# The 43 Foot Vertical

**The 43 Foot Vertical **

**Bill Leonard **

**N0CU **

**9/3/2016 **

**This presentation is based upon charts from: **

**“The 43-Foot Vertical” by Phil Salas -AD5X [email protected] **

**(Comments in BLUE are mine, not Phil’s) **

**Multiband Antenna Options **

1) Multiband Fixed Height Vertical using Traps

2) Multiband Variable Height Vertical using the SteppIR BigIR III

**3) Multiband Fixed Height Vertical using an antenna matcher in **

** the shack – such as 43 footer **

**4) Multiband Fixed Height Vertical using an antenna matcher at **

** the antenna base – 43 footer again **

5) Forget the vertical and get a multiband dipole

**Multiband Antenna Options **

1) Multiband Fixed Height Vertical using Traps

2) Multiband Variable Height Vertical using the SteppIR BigIR III

3) Multiband Fixed Height Vertical using an antenna matcher in

**No one antenna is best for all applications! **

4) Multiband Fixed Height Vertical using an antenna matcher at

the antenna base – 43 footer again

5) Forget the vertical and get a multiband dipole

**Concept Behind the 43 Foot Vertical **

-** Take a resonant vertical monopole antenna that **

** works good one band, but is unuseable on most **

** other bands, and change it so it is useable on a **

** number of bands. **

-** The 43 foot length is non-resonant on any band **

** (impedance matching is required on all bands) **

**AD5X Outline **

-** Why a vertical? **

-** Important characteristics of a vertical antenna **

**- Ground Losses and Antenna Efficiency **

**- Why a 43-foot vertical? **

**- SWR-related coax and unun losses **

**- RF Voltages **

- Matching Networks for 160-and 80-meters

- Building your own 43-foot vertical

**(Last two topics not covered in this presentation) **

**Why Use a Vertical? **

**Advantages: **

** - Generally are inexpensive **

** - Relatively unobtrusive **

** - Self-Supporting **

** - Easy to ground mount **

** - Low angle of radiation (maybe, maybe not) **

** - Good DX performance (maybe, maybe not)**

** - Omni-directional (no rotator needed!) **

**Disadvantages: **

** - Omni-directional (no gain or F/B) **

** - Needs a good radial system for best performance **

** - Needs good ground characteristics for best **

* performance *

**Important Characteristics of a Vertical Antenna **

**- Efficiency: **

**- How much of the transmitter power is being radiated **

-** Can be a significant problem with vertically polarized **

** monopole antennas **

**- Determined by: **

**- Antenna design (radiation resistance) **

**- Ground characteristics in the NEAR FIELD (~1/2 wavelength) **

**-Conductivity & permittivity **

**- Pattern **

**- Is the transmitted power going where you want it to? **

**- Peak gain **

**- Take-off angle **

**- Determined by: **

**- Antenna design **

**- Ground characteristics in the FAR FIELD (~10 wavelengths) **

**Important Takeaway **

-** A vertical monopole antenna installed over a poor **

** ground with no radials will have: **

**- Very poor efficiency and **

**- Poor pattern (low gain and high takeoff angle) **

-** A vertical monopole antenna installed over a poor **

** ground with an ideal radial system will have: **

**- Near 100% efficiency and **

**- Poor pattern (low gain and high takeoff angle) **

-** A vertical monopole antenna installed over an **

** excellent ground (without any radial system) will **

** have: **

**- Near 100% efficiency and **

**- Good pattern (good gain and low takeoff angle) **

**Vertical Antenna Efficiency*** *

-** Radiation Resistance (Rr) is the “effective” resistance **

** of the antenna **

-** Hypothetical resistance (not a real resistor) **

-** Value varies from milliohms to thousands of ohms **

-** Ground loss (Rg) is power lost due to heating of the **

** ground **

-**Antenna Efficiency (%) = 100 x Rr/(Rg + Rr) **

-**Assumes X is tuned out by impedance matching network **

**X **

**Antenna **

**Rr **

**Rg **

**Simple Calculations **

**- 43 foot antenna on 160 meters: **

** Rr =** 43/128 X 36 = **4 ohms **

- EZNEC = 3 ohms

**C =** 3.5 x 43 = 150.5pf = **-j580 ohms **

- EZNEC = -j640 (VNA actually measured –j580)

