Re: [IRCA] DKAZ Construction Help Request

[Neil Kazaross <neilkaz58@xxxxxxxxx>]

Sorry I am late to this thread and working on my own DKAZ's today reminded
me to reply here. While I won't be suggesting the cheapest idea I will be
suggesting the easiest and most simple method to have a very fine working
DKAZ.

1) Feed it with the FLG100LN amp directly at the antenna and use cable to
get back to the rx. The amplification is definitely useful for the low end
and doesn't hurt higher freqs. If you can make your own xfmr's and amps you
mish wish to do otherwise, but this is the easiest way.

2) Use a Vactrol for the termination (Rt). Well worth the money and saves
much aggravation from manually tweaking Rt and never being sure that things
still can't improve. I recommend using a multi-turn pot or having a second
low value pot in line for fine tuning. You can always replace with a fixed
Rt later if needing the Vactrol setup for another antenna. But for best DX
results I'd use the Vactrol.

Note that 1 and 2 create a fixed direction antenna.

Michael, I am afraid you've been misinformed concerning beamwidth. The 3dB
BW of a DKAZ is about 100 degrees. If you want a more narrow BW you have to
array two or even more of them. I array two here side by side currently
spaced 214 ft  and high end results clearly show a more narrow BW as
expected per theory and modeling. If I had more room I'd space them about
100m (328 ft) apart or a bit further.

>From your QTH, 75 deg bearing is fine for TA's but with so much of the
action now coming from the middle east I'd prefer 65 deg if that is
possible. That should get you a nice back null aiming down the eastern
seaboard where much of your QRM in NS will come from.

>From your QTH for southerly DX I would NOT aim 190 deg as you'll get lots
of QRM and you'd rather have less from Cuba and Venezuela and more from the
eastern Carib and Brazil I'd presume. I'd aim 155 deg if possible and that
should also provide chances for southern Africans.

73 KAZ



On Sun, May 8, 2016 at 12:20 AM, Nick Hall-Patch <nhp@xxxxxxxx> wrote:

> Hi Michael,
>
> So... were you proposing the terminated end of the DKaz will actually not
> be terminated until it reaches the Vactrol after a 70' length of twisted
> pair?  And the extension from the feedpoint end will also simply be
> another  70' of twisted pair eventually terminated in a balun (and the
> balun would be unnecessary if  you used a FLG100 at that point)?   I never
> say never,  especially as I have done something similar with an ALA100 in a
> difficult situation, but it was only a few meters of twisted pair in that
> case.    I'm not sure that it's a very RF sanitary arrangement if you're
> trying to get deep nulls.
>
> If that's so, then I maybe it would be better to look at Mark's scheme,
> page 5 of his document.
>
> But....there's a 9:1 impedance transformation at both ends in Mark's
> scheme, so at his switching point, you are looking at about 100 ohms
> impedance.   FLG100 is a wonderful device, but its input impedance is
> closer to 1000 ohms, so there will be a fair impedance mismatch, and you
> may be disappointed if you plan to make a special purchase for this
> project.  If you have an ALA100 already, that may work as well as the other
> two amplifiers.   Both it and the FLG100 are designed to be used with coax
> however, and if I'm not mistaken, you want CAT5 back to the shack with one
> pair for signal, one for power, one for Vactrol control and the remaining
> pair for controlling the relay (do you have enough pairs?). This is
> complicated enough that you may as well design in the receiver interface
> box for the FLG/ALA100 out there as well, popping in a matching transformer
> / balun from 50:100 ohms, and at that point, I admire your ingenuity, but
> hope that you are not paying yourself by the hour!
>
>  The Vactrol  is also meant to work at around the 900 to 1000 ohm
> termination of the DKaz, not the 100 ohm approximately that would be found
> with Mark's system (he uses a low value pot rather than a 1kohm pot at that
> point, see page 11 of his document).  So some parallel resistance needs to
> be shunted to the Vactrol's resistance also.   Things are not impossible,
> but they are getting complicated.
>
> Like Mark says, shout if anything here sounds useful.   I don't want to be
> discouraging, but you have set yourself quite a fine engineering problem
> here!
>
> best wishes,
>
> Nick
>
>
>
>
>
> At 23:02 07-05-16, you wrote:
>
>> I would like to install a couple of reversible DKAZ's (DKAZi?) and am
>> wondering what you all think about extending the two ends towards the
>> middle using CAT5 and attaching them to a 4PDT relay. I would have a
>> Patented Colin Newell Vactrol and a balun at that point and run these back
>> to the house, also using CAT5.
>>
>> I thought that bringing the end points back the 70 feet to the middle
>> would keep the Vactrol within the 100 foot length limit recommended to
>> maximize null depth, but am a little concerned about any interaction with
>> the antenna because they would be running more or less in parallel.
>>
>> I am also wondering what you would recommend for a broadband amplifier -
>> it seems that the options are Wellbrook, Kiwa, and DX Engineering. I wanted
>> to use CAT5 instead of coax to keep feedline costs down if at all possible,
>> and it's likely that the feedline length will be on the order of 250 feet.
>> With a length like that would it be better to have the amp at the antenna
>> or is it OK to have it in the house? What configuration are others using to
>> do this?
>>
>> I really appreciate any help you could offer. This is my first antenna
>> project in many years!
>>
>> Kind regards,
>>
>> Michael Yule
>> Upper LaHave, NS
>>
>>
>> Sent from my iPad
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>
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