[TowerTalk] TH7 installed but not resonant--well now sorta
W5XB
w5xb at att.net
Mon Nov 21 20:43:53 PST 2011
Hi Gerald,
The balun is a HyGain, installed under the boom with the factory straps connected directly to the first (Front) driven element as the manual shows. The straps are arranged in a semi circle like the manual shows. The crossover straps are about 1/2 inch apart. The rear driven element is connected via wires. All these parts look like the manual pictures.
It does seem like their is a fundamental problem, elements long (low resonant frequency, but it went together with very little assembly. The elements were just take off of the boom, and the boom was parted.
Since it all looks like the manual, this is why I am not seeing the problem(s).
73,
Grant
----- Original Message -----
From: TexasRF at aol.com
To: w5xb at att.net ; towertalk at contesting.com
Sent: Monday, November 21, 2011 7:56 PM
Subject: Re: [TowerTalk] TH7 installed but not resonant--well now sorta
Hi Grant, what balun are you using and how is it connected to the driven element?
The feed impedance is affected by the balun connection wire length and spacing and needs to be just as shown in the assembly manual.
73,
Gerald K5GW
In a message dated 11/21/2011 6:36:38 P.M. Central Standard Time, w5xb at att.net writes:
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 at tampabay.rr.com>
To: "'W5XB'" <w5xb at 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 at contesting.com
> [mailto:towertalk-bounces at 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 at gvtc.com>
> To: "W5XB" <w5xb at att.net>
> Cc: "Towertalk" <towertalk at 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 at contesting.com
>> > [mailto:towertalk-bounces at contesting.com]On Behalf Of
>> W5XB
>> > Sent: Sunday, November 20, 2011 3:02 PM
>> > To: towertalk at 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 at contesting.com
>> > http://lists.contesting.com/mailman/listinfo/towertalk
>>
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>>
>>
>>
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