[Wswss] [Magic Band EME] [Fwd: Re: Sample of 6m Antenna Comparison Table]

[Lance Collister]

b_mcquarrie at minidata.co.nz wrote:
> Hi Lance
> 
> I am considering an array of 4x5el yagis and would be interested in other people's 
> experience, currently I use 2x6el. However I am comfortable with coming up with a 
> design which would work in my situation, if there is no demand for Lionel's analysis.
> 
> Only 4 EME QSOs on 6m last year so I need to get more active on 6m before the F2 
> returns.
> 
> 73
> Bob ZL3TY
> 
> 
Hello Bob,

Thanks for your email and comments regarding the 6m antenna comparison table that 
is underway.  One of the primary reasons for this project was the growth in 6m 
antenna arrays recently, and the desire to provide a helpful tool to people as 
they built bigger antennas.  I see that Lionel has already addressed your inquiry 
directly, so I will defer to his suggestions.

I don't think there is any doubt that one of the reasons you have not completed 
more EME contacts is the lack of elevation to be able to match the 
moonrises/moonsets of horizon-only stations.  Of course, if you do decide to put 
up an array with elevation, you will of course lose ground gain.  You therefore 
need to assemble an array with enough gain without relying on the valuable extra 
ground gain that can accrue when an antennas is aimed on the horizon.

I generally suggest 14 dBD as a good minimum free space gain to shoot for in a 6m 
EME that is going to be elevated.  Using JT65A mode, that is enough to work 
similarly sized arrays and good single yagis on the horizon.  Of course, every dB 
above that also makes it easier ;-)  Four good 5 element yagis should have more 
gain than this minimum figure.  You may want to ask K1SG about his experiences 
with four of the 6M5X yagis.

You also may want to contact ON4IQ for his thoughts regarding a 4x5 array.  I know 
he has done some computer modeling that suggests that arrays of shorter boomlength 
yagis may not perform as expected when elevated, especially with lower tower 
heights.  VE7BQH has also suggested that a good guideline is to make sure that you 
clear the ground by at least a half a stacking distance when the antenna is 
elevated...I think this is even more important for short boom yagis.  You may find 
my SPACE spreadsheet helpful in modeling the lowest clearance of various arrays:

http://www.bigskyspaces.com/w7gj/SPACE.xls

I can't wait to hear you with your new antenna!  GL and VY 73, Lance

-- 
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8)
P.O. Box 73
Frenchtown, MT  59834  USA
QTH: DN27UB
TEL: (406) 626-5728   URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11, 6m DXCC #815