[Lowfer] Excellent VLF condx this morning! - pa0rdt in a tree

[Laurence KL7UK]

Mitch  - The choke was for that intent but it could probably do with more turns (dependant on your favored band but Im sure its not having a large affect at VLF) but Im using RG6 and there are limitations there. I do the same at the shack end and use a toroid with many 30T on J type (which really does improve VLF)- all in an attempt to limit common mode noise from either going up or down the "feed". Ive made a large improvement in noise induction at the RX end by using a good RF tight Hammond type box for the power injection and added a load of chokes and caps across the power input and reducing the intercapacity of the winding by keeping them apart and paying attention to which sides the winding on the  coax towards the probe are side is used for the outer - it does make a difference in noise here. Using a poor bonded box I was getting loads of magnetic coupling dependent on where I placed the injector on the bench - now it doesnt....only taken me 10 years to figure than one out!

On the Tree thing - youll maybe recall my attempts at classifying different types of tree and which types and seasons appear best suited for hanging up a probe as I wandered around the Globe - and either aiding reception or causing less dumping - the Acacia still tops that list so far for me. Pecans arent too bad - and are far better than hanging in free air beneath lush palm trees for some reason I havent been able to figure out...

Off to cycle to Lowes as a Sunday outing....

Laurence

> From: mitch.powell at sympatico.ca
> Date: Sun, 18 Sep 2011 15:28:57 -0400
> To: lowfer at mailman.qth.net
> Subject: Re: [Lowfer] Excellent VLF condx this morning! - pa0rdt in a tree
> 
> Thanks Laurence:
> That's very helpful.... it would appear ( based on previous comments about the active antennas ) that
> your vertical portion would end at the 15 ft point where you added the 77 toroid "choke".
> II think I may try that - as I have a couple of the amrad antennas - and will see if 7 turns is
> adequate at these frequencies....as a choke. I have some 20 and 30 foot used telephone poles
> that might serve as starting points - and several 50-90 ft spruces and cherry trees.
> Now, where did I put the spud gun ?
> 
> 73
> 
> Mitch
> 
>  
> 
> 
> On 2011-09-18, at 3:11 PM, Laurence KL7UK wrote:
> 
> > 
> > 
> > 
> > I found there was a small improvement at LF/MF and a "larger" one at VLF (Im being vague) hoisting the whole lot thru and above the Pecan tree canopy. The hanging coax is choked down about 15ft down using 7T thru large  77 material (I had to hand) - coax outer is bonded to a number of earth paralleled  Earth rods on the way to the shack. This apartment is RF wise transparent so I still get direct radiation from the house equipment and dont have the ability to bond to a rebar/building reinforcing acting as a Faraday cage.
> > 
> > The jpg shows how it worked but it was such a contraction and the gains were so small Ive going back to supporting the probe inside the tree canopy but away from the branches a few feet. Bit less of a target too. Im guessing as the Z of the probe isnt so high as say a portable VLF receiver with say 10Meg Z impedance we are getting less shunting. Certainly walking up the road with such a receiver (marveling at the Hum) tree "dumping" is noticeable within 30 or more feet with the much higher Z unit.
> > 
> 
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