[TenTec] 17 Meter Antenna

Sun Nov 23 12:31:52 EST 2014

I drank the ON4UN coolaid regarding compressed delta loops and built a 
batch of 40M loops for field day, 2 tuned to 7.050 MHz and another pair 
tuned for 7.175 MHz. They were fed with 1/4 wave sections of RG-11 that 
were carefully trimmed to length for velocity factor. I also carefully 
trimmed a 1/4 wavelength section of RG-213 so I use two delta loops as a 
2 element driven array. I did not use a hybrid power divider at the feed 
point - just a coaxial tee connector. My initial thought based upon 
successful deployment at field day 2014 (W7PIG 6A WWA) that these arrays 
were going to be my new equalizer for a local club (K7LED 6A WWA) that 
uses a phased vertical array on a saltwater beach.
I promptly set up a contesting buddy with one of the 2 element delta 
arrays for him to do more beta testing during this winters contesting 
season. His first observation is that the 2 element delta loop array had 
more RX QRN than his dipole that is a flat top at 70ft high. His second  
observation was that the 2 el driven array was only slightly better on 
transmit.
The difference was significant enough that he routed his dipole to the 
2nd receive port of his K-3.
It is a well know fact that a dipole has 8dBi gain when it is 1/2 
wavelength high do to the ground reflection. ON4UN is saying in his book 
that these compressed delta loops only have 1.6 dBi gain over average 
ground.
Based upon real world A - B comparisons of my buddies dipole to the 2 el 
driven delta loop array, I am left to wonder if the apexes of the delta 
loops need to be raised so the average height is 1/2 wavelength.
At 17M this is not very difficult, at 40M we're looking at 80+ ft high.
Just my 2 bits with real world A - B comparisons to back up my wild claims.
Vy 73, Don KO7i

On 11/23/2014 8:15 AM, Rick - DJ0IP / NJ0IP wrote:
> GM George,
>
> The advantage of this type of delta loop is, at low heights, the loop fed vertically polarized has a lower radiation angle than the dipole. The dipole will have to be raised a lot higher to match its radiation pattern.   The loop is also more broad banded.  Its advantage over a quarter wave vertical is, you don't need to put lay a bunch of radials, which often can be a nuisance.
>
> As for how to feed it, well I have been feeding loops like this for 35 years and they have been giving me outstanding results.  That does not mean a perfect match but good enough to use without a matchbox.  Of course the impedance varies with height above ground.
>
> If you have a better idea on how to feed it, please share it with us.
> I'm always happy to learn something new.
>
> My source of information on how to feed this type of antenna is from DL1BU (SK, and ex- chief technical Engineer of the DARC) in his article on loops, printed in the 1979 issue of CQDL magazine, page 154.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of george fritkin via TenTec
> Sent: Sunday, November 23, 2014 4:40 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] 17 Meter Antenna
>
> Delta loops show marginal gain over a dipole (1.1db), and are much more of a pain to erect.  As far as noise no real proof that is true.  And one more thing, feeding with 1/4 wave of 72ohm is more voodoo engineering you find here George, W6GF
>
>       On Saturday, November 22, 2014 11:18 PM, Rick - DJ0IP / NJ0IP <Rick at DJ0IP.de> wrote:
>     
>
>   Use a telescoping fiberglass pole.
> They don't have to be very high.
> 25 ft. is high enough if you make the horizontal bit a little longer.
> That still leaves about 7 or 8' under the antenna so that people can walk under it.
> Scott (W4PA) sells 40' poles.  One of those would be perfect.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Reed
> Sent: Sunday, November 23, 2014 4:17 AM
> To: tentec at contesting.com
> Subject: [TenTec] 17 Meter Antenna
>
> I'm sure Gary they are the best antenna for the dollar, but not enough trees here for support.  I was raised on a farm & my late father, W4PFP & elmer, had some serious wire antennas.  I miss the real estate, but not the farming.
>
> Reed  W4JZ
>
>
> Reed,
>      I had a 80M Delta loop up for quite a few years. It worked extremely well. Very quiet. It was fed in the corner with 75 ohm coax, then 50 ohm to the shack. My matching piece of 75 ohm coax was abt
> 46.5 feet long (1/4 wave x velocity factor of the cable). I'd put another up but all my trees have grown up.
>
> Gary - KN0V
>
>
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