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Author Topic: RF Leak/Coax  (Read 3199 times)
W9GB
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Posts: 2597




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« Reply #15 on: January 17, 2013, 08:52:31 AM »

Quote from: KK4NJC
I have a dipole up.  I got the IMAX 2000 vertical as advice from a couple of local hams.
LOTS of Bad Advice out there, especially from the former CB/pirate operators looking to sell their bad purchases ($$$) to a new operator.

SO, now you know a couple of amateurs to not ask for advice in future (not Elmers).
===
You have a dipole.  HEIGHT is a key requirement for antennas !!
« Last Edit: January 17, 2013, 08:54:51 AM by W9GB » Logged
AC2EU
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Posts: 331


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« Reply #16 on: January 17, 2013, 08:57:01 AM »

I have a dipole up the I got the vertical at the adviae of a couple of local hams

It happens.
You will get lots of "shoot from the hip advice" as you continue in the hobby. The best thing you can do is research the advice before you act on it. Some will be good, some will be what happened to you...

When I started a few years back, a seasoned ham of 30 or so years experience suggested that I put up a G5RV !!!!  Huh  Roll Eyes  After looking into it , I decided that it wasn't for me!  Grin
« Last Edit: January 17, 2013, 08:59:02 AM by AC2EU » Logged

YONU
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Posts: 57




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« Reply #17 on: January 17, 2013, 08:58:55 AM »

I just went and tried the dipole and I get the same result on and stuff acting up I only have the dipole up about 15ft at moment since I was tuning it.
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WB2WIK
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Posts: 20542




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« Reply #18 on: January 17, 2013, 10:30:08 AM »

I have a dipole up the I got the vertical at the adviae of a couple of local hams

I would suspect those local hams were also fairly new.

Any old-time hams in your area with a lot of antenna expertise?
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YONU
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Posts: 57




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« Reply #19 on: January 17, 2013, 10:40:29 AM »

Yeah the one that sold it to me he is going on 50yrs now
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W9GB
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Posts: 2597




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« Reply #20 on: January 17, 2013, 10:44:15 AM »

Quote from: KK4NJC
I just went and tried the dipole and I get the same result on and stuff acting up I only have the dipole up about 15 feet, at moment since I was tuning it.

1.  Get the antenna UP, away from the operating position.

2.  Get a Choke balun at that dipole feed point.

3.  You said you were using some RG-58/U coaxial cable (unknown source).
Coaxial cable needs to be GOOD QUALITY (shielding) -- stay with KNOWN brands with properly installed PL-259 connectors.  SHOP at the major amateur radio stores.
AVOID the olde CB shops, truck stops, and garage sellers easily found in SE USA, at this point.

4.  Pick up telephone and talk to Pres Jones, N8UG at The Wireman in Landrum, SC.  
I have known Pres for over 30 years -- this is the person you ask for advice from --
for your DIY antenna supplies. (coax cable, antenna wire, insulators, rope)

http://www.thewireman.com/

Quote
Yeah the one that sold it to me he is going on 50yrs now
Birth age means nothing.  Passing an amateur radio FCC license since 2000 only means you can memorize multiple choice questions and answers.
Selling an IMAX 2000 to you tells me he was likely into CB (maybe since 1970s CB craze) and only became an amateur after 2000, when the FCC dropped Morse Code requirement.

Quote from: AC2EU
When I started a few years back, a seasoned ham of 30 or so years experience suggested that I put up a G5RV !!!
After looking into it , I decided that it wasn't for me!  
In early 1970s, I got some good advice and bad advice about antennas.
Using SOLID Copperweld wire for my simple Novice antenna was BAD advice.  #14 AWG Stranded copper wire would have been a better recommendation.

w9gb
« Last Edit: January 17, 2013, 10:57:49 AM by W9GB » Logged
AC2EU
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« Reply #21 on: January 17, 2013, 11:08:22 AM »

I just went and tried the dipole and I get the same result on and stuff acting up I only have the dipole up about 15ft at moment since I was tuning it.


If you have a resonant dipole you should be able to use it without a tuner. If you have problems at the resonant frequency, I would suspect that you have connection or coax problems. One of the things I see a lot with other hams' installations are badly soldered pl 239 connectors.
Earth grounding the coax before it enters the shack is still a good idea no matter what the problem turns out to be.

