[600MRG] More 630m antenna efficiency...
William E. Isakson
bill.isakson at gmail.com
Sun Sep 2 11:41:21 EDT 2018
Ike, I have used the method of fishing pole casting to get a line over a
tree limb and it works. I have also tried the bow and arrow and that works
but there is a little fear when doing it about exactly where that arrow is
going to end up, particularly what if the line breaks. An arrow releases
with a lot of immediate speed and snap of line. 40 feet seems to be my
limit with these, though you would think more. Another method was a tether
to a solid weight which a neighbor managed to fling over a similar tree
branch height. I thought it would be cool to use another neighbor's kid's
drone to fly a thread over a tree, but I have not tried that one yet.
Also there was a time when I was called Ike. It was a long time back but
seeing the name again always grabs my attention.
Bill
--------
Bill Isakson AC6QV
Roseburg, Oregon USA
bill.isakson at gmail.com
On Sun, Sep 2, 2018 at 6:21 AM Dwight Blevins via 600MRG <
600mrg at mailman.qth.net> wrote:
> Dave,
>
> Sounds like our situations are similar. Dirt here in western Colorado is
> mix of sandstone and ground glass. With about 5 to 6 inches of precip per
> annual, might as well forget the verticals, though I do have one. Couple of
> 40 ft. tall trees in the back yard, so I'm trying to figure out how to get
> a wire up and over without breaking my 72 year old neck.
>
> Anybody ever tried casting a fishing line? Probably a bow would work best,
> but I've never had to use this sort of thing to get a wire over a tree top.
> No way to get a bucket truck back there, so I'm still scratching my head on
> how to get my wires up higher, at least on one or two sides of the loop.
> After reading all the comments on ground loss the past couple of days I'm
> convinced more effort with the vertical is probably a bad idea.
>
> Time is flying by, with only a few weeks to go before 630m fall activity.
>
> Ike, KW7T
>
> On Sunday, September 2, 2018, 3:32:34 AM MDT, Dave Riley <
> dave.riley3 at verizon.net> wrote:
>
>
> Aye, Pat,
>
> The possibilities become endless with new technology but I still struggle
> with a self imposed beer budget left over from that great depression...
> Mainly because it is cheap, fun, and really taxes my mojo or what is left
> of any creative juices...
>
> If one is blessed or cursed with high pines trees then nirvana is either
> here or gone...
>
> A compound bow, air gun, or sling shot is the new and cheaper bucket truck
> with dacron rope so strong and cheap that it doesn't even get recycled...
>
> The latest attempt here at cheating nature is to rig wires and feed till
> the DX goes up... I'm always harping on groundless antennas cuz let's face
> it, that's where most power is lost...
> Trillions of idle radials can't be wrong...
> Sixr inch copper strap makes a wunnerful loop for efficiency until the
> breeze comes up then the copper goes airbourne and another disappointment
> needs to be forgotten...
>
> Today's new scientific observations suggest that a loop of wire suspended
> within the pine tree opening says that if the bottom of the loop (
> horizontal wire ) wire rests upon the ground that the BW of the loop goes
> way up and so do the losses...
> Raising the bottom wire just a few feet above the ground narrows bandwidth
> and losses significantly... So today I will spend hoisting the bottom wire
> of this loop to about 10' off the ground and see what those numbers say...
>
> Ground conductivity here on the BC band is between poor and rotten and is
> mostly silica sand... So I imagine an efficient loop in 'free space', but
> that is not the case as yet...
>
> After today there is one remaining try at reducing 'ground losses' and
> hopefully that will not be a secret by sundown... After that, back to
> microwave like wire antenna modeling for seniors... 50 mhz. seems best for
> model building/scaling...
>
> Maybe skydiving is next...
>
> 73s de Dave, still stuck in reality...
>
>
> On 9/1/2018 11:02 PM, patrick hamel wrote:
>
> Impractical??
> When I was a novice someone gave me an old (1930 vintage) Handbook
> including wooden lattice tower construction.
> A 100 foot lattice tower with cross arms and side ropes to hold the loop
> in shape is possible.
> If you have the room and money for the tower you might be able to afford
> rigid (threaded) aluminium conduit for the radiator (it does exist). Today
> we have various plastics which would make a lattice tower long-lasting
> instead of the treat-it-yourself wood (barrel of creosote) I remember being
> discussed. Today we have bucket trucks for tree-trimmers and construction
> cranes that could make erection of such a tower a safe and practical.
> 73,
> Pat W5THT
>
>
> ------------------------------
> *From: *"J Mcvey via 600MRG" <600mrg at mailman.qth.net>
> <600mrg at mailman.qth.net>
> *To: *600mrg at mailman.qth.net, "Dave Riley" <dave.riley3 at verizon.net>
> <dave.riley3 at verizon.net>
> *Sent: *Saturday, September 1, 2018 9:23:33 AM
> *Subject: *Re: [600MRG] More 630m antenna efficiency...
>
> I played with the loop calculator at the link that you provided.
>
> Got some impractical results:
> diameter 90.5 feet ( I used a length of 300 ft which was in the range
> they suggested)
> conductor 0.9 inch
> Q= 497 !!!!
