Hello Berne,
I couldn’t access your diagram / picture on Imageshack dot com but I’ll attempt to address the Grounding Issues that you’re wondering about. Since your future ham shack will be located on the second floor of the structure, then here’s what I will discuss and recommend.
What type of a Ground System are you attempting to build?
Most grounding systems implemented in commercial two-way radio installations is used to prevent major lightning damage to the radio equipment if the antennas should be struck by lightning. They’re also installed to eliminate stray RF and AC power voltage differences between the different pieces of equipment within the station system, eliminating electrical shock hazards. In an Amateur Radio Station you’re essentially trying to incorporate the same techniques. Remember, Safety First!
You want to keep all ground leads as short as possible within reason therefore providing the least resistance to the actual earth ground itself. When measuring ground systems most electrical power and/or telecom companies use an instrument called a “Megger” for measuring the resistance between the earth ground rods and equipment. In most cases, hams do not have access to this device so we have to research and refer to publish electrical specification from known sources such as the EIA/TIA, the Reference Data For Radio Engineers, the RSGB or the ARRL handbooks.
Grounding is very important to provide a common ground bonding point between the structure’s (building) electrical 121/220/240V AC primary power source and the new antenna system / station ground. Lightning has been known to come down an antenna feedline and/or antenna structure (tower) and having a potential difference between the antenna system when properly grounded Negative Charged and if the structure’s primary power and/or telecom wiring ground is not tied together properly this ground appears to be a Positive Charge. Then the lightning will arc over, coming back up on the primary power and Telco lines blowing electrical breakers, damaging consumer electronic equipment and land-line telephones inside the structure on its destruction path.
Since I have no idea what your multi-floor structure construction is comprised of, wood, brick, concrete or metal, but you have provided a length of 20 feet between earth ground and the second level then I would suggest to purchase the required length of
.257 inch stranded copper wire with a Black or Green insulation to install between the 10 foot copperweld ground rod (driven into the earth ground) and the second level. The larger the copper cable is, the less it appears as an inductance or inductor in a grounding system. I’m not sure since you reside in Europe whether you have access to building supply stores similar to the U.S. Retail Outlets like The Home Depot or Lowe’s, which are Do-It-Yourself type stores.
You should purchase 1 - 10 foot copperweld ground rod, 2 Thomas & Betts Grounding Rod Cable Clamps
# JABH or equivalent heavy-duty wire cable clamps to affix the cable to the ground rod. Add a second
# 4 or
# 6 AWG wire / cable with a Green insulation at the required length to the building’s
240V AC electrical primary power panel ground terminal to prevent voltage differences between the new antenna / radio equipment ground and the existing primary electrical power source to the structure. Green insulation indicates that the wire cable is associated with the ground circuit.
At the second level providing you can get approval from the owner of the structure / building, measure the thickness between the outside & inside walls and drill a hole directly through the structure’s wall. Purchase a Steel threaded rod
.25-inch diameter at the required length with 4 nuts, couple of locking washers and a pair of
4 X 4 X .125 inch Aluminum or Steel metal plates to mount the threaded rod through the wall and to prevent the hardware from crushing the drywall interior wall when tightening the hardware.
Thomas & Betts also manufactures and sells large cable clamps
BTC3104-B2 or equivalent manufacture to affix to the large copper cable and the threaded rod. Once all the exterior electro-mechanical connections are tightened in place, brush on
3-M Liquid Electrical Tape on the connections preventing any corrosion from starting.
Harger – OEM Lightning Protection Supplier
http://www.harger.com/
Thomas & Betts – OEM Electrical Connector & Grounding Supplier
http://www-public.tnb.com/ps/util/index ... _grounding
Surplus Sales of Nebraska – New & Used Equipment Supplier
(WBR) GB-500 Tinned Braid
http://www.surplussales.com/
Do all the radio components need to be connected together?
Yes because this reduces electrical shock hazards between the individual component boxes within the radio room. I would recommend purchasing a minimum of 25 feet by .5 inch Width of Tinned Braid. The Braid is a non-resonant RF wire preventing RF ground loops. On most pieces of radio equipment in the rear there’s a winged nut for connecting the ground braid / wire too and then running the braid to the common earth ground connection. In your situation it will be the .25 inch threaded rod.
How close does the antenna tuner need to be to Ground?
In your situation the Antenna Tuner could be placed within 4 to 10 feet of your new grounding system. Naturally the shorter the braid ground length would be wiser.
What type of feedline are you intending to use with the MFJ-971 Tuner?
Now here’s an interesting question in regards to the type of RF transmission line to be used with the antenna tuner. Using the IC-718 H.F. transceiver, you should purchase a good grade 1 KW Loss Pass Filter and place it in between the transceiver and the antenna tuner. The Low Pass Filter reduces all unwanted spurious RF harmonics from the H.F. transceiver. Use RG-213/U 50 Ohm (95% Shielded) coaxial cable with PL-259 connectors on both ends of the coaxial cable.
