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Lucassheehan
Junior Member
Username: Lucassheehan
Post Number: 16
Registered: 4-2008
| | Posted on Tuesday, May 27, 2008 - 4:49 pm: | 
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I am setting up a second base station at home and have installed a new "Top One" antenna based on some of the great reviews I have read. I have the unit on a chimney mount with 20' of masting. The top of the antenna is about 45' up, so I'm hoping it will do well. I have an swr issue and below is what I have checked and tried.
SWR currently comes in at 2:1 ~ 2.5:1, which is UGLY. Tested with paradynamics meter, dosy meter and built in 148gtl meter. All readings are very close to the same.
1. Tried two different radios, both cobra mobile units. On my other antenna A99+GP they run great, swr is flat preformance is great so they are known good radios. No luck.
2. I have a frequency counter and amp in the mix so I removed all of that to see if it was a jumper problem. I also tested the jumpers, amps, meters on the known good setup and they were fine.
3. I dont have a replacment coax run to test that but its a brand new 75' length with ends put on by copper so I doubt any issue there.
4. All connections on the antenna bolts, coax, mouting etc... seem fine.
So any suggestions? Should I ground the antenna beyond the mount. Run a ground line to the house plumbing or even to the actual ground outside? If so where should I attache the ground on the unit? To the bottom ring of the antenna, the masting, they mount straps, somewhere on the top?
Thanks for any advice.
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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Foxhunter
New member
Username: Foxhunter
Post Number: 9
Registered: 4-2008
| | Posted on Tuesday, May 27, 2008 - 6:46 pm: |
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I haven't seen the antenna described but wonder---does it have ground plane radials built into the antenna? At that height you would likely be having issues with "lack of ground plane" without a reflective mass directly below the antenna. If you already do this is a moot point. Being so far off the ground the antenna starts to no longer "see" the earths ability to provide (moisture/soil conditions permitting) and that would be why many amateurs incorporate ground plane radials into the antenna scheme either at the antenna's base or into (or on) the ground, laying out refective radials to help with this issue. It would cause problems with SWR as you described. Do you think you fall into this category? |
Marconi
Advanced Member
Username: Marconi
Post Number: 763
Registered: 11-2001
| | Posted on Wednesday, May 28, 2008 - 2:56 am: |
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Can you check the continuity of this antenna? There are two threaded points to be noted during construction that can cause problems unless attached carefully and properly.
1) Care must be taken when installing the first 1/4 wave radiating element into the hub that contains the feed point. There is a small pin with-in the hub that can be broken if care is not taken during the process of screwing the element into this hub.
2) Care must also be taken when screwing the top element with the two wires into the top of the hub opposite the feed point. If this element is not screwed into the hub completely and properly then it will not make good continuity and will ill-affect how the antenna responds.
To aid in both areas I add a bit of petroleum jelly or lub to the threads. I also apply a little to the metal part of the aluminum tubing on each element where they touch the insulation material in the hubs. Both installation areas are tight fits with close tollerances and must be done with care and correctly. So, do not over tightened either.
The feed point alone, shield to center without the antenna being constructed, will show and open circuit, no continuity as you would expect. However, when the antenna is fully constructed with the bottom loop installed, the antenna will show continuity at all points on the antenna even at the feed point end of the coax and this is not as you might expect. |
Lucassheehan
Junior Member
Username: Lucassheehan
Post Number: 17
Registered: 4-2008
| | Posted on Friday, May 30, 2008 - 2:40 am: |
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Thank you! I will check this out. I'll be up there this afternoon and have a look.
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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Marconi
Advanced Member
Username: Marconi
Post Number: 764
Registered: 11-2001
| | Posted on Friday, May 30, 2008 - 7:22 am: |
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Lucas, this antenna is factory set and tuned for near the middle of the 11 meter band and requires no adjustments.
There are several caution notes in the instructions I have that talks about insuring a good electrical connection where the mast attaches to the hub of the antenna and do not let the mast extend above the top of the hub.
BTW, OHM's testing is also good for checking coax connections, but just to make sure I always check a new coax run with a good dummy load and meter for thru-put, before I install it. You always want to make sure you don't have a cable maker's patch in your coax run. Sometimes these patches aren't easy to detect even while running your hands over the coax. |
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