their name in their post and it will bring up their e-mail address/contact information. |
Marconi
Advanced Member
Username: Marconi
Post Number: 692
Registered: 11-2001
| | Posted on Tuesday, April 10, 2007 - 11:09 am: |
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Your pigtails are probably too long and are affecting the tune length of the gamma rod and thus is likely why the tap bracket is coming up very close to the boom.
Did you have that ground idea attached to your 213 coax when using it before when the gammas tuned up normally along the lines of Maco's construction documents?
What is the point of adding the grounding feature? |
Showtime
Junior Member
Username: Showtime
Post Number: 13
Registered: 2-2007
| | Posted on Wednesday, April 11, 2007 - 8:13 pm: |
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well with the 213 i only had the shield striped back about 5-6in. and as far as the ground go's the 10k gammas i got dont have the 259 hook up so i had to hard wire it and i figuredu i had to grond the shield to the boom..well i soldered a braid to the shield and put it to the boom.... but there is about a foot or more of coax with out the shield going to the gamma....thanks.. |
Marconi
Advanced Member
Username: Marconi
Post Number: 694
Registered: 11-2001
| | Posted on Friday, April 13, 2007 - 7:26 am: |
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The feeding end of the coax should be laying along side of the boom and the end of the gamma should be very near the center of the boom. Thus both attachment points are very close together and should allow for a very short pigtail connection just like your 213 coax was. Try that.
I don't think having the shorting strap closer to the boom will hurt, but I believe you are saying you are out of adjustment and probably having the pigtails so long is why.
You can use SS hose clamps to secure both ends of the pigtails to the gamma and the boom, but keep them short and protect them both from moisture. |
