I also have that 'poop' sheet and the original manuals for both the 6 and
the 7. When I lived in Virginia, outside Manassas, I had a 5 acre lot with
5 towers up. A 160ft stick of 45G with 4 over 4 over 4 on 20 mtrs, using
modified 204BAS. The side mounting of the lower two made it a little bit of
a challenge to get full rotation as I recall. The IIX Industries side mounts
and Ham IV rotators were used. But the element spacing along the lengthened
booms did get in the way of the tower as I recall, and I only got about 300
degrees of rotation. I think I arranged them to give up the south. That was
back in 1990 - 1998 and I am a little fuzzy on the details, other than to
say I had a lot of fun with that setup, which was switchable of course. The
other antennas on the tower were a 3 element Hygain Discoverer 3 on 40 at
the 160ft mark ( the top 204bas was above that), and I had a 3 element
Moseley monobander on 17m down the side someplace too...forget exactly how
high up that was....getting too old to remember.
- Mike, K4CVL
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Robert
Sent: Thursday, November 13, 2008 1:33 PM
To: Tom Haavisto; Bill
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] TH6 into a TH7?
I used the TH-6 antenna for many years and was very pleased with it in every
way. It has been said that the TH-6 was probably the best tri-bander ever
made in its time.
I do have a four page paper called the "TH7 Engineering Report" issued by
Telex Communications in the 80's. The report makes a direct comparison
between the TH-7 and the TH-6 as measured on the Hy-Gain antenna test range.
The report outlines the differences between the two antennas in power gain,
one half power beamwidth, front to back ratio and 2:1 VSWR bandwidth among
other things. For an example:
The average power gain increase of the TH-7 vs TH-6 is stated to be:
+0.3db for 20m
+1.4db for 15m
+1.7db for 10m
The front to back ratio increase of the TH-7 vs TH-6 is:
+4.0db for 20m
+5.8db for 15m
+0.0db for 10m
2:1 VSWR bandwidth of the TH-7 vs (TH-6):
440 (250) for 20m
460 (380) for 15m
1710 (870) for 10m
What value one places on the refinements of the TH-7 is up to potential user
to decide.
As far as the Hy-Gain 204BA, I am sure you are probably aware that there are
modified element spacings and element lengths to make that a better
performing antenna.
Good luck!
73 de W7KD
----- Original Message -----
From: "Tom Haavisto" <kamham69@gmail.com>
To: "Bill" <bill_fries@mail.ncats.net>
Cc: <towertalk@contesting.com>
Sent: Thursday, November 13, 2008 5:12 AM
Subject: Re: [TowerTalk] TH6 into a TH7?
> Hi Bill
>
> Hi Bill
>
> I understand the difference between aTH6 and a TH7 - the later has an
> extra driven element so you can get a flatter SWR across the band.
> IMHO, it seems like a waste of money.
>
> I picked up an older TH6, and cleaned it up. For a variety of reasons
> I decided to upgrade to a 204, so I sold the TH6 to a friend - he
> disassembled the traps, cleaned it up, and made sure it was in close
> to new condition. We reset the antenna to low phone and installed it
> on a 50 foot tower. Anyway - SWR is 1.2 at the band edges, and flat
> in the middle on all three bands.
>
> My point being - I am not sure what value adding an extra driven
> element will add to the antenna. All rigs are quite happy to work
> into a slight SWR, cable losses at HF are not a major concern unless
> you have really long runs. A stock TH6 is a good performing antenna
> with a good SWR curve, and I don't see the value in adding an extra
> driven element.
>
> Tom - VE3CX
>
>
>
>
> On Wed, Nov 12, 2008 at 8:34 AM, Bill <bill_fries@mail.ncats.net> wrote:
>> I have a not assembled TH6 antenna. I also have a copy of the TH6 that
>> was
>> disassembled after years in use. I've been looking at assembling the new
>> TH6 when I read the assembly manual for the TH7.
>>
>> My question: Would it be possible to use my current parts and make a
>> TH7?
>> For example, would the traps be the same?
>>
>> I asked Hy-Gain and they thought this was going to cost $500. I'm
>> skeptical. Or wondering.
>>
>> Bill, AB8SC
>>
>> No virus found in this outgoing message.
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>> 7:53 AM
>>
>>
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>>
>>
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>
>
>
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