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Message-ID: <007c01c6a219$4d3e79e0$6501a8c0@eagles>
From: "J. Allen" <vy1ja@northwestel.net>
To: "Dave Brown" <tractorb@ihug.co.nz>,
	"LF \(RSGB\)" <rsgb_lf_group@blacksheep.org>
References: <004b01c6a1ec$92156fb0$6501a8c0@eagles> <014d01c6a217$9c3cdde0$7900a8c0@athlon1200>
Date: Fri, 7 Jul 2006 23:01:37 -0000
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Subject: LF: Re: Antenna Tuning
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Status: O

No, Dave,  I was told long ago by Steve, to short the coax at the  bottom 
end and feed both sides off the top of the variometer.  When I did that my 
reception really improved.  That has never changed since then.  the antenna 
is an inverted L where the riser is coax shorted at its base.

The coax is OK I find no problem with it by using the Ohm meter on the 
shield portion.

Everything is back together.  Today, however, I am finding that the antenna 
is consistent and shows a resonant point at about 98 kHz which is changing 
in relationship to the amount of inductance.  There is another problem which 
I mentioned in my last message, however... At resonance the voltage waveform 
becomes a mess.  I am following Scotts advice and building an isolating 
transformer.  Once that is in play, I may be able to tune the antenna, and 
YES it looks like I had WAY too much inductance.

J.


----- Original Message ----- 
From: "Dave Brown" <tractorb@ihug.co.nz>
To: <vy1ja@northwestel.net>
Sent: Friday, 2006/07/07 22:49 PM
Subject: Re: Antenna Tuning


> So how did the coax look?
> I was going to ask if you could provide a rough sketch of the 
> interconnections of everything as its so easy to misinterpret a written 
> description and make assumptions that are wrong about these sorts of 
> things-but just to confirm-
> I understand this is the setup.
>
> You have a coax feedline (for LF)  that has its outer grounded at the 
> tower base to the common ground point there. The coax inner is connected 
> to either a tap on the loading coil or the 'hot' end of a link winding 
> wound over the cold end of the loading coil.
>
> The bottom end of the link, if you are using one, is also grounded to the 
> common grounding point.
>
> The loading coil has its cold end grounded to the common tower base 
> grounding point and the top end is connected to the vertical part of the 
> LF antenna-be it the coax or a semi-vertical random wire etc- and 
> either/both of these have some/none top loading.
>
> The cable 'radiator' is spaced from the tower with what sort of clamps and 
> what are the details of the insulation at the clamp points? These need to 
> be able to sustain very high voltages even with quite low power.
>
> I understand the tower can be ungrounded or grounded at the base, to the 
> common grounding point. Normally it is grounded.
>
> Re the coax 'radiator', is the inner bonded to the outer at both the top 
> and bottom of the cable, or what configuration do you have?
>
> Just using the braid should work fine (ie inner not connected to anything 
> at both top and bottom)  but it's worth knowing what you have done with 
> the inner as one possibility is all or part of the inner-outer cable 
> capacitance is somehow appearing in series with the top loading, so 
> details of the connections at top and bottom of the cable may be 
> significant.
>
> Hope reviewing these details helps some.
> 73
> Dave
> ZL3FJ
>
>
>
>
>
>
>
>
> ----- Original Message ----- 
> From: "J. Allen" <vy1ja@northwestel.net>
> To: "LF (RSGB)" <rsgb_lf_group@blacksheep.org>
> Sent: Saturday, July 08, 2006 5:41 AM
> Subject: LF: Antenna Tuning
>
>
>> Mike and All,
>>
>> The reason the tower has been bonded to ground is that the tower supports 
>> HF antennas as well.  The feed lines, rotor cable, and remote antenna 
>> relay control cable would need to be decoupled at LF which I am 
>> unfamiliar with accomplishing.  My attempt to decouple was to put the 
>> feedline out at 4 feet from the tower.  I do not want to get too far from 
>> the tower, because my ground system is tied to two 10 foot ground rods at 
>> the tower base.  These ground rods are required by local electrical code 
>> for grounding the tower. If I unground the tower for LF, I have to find a 
>> way to connect the rods but have them decoupled at LF.
>>
>> Yesterday, to make sure that the HF wire antennas were not part of the 
>> problem, I took them all down.  The only antenna left on the tower is a 
>> small A4 tribander.  When this was done, it made no difference at all on 
>> the LF tuning.
>>
>> Does anyone know how far out from the tower will be the best distance for 
>> a 100 foot vertical riser of 1/2 inch coaxial cable? Would I be better 
>> off by making the vertical riser a single #11 wire instead of the coaxial 
>> cable?
>>
>> Mike, you said that this may not be the problem at all, because you had 
>> done a similar installation without these problems.  What is different 
>> about your installation?
>>
>> Anyone who has been following, please brainstorm and think of any 
>> possibility which I should be looking for.  Because I get confused, I 
>> could have made just about any kind of mistake imaginable in the 
>> construction of the antenna, but whatever it is, that antenna sure works 
>> on receive!
>>
>> I will be leaving for Edmonton for neuropsychological testing related to 
>> early Alzheimer's on July 9 and will be back on July 12. Please think 
>> about the antenna problems.  I hope that someone can find the little fox 
>> in my antenna vineyard.
>>
>> J.
>>
>>
>>
>>
>>
>> -- 
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>>
>
>
>
> -- 
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> Checked by AVG Free Edition.
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