> BW = 1.27 KHZ
> Cap voltage = 5000 volts RMS
>
> Even with a conductor almost 1 inch in diameter , the Q is 497 and the BW
> is 1200 HZ
> 1) 90.5 foot diameter ? how does one build and install such a structure?
> 2) How does one tune ( and keep tuned) something with a Q of 497? Servos
> with continuous feedback?
>
> I thought the whole thing was "loopy"
> On Saturday, September 1, 2018, 9:37:42 AM EDT, Dave Riley
> <dave.riley3 at verizon.net> <dave.riley3 at verizon.net> wrote:
>
>
> It's fun to see the banter and playback all around... Termination of this
> discussion ended up around 1.65/1 SWR, ( self written results ) ...
> Brain food, that's all it is, and maybe a good antenna...
>
> Now for the next batch of toil and trubble to wrestle over...
>
> I am a confirmed loopest and have sworn NEVER to divert ANY RF in to a
> lossy ground system... EVER...
> To that end I promise to keep all power possible in the LOOP, as it
> were... Enuf of it gets lost in the ground as it stands already...
>
> The next personal challenge here is to arrive at the possible EIRP from
> this loop, 5W eirp for the very least RF power input...
> Right now it is costing me about 13 watts in order to claim 5W eirp +/-...
>
> I started out with a monster dog wire loop 630m antenna made from e-bay
> for very cheap $$ and I was astounded by how simple a single wire antenna
> on our new band could perform...
> I only added a good vacuum variable cap. in series and used a good mix for
> the Ferrite coupling transformer...
>
> I use this small loop transmit formula which may or may not be the best
> bottom line in computation...
>
> http://www.66pacific.com/calculators/small-transmitting-loop-antenna-calculator.aspx
>
> I am now at the stage of trying to increase the wire diameter from #14
> stranded copper to something larger for cheap money and lots of gain, say
> 1/4"...
>
> Here is what I have up now:
> 450' circumference loop, using double CATV RG6a coax with a copper
> runner...
>
> https://www.ebay.com/itm/Directv-Dual-Black-CR03BDR0-05-Ground-RG6-Coax-Cable-on-EnviroReel-ReeLogic-Reel/163202369537?hash=item25ff9e8801:g:WRgAAOSwc2FaLfFs
>
> It is lightweight, contains 5 separate conductors, and when paralelled
> together must add up to something more than .25" diameter or so...
> Maybe today I will measure say 25' of each wire on the RF bridge and
> report back...
> Below is a 'rac' table taken from Bill Ashlock's work as my starting point
> of reference;
>
> We read in the book of Bill's, the efforts derived from the following;
> ConductorType Rac ohms Tot Rac ohms
> #12 awg 1.15 1.37/1.48 0.83/.80 0 db ** Reference
> start point...
> #10 awg 0.92 1.14/1.25 0.91/.87 +0.8 db
> #8 awg 0.72 .92/1.03 1.02/.96 +1.8 db
> #6 awg 0.57 .79/.90 1.09/1.03 +2.4 db
> #4 awg 0.45 .68/.79 1.18/1.10 +3.1 db
> #2 awg 0.36 .57/.68 1.29/1.18 +3.8 db
>
> #12 x 4 0.32 .55/.66 1.31/1.20 +4.0 db
> #12 Litz 0.57 .79/.90 1.10/1.03 +2.4 db
> #12 Litz x 2 0.30 .59/.70 1.27/1.16 +3.7 db
> #12 Litz x 4 0.16 .38/.49 1.58/1.39 +5.6 db
> RG-8/11 0.38 .60/.71 1.26/1.16 +3.6 db
> ½” Cu pipe 0.15 .37/.48 1.60/1.41 5.7 db **** BEST by far
> LOWEST a.c. 'R' measured
>
> This table is based on Bill Ashlock's testing @ 185kc. and a 200'
> circumference square loop... 50' on a side...
>
> My question now is what will the RAC be of the 5 separate RG6A conductors
> wired together in parallel??? I guess @ .4" equivalent diameter +/- for;
> Antenna efficiency: 34% (-4.7 dB below 100%)
> Antenna bandwidth: 2.07 kHz
> Tuning Capacitance: 622 pF
>
> Capacitor voltage: 1,573 volts RMS
> Resonant circulating current: 2.92 A
> Radiation resistance: 0.402 ohms
> Loss Resistance: 0.772 ohms
> Inductance: 181 microhenrys
> Inductive Reactance: 539 ohms
> Quality Factor (Q): 230
> Distributed capacity: 369 pF
>
> Antenna "circumference": 450 feet
>
> That is with one copper wire carrier, two solid shields of 75 ohm coax.
> approx .240" each, and two center conductors ( copper ) #18 or so...
>
> It is very tempting to go to Lowe's and buy 10' sections of 3/4" schedule
> 'M' copper pipe!!! Am resisting...
> It is already too easy to make 5W eirp from the low power transverter
> here... Why re-invent the wheel??
>
> Comments??
>
>
>
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