[TenTec] 17 Meter Antenna

Sun Nov 23 13:12:42 EST 2014

Don,

Excellent report and reflects some of what I experienced.
The answer is found by looking closely at the details.

First, the dipole was indeed quieter (as per noise) than the vertically
polarized loop.
But that's just the first snapshot. 

Noise is not just limited to atmospheric noise.
QRM is also noise that makes it difficult to work DX.
In a big contest on a crowded 40m band, there is a lot of loud QRM, most of
it from within your own continent.
This makes it very difficult to hear the DX.

The vertical and vertically polarized loop both reduce the received signal
strength of local QRM a couple of S-Units, which, during a contest, usually
results in hearing better on the vertically polarized antenna.
If you repeat this test on a non-contest day, the results won't be the same.

Next, on 17m clearly it is easy to get the dipole 1/2 wavelength into the
air.
On 40m that is not so easy for most city dwellers.
I have never had my 40m dipole higher than 12m (40 ft.) when operating from
a home QTH.
My loop was always just high enough that I could walk under it.

So the reality check is, erect both antennas in your own real life
environment and compare them.
In my case, DX was much easier to work (they heard me better) on the loop
and most of the time during contests, I could copy them better on the loop
as well, even though there was a slight increase in static noise.

There is never going to be one single antenna that works best for all
people, all the time.

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Don Jones
Sent: Sunday, November 23, 2014 6:32 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] 17 Meter Antenna

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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