Well I’ve put a KW on rtty on Hy- Gain and Mosley and have not seen any I’ll
effects. When I was in Missouri one of the engineers told me that the 600 watt
rating was for out of band operation but the antenna can handle a KW as he
showed me and what I tested.
Glenn, VA7UO
Sent from my iPhone
> On Nov 23, 2019, at 8:52 AM, Jim Thomson <jim.thom@telus.net> wrote:
>
> Date: Fri, 22 Nov 2019 12:39:45 -0800
> From: Glenn Pritchard <gpritchard7000@gmail.com>
> To: "Joe Subich, W4TV" <lists@subich.com>
> Cc: towertalk@contesting.com
> Subject: Re: [TowerTalk] "different" trap
>
> <That false narrative about high loss is just not true.
> <I?ve been working with traps for over 30 years and have never seen the
> losses that those two claimed.
>
> <Glenn, VA7UO
>
> ## The full sized Mosely 10m ele becomes aprx 75% FS on 15M.
> The 10M trap now becomes strictly end loading on 15M.
> You require abnormal sky high coil uh values, if a loading coil is
> inserted at the ENDS of a shortened dipole. You can easily see
> that effect on any loading coil software calculator. The software I
> use will depict the required loading coil uh in 7 different locations
> simultaneously..... or spit out required coil values for any
> location. Current through the end loading coils is very low.
>
> ## say u wanted to build a 15M monoband shortened yagi, 75% of FS.
> The LAST place you would choose to insert loading coils is the extreme
> ends!
> Uh vales would be extreme, and the SRF...self resonant freq of the
> coil will get u into trbl every time..... its now too low. Mosely
> uses low Q traps on 10M.... IE: high L, low C...so they can
> obtain the required uh for end loading on 15M.
>
> ## In the case of the Mosely, we now have to follow up the 15m end
> loading....with a 15m TRAP. Traps are parallel resonant, with extreme
> high
> circulating currents through the coil, and extreme high peak Vs across
> the capacitor. The cap is not like how telrex constructed traps,
> with a NPO TX doorknob cap
> In parallel with a coil. Mosely derives the capacitance between the AL
> cover and coil windings....its distributed capacitance.
>
> ## Calculate or better yet, measure the circulating current and u will
> gag. The puny 10 gauge AL wire gets hot enough, from localized
> heat, to melt and deform
> the grooved polystyrene former. One would think the thermal heat
> would be heat sinked to the adjacent AL tubing on either side, but it
> does not, its localized.
>
> ## I can see the same effect on tapped tubing coils on a linear amp.
> The active 15M portion of the 20m tank coil gets hot, but the
> adjacent un used 20m turns are room temp.
> ## Swap out a copper tank coil for an identical AL tubing coil, and you
> will now find out what HOT is all about.
>
> ## 10 gauge AL wire is simply too small in gauge, freq is too high,
> and AL only conducts 60% as good as copper... at any freq from DC,
> 160m, 80, 15 etc.
> Run the numbers through brian Beasleys, K6STI coil 3.14 coil
> program, and u will see the problem right away.
>
> ## toss In the slightest bit of a loss from lousy coil connections , at
> each end of each trap, and u just compounded the issues.
>
> ## There is a reason Mosely rates their yagis at only 600 watts average
> power output...= 3.5A into 50 ohms. One partial work around is the
> use of dual driven eles. After melting the polystyrene formers on
> several trapped yagis and several trapped verticals, I gave up on traps,
> they wont work for my application. HB traps that will work are simply
> too large, and too heavy, too expensive, constructed of .25 and .375
> OD silver
> plated tubing and paralleled HEC HT-57/ 59 NPO caps.
>
> Jim VE7RF
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|