[Antennas] Re: [dx-list] Yagi height and DX

2002年4月12日 17:04:03 -0700

My guess would be that the improvement on receive would
outweigh the improvement on transmit here. Remember
that an antenna that's only 20 feet high is in close proximity
to a lot of power lines running around the house and carrying
conducted noise from RF noise sources down the street.
----- Original Message -----
From: "Mark Fancher" <[email protected]>
To: <[email protected]>; <[email protected]>;
<[email protected]>; "John Geiger" <[email protected]>
Sent: Friday, April 12, 2002 15:38
Subject: Re: [dx-list] Yagi height and DX
> John,
>> Hope this helps. I modeled a few different MONOBAND yagis at 20' and 40'
> using EZNEC. These were models I already had, so I couldn't give you a
> tribander model (I didn't have one already). Please take these results
with
> this in mind. Especially for 20m the yagi is quite good (5 element)!
>> In anycase, it should give you an idea about how the radiation patterns
> varies for each frequency at different heights (20 and 40').
>> Each antenna was modeled over average real ground.
>> 20' over ground:
> *******************
> Band Gain (dBi) Takeoff Angle (degs)
> 10m 12.38 25
> 15m 11.27 30
> 20m 11.34 30
>> 40' over ground:
> ******************
> Band Gain (dBi) Takeoff Angle (degs)
> 10m 12.38 10
> 15m 12.59 15
> 20m 13.73 20
>> So there you go. Look's like you get a little bit more gain at a little
> lower radiation angle for the 20' extra. If you believe EZNEC, I'd go
with
> saving the money and buying something other than a tower.
>> BTW, take a look at the propagation indexes for the past 24 hours. Pretty
> bad. Maybe its not your antenna.
>> Enjoy!
> Mark, AA4MF
> ----- Original Message -----
> From: "John Geiger" <[email protected]>
> To: <[email protected]>; <[email protected]>;
> <[email protected]>
> Sent: Friday, April 12, 2002 11:55 AM
> Subject: [dx-list] Yagi height and DX
>>> > I am currently using a Cushcraft MA5B mounted on a
> > tripod on top of a one story house-approximately 20
> > feet off the ground. This antenna has worked well,
> > but I am wondering if I am hitting the performance
> > plateau with it. I have 294 worked, including 4 new
> > ones this year-JD1o, PW0T, VP6DI, and XW0X.
> >
> > It seems that I am not hearing so well, though. Last
> > night several 5 land stations reported SV2ASP/A as Q5
> > on 20 meter SSB, but I could not hear a thing. Also
> > could not hear VK9L on 15 ssb that other stations were
> > putting on the reflector.
> >
> > I plan on replacing the MA5B with a full size
> > tribander right after the KH1 dxpedition. WOuld like
> > to do it before,but need to make sure I have something
> > up for that station. HERE IS MY QUESTION: WOuld
> > getting a tower and going to 40 feet make a hugh
> > difference over 20 feet? Is it worth the trouble of
> > getting a tower and putting it up (do not look forward
> > to this). Will that extra 20 feet allow me to hear
> > THAT much better?
> >
> > Figured I would get some profession opinions before
> > jumping into anything. WOuld have to sell some gear
> > that I like to get the tower also.
> >
> > 73s John NE0P
> >
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