[600MRG] 600m Antenna

[Marshall Cross]

All, just consider QST results as same as one with all dimensions 4x for installation at 475 kHz site with ground conductivity 1/4th of what Dave used for his NEC runs which I have not looked at. In effect he analyzed, built and measured a 1/4th scale model for us, again assuming his ground conductivity was 4 times greater that at 475 kHz and all dimensions of the entire system will be 4 times greater. Then no further NEC runs are necessary. In constructing an EM scale model, all values (dimensions, frequency and conductivity) are scaled by the scale factor except at both 1900 and 475 kHz the earth's dielectric constant (which does not scale) can be ignored for most ground conditions anyway. Of course if he simply assumed a perfectly conducting earth in his NEC modeling then don't worry about ground conductivity and just build one with 4x dimensions and all electrical parameters (impedance and efficiency) should be close to his 160 meter version.  Hope this helps, 73, Marshall, W1HK #41.

Sent from my iPhone

> On Apr 28, 2018, at 4:29 PM, Alan Cooper <w7aln at netzero.com> wrote:
> 
> Hello All,
> That was an interesting design! My thought was to lift that drop at the end of his top wire
> and layout the 90degree turn out horizontal in some direction if needed. Then add a counterpoise  to follow that top wire somewhere near the ground as much as possible.
> That would increase the total capacitive loading of the slinky for 630m. Use the loading
> coil and the auto gyro 5gallon bucket setup like we do now and it should tune just fine
> on 630m….maybe….  it did cause some creative thought to get going at least if nothing
> else.
>  
> 73 Alan w7aln
>  
> From: 600mrg-bounces at mailman.qth.net [mailto:600mrg-bounces at mailman.qth.net] On Behalf Of Brian, WA1ZMS
> Sent: Saturday, April 28, 2018 5:02 AM
> To: Bob and Jane
> Cc: /600MRG /600MRG
> Subject: Re: [600MRG] 600m Antenna
>  
> Bob-
>  
> My 2 cents....
>  
> Seems like there's a lot going on within that antenna design.  I have not looked at the NEC model but I expect what makes it "work" comes down to the radials he has. A few 1/4-wave radials makes a big difference.
>  
> The slinky could very well be replaced with just a single loading coil. And the drop wire at the far end of the horizontal wire is likely cancelling some vertical radiation from the slinky. That's counter productive.
>  
> My feeling is that if you could scale every dimmension he used by 4x, then you'd have the same antenna performance it gives but on 630m.  But for all that effort.....you'd be better off putting up a single vertical wire with lots of capacity hat wire and forget the slinky part.
> 
> -Brian, WA1ZMS
> 
> On Apr 27, 2018, at 4:03 PM, Bob and Jane <bobjane99 at sbcglobal.net> wrote:
> 
> Has anyone looked at the 160m antenna design described in the May issue of QST (page 43)?
> 
> Would something like that work on 600m if scaled correctly?
> 
> The NEC data is available on the ARRL website, which someone who knew what they were doing (that leaves me out), could play with the parameters to see if a reasonable antenna design could be created.
> 
> Bob, WB8ILI
> -- 
> 
> bobjane99 at sbcglobal.net
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