Insert one PL259 into the transceiver’s SO239 RF Output connector and the other end of the coaxial cable with its PL259 into the Input SO239 of the Low Pass Filter. Take a second RF coaxial cable with PL259 connectors on both ends and insert one PL259 connector into the Low Pass Filter SO239 Output connector and the opposite end with it’s PL259 connector will insert into the MFJ-971 antenna tuner RF Input SO239 connector. The MFJ-971 antenna tuner has 2 or 3 different output connectors, one being a SO239 Coaxial, a second pair for open ladder line like used on the G5RV antenna and the third configuration would be for load a single open line or a inverted “L” antenna.
First you need to realize that the MFJ-971 Antenna Tuner does nothing more than present a 50 Ohm load to the H.F. transceiver by the inductors and capacitors in the tuner compartment itself when a non-resonant antenna is connected to the units output connectors. It doesn’t perform any RF filtering or improve antenna performance. It’s just a matchbox between the transmitter and the antenna.
The reason a Grounded antenna tuner is important is it allows the user to tune the antenna circuit easier and having less stray RF in the operating room. You should have minimal frequency degradation on transmit or receive of RF signals while using the IC-718 H.F. Transceiver and the MFJ-971 Antenna Tuner.
Let me take this issue one step further in relationship to the Voltage Standing Wave Ratio or VSWR of the antenna load indicated below:
A 3 to 1 VSWR equals 25% of the Transmit RF signal is Reflected
A 2 to 1 VSWR equals 11% of the Transmit RF signal is Reflected
A 1.5 to 1 VSWR equals 4% of the Transmit RF signal is Reflected
A 1.4 to 1 VSWR equals 3% of the Transmit RF signal is Reflected
A 1.3 to 1 VSWR equals 2% of the Transmit RF signal is Reflected
A 1.2 to 1 VSWR equals 1% of the Transmit RF signal is Reflected
A 1.1 to 1 VSWR equals a perfect match
In the Commercial Land Mobile Radio FM and SSB communication systems, any reading of 1.5:1 VSWR or lower is perfectly acceptable and trying to reduce the 1.5:1 to 1.4:1 or lower is only a waste of your time because it will
never change the received signal.
Lets look at the transmission line or feedline Pros and Cons. Did you know that properly installed “Open Ladder Line” has LESS RF signal loss than the best 50 Ohm Andrew’s Heliax RF Coaxial Cable? Yes, it’s true even up into the 500~600 MHz UHF Frequency range. Ladder line presents a constant 300, 450 or 600 Ohm Balanced Impedance depending on the open ladder line used in the antenna system. The drawbacks happen when there’s a change in our weather conditions such as rain, snow or ice that collects on the open wire lines changing the impedance and your transmitter will always require some sort of an antenna tuner or matchbox. Ladder line is not suitable for mobile applications.
Using a good grade of 50 Ohm Coaxial Cable for the H.F. bands such as
RG-213/U Military Spec which has 95% shielding and solid dielectric between the shield and the center conductor oppose to RG-8/U provides an all purpose RF transmission coaxial cable in any kind of weather or mobile application. The only disadvantage is the RF line losses above 40 MHz, which is 1.2 dB per 100 feet or 22% of the RF Output Power is lost in the feedline. As the frequency increases to 150 MHz the line losses increase to 2.8 dB per 100 feet or 48% of the RF Output Power is lost in the feedline and at 450 MHz, which is 5.2 dB per 100 feet or 72% of the RF Output Power is lost in the feedline.
Above 30 MHz the use of Andrew’s or RFS Cablewave Heliax RF coaxial cable takes over because this type of feedline has much lower “dB’ Losses Per 100 Feet / Meters characteristics at 30 MHz, 50 MHz, 70 MHz, 150 MHz, 220 MHz, 450 MHz, 900 MHz and Microwave Frequencies. This cable is not normally suited for mobile applications.
Whether you use the G5RV Open Ladder Line connected directly to your MFJ-971 Antenna Tuner which will require 2 individual Porcelain type feed-through to get the line outside or RG-213/U coaxial cable which again will require a bulkhead SO239 feed-through. These come in many lengths up to 8 to 10 inches long with mounting nuts, is strictly your choice.
If you’re using a G5RV antenna in an inverted “V” configuration, the top of the “V” should be between 30 or 40 feet above earth ground and the inverted “V” will act as an Omni-directional antenna. Remember to keep the wire ends insulated and above earth ground by 2 or 3 feet.
The equipment and DC power voltage requirements.
In your text you’ve mentioned using a 22V Power Supply for the ICOM IC-718 transceiver. I hope that was a typo and you meant 12V DC. Most if not all solid state Amateur Radio equipment operates off of
+13.8V DC Negative Ground Power Supplies or Automotive electrical systems. If you’re intending to use
22V on that transceiver, I think it’s heading to the repair shop immediately if not sooner!
73,
Dan
WA9WVX