- Nearby objects add some stray capacitance

**Efficiency Calculation **

-** A ¼-wave vertical has a radiation resistance of 36 ohms **

-** Assume 10 ohms of ground loss **

** - Probably a much better ground than most hams have **

-** SWR = 1.09:1 **

-** Rr + Rg = 36 + 10 = 46 ohms **

-** SWR = 50/46 = 1.09 **

-** Antenna efficiency is 78% **

** - If you have a 100 watt transmitter, you will radiate 78 watts **

**Note: **

** - Higher ground loss can result in a BETTER SWR! **

**Electrically Short Antennas*** *

-** The shorter the antenna, the lower the Rr **

-** A Hustler 6BTV 80/40/30/20/15/10 meter vertical is 24 **

** feet tall **

-** On 80 meters, it is only 0.092 wavelength long **

-** Rr decreases approximately as 1/(length)**

**2**

-** So Rr is approximately 5 ohms **

-** With 10 ohms ground loss, the efficiency is 33% **

**- Assumes no trap/inductor losses (trap loss could add 2dB) **

-** Now your 100 watt transmit signal results in only **

** 33 watts being radiated **

**Electrically Short Antennas (cont’d)*** *

-** A Butternut HF-9VX with TBR-160 160M loading coil is **

** 26 feet tall **

-** On 160 meters, it is only 0.051 wavelength long. **

-** Rr decreases as 1/(length)**

**2**

-** So Rr is approximately 1.5 ohms **

-** With 10 ohms ground loss, the efficiency is 13% **

-** Assumes no inductor/loading coil/matching losses **

-**Now your 100 watt transmit signal results in only **

** 13 watts being radiated **

**Matching losses could easily drop this number below 10 W **

**The 43-foot Vertical Antenna*** *

**Advantages **

-** Still can be self-supporting & moderately unobtrusive **

-** Approximately 3x higher radiation resistance than the typical **

** trap or loaded vertical. **

-** No trap or loading coil losses to worry about**

-** Modest compromise SWR from 60-10 meters when fed with a **

** 1:4 unun.**

**(UNUNs are designed to work with resistive loads!) **

**Disadvantages **

**- Take-off angle is not optimum on 12/10 meters **

**- More on this later **

**- You need an in-shack tuner (remote tuner is much better) **

**43-foot SWR over Perfect Ground with 1:4 Unun at the Antenna (EZNEC) *** *

**14.1 **

**18.1 **

**21.1 **

**7.1 **

**Note: **

** - These values will be different with a real (lossy) ground **

** - Many built-in HF antenna tuners only go up to 3:1 SWR **

**28.5 **

**Efficiency Comparison **

**- The Hustler 6BTV on 40 meters **

**- The 24-foot Hustler is 0.188 wavelengths long **

**- Rr = 20 ohms **

**- Efficiency = 67% (assumes Rg = 10Ω & no coil losses) **

**- Note:There are multiple inductors (traps) in-line on 40 meters **

**- The 43-foot vertical on 40 meters **

**- Antenna is 0.34 wavelengths long **

**- Rr = 65 ohms **

-** Efficiency = 87% (with Rg = 10Ω with no coils/traps**

**)**

-** The required tuner may have more loss than coils/traps **

**43-foot Antenna Disadvantages*** *

-** Can be moderately **

**(very) expensive **

-** High take-off angle above 15 meters **

-** DX performance >1/4-wave vertical 60-15 meters, but 5dB **

** down from 10 meter ¼-wave vertical at 10 degree take off **

** angle (but higher Rr compensates some) **

-** Really needs base matching on 160/80-meters **

-** Regardless of what the 43-foot antenna vendors say **

-** Example: With Rg = 10Ω **

**- 160 Meter SWR = 324:1, 80 Meter SWR = 41:1 **

**Matching & Coax Losses*** *

-** Some 43-foot antenna vendors claim the antenna can be **

** matched from 160-10 meters with your in-shack tuner. **

-** One vendor says to use 150 feet of RG-213 for best all-band **

** operation of the 43-foot antenna (so you can tune from the **

** tuner in your shack). Another vendor says to ADD 150 feet of **

* RG-213 to your cable run. *

-** The typical 160 meter base impedance of a 43-foot antenna with **

** the 1:4 UNUN is 2-j183. 150 feet of coax transforms this to a **

** matchable 38 + j180 (?) at the shack. **

-** But the antenna SWR is ~ 150:1 resulting in 12dB (two S-units) of **

* coax losses due to the SWR at the antenna. Plus about ≥6dB *

* ground loss. *Total loss ~18dB.

