Multiple monopoles on same feed-line?

Discuss commercial and home made antennas.
Post Reply
JEL
Posts: 92
Joined: Wed Feb 07, 2018 2:08 am

Multiple monopoles on same feed-line?

Post by JEL » Tue Feb 13, 2018 2:40 pm

I'm still experimenting :)

So I made a feed-line... and currently have 5 different length wires attached to it...

Here are the calculations I made, and cut the 5 wires to:

Code: Select all

Wire length in centimeter.
Resonant frequencies of that wire length.

------------------------------------------------
185 cm

freqs:
1/1 = 162 MHz
3/4 = 121.5 MHz
5/8 = 101.25 MHz
1/2 = 81 MHz
1/4 = 40.5 MHz
1/8 = 20.25 MHz
------------------------------------------------

------------------------------------------------
154 cm

freqs:
1/1 = 194.4 MHz
3/4 = 145.8 MHz
5/8 = 121.5 MHz
1/2 = 97.2 MHz
1/4 = 48.6 MHz
1/8 = 24.3 MHz
------------------------------------------------

------------------------------------------------
42 cm

freqs:
1/1 = 731.6 MHz
3/4 = 535.2 MHz
5/8 = 446.0 MHz
1/2 = 356.8 MHz
1/4 = 178.4 MHz
1/8 = 89.2 MHz
------------------------------------------------

------------------------------------------------
128 cm

freqs:
1/1 = 233.28 MHz
3/4 = 174.96 MHz
5/8 = 145.8 MHz
1/2 = 116.64 MHz
1/4 = 58.32 MHz
1/8 = 29.16 MHz
------------------------------------------------

------------------------------------------------
61 cm

freqs:
1/1 = 486 MHz
3/4 = 364.5 MHz
5/8 = 303.75 MHz
1/2 = 243 MHz
1/4 = 121.5 MHz
1/8 = 60.75 MHz
------------------------------------------------
I am receiving on it, but I'm wondering if there are some ill-effects of this I'm not aware of (Like phase-cancellations I haven't yet noticed. I just put it up an hour ago, so the testing I've done is still limited)

All the antenna-wires are just thin speaker-cable, which are all mounted in the same little socket (I used a simple "Screw Type Wire Connector") which also has the lead of the feed-line connected.

I first tried with a single antenna connected, which worked fine, and now I'm trying with all 5 connected, and it still works fine (Based on my initial and early testing.)

One other thing to note; I have this 'antenna array' hanging upside down below a long horizontal metal-pole. The idea is that this metal-pole then serves as '2 ground radials' (I live in an apartment and I don't think the floor has anything in it that would work as antenna-ground)

I hope it's ok I ask all these (Probably very newbie to the more experienced) questions :)

My goal is to have a somewhat 'united setup', so I don't have to switch antenna each time I switch to listen to different bands of interest.
And I plan on also attaching a 10 meter wire to this 'array' (So I also have short-wave signals), unless somebody tells me this whole 'array' thing is a stupid and counter-productive idea.

JEL
Posts: 92
Joined: Wed Feb 07, 2018 2:08 am

Re: Multiple monopoles on same feed-line?

Post by JEL » Fri Feb 16, 2018 5:39 am

Just a short progress-report (For anybody contemplating a similar setup)

I now have 9 wires running in the array.

The 8 listed in the code-section, and a 10 meter long wire:

Code: Select all

Prime freq
Prime ratio and actual wire-length in meter

Additional freqs the wire will receive
(Not sure if the 1/1 ratios produce any usable energy)

