[600MRG] More 630m antenna efficiency...

Sun Sep 2 09:21:02 EDT 2018

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>
 To: 600mrg at mailman.qth.net, "Dave Riley" <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> 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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