-**TX = 100W results in 2-watts radiated **

*(No! 2 W reaches ant) *

* Some antenna mfgs don’t understand the basics! *

**To Maximize Efficiency*** *

-** Minimize coax loss: **

-** Use shortest length possible **

-** Heliax semi-rigid cable **

-** **

**LMR-400 coax **

-** **

**RG-213 coax **

-**Do matching AT**

**the antenna**

-** Install the best radial system you can afford **

-** Do the matching at the base of the antenna **

-** For high power & high SWR, may need to use relay switching **

-** Matching on 160/80 meters is difficult **

-** The mismatch may be too great for most manual/auto antenna **

** tuners **

-** VERY high RF voltages & currents **

**RF Voltage & Current*** *

-** An electrically short antenna has high capacitive **

** reactance. This WILL cause high RF voltages across a **

* matching network. *

-** Example: Assume 1500 watts and a perfect ground **

** system (Rg = 0) on 160 meters. In this case all power **

** is delivered to Rr. **

**At the base of the antenna: **

** I = √(1500/3) = 22.4 amps rms **

** |Z| = √(3**

**2**

**+ 600**

**2**

**) = 600 (?) **

** So, Vrms = 22.4 x 600 = 13,440 and Vpk = 19,007 volts (?) **

** Don’t overlook UNUN current & voltage limitations **

**Matching Network Issues*** *

-** Any antenna with low Rr will have large RF current **

-**Inductor & capacitor heating & contact degradation on **

** switches & relays **

-**Any antenna with high X will have large RF voltage at **

** the feed point **

-**Safety concern! **

-**Capacitor/switch/relay breakdown in matching network **

**Vertical Antenna Pattern Over Real Ground*** *

**Ground characteristics affect both efficiency and radiation pattern **

**¼ Wave Monopole **

**-Peak gain down 8 dB **

** from ideal vertical **

**-Peak gain @ 30 o **

** (not 0 o**

**)**

**Perfect Ground **

**Lossy Ground **

-** Lossy ground results in: **

**Peak gain down 6 dB compared to dipole**

-** Lower gain **

-** Higher takeoff angle (pattern may be no better for DX than a dipole) **

**Vertical Antenna Pattern Over Real Ground*** *

**Ground characteristics affect both efficiency and radiation pattern **

**¼ Wave Monopole **

**Perfect Ground **

**Lossy Ground **

**Dipole @ ½ **

l

-** Lossy ground results in: **

-** Lower gain **

-** Higher takeoff angle (pattern may be no better for DX than a dipole) **

**Pattern Over Real Ground (cont’d)*** *

**- Peak Gain for 43 Foot Vertical: **

** ~ 5 dBi @ 57° for 10 meters – impressive, but high angle **

** ~ 4 dbi @ 37° for 15 meters **

** ~ 1 dBi @ 16° for 20 meters – nice low angle **

** ~ 0 dBi @ 25° for 40 meters **

**~ -2 dBi @ 29° for 80 meters – this is quite functional **

**~ -8 dBi @ 23° for 160 meters – lossy, but it does work **

**- Peak Gain for a Dipole is 5-9 dBi (depends upon height above ground) **

**Pattern Over Real Ground (cont’d)*** *

**- Peak Gain for 43 Foot Vertical: **

** ~ 5 dBi @ 57° for 10 meters – impressive, but high angle **

** ~ 4 dbi @ 37° for 15 meters **

** ~ 1 dBi @ 16° for 20 meters – nice low angle **

** ~ 0 dBi @ 25° for 40 meters **

**~ -2 dBi @ 29° for 80 meters – this is quite functional **

**~ -8 dBi @ 23° for 160 meters – lossy, but it does work **

**- Peak Gain for a Dipole is 5-9 dBi (depends upon height above ground) **

**Dipole @ 0.1 **

l

**Dipole @ ½ **

l

**(260 ft @ 1.8 MHz) **

**Summary*** *

-** The more metal in the air, the better the antenna **

-** Radiation resistance increases as the square of the length change. **

-** Increased radiation resistance improves antenna efficiency over real **

** ground. **

-** A 43-foot antenna is very **

**(?) good for 60-10 meters **

-** Modest to low gain **

-** High takeoff angles on higher bands **

-** Not a very good DX antenna for 160/80 meters, but probably better than **

** a dipole up only 40 ft (if the losses are low) **

-** A 43-foot antenna needs base matching to provide good **

**(?)**

** results on 160-and 80-meters. **

-** Detailed matching network details at www.ad5x.com **

**Summary cont’d*** *

-** This is not a cheap antenna (>$1300) **

-** Antenna $400 **

-** High power remote antenna tuner $800 **

-** High power UNUN $150 **

-** Radial system $100 **

-**Vertically polarized antennas installed over poor ground are not **

** good DX antennas **

-** Not an easy antenna to install **

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