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System with 8 K9AY loops

By Al Merriman - K4GLU
K9AY web group, October 11, 2000

Having spent some additional time on testing a 2 / 8 loop system, I have found this:

1. The system definitely works. I'm able to get nulls in all 8 directions.
2. When the two loops are connected in series - NE/SE/SW/NW - there is some improvement in signal strength - I'm seeing 2-4 db typical.
3. Unfortunately I'm unable to get nulls with the 2 / 8 setup that equal what I'm currently getting from my two 2 / 4 setups where I use separate Vactrols on on each loop. This is in all directions - not just when the loops are connected together in series.
Most testing has been done during the day when signals were steady and was done in two ways. Head to head where I used one setup on each of my two sets of loops with the loops oriented as closely as I could get them in the same direction and I also tested the two systems by swapping them on the same set of loops so there could be no question of slightly different loop orientation affecting the results.

In all tests my 2 / 4 setup with two Vactrols out performed the 2 / 8. Understand this is not in every instance - on some frequencies they were virtually equal but on others there was enough difference that it affected readability.
One example.
On 1160 kHz my dominant station is WOBN in New Jersey to the North. With my 2 / 4 setup when I switch South I can completely eliminate WOBN and hear VSB Bermuda in the clear. With the 2 / 8 setup while I was able to null WOBN in no direction was I able to completely take them out like I can with the 2 / 4. There were a number of others frequencies where this same situation existed.

Since I already have a 4 / 8 setup using two sets of two loops that works extremely well I don't plan at this time to do any more testing with the 2 / 8 setup. Also my setup with two sets of two loops allows me to select one loop from each set and use them with a phasing unit. This works very well and allows me to deal with the few situations where I can't get nulls with the K9AY's alone.

A few words about the two Vactrol setup.
Back in 1998 one of the things I experimented with was the possibility of using the two loops in a standard two loop setup to each side of a phasing unit. Since the loops were at right angles to each other I thought that there might be enough difference in pickup pattern of the two to make this work. I built a set of loops that were conventional in the fact that both loops were hung form the same center support.
Beyond that I built a head/control unit that treated the two loops as being completely separate antennas with each having its own Vactrol termination, matching transformer and feedline coming into the shack.

This setup worked fairly well but there were some situations where nulls were difficult to get. One thing I did find out was that in some instances when using the antennas as a conventional K9AY that nulls on the loop in use could be improved by varying the termination of the loop that was not in use.
This seems to indicate that there is some interaction between the two right angle loops. At times this null improvement made the difference between completely eliminating a dominant and leaving it mixed with the station you were trying to hear.
Also, when comparing this system against a normal 2 / 4 setup with a single Vactrol the two Vactrol setup gives better, deeper nulls in some but not all situations.

Hopefully others will do some testing with the 2 / 8 setup. Although I have no plans to do any additional testing with mine I may get it out from time to time and play with it a bit.
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