Frequently Asked Questions

RF Connector Torque Wrench Guide

RF connector torque wrench settings for SMA, SSMA, SMC, SSMC, 1mm, 1.85mm, 2.4mm, 2.92mm, 3.5mm, 7mm, TNC Type N, HN, 4.1/9.5 Mini DIN and 7/16 connectors. These radio frequency connector torque settings are for brass and stainless steel connectors where applicable.

Connector	Material1	Minimum2	Recommended3	Click-Type4	Breakover-Type5	Screwdriver-Type6
SMA	Brass	3 in-lbs .34 N-m	5 in-lbs .56 N-m	74Z-0-0-79 (5/16" 4 in-lbs / .45 N-m) ST-SMA5 (5/16" 5 in-lbs / .56 N-m)	ST-SMA-516-BO5 (5/16" 5 in-lbs / .56 N-m)	ST-SMA9 (5/16" 5 in-lbs / .56 N-m)
	Stainless Steel	6 in-lbs .68 N-m	7.5 ~ 9 in-lbs .85 ~ 1.07 N-m	ST-SMA1 (5/16" 7.5 in-lbs / .85 N-m) ST-SMA2 (5/16" 6 in-lbs / .68 N-m) ST-SMA3 (5/16" 8 in-lbs / .90 N-m) 74Z-0-0-21 (5/16" 8.85 in-lbs / 1 N-m)	ST-SMA7 (5/16" 8 in-lbs / .90 N-m) ST-SMA-516-BO8 (5/16" 8 in-lbs / .90 N-m)	ST-SMA8 (5/16" 8 in-lbs / .90 N-m)
SSMA	Brass	3 in-lbs .34 N-m	5 in-lbs .56 N-m	ST-SSMA1 (1/4" 5 in-lbs / .56 N-m)	ST-SSMA-14-BO5 (1/4" 5 in-lbs / .56 N-m)	*
	Stainless Steel	7 in-lbs .79 N-m	8 in-lbs .90 N-m	ST-SSMA2 (1/4" 8 in-lbs / .90 N-m)	ST-SSMA-14-BO8 (1/4" 8 in-lbs / .90 N-m)	*
SMC	Brass	1.9 in-lbs .21 N-m	3.1 in-lbs .35 N-m	ST-SMC1 (1/4" 3 in-lbs / .34 N-m)	ST-SMC-1564-BO3 (15/64" 3 in-lbs / .34 N-m)	*
SSMC	Stainless Steel	1.75 in-lbs .2 N-m	2 in-lbs .23 N-m	ST-SSMC (5/32" 2 in-lbs / .23 N-m) ST-SSMC1 (5/32" 2 in-lbs / .23 N-m low-profile)	ST-SSMC-532-BO2 (5/32" 2 in-lbs / .23 N-m)	ST-SSMC2 (5/32" 2 in-lbs / .23 N-m)
	Brass	0.75 in-lbs	1 in-lbs
1mm	Stainless Steel	4 in-lbs .45 N-m	4 in-lbs .45 N-m	ST-1mm1 (6mm 4 in-lbs / .45 N-m)	ST-1MM-1564-BO4 (15/64" 4 in-lbs / .45 N-m)	*
1.85mm	Stainless Steel	9 in-lbs 1.02 N-m	9 in-lbs 1.02 N-m	ST-MW1 (5/16" 9 in-lbs / 1.02 N-m)	ST-SMA-516-BO12 (5/16" 12 in-lbs / 1.36 N-m)	*
2.4mm	Stainless Steel	9 in-lbs 1.02 N-m	9 in-lbs 1.02 N-m	ST-MW1 (5/16" 9 in-lbs / 1.02 N-m)	ST-SMA-516-BO12 (5/16" 12 in-lbs / 1.36 N-m)	*
2.92mm	Stainless Steel	9 in-lbs 1.02 N-m	9 in-lbs 1.02 N-m	ST-MW1 (5/16" 9 in-lbs / 1.02 N-m)	ST-SMA-516-BO12 (5/16" 12 in-lbs / 1.36 N-m)	*
3.5mm	Stainless Steel	9 in-lbs 1.02 N-m	9 in-lbs 1.02 N-m	ST-MW1 (5/16" 9 in-lbs / 1.02 N-m)	ST-SMA-516-BO12 (5/16" 12 in-lbs / 1.36 N-m)	*
7mm	Stainless Steel	10 in-lbs 1.13 N-m	12 in-lbs 1.36 N-m	ST-7mm (3/4" 12 in-lbs / 1.36 N-m)	*	N/A
TNC	Brass	6 in-lbs .68 N-m	6.1 in-lbs .69 N-m	*	ST-TNC-58-BO6 (5/8" 6.1 in-lbs / .69 N-m) ST-TNC-916-BO6 (9/16" 6.1 in-lbs / .69 N-m)	N/A
	Stainless Steel	12 in-lbs 1.36 N-m	13 in-lbs 1.47 N-m	ST-TNC1 (9/16" 13 in-lbs / 1.47 N-m) ST-TNC2 (5/8" 13 in-lbs / 1.47 N-m)	ST-TNC-58-BO12 (5/8" 12 in-lbs / 1.36 N-m) ST-TNC-916-BO12 (9/16" 12 in-lbs / 1.36 N-m)	N/A
Type N	Brass	6.2 in-lbs .7 N-m	8.85 in-lbs 1 N-m	ST-N5 (20mm 8.85 in-lbs / 1 N-m)	ST-N-2532-BO8 (25/32" 8.1 in-lbs / .92 N-m) ST-N-34-BO8 (3/4" 8.1 in-lbs / .92 N-m) ST-N-1316-BO8 (13/16" 8.1 in-lbs / .92 N-m)	N/A
	Stainless Steel	12 in-lbs 1.36 N-m	13 ~ 14 in-lbs 1.47 ~ 1.58 N-m	ST-N1 (13/16" 14 in-lbs / 1.58 N-m) ST-N2 (3/4" 13 in-lbs / 1.47 N-m) ST-N3 (18mm 13 in-lbs / 1.47 N-m) ST-N4 (19mm 13 in-lbs / 1.47 N-m) ST-N8 (20mm 13 in-lbs / 1.47 N-m)	ST-N-2532-BO14 (25/32" 14 in-lbs / 1.58 N-m) ST-N-34-BO14 (3/4" 14 in-lbs / 1.58 N-m) ST-N-1316-BO14 (13/16" 14 in-lbs / 1.58 N-m)	N/A
HN	Brass	15 in-lbs 1.69 N-m	16 in-lbs 1.81 N-m	ST-HN1 (7/8" 16 in-lbs / 1.81 N-m)	*	N/A
4.1/9.5 MINI DIN	Brass	88 in-lbs 9.94 N-m	90 in-lbs 10.17 N-m	ST-4195 (22mm 90 in-lbs / 10.17 N-m)	*	N/A
7/16	Brass	221 in-lbs 24.97 N-m	221 in-lbs 24.97 N-m	ST-D1 (32mm 221 in-lbs / 24.97 N-m) ST-D2 (27mm 221 in-lbs / 24.97 N-m) ST-D3 (1 3/8" 221 in-lbs / 24.97 N-m)	*	N/A

