[TowerTalk] Fwd: Doublet vs Yagi

[Hans Hammarquist]

 I suggest you terminate the yagi but connecting 50 ohm to the feeder. That would show if the yagi is affecting the doublet.

Hans - N2JFS

 

 

-----Original Message-----
From: Tony <dxdx at optonline.net>
To: towertalk <towertalk at contesting.com>
Sent: Wed, Mar 2, 2016 8:33 pm
Subject: Re: [TowerTalk] Doublet vs Yagi



On 3/2/2016 7:56 PM, Mike Fahmie via TowerTalk wrote:
> It would be interesting to know if the signal strength on the doublet changes when you rotate the Yagi. Mike-WA6ZTY

Mike:

That's a good suggestion. I'll give it a try and report back if there's 
any interaction.

Thank you.

Tony


>
>   
>        From: Tony <dxdx at optonline.net>
>   To: towertalk at contesting.com
>   Sent: Wednesday, March 2, 2016 4:50 PM
>   Subject: [TowerTalk] Doublet vs Yagi
>     
> All:
>
> I have a flat-top doublet approximately 100 feet long with it's apex 30
> feet above the ground. It's fed with 300 ohm ladder line. I also have a
> 20 meter, 5 element mono-band Yagi that's twice as high at 60 feet above
> ground.
>
> When comparing the Dx reception of the two antennas, the signal strength
> on the Yagi is many S-units above that of the doublet, but there is one
> 30 degree swath of azimuth where the doublet is only an S-unit or 2
> below the Yagi.
>
> The direction where the doublet has the most gain centers about 20
> degrees off the wire dipole itself so it's far from broadside. It's as
> though the gain exists close to where the greatest null should be; off
> the end of the dipole.
>
> My question is: what's most likely to cause the doublet to have that
> much gain in one particular direction? Is it the terrain, the electrical
> / physical properties of the doublet, the signals angle of arrival or
> some interaction with the two antennas?
>
> I should mentioned that the Yagi sits 40 feet behind the doublet in the
> direction where the doublet shows the most gain. Someone suggested that
> the ladder line may contribute some vertical component that helps
> reception.
>
> Thanks,
>
> 73, Tony
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