Several delta loops - one feed?

[misterpaul71]

Hi all,

heres a question for any antenna gurus out there. I want to put several delta loops on one boom and feed them with one line. Is this possible?

I saw a picture in Les Moxon's HF antenna book showing two delta loops one for 15 and one for 10 m connected in parallel with "low impedence line" what Im wondering is - whats the line value, is it 75 ohm open wire? The pic refers to a CQ magazine article but doesnt say what the line value is.

I want a multi loop set up for Low VHF reception with loops cut for 33.7 35.5 37.5 etc but all fed with one line.

Anyone got any ideas on achieving this?

I'd like to do it without use of a 4:1 balun which is the usual method of getting one loop to tune several bands. I'd like several resonant loops inside each other on the one support with one feed ideally.

Any ideas would be very interesting.

Paul Logan
Lisnaskea, Ireland.

 

[LtDoc]

Paul,
One loop inside another is the usual way the driver is arranged for a multiband 'quad' antenna. The feed point impedance will be larger than 50 ohms, normally, but adding the other elements like a typical 'quad' lowers that feed point impedance to something near 50 ohms. The more elements added (directors/reflector) the lower the input impedance. So, without those other elements you can count on a higher than 50 ohms input impedance. There are ways of lowering that impedance but 75 ohm cables aren't going to work too well, they are all frequency related, one for one band isn't going to work on another band.
Good luck with it.
- 'Doc

 

[misterpaul71]

Several Loops one feed

Hi Doc,

so what is the typical way of feeding the driven elements within a quad?

I tried two loops inside each other fed at the same point but resonance was all thrown out, so I put the idea on hold. Im using a rectangular loop for low vhf. its cut for 33.7 and working quite well, but i'd still like to put some smaller loops inside it to cover up to say 50 mhz.

Paul.

 

[k9rzz]

For reception only, I would just run with one loop set for the center of your range and forget the others. You won't notice any difference. FWIW, for long distance reception and since most VHF sigs are vertically polarized, I suggest putting the feed on the side, not the bottom.