The Nashua Area Radio Society tries to do something new each time we engage in an Emcom or other major operation. We decided to try Winter Field Day for the first time this year and we made one of our new elements a capable 160m portable antenna system and station for 160m.
It’s almost impossible to field an effective 160m station with only a Transmit antenna. Transmit antennas typically are too noisy for effective operation on the low bands. We decided to try a Beverage On The Ground antenna for the receive side of our 160m station. This proved to be a great choice.
We’ve been using the Icom IC-7300 Transceiver almost exclusively for our Field Day stations for the last several years. Many of our members have this rig and its performance and excellent ergonomics make it a great choice. The problem was that we needed a receive antenna input to make the IC-7300 work with our 160m station plans.
Fortunately, INRAD came to the rescue with a simple mod for the IC-7300 to add a separate Rx antenna input to the rig.
This mod is simple and is super easy to install. It took me about 30 minutes to do the mod and it worked great. Removed the jumper and you have a separate Rx antenna input. Put the jumper back and the radio performs as stock.
Rx antennas typically benefit from the inclusion of a low-noise preamplifier to boost the relatively weak signals from the antennas. We also want a bandpass filter to protect our 160m radio from overload and potential damage which might eliminate from the other transmitters in our Winter Field Day setup. The KD9SV Variable Gain Pre-Amp filled the bill nicely.
We also added a KD9SV Front-End Saver to ground the input to the preamplifier/radio combination when the IC-7300 goes into transmit to further protect the electronics from overload or damage when transmitting on 160m.
We used KD9SV Reversible Beverage On The Ground (RBOG) Transformers to build our receive antenna. The length of the beverage wire is critical in an RBOG setup as an RBOG antenna is a resonant antenna. We used the recommended 180 ft of dual conductor RBOG Antenna Wire to create an antenna for 160m.
An RBOG Antenna such as our must be well grounded at each end. This was accomplished with a pair of 4 ft ground rods and three 50 ft long radials at each end in a crows-foot configuration. All of the need components for the antenna including interconnect and power cables, ground straps, and the electronics were package in a case to keep everything together.
The photo above shows one end of the RBOG antenna installed in the Field. You can see both the radials and the feed line transformer attached to one of the ground rods. Our antenna was fed with 300 ft of 75-ohm flooded coax terminated with F connectors. The direction of the antenna can be easily reversed by interchanging the feed line and the 75-ohm terminator at this end of the antenna.
We decided to set up and test the receive side of 160m station at our Winter Field Day site in advance to work out any installation issues and to gauge the system’s potential performance. Unfortunately, we ended up doing the test in the middle of the day when 160m was basically dead. We also tested the antenna on the AM broadcast band which is just below 160m and we heard 2-3 AM station on every AM frequency in the middle of the day! This was a very good sign of what was to come…
We built a 160m dipole for the transmit side of our 160m Portable Station. The heart of this antenna was a Balun Designs Balun optimized for operation on the low bands. Tuning of the antenna for best operation on the 160m band would have to wait until we had adequate space to set it up at our Winter Field Day site.
Setting up our 160m Transmit Antenna was the first order business for the Wire Antenna Team at Winter Field Day. We put up a 50 ft guyed push-up mast and used a pull-rope to hoist the 160m Tx Antenna’s Balun to about 48 ft. We used an air cannon to shoot ropes through two tall trees at the ends of the antenna and got it close to flat-topped.
After a little bit of careful tuning, we ended up very pleased with the end result. We had over 60 kHz of usable Tx bandwidth at the bottom of the 160m Band. We used the antenna as high as 1.838 MHz during Winter Field Day, and it performed great.
So how did the combination perform for us? Well, we made 133 CW contacts on the 160m band during the 24-hour Winter Field Day period, with the longest being to Missoula, MT – a 2,100 mi contact from here in New Hampshire. This is not bad for 100W and portable antennas on Top Band!