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TECH NOTES—GROUND RADIAL SYSTEMS

MOUNTING TUBE INSTALLATION

When tube w/insulator (A) is ground mounted, it should be protected against

corrosion if placed in concrete, damp acidic or alkaline soil.  Asphalt roofing

compound, polyurethane varnish or other sealant that protects against moisture

may be used.

Concrete may be used in areas of high winds for greater strength, in which case

the post may be twisted slightly during setting for easy removal later.

Tube w/insulator (A) must be installed in a hole approximately 21 in (53.3 cm)

deep so that the upper end of the fiberglass insulator is approximately 7 in (17.8

cm) above ground level.  Pack earth tightly around tube w/insulator (A) so that it

remains vertical.

NOTE: HAMMERING TUBE W/INSULATOR (A) INTO THE EARTH MAY CAUSE THE

INSULATOR TO SPLINTER.  If the post must be hammered into the earth, protect

the end of the insulator with a block of wood

NOTE: DO NOT USE U-BOLTS TO ATTACH TUBE W/INSULATOR (A) TO A MAST,

TOWER ETC.  U-BOLTS WILL EVENTUALLY CUT INTO THE TUBING AND

WEAKEN THE INSTALLATION.  If U-bolts must be used, place a larger diameter

metal, such as the MPS Mounting Post Sleeve over tube w/insulator (A).  Similar

precautions should be observed when using TV style towers with locking bolts.

The RMK-II Roof Mounting Kit includes the MPS as well as the STR-II Stub Tuned

Radial Kit.

GROUND MOUNTING

A vertical antenna in its simplest form, is electrically equivalent to

one-half of a dipole antenna stood on end.  When the antenna is

mounted close to the ground, the earth below takes the place of the

"missing" half of the dipole.  If ground conductivity is fair to good, a

short metal stake or rod may provide a sufficiently good ground

connection for resonant and low SWR operation on the bands for

which the antenna is designed.  This basic arrangement is shown in

figure 1.

The way it works is that the capacitance between the vertical radiator and the

ground causes 

return

 currents to flow along the earths surface back to the

transmitter.  If they have to come back along untreated lossy earth thy get back

to the source greatly attenuated.  This 

return

 loss is like a resistor in series with

the antenna radiation resistance and will therefore affect the feed point

impedance.

Содержание HF9V

Страница 1: ...GROUND IT IS ALSO RECOMMENDED THAT ALL STATION EQUIPMENT BE DISCONNECTED FROM THE POWER MAINS BEFORE CONNECTING THE FEEDLINE TO THE ANTENNA PLEASE CONSULT THE A R R L HANDBOOK OR OTHER REFERENCE MANU...

Страница 2: ...he end of the tube Pass a 8 x 1 1 2 screw through both parts and secure with a lock washer and hex nut 4 From the center of the insulator measure downward to a point that is 13 in 33 cm along tube B a...

Страница 3: ...t 40 meter D2 and install on the smaller 67 pF capacitor as above 12 Install the above assembly onto the 10 screw protruding from the tab of the center clamp on the coil assembly 80 40 meter C Align c...

Страница 4: ...et O1 around the fourth turn of the 40 meter coil on coil assembly 80 40 meter C Secure with a 8 x 3 4 screw lock washer and hex nut 24 Attach strip 17 meter X to the bolt that fastens the coil to the...

Страница 5: ...so the top edge is 33 1 4 in 84 5 cm from the upper end of the tube 38 Pass the free end of the stranded wire from wire clamp 0 625 6 M w wire T through the small hole in wire clamp 0 750 6 M w insula...

Страница 6: ...he uncapped end of tube J into the slotted end of tube I until only 25 in 63 5 cm extends and secure with compression clamp small adjustable NOTE In the following steps the antenna will be assembled a...

Страница 7: ...and may be as much as 100 kHz at the high end of the band depending on the efficiency of the ground system used greater bandwidth being associated with lossy ground systems It should be remembered th...

Страница 8: ...e and lowest VSWR NOTE To minimize interference to other stations and to avoid erroneous reading use only enough power to produce full scale deflection of the meter in the forward or r f out position...

Страница 9: ...re clamp 0 875 15 M w insulator K A change of 2 in 5 1 cm will shift the VSWR curve approximately 300 kHz 6 Check VSWR on 10 meters To raise the resonant frequency loosen the small hose clamp over the...

Страница 10: ...equency in all installations In the preceding steps it has been assumed that the antenna has been installed in a more or less clear spot away from other vertical conductors such as TV antenna feedline...

Страница 11: ...nnas an electrical 1 4 8 section of 75 ohm coax is used as a geometric mean transformer to match the 100 odd S of feedpoint impedance on that band to a 50 S main transmission line of any convenient le...

Страница 12: ...ylene rope may be used but because some grades tend to deteriorate fairly rapidly periodic inspection should be made A single set of guys placed just above the 30 meter circuit will contribute greatly...

Страница 13: ...ter L Bracket P 00249SZV Coil Capacitor Assembly 30 Meter Q 00137SZV Coil Q Base Matching R 290 08 Coax 75 Ohm Matching S 00228GZV Connector PL 258 T 00331RZV Wire Clamp 5 8 6 M W Wire U 00332RZV Wire...

Страница 14: ...14 Feedline Detail PICTORIAL...

Страница 15: ...G AND WEAKEN THE INSTALLATION If U bolts must be used place a larger diameter metal such as the MPS Mounting Post Sleeve over tube w insulator A Similar precautions should be observed when using TV st...

Страница 16: ...cken wire may be used as a substitute for radial wires and or a ground connection the mesh or screen acting as one plate of a capacitor to provide coupling to the earth beneath the antenna It should b...

Страница 17: ...verticals for reasonable efficiency If the ground loss of resistance of 15 ohms from the preceding example could be reduced to zero ohms it is easy to show that the efficiency of our one eighth wavele...

Страница 18: ...that band It s important to note that cutting each conductor of rotator cable to a specific frequency will not work unless you separate it angling each conductor away for most of its length because t...

Страница 19: ...a supporting metal structure for antenna currents that might otherwise flow on the structure and thus turn the vertical antenna system into a vertical long wire with unwanted high angle radiation OTHE...

Страница 20: ...but it is generally considered that the best possible location for a mobile antenna is in the middle of the roof of the vehicle i e at the center of the vehicle s ground plane and at a point where the...

Страница 21: ...building Steel TV mast sections are readily available in lengths of ten feet and the mounting posts of Butternut HF verticals will slide into those which have an outside diameter of 1 1 4 inches and...

Страница 22: ...tion 6 in or less Symptom High SWR on one band when antenna is roof mounted Radials are in place but antenna will just not tune Look for Radials of wrong length or running close to metal rain gutters...

Страница 23: ...ged or damaged Build up of salt or pollution deposits on insulators and capacitors Radial system corroded or rotted away Owner must do routine maintenance at intervals according to local conditions Sy...

Страница 24: ...ure of an antenna to wind or weather c from improper assembly installation or use of an antenna or d from failure periodically to inspect and maintain an antenna and its installation The Customer is r...

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