No guesswork Tom, sorry to dissapoint; just a little tongue in cheek.
For most of us that use seperate receiving antennas the Comtek style is
sufficient and is easily duplicated as a homebrew.
I havent seen any in depth review of the DXE as to how it really performs
for TX and RX under a wide range of site and propagation conditions.
Carl
KM1H
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "Carl" <km1h@jeremy.mv.com>; "Mike Greenway" <K4PI@BELLSOUTH.NET>;
<topband@contesting.com>
Sent: Friday, August 01, 2014 11:06 AM
Subject: Re: Topband: Topband Digest, Vol 139, Issue 20
Poor guessing by Carl.
The control units are entirely different. One is just a switch, and the
other is a microprocessor based system that has an omni function and a hot
switch lockout for relay protection. It also has a relay clean function.
I this the original poster was asking about Array Solutions vs. DXE, and
not Comtek.
The original poster might have been asking about the phasing box???
The control head is in the house on the desk. The phasing box is out at
the antenna. The various subparts of the system are very commonly called
incorrect names, even by sales people. For example, the phasing box or
outdoor unit is called a controller. The Q-sections that are nothing more
than feedlines are called phasing lines. I never really am sure what part
someone is asking about. :)
Another point about guessing...
The original error in hybrid 4 square design was from ignoring mutual
coupling, and assuming element impedances were ~35 j0 for all four
elements. The original thought was to transform the antennas to 100 ohms
at the phasing box ports by using 1/4 wave 75-ohm Q sections. The 100 ohm
ports were paralleled to get 50 ohms.
The problem with that idea is mutual coupling changes the antenna
resonance and impedance. The antennas are not even close to the correct
impedance, and are reactive with different signs when phased. The elements
also require equal currents, not equal power. A hybrid tries to force
equal power.
As far as I know, ****NONE**** of these units are true hybrids. This is
because a true hybrid would have terrible F/B ratio and gain in this
application. This is because:
1.) None of the elements or feedlines are 50 j0 when phased. They are all
different impedances, except the center two elements. A hybrid ONLY
provides the design phase when the termination is the design value, and
that does not happen.
2.) None of the element groups require equal power. Equal power would
result in a terrible F/B ratio.
The DXE outdoor unit, besides an omni function and sophisticated
controller, is much better optimized for the impedances actually presented
in the working system. Rather than accidentally working through a design
shortfall in hybrid, like the original system many years ago was, it is
planned for the loads presented by the system. Because none of these units
are really hybrids (they would not work very well if they were), they are
all different.
73 Tom
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "Mike Greenway" <K4PI@BELLSOUTH.NET>; <topband@contesting.com>
Sent: Thursday, July 31, 2014 8:00 PM
Subject: Re: Topband: Topband Digest, Vol 139, Issue 20
More like a Chevy vs one thats been dolled up a bit for more money (-:
----- Original Message -----
From: "Mike Greenway" <K4PI@BELLSOUTH.NET>
To: <topband@contesting.com>
Sent: Thursday, July 31, 2014 2:25 PM
Subject: Re: Topband: Topband Digest, Vol 139, Issue 20
Hi Paul.. I have used two Comteks for over 20 years and they have never
had a problem. The DXE looks like a very nice unit and it appears to me
the circuitry is about the same.. Either should work well I think...
Ford versus Chevy... 73 Mike K4PI
From: topband-request@contesting.com
Sent: Thursday, July 31, 2014 12:00 PM
To: topband@contesting.com
Subject: Topband Digest, Vol 139, Issue 20
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----------------------------------------------------------------------
Message: 1
Date: Wed, 30 Jul 2014 21:32:30 -0700
From: Paul Baldock <pbaldock@frontier.com>
To: <topband@contesting.com>
Subject: Topband: 4-square controllers
Message-ID: <20140731043244.B6490AC9F9A@mx.contesting.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed
Does anybody have an opinion on the DX Engineering verses the Array
Solutions 4 square controller?
- Paul KW7Y
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