It's been a while, but both of my TH7DXs were right on the manual specs
for SWR all bands. All bands bad is your best lead.
Could an element slipped position? or a bad balun? I heard disparaging
remarks about the balun, but others say it's FB. I've seen a fried
one. You could try a sleeve or type 31 ferrite choke balun in place of
the HyGain.
One more possibility - your MFJ is being overloaded by a nearby
transmitter, it is not frequency selective - any AM or FM transmitters
within a mile or two? Check the MFJ against a transmitted signal SWR
measurement.
Grant KZ1W
On 11/21/2011 4:39 PM, W5XB wrote:
> Hi Mike, Bob, Jim, Jim H., and other TH7 experts,
>
> Installer didn't show, got hung up on morning job that
> turned out to be a "monster," and I don't mean SteppIR
> Monster.
>
> So...against the XYLs protests, gathered tools and went up
> the tower...wasn't too bad, just took it easy.
>
> Found tuning rods 1/4" from boom to mast plate...loosened
> all the 3/8" nuts and rotated the rods about 3/4+" away.
>
> Found 10m director attach nut 1/4" from gamma match over it.
> Can't reach that far...so I got a wood wedge and raised rod
> to 1/2" + above attach point.
>
> Blew leaves off of roof--now that hurt.
>
> Checked with MFJ analyzer.
>
> 10m SWR 2:1 (never lower) from bottom up 800 KHz.
>
> 15m SWR 2.6 (best it gets) at 20.9 Mhz.
>
> 20m SWR 2.9 (best it gets) at 13.7 Mhz.
>
> The curves: 10m decreasing SWR from 28.0 Mhz and flat at
> 28.8
>
> 15m increasing SWR from 21.0 Mhz
>
> 20m increasing SWR from 13.7 Mhz
>
> This one has me, elements would appear to be long, sorta,
> but they are exact lengths former CW owner had reporting all
> SWR under 2:1
>
> Coax is LMR 400 which was fine on TA33 at a kw.
>
> So it is still something wrong in matching? Bad balun? Bad
> driven element traps?
>
> Ideas or past experiences welcome.
>
> 73s,
>
> Grant
> W5XB
>
>
> ----- Original Message -----
> From: "Mike Ryan"<mryan001@tampabay.rr.com>
> To: "'W5XB'"<w5xb@att.net>
> Sent: Sunday, November 20, 2011 8:15 PM
> Subject: RE: [TowerTalk] TH7 installed but not resonant
>
>
>> Grant, The TH7 differs from the TH6 in a number of
>> ways...lots of people
>> think they are the same antenna. They are decidedly no.
>> The TH7 has FIVE
>> elements on 10 meters. It was designed to be more broad
>> banded on that band.
>> I hope that you have a TRUED assembly manual. I read the
>> ideas passed to you
>> and the hints on what to look for. I had one up in
>> Virginia in the early 80s
>> and again ( the same antenna ) in the mid 90s. I thought
>> it was a great
>> antenna. Good luck with it. - Mike
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of
>> W5XB
>> Sent: Sunday, November 20, 2011 7:36 PM
>> To: Towertalk
>> Subject: Re: [TowerTalk] TH7 installed but not resonant
>>
>> Thanks, Jim, Bob, and Jim H.,
>>
>> Excellent suggestions all. I will summarize these and give
>> them all to him before he goes up the tower.
>>
>> Thanks guys, these were just the kind of ideas I was
>> looking
>> for.
>>
>> Cheers all around,
>>
>> 73s,
>>
>> Grant
>> W5XB
>>
>>
>> ----- Original Message -----
>> From: "Jim Hargrave"<w5ifp@gvtc.com>
>> To: "W5XB"<w5xb@att.net>
>> Cc: "Towertalk"<towertalk@contesting.com>
>> Sent: Sunday, November 20, 2011 5:52 PM
>> Subject: Re: [TowerTalk] TH7 installed but not resonant
>>
>>
>>> Grant,
>>>
>>> I would be concerned about the bolt. It could be shorting
>>> something out.
>>>
>>> I would also have him check the straps from the balun to
>>> the driven element.
>>>
>>> Also make sure the coax has not pulled out of the
>>> connector on the balun.
>>>
>>> Its also possible the link between the two driven
>>> elements
>>> was bent and
>>> shorted together during installation. These tubes cross
>>> over between the
>>> elements.
>>>
>>> 73s de Jim
>>> W5IFP
>>>
>>>
>>>
>>>
>>> > -----Original Message-----
>>> > From: towertalk-bounces@contesting.com
>>> > [mailto:towertalk-bounces@contesting.com]On Behalf Of
>>> W5XB
>>> > Sent: Sunday, November 20, 2011 3:02 PM
>>> > To: towertalk@contesting.com
>>> > Subject: [TowerTalk] TH7 installed but not resonant
>>> >
>>> >
>>> > Looking for help on my "new to me" TH7DX.
>>> >
>>> > Was not used couple of years, cleaned it up, read and
>>> used the
>>> > manual, put it together, and put it on top of an
>>> asphalt
>>> > shingle roof at 25 ft.
>>> >
>>> > Checked with MFJ analyzer, and found it resonant low,
>>> about
>>> > 13.7 Mhz as expected. The other bands were low too,
>>> but
>>> 10 m
>>> > was about 2:1. It "heard" almost as well as the TA33.
>>> Figured, all ok.
>>> >
>>> > Due to back injury (lawn mower accident!) can't climb
>>> right
>>> > now, so I had an installer take the TA33 down and put
>>> the TH7
>>> > up on 65' self supporting tower with no surrounding
>>> obstacles.
>>> >
>>> > Now the antenna is not resonant anywhere. Best SWR is
>>> 9:1 at 14
>>> > Mhz, resistance is 10 ohms, x=57. Coax checks with .9
>>> db loss.
>>> > The "hearing" is now about nil, like a wire hooked to
>>> a
>>> piece of coax.
>>> >
>>> > Have looked at the antenna with binoculars. The attach
>>> points
>>> > for both driven elements look as they should, but I
>>> can't see
>>> > the gamma match from the ground.
>>> >
>>> > The installer is not familiar with the TH7, but has
>>> put
>>> up
>>> > dozens of SteppIrs, and monobanders. He did mention
>>> something
>>> > about "adding a bolt near the Gama match tubes" ...
>>> not
>>> sure
>>> > what he did. Boom support is Philly Strand.
>>> >
>>> > Will of course show installer, the assembly manual and
>>> ask
>>> > about the added bolt.
>>> >
>>> > Installer is coming back Monday afternoon to check
>>> out.
>>> >
>>> > Any clues about what to check, greatly appreciated!
>>> >
>>> > Many thanks and 73s,
>>> >
>>> > Grant
>>> > W5XB
>>> >
>>> >
>>> > _______________________________________________
>>> >
>>> >
>>> >
>>> > _______________________________________________
>>> > TowerTalk mailing list
>>> > TowerTalk@contesting.com
>>> > http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>> _______________________________________________
>>>
>>>
>>>
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