SKCC 5123T----- FISTS 14979----- Flying Pigs 2331----- NAQCC 3610-----QRP ARCI 14176-----Polar Bear 257

Monday, May 22, 2017

N4KGL Field Day Loop Antenna Refinements

On Sunday afternoon I spent some more time on my Field Day Loop. I measured it out and put the insulators at the right places. I also setup a feed point at the bottom center and the bottom corner. I made a 300 ohm jumper to the AH-4 tuner. I have not tested it with the AH-4 yet. Thanks to Myron WV0H for help with analysis of this antenna. 

This is a 100 ft wire loop 30 ft across by 20 ft high. The bottom wire is 10 ft above the ground. It is NVIS antenna on 40 meters and has 39 deg elevated lobes broadside on 20 meters when fed at the  bottom center. It has low angle radiation on 20 through 10 meters when fed a the bottom corner. The three poles are strapped to angle iron driven in 1ft in the ground. The poles allow raising the loop in push-up fashion. It is designed to fit in a camp site without using trees or extending beyond the bounds of the camp site. I can use the Icom AH-4 tuner or a matching transformer with a tuner at the rig. The 300 ohm feed line and tuner can be switched from bottom center to bottom corner.







Wednesday, May 17, 2017

The May 2017 Second Saturday Sprint

The 2017 Second Saturday Sprints sponsored by QRP Field Ops Google Plus Community began on May 14th. These are two hours 1900 UTC to 2100 UTC. See the rules at this link. The goal is to work other members of the group. However, any contacts you make will count. Therefore you can leverage off of other events. This is good practice for RaDAR style ops. I leveraged off of SKCC contacts and Arkansas QSO Party. Likewise I have a cadre of local chasers. They had no problem working me in town on HF. I also made contacts with them on 2 meter simplex.

Note the three poles for the loop antenna.

I setup in the front yard of my house. I wanted to test an antenna configuration for the upcoming Field Day. The antenna is a 30 ft long by 20 ft high loop supported by three 30 ft fiberglass poles. The motivation for the loop is to stay within the confines of the camp site at Falling Waters State Park. I anchored the poles with a length of angle iron. I pound them in the ground about one foot and strap the poles to them. I can attach the wires at the top of the poles and push the poles up. There is no weight at the top other than the wire going across. This is pretty easy to erect. The loop is fed at the bottom center which is about ten feet high. I used a Chameleon 5 to 1 transformer at the feed point and 30 feet of  RG-8X to the tuner which is an LDG IT-100. The rig was my Icom 7100 on battery.

The Chameleon 5 to 1 transformer at the bottom center of the loop
For the sprint I started on 40 meters. There was very little activity on the band perhaps due to conditions. I did snag local chasers Rick NZ2I, Bob WB4BLX and Bob KK4DIV. So I don't think I can draw any conclusions about the antenna on 40. I hope on the next test the band is more active. On 20 meters the band was better. I worked six stations out of town with no problem I also got WB4BLX, KK4DIV and Phil N4STC near by. So I will give the loop antenna a passing grade on 20 meters.

Angle iron at the base of the Jackite 31 ft poles.

Myron WV0H kindly did some analysis on the antenna configuration. The analysis indicated that using larger coax like LM400 would be beneficial to reduce losses. I have many options for feeding and matching the antenna. I may try 300 ohm line as well. Note, I plan to dry run Field Day on June 2nd at the Falling Water Camp site. Then I can custom fit this antenna to the site. Of course I have many antenna options to consider.

Operating from the shade

I am looking forward to future Second Saturday sprints. I hope to work some members next time. I also did some satellite work earlier in the day. I met with Bob KK4DIV and Bob WB4BLX behind the PCARC Club house. I was able to get three on FO29. So I got a good dose of ham radio on Saturday.

FO 29 linear Satellite Ops. Photo by Bob KK4DIV