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Basic Cable Properties

P/N	Diameter (inches)	Loss/Foot (1 GHz dB)	Loss/Foot (3 GHz dB)	Loss/Foot (6 GHz dB)	Max Power (@ 1 GHz)	Freq Max (recommended)	Notes
RG58	0.195	0.15	n/a	n/a	90 Watts	1 GHz	Very popular for low-cost, general purpose applications. RG-58/U has a solid center conductor and PVC outer jacket. RG-58A/U and RG-58C/U have a stranded Tin-coated center conductor and PVC outer jacket. RG-58C/U has a non-contaminating PVC outer jacket.
RG59	0.24	0.08	n/a	n/a	80 Watts	1 GHz	Impedance 75 Ohms
RG142	0.195	0.13	0.24	0.39	500 Watts	6 GHz	Double Shielded
RG174	0.11	0.34	n/a	n/a	20 Watts	1 GHz
RG178	0.08	0.45	0.81	n/a	65 Watts	3 GHz
RG214	0.425	0.07	0.14	0.3	175 Watts	11 GHz	Double Shielded; Good general purpose low loss cable for applications to 11 GHz
RG223	0.212	0.145	0.25	0.37	90 Watts	12.4 GHz	Double Shielded; Good general purpose low loss cable for applications to 12.4 GHz
RG316	0.098	0.29	0.47	n/a	170 Watts	3 GHz	Very popular for short cable runs.
RG316DS	0.114	0.29	0.47	n/a	170 Watts	3 GHz	DS = Double shielded version of standard RG-316
RG393	0.39	0.07	0.14	0.20	1275 Watts	6 GHz	Double Shielded; Used for high power applications.
RG402	0.145	0.13	0.24	0.35	417 Watts	18 GHz
RG405	0.086	0.2	0.39	0.57	162 Watts	20 GHz
LMR195	0.195	0.12	0.21	0.304	140 Watts	6 GHz	Drop-in replacement for RG-58 and RG-142
LMR200	0.20	0.10	0.19	0.27	170 Watts	6 GHz
LMR240	0.24	0.08	0.14	0.22	240 Watts	6 GHz	The most popular cable for 1-4 GHz applications. "LMR240UF" = Ultraflex version, good for applications required periodic or repeated flexing.
LMR400	0.40	0.04	0.7	0.11	500 Watts	6 GHz	"LMR400UF" = UltraFlex version, good for applications requiring periodic or repeated flexing. Drop-in replacement for RG-8 Air-Dielectric type Cable.
LMRSW540	0.61	0.06	0.11	0.15	1330 Watts	6 GHz	Low PIM cable (<-170dBc)
LMR600	0.59	0.027	0.049	0.075	900 Watts	6 GHz	One of the larger diameter cables. Not very flexible but can be used for high power application and has low loss.
HS086	0.105	0.227	0.41	0.588	140 Watts	40 GHz	Huber and Suhner™ Cable
HF047	0.067	0.45	0.68	0.98	32 Watts	40 GHz	Haverhill™ Cable
HF086	0.104	0.23	0.52/td>	0.6	130 Watts	18 GHz	Haverhill™ Cable
HF141	0.163	0.13	0.23	0.35	450 Watts	18 GHz	Use for 6-18 GHz applications