------------------------------------------------
121.5 MHz
3/4 = 1.8505707283950619

sub-freqs:
1/1 = 162 MHz
3/4 = 121.5 MHz
5/8 = 101.25 MHz
1/2 = 81 MHz
1/4 = 40.5 MHz
1/8 = 20.25 MHz
------------------------------------------------
------------------------------------------------
121.5 MHz
5/8 = 1.5421422736625514

sub-freqs:
1/1 = 194.4 MHz
3/4 = 145.8 MHz
5/8 = 121.5 MHz
1/2 = 97.2 MHz
1/4 = 48.6 MHz
1/8 = 24.3 MHz
------------------------------------------------
------------------------------------------------
446.0 MHz
5/8 = 0.42011274943946186

sub-freqs:
1/1 = 731.6 MHz
3/4 = 535.2 MHz
5/8 = 446.0 MHz
1/2 = 356.8 MHz
1/4 = 178.4 MHz
1/8 = 89.2 MHz
------------------------------------------------
------------------------------------------------
145.8 MHz
5/8 = 1.2851185613854597

sub-freqs:
1/1 = 233.28 MHz
3/4 = 174.96 MHz
5/8 = 145.8 MHz
1/2 = 116.64 MHz
1/4 = 58.32 MHz
1/8 = 29.16 MHz
------------------------------------------------
------------------------------------------------
121.5 MHz
1/4 = 0.6168569094650206

sub-freqs:
1/1 = 486 MHz
3/4 = 364.5 MHz
5/8 = 303.75 MHz
1/2 = 243 MHz
1/4 = 121.5 MHz
1/8 = 60.75 MHz
------------------------------------------------
------------------------------------------------
137.5 MHz
1/4 = 0.5450771963636364

sub-freqs:
1/1 = 550 MHz
3/4 = 412.5 MHz
5/8 = 343.75 MHz
1/2 = 275 MHz
1/4 = 137.5 MHz
1/8 = 68.75 MHz
------------------------------------------------
------------------------------------------------
137.5 MHz
3/4 = 1.635231589090909

sub-freqs:
1/1 = 183.33 MHz
3/4 = 137.5 MHz
5/8 = 114.58 MHz
1/2 = 91.67 MHz
1/4 = 45.83 MHz
1/8 = 22.92 MHz
------------------------------------------------
------------------------------------------------
864 MHz
1/4 = 8.674550289351853 cm

sub-freqs:
1/1 = 3456 MHz
3/4 = 2592 MHz
5/8 = 2160 MHz
1/2 = 1728 MHz
1/4 = 864 MHz
1/8 = 432 MHz
------------------------------------------------








////////////////////////////////////////////////////
freqs covered

20.25 MHz
22.92 MHz
24.3 MHz
29.16 MHz
40.5 MHz
45.83 MHz
48.6 MHz
58.32 MHz
60.75 MHz
68.75 MHz
81 MHz
89.2 MHz
91.67 MHz
97.2 MHz
101.25 MHz
114.58 MHz
116.64 MHz
121.5 MHz
137.5 MHz
145.8 MHz
162 MHz
174.96 MHz
178.4 MHz
183.33 MHz
194.4 MHz
233.28 MHz
243 MHz
275 MHz
303.75 MHz
343.75 MHz
356.8 MHz
364.5 MHz
412.5 MHz
432 MHz
446.0 MHz
486 MHz
535.2 MHz
550 MHz
731.6 MHz
864 MHz
1728 MHz
2160 MHz
2592 MHz
3456 MHz

////////////////////////////////////////////////////
The good: It gives lots of signal.

The bad: it gives lots of signal.

It doesn't seem to create any 'black holes' (Phase-issues), but I'm not sure about that.
If there are black-holes they may be on bands where I didn't receive any traffic before, because I haven't lost any traffic in the bands I had traffic on with single antenna setups.

However, the noise from strong bands interfere much more now than when using single antennas.

So it's good when doing broad-band scanning of larger bands, to find traffic, but not so good when focussing on particular bands.
For example; with a single antenna tuned for the aviation-band I get low noise and good signal. With the multi-array I get lots of noise/interference and still good signal (Except where the interference interferes, it can really become a 'battle of carriers')

Another lesson learned I suppose :)

I'm planning an experiment with large hollow aluminum tubes (As wide as a fist), that I want to turn into a vertical dipole (For the aviation-band, which is my main focus)

Post Reply