160 Meter Inverted "L"

My 160 meter inverted “L” was an antenna of necessity. I had up a OCF dipole for 160, it was constructed with 14 ga. solid copper wire and fed with a 4:1 balun. It was a lot fitter in that I don’t have a lot of tall trees to support antennas. Well one not so fine winter day last December I was getting things ready for the Every Night 160 Meter Net on 1.895 Mhz and the antenna would not tune, I checked coax and connectors inside and out and discovered that there was a break in the antenna at one of the insulators and the support rope had grown into the 80 foot white pine I had supporting that leg so fixing it was not possible until spring. I really wanted to run the CQ 160 meter contest the end of February so the planning started. I had heard a lot of L type antennas on the air and had heard good things from the guys running them, and based on my location and tree situation I elected to put up an inverted “L”.

So Construction starts. I went to E-Bay (Harold W8GEG at www.hamradiodeals.com  and ordered 48 foot of that green aluminum mask that they use to support camo netting and in the field expedient antenna kits. I bolted these together with ¼” bolts and star washers and ensured a good electrical connection with self–tapping sheet metal screws. I welded ¼” thick by 3” wide tabs on the bottom section so I could mount it to a treated 4X4. The overall length once assembled was 44’ – 6”. I set guy rings at 2 points on the mast, 1 section down from the top and 4 sections below that. I mounted an eye bolt on the top and attached a dog bone insulator with 3/16 “ nylon rope (See Photo). Using the formula 234/frequeny I determined that the total antenna length needed to be 130', I added 5' for a total of 135'. The wire part of the antenna was 14 ga. copper clad steel wire, purchased from www.thewireman.com, the length was 90 foot. I attached it to the dog bone insulator at the top section then used a piece of copper braid to connect it electrically to the mast. One day towards the end of January I recruited stalwart amateur radio operators to erect and guy my newly constructed master piece. I had to feed them a good breakfast of sausage gravy and biscuits, eggs and juice to fortify them for the January cold here in northern Michigan, but it was well worth it. I had all the guys set up ahead of time and all anchor points ready. We snapped it into place on the second try and then evened the guy lines. I had already driven a 10’ copper clad ground rod into the swamp were I set the antenna support. I fed the mast with a 1:1 5/10KW balun from DX Engineering, (Balun - 1:1 5 KW / 10 KW For Use With Antenna Tuner - DXE-BAL050-H10-AT )   www.dxengineering.com , one post to the antenna mast and the other to the ground rod. I had already laid out 3 ground radials 135’ long . I anchored the wire from the top back to the peak of my roof on the house. I also put a 10 Meg Ohm 30 Watt non-inductive resistor across the balun posts to bleed off any static build-up on the antenna. Now it is time to tune it up.
I connected my Autek VA-1 antenna analyzer and it came up resonant at about 2.100 Mhz, about 300 Khz short. I got the calculator and antenna analyzer out and ran the numbers from the analyzer and added 16’ more wire to the antenna. I tested again and it came up resonant at 1.821 Mhz. I was shooting for 1.830 Mhz. so I left well enough alone as it was getting late in the day and the temp was about 8 degrees F. The SWR at resonance was 1.4:1. It stays under 2:1 until 1.900 Mhz. then the SWR rises fast. For the upper part of the band I have to use the antenna tuner. Very little inductance is required, and with some input and antenna capacitance it is good to go for all of the 160 meter band.

We worked the CQ SSB contest the end of February 2011. We worked Bosnia and Portugal, as well as eight South American and Caribbean stations, 47 of the lower 48, missed out on Nevada. We had a total of 287 contacts on 160, and most of all we had a blast. The operators were WY8F, N8WLU, KB8UFJ, (the same stout lads who helped erect the antenna in January), and myself W8CT.

Since I first posted this I have changed the ground radial system to 4 radials elevated to 6 foot above the swamp, tuning changed very little but bandwidth decreased slightly. I am awaiting the sure to arrive winter here in northern Michigan and I hope good 160 conditions to see if the juice was worth the squeeze. 
 

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