*LMR® is a registered trademark of Times Microwave

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What are the mating rules for similar type RF connectors?

SMA, 2.92 mm, and 3.5 mm connectors can be mated. However, a damaged or out of spec SMA can damage a 2.92 mm or 3.5 mm connector. This is due to the 2.92 mm and 3.5 mm use of air dielectric construction, which makes them fragile. The SMA's pin engages first, the threads are second. The 2.92 mm and 3.5 mm connectors are the opposite. The threads mate first, then the pin mates second. Please note: The lowest frequency connector sets the highest frequency use of that connector combination. Example: If one uses an SMA connector (18 GHz) with a 3.5 mm connector (34 GHz), the highest useable frequency is 18 GHz (set by the SMA connector).

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RF Connector Mating Matrix for Similar Type Connectors

Connector Type	Frequency Range	Mates With	Notes
SMA	18GHz	3.5mm 2.92mm	SMA connectors use Teflon as the dielectric.
3.5mm	34GHz	SMA 2.92mm	3.5 mm connectors use air as the dielectric.
2.92mm	40GHz	SMA 3.5mm	2.92 mm connectors use air as the dielectric. This connector is also known as a K™ connector, which was developed by Anritsu.
2.4mm	50GHz	1.85mm	2.4 mm connectors use air as the dielectric.
1.85mm	70GHz	2.4mm	1.85 mm connectors use air as the dielectric. This connector is also known as a V™ connector, which was developed by Anritsu.
1.0mm	110GHz	1.0mm	1.0 mm connectors use air as the dielectric. They cannot be mated with other type connectors.

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Are GPO and SMP connectors compatible?

GPO™ is a trademark of Gilbert Engineering who developed this connector. A military specification was written so the defense department could use multiple sources for this connector. Only Gilbert can call this connector GPO. Other suppliers claim their connector is equivalent and call it SMP.

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Can damage occur to high power attenuators if connected incorrectly?

Some of the high power attenuators from Fairview Microwave have an input and output connector. They are labeled as "unidirectional" (one way) attenuators. If they are connected incorrectly (high power applied to the output of the attenuator), the attenuator may be damaged. If the attenuator specification states the attenuator is "bidirectional" then one may connect either the input or output connectors of the attenuator to the device under test.
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What are reverse threads?

One method used to meet FCC Part 15 and 802.11 standards is to reverse the thread on connectors with threaded coupling. These are referred to as reverse or left-handed thread connectors. They are otherwise identical to standard SMA connectors, but will not mate. To attempt to do so could damage both connectors.
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What is a feed thru termination (for products such as: ST0175, ST01833, ST0150)?

A feed-thru termination is designed to connect a high impedance probe/device to its output. If you connect a 50 ohm device to a feed-thru, then the 50 ohm resistor will be in parallel with the 50 ohm device, which will result in a 2:1 VSWR mismatch.
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What is a hybrid coupler?

Hybrid couplers are the special case of a four-port directional coupler that is designed for a 3-dB (equal) power split. Hybrids come in two types, 90 degree or quadrature hybrids, and 180 degree hybrids.
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Do isolators and circulators have a magnet inside the case?

All isolators and circulators have a magnet inside the case. Care must be taken to keep them away from other magnets, because the performance (isolation) may decrease. We need to minimize degaussing of the magnet. Degaussing is the process of decreasing or eliminating a remnant magnetic field.
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What is the definition of directivity for directional couplers?

Directivity is a measure of how well the coupler isolates two opposite-travelling (forward and reverse) signals. In the case of measuring reflection coefficient (return loss) of a device under test, directivity is a crucial parameter in the uncertainty of the result.
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What happens when two different signals are applied to a limiter of different amplitudes?

