Topband: Topband Digest, Vol 139, Issue 20

Fri Aug 1 21:43:34 EDT 2014

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 at w8ji.com>
To: "Carl" <km1h at jeremy.mv.com>; "Mike Greenway" <K4PI at BELLSOUTH.NET>; 
<topband at 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 at jeremy.mv.com>
> To: "Mike Greenway" <K4PI at BELLSOUTH.NET>; <topband at 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 at BELLSOUTH.NET>
>> To: <topband at 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 at contesting.com
>>> Sent: Thursday, July 31, 2014 12:00 PM
>>> To: topband at contesting.com
>>> Subject: Topband Digest, Vol 139, Issue 20
>>>
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>>> Today's Topics:
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>>>   1. 4-square controllers (Paul Baldock)
>>>
>>>
>>> ----------------------------------------------------------------------
>>>
>>> Message: 1
>>> Date: Wed, 30 Jul 2014 21:32:30 -0700
>>> From: Paul Baldock <pbaldock at frontier.com>
>>> To: <topband at contesting.com>
>>> Subject: Topband: 4-square controllers
>>> Message-ID: <20140731043244.B6490AC9F9A at 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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