Antenna quests - Random Wire

Advantages

• Multiband
• Short feedline or no feedline at all
• Only two contact points when deployed as a slopper
• Lightweight
• The tuner is able to compensate the deviations from the optimal deployment configuration

Disadvantages

• Non-resonant antenna (needs tuner)
• Needs counterpoise
• Too long for vertical deployment
• Impedance higher than 50Ω, needs a transformer

Deployment

Telescopic mast (6m), slopper configuration

[mast] ------ radiator ------ [transformer] --- coax (10') --- [tuner] --- coax (3') --- [rig]

Transformer

The goal here is to bring the impedance as close to 50Ω as possible for the differends bands and leave the tuner do the rest. So 9:1 transformer is OK.

Tuner

I am suing ATU-10, because the popular Elecraft and MAT equivalents are no longer available. ZM-2 would have been another nice alternative but I found out about it when the ATU-10 was already on the way.

Test 1

I was told that for this type of antenna, the length of the coax is a variable to take in consideration (it is part of the radiator). My initial test was with 3m RG316 coax, 9m radiator wire, 7.5m counterpose lying on the ground and a homebrew 9:1 transformer. It had a good SWR on 40, 30, 20, 15, but not on 17. I was even able to work a local ham on 10M SSB with this setup :)

Test 2

The second test was combination of EFHW and RW

1. For 17 and 20 meters band, I used linked radiator and 81:1 transformer.
2. For 30 and 15 meters band, I used the same radiator with the tuner and the 9:1 transformer and 9.5m counterpoise lying on the ground (my backup EFHW radiator).

I am very pleased with the result. The SWR on 30m was 1:1.16 and on 15 it was 1:1.04 This will probably be my main POTA setup.

Test 3

Trying to trim the radiator so that the tuner can find an acceptable match on 30-20-17 bands. The coax from the 9:1 transformer to the tuner was 10' RG316 and the coax from the tune to the rig was 3' RG316.  The theoretical sweet spots are supposed to be somewhere around 29', 35.5' and 41' Knowing that the setup and the coax length affect these numbers, I  got a long piece if wire ans stared cutting down. The table shows the SWR values of the tuner; the radio 9TX-500) had more optimistic values (about 0.4 lower).

L (m)	L (ft)	30M	20M	17M	15M
13.0	42.7	1.34	1.30	1.30	3.00
12.6	41.3	1.17	1.60	2.09	2.20
12.3	40.4	1.23	1.90
12.0	39.4	1.23	1.77
11.6	38.1	1.02	1.77	1.47
11.3	37.1	1.09	1.61	1.17	1.61
11.0	36.1	1.38	1.42	1.19	1.07
10.6	34.8	1.11	1.22	1.29	1.01
10.3	33.8	1.14	1.09	1.52	1.02
10.0	32.8	1.01	1.17	1.85	1.15
9.5	31.2	1.05	1.91	2.20	1.10
9.0	29.5	1.15	3.30	2.60	1.00
8.6	28.2	1.46	2.70	2.80	1.07
8.3	27.2	2.00	5.00	3.00
8.0	26.2	2.50	1.85	2.66

The best results were somewhere around 10.6m (34.8') of radiator length. I am surprised that the 29' zone did not work. Either the tuner is not so capable or I should have used smaller cutting steps.