If one applies a large signal (to create limiting) and a 2nd smaller signal (>60 dB down), the smaller signal will be reduced in amplitude by 1-3 dB. When the diode begins to conduct, some of the signal will be shunted to ground, causing a 1-3 dB reduction in amplitude. Also, the RF impedance may change slightly (because of the path to ground).
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What is the definition of "cold" and "hot" switching for RF switches?

Cold switching: No signal is applied to the switch while the switch is changing states. Hot switching: The switch changes states while a signal is still being applied to the switch. RF electromechanical switches should not be "hot" switched because the contacts may be damaged during switching. RF power should be removed from the switch before switching.
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What is the definition of coupler sensitivity (or flatness)?

The frequency sensitivity or “flatness” of a coupler is a measure of how coupling varies over a given frequency range. Optimum coupling frequency response is achieved by “centering” the design within the specified band of interest. Typical coupling flatness for a quarter-wavelength coupler operating over an octave band is within ± 0.75 dB of nominal. All things being equal, stronger coupling factors (3, 6 and 10 dB) exhibit greater flatness than weaker coupling factors (20 through 50 dB). When operating over frequency bands greater than an octave, the flatness tolerance may need to be relaxed due to the inherent characteristics of coupling roll-off.
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What is the difference between a resistive divider and a reactive divider?

Resistive divider incorporates resistors in the paths of the divider. An advantage for a resistive divider design is wide bandwidth with a disadvantage of 6 dB loss (for a 2 way divider). An advantage for a reactive divider design is lower loss of 3 dB (for a 2 way divider), but typically has a narrow bandwidth of 1 or 2 octaves. Isolation is 6 dB for resistor dividers and for reactive dividers > 6 dB.
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Can a divider be used as a combiner or a combiner as a divider?

The answer is yes. A divider/combiner can be interchanged. However, resistive dividers designs include 6 dB loss (for a 2 way) and reactive dividers 3 dB (for a 2 way).
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What type of dielectric is typically used for connectors >18 GHz?

Air dielectric is typically used for RF/microwave connector types for frequencies > 18 GHz. A plastic bead supports the center pin, which often is made from Rexolite® material. Rexolite® is a unique cross linked polystyrene microwave plastic that excels in applications where resistance to radiation and dielectric properties are of primary concern.
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Can high power combiners accept non-coherent (out of phase) input signals?

Typically high power combiners can only accept coherent (in phase) inputs. If the combiner inputs are non-coherent (out of phase) they may have a very high VSWR. The design of a high power non-coherent combiner is different than a low power combiner, because the internal resistor that supports low VSWR/isolation between ports has been removed. By removing the internal resistor, high power can be applied at the inputs. If the input signals are not coherent, a large mismatch may be present (6:1 VSWR) at the other inputs, even if they are terminated.
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Can 50 ohm N type connectors mate with 75 ohm type connectors?

The answer is no. The N type 75 ohm center pin and socket is smaller than the N type 50 ohm center pin and socket. You can connect the two together, but you will damage the 75 ohm female with a 50 ohm male or there may be no contact if using a 75 ohm male with a 50 ohm female.
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How do you calculate phase shift for the SMP2018 phase shifter?

The SMP2018 phase shifter is capable of 3.5 degree per GHz. The phase measured on the vector network analyzer at 10 GHz with the device closed is -16 degree, 1 turn (+26 degree), 10 turns (-165 degree) and 20 turns (+139 degree) turns. Each turn is approximately 32 degree @ 10 GHz (which is close to the 3.5 degree per GHz spec). 20 turns is about the maximum for this device, which would be 32 x 20 = 640 degree of phase shift for 10 GHz. Maximum phase shift will be up to 640 degree, but it may be difficult to meet phase shift tolerance as 1 turn = 32 degree (1/2 turn 16 degree, ¼ turn 8 degree) @ 10 GHz.
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What is the minimum phase shift for the SDPS-0502-360-SMA, SMA 8 Bit Programmable Phase Shifter?

The SDPS-0502-360-SMA (500 MHz to 2 GHz) programmable phase shifter has 8 bits of control that allows 256 discrete values of phase shift. Example: 360/256 = 1.41 degrees of phase shift per bit at any frequency in its range.
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Why do certain products not specify insertion loss?

Several of our components (like adapters) have insertion losses of 0.1-0.3 dB. If the adapter is connected to another component with a large mismatch, the mismatch itself may create more insertion loss than the insertion loss of the part due to constructive/destructive (superposition) of the two sine waves.
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What is the difference between transfer switch and DPDT switch?

The transfer switch is essentially a modified double-pole-double-throw (DPDT) device. However, a true DPDT switch is a six port device that contains two totally independent transmission paths. In a transfer switch