I have tried an aftermarket balun on my TH7. It didn't work very well. I had
high SWR on most bands. Changed nothing but the balun and everything came
into specification.
I use a BN-86 and run 1500 watts on RTTY contesting. Never had a problem in
15+ years of running TH6 and TH7 antennas. I do pop the top off and clean
out the spiders and their friends. Just pry of the top and clean it out.
Check the solder connections, and make sure the rod is not broken. Then glue
the top back on.
73
Jim W7RY
--------------------------------------------------
From: "Grant Saviers" <grants2@pacbell.net>
Sent: Monday, November 21, 2011 6:10 PM
To: "W5XB" <w5xb@att.net>; <towertalk@contesting.com>
Subject: Re: [TowerTalk] TH7 installed but not resonant--well now sorta
> 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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