SWL GRUNGE-MASTER .625 WAVE CB RADIO BASE STATION ANTENNA
SWL GRUNGE-MASTER .625
The diagram for the $150 SIRIO Gain-Master 5/8 wave CB radio base station antenna is on the antenna's brochure. Inside the fiberglass shell of the Gain-Master 5/8 wave base antenna is a ham radio 'Flower Pot' like antenna design, that is constructed from high quality coaxial cable and wire.
I am going to build an antenna that is similar in design, using cheap coaxial cable and 14 gauge wire. I am going to disregard the matching section / coaxial cable stub that is normally used with this design, as this antenna will be used in an SWL / SDR Radio / receive only application.
THIS ANTENNA REQUIRES AN ANTENNA TUNER FOR TRANSMIT USE
: MATERIALS USED :
25 FEET RG-58 A/U COAX ($10)
15 FEET OF 14 GAUGE STRANDED COPPER WIRE ($5)
:DIRECTIONS: (THE DIRECTIONS CORRESPOND TO THE PICTURES BELOW)
1: RF Choke: Wrap coax 16 times around a 66mm plastic tube.
2: Measure 141.7 inches up from the top loop of the RF choke. Cut coax.
3: Measure 135.8 inches up from the top loop of the RF choke and mark that point. Then measure one inch higher and mark the point. Carefully remove the coax insulation and coax braid inside that 1 inch area of the coax, without cutting in to the center of the coax.
4: Measure 3.4 inches above the point where you have removed the coax insulation and braid. Whatever coax remains after that 3.4 inches, expose the coax outer braid and tin with solder. Insulate the center conductor of coax.
5: Solder 11 feet of wire to the coax braid on the end of the coax portion of the antenna.
Total length of antenna from top of RF choke to tip of antenna = 22.7 feet / 6.9 meters
The SWR of the antenna is 2.5 to 1 to 3 to 1. This SWR is acceptable for a five dollar garage sale CB radio, but, most users are going to need an antenna tuner.
I connected the antenna to an MFJ-949E Desktop Antenna Tuner and stock Uniden Bearcat 680 CB Radio. (4 watts) A station 5 miles away reported a signal of S9+20dB. A station 12 miles away reported a signal of S8. The furthest contact was a trucker located 22 miles away.
After adding a power microphone to the stock CB radio, I was able to make a stateside skip contact with a station in Georgia. (1400 miles)
With the base of the antenna only a few feet above the ground, transmit performance is that of using a popular CB radio base station antenna on a 15 feet long pole.
POWER HANDLING CAPABILITY
The SIRO Gain-Master has a power handling claim of 500 watts. Considering that this home brew antenna is made of cheap, lower grade materials, I personally would not load this antenna up with more than 100 watts.
THE SIRIO GAIN-MASTER IS WORTH BUYING
When I first saw the SIRO Gain-Master antenna's $150 price tag, I considered it to be a bunch of hype surrounding an overpriced product. My views on this matter have changed. With the price of an Antron 99 being $100, the Gain-Master's performance is worth the extra $50. Especially if you value features like low noise floor, improved local reception and high performance when mounting the antenna near the ground.
The SIRIO Gain-Master would make the world's best HOA / covert Flag Pole Antenna. With the base of the Gain-Master antenna sitting on the ground, inside of a 25 feet tall plastic flag pole, the antenna will perform like a base station antenna that is 11 feet above the ground.
Both ends of a vertical dipole radiate / receive, but, the top section is obviously doing most of the relative work.
HANGING THIS ANTENNA
I cut up a few old fishing poles and taped them together, which produced a sturdy pole that is 13 feet in length. I attached the 13 feet of fishing pole to a 10 feet section of PVC pipe, which produced a very lightweight pole that is 23 feet in length.
I cut the top and bottom ends off of a plastic water bottle, creating a cylinder shaped object. I taped the plastic cylinder to the end of the 23 feet long pole.
I cut a plastic clothes hanger in to a fish hook like shape. I attached this plastic hook to the end of the wire antenna. I lightly stuffed that hook in to the plastic cylinder on the end of the pole. While standing on a step ladder, I guided the end of the pole up to a small tree branch that is 28 feet above the ground. When the plastic hook was around the small tree branch, I pulled the pole away, causing the hook to come out of the plastic cylinder on the end of the pole, thus hanging the antenna.
This primitive installation has survived several wind, ice and snow storms. Snow and ice does not collect on the antenna, as the plastic insulation on the coax and top section wire is too oily to allow accumulation. If it ever comes down I'll wipe it down with WD-40 and put it back up.
Here is a video to showcase the antenna's DX reception.
HOME MADE 5/8 WAVE CB RADIO BASE STATION ANTENNA
AMAZING RECEPTION! With the base of the antenna only 3 feet above the ground, it performs like a 5/8 wave base station antenna that is mounted 15 feet above the ground. There is a logical explanation for this outstanding performance.
The SIRIO Gain-Master design is a center fed 5/8 vertical dipole. It is a balanced / decoupled antenna, therefore it does not require a counterpoise / ground plane. When the base of the antenna is sitting on the ground, the business end of the antenna is 11 feet above the ground.
This antenna has a very low noise floor, thus providing excellent signal to noise ratio. More desired signals and less noise. This dramatically improves the listening experience on the inherently noisy CB radio band.
Here is a video to showcase the antenna's local reception.