[TowerTalk] TH6 into a TH7?

Thu Nov 13 13:43:09 EST 2008

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 at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Robert
Sent: Thursday, November 13, 2008 1:33 PM
To: Tom Haavisto; Bill
Cc: towertalk at 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 at gmail.com>
To: "Bill" <bill_fries at mail.ncats.net>
Cc: <towertalk at 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 at 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
>>
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