[AMRadio] Re: new antenna...


Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Tue Feb 6 14:02:05 EST 2007


Craig,
I think you may have tried to do to much with loading
coils. Where did you put your coils?

I had a 90 foot antenna resonant on 3880 with some very small 
coils (B+W coil stock) over an insulator, 3/4 the way out.
#20 wire, or #18, the spacing was quite close, worked for years
at full power, despite getting quite crusty and having bug
houses in them.

Closer to the center the current goes up, you need less coil,
and the worse the antenna works. The more you go out the
bigger the inductance needs to be, but the better the antenna
radiates.

In order to make a 40 meter dipole work on 80, you would need
LOTS of inductance 3/4 the way out I would think.

I think it would work very poorly on 80 as well,
just not enough wire...

Brett


 
> 
> Hi Brett,
> 
> I've played with loading coils on a 40 meter dipole feed with 
> 600 ohm open
> wire trying to get it on 3.870 MHz. Transmitter was a Johnson 
> 500, about 350
> watts of carrier.
> 
> The short answer is use "large" diameter wire for the coils & 
> wide spacing.
> My loading coils arced with the 500 in the tune position and 
> tripped the
> overload relay in the PA circuit. I did get it so I could 
> whisper into the
> mic at low power (not a good impedance match for the mod 
> tranny) at about
> 50% modulation of the carrier. Anything more and the overload 
> relay tripped.
> Receive was as good as my 75 meter full wave loop.
> 
> Where on the dipole the coils are going to be placed will be 
> important,
> running 600 watts of carrier could mean "strapping" coils.
> 
> Craig,
> 
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net]On Behalf Of Brett gazdzinski
> Sent: Tuesday, February 06, 2007 5:52 AM
> To: 'Discussion of AM Radio in the Amateur Service'
> Subject: RE: [AMRadio] Re: new antenna...
> 
> 
> 
> after a while on full power (600 watts carrier), which
> is likely normal, its not hot...
> 
> 
> 
> The question is: Does a resonant antenna work better on
> receive?
> 
> AThe antenna is 100 feet long now, and the ends are right up
> against the trees, but I could add loading coils to make
> the antenna resonant at say 3880.
> Would that improve receive any?
> 
> What do you guys think would happen if I added loading coils?
> 
> Brett
> N2DTS
> 
> 
> 
> 
> 
> ______________________________________________________________
> AMRadio mailing list
> List Home: http://mailman.qth.net/mailman/listinfo/amradio
> Partner Website: http://www.amfone.net
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio at mailman.qth.net
> To unsubscribe, send an email to amradio-request at mailman.qth.net with
> the word unsubscribe in the message body.
> 
> 
> ______________________________________________________________
> AMRadio mailing list
> List Home: http://mailman.qth.net/mailman/listinfo/amradio
> Partner Website: http://www.amfone.net
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio at mailman.qth.net
> To unsubscribe, send an email to amradio-request at mailman.qth.net with
> the word unsubscribe in the message body.
> 




More information about the AMRadio mailing list

This page last updated 18 Oct 2017.