You are going to have to do some troubleshooting...
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YONU
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Posts: 57




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« Reply #22 on: January 17, 2013, 11:42:08 AM »

well I will go resolder the 239 to earch ground the coax can I simply solder a wire to the 239 outside or do I need to get a grounding block
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YONU
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Posts: 57




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« Reply #23 on: January 17, 2013, 12:58:05 PM »

ok I just redid the 239 on the Dipole and that helped some,  when I said 50 I mean as in 50yrs as a HAM, I put a choke Balun on the Dipole I can tell if that helped or not.  As to getting it away from the shack there is only so far I can move it atleast not without major cable runs in excess of 200ft
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G8HQP
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Posts: 120




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« Reply #24 on: January 18, 2013, 08:41:49 AM »

When someone tries to sell you an antenna never believe what he says, especially if:
1. the antenna is second-hand, or
2. the antenna is new, or
3. he says it doesn't need a balun/ground/counterpoise.

Most antennas need one of the items mentioned in point 3. If not given it they will use your feed cable and shack equipment as a balun/ground/counterpoise. About the only exception is a dummy load masquerading as an antenna, which will 'work' quite happily and give low SWR with no assistance.
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YONU
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Posts: 57




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« Reply #25 on: January 18, 2013, 08:54:07 AM »

I actually took it down myself so let me ask this he had to mounted to a Aluminum mast drove in the ground with a ground wire on the mast could that be why he said it didn't need radials?  (Sorry I am very bad for giving folks the benefit of the doubt)
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N1UK
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Posts: 1390




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« Reply #26 on: January 18, 2013, 11:16:00 AM »

Quote
I actually took it down myself so let me ask this he had to mounted to a Aluminum mast drove in the ground with a ground wire on the mast could that be why he said it didn't need radials?  (Sorry I am very bad for giving folks the benefit of the doubt)


It may well have worked for him. He has a different setup and a different length of feedline etc etc.

I hear that a lot of locals use the Antron vertical on 10m. Have you looked at that.

There is a lot of incorrect and half information on the local repeaters. You need to listen and filter it carefully.

Looks like lots of good advice here though.

Mark N1UK
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YONU
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Posts: 57




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« Reply #27 on: January 18, 2013, 11:44:31 AM »

Well that makes sense and yeah I am learning about filtering the info

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WB6BYU
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Posts: 13010




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« Reply #28 on: January 18, 2013, 12:11:11 PM »

Quote from: N1UK

It may well have worked for him. He has a different setup and a different length of feedline etc etc.



Mark has a good point to remember.  What "works" for one ham may not "work" for another
if their situations, operating habits, or expectations are different.

This is especially true for common mode current problems, because the severity of the
problem depends on the length of feedline, what is connected to the station at the other
end, the operating frequency, and, in the case of interference, the sensitivity of the
other equipment to stray RF pickup.

For example, if his mast was 1/4 wavelength long (about 9 feet), it would provide a good
RF ground if it were insulated from the ground at the base, but would be a poor ground
if the base were actually connected to ground.  With a half wave mast (about 17') the
opposite is true.  The same goes for the length of coax and what is connected to it at
the shack end:  if that presents a high impedance, common mode currents will be small.
With a low impedance, they can be higher.  This can change based on such things as
plugging in a set of headphones with the wrong length cord.


I also have to add that the number of years being a ham (or class of license) does not
necessarily imply a good understanding of technical issues.  Unfortunately, many hams
get stuck in their ways as they age, and their misconceptions get solidified to where
they no longer search for the truth, and can't recognize or accept it if they happen to
bump into it by accident.

You can also see, on these forums as in other places, that often hams giving advice
assume that the other person is interested in the same aspects of the hobby.  You'll
get different answers about 80m antennas from an active DXer or a rag chewer, for
example, because they have different needs for radiation patterns.  That's not to say
that either is wrong, but rather that you need to gauge how well their operating
style matches yours to tell which is more appropriate to your needs.

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VE1CZ
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Posts: 70




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« Reply #29 on: January 21, 2013, 07:16:17 PM »

I have been using a Imax 2000 for a few years now and no problems with RFI.It is mounted on a tripod on the garage roof on a mast about 12 feet.I hang my 80 meter inverted v and a 40 meter delta loop below that, as well as a coaxial choke at the base of the antenna with absolutely not RFI issues,but the antenna is mounted about 50 feet away from the house and very close to the sat.dish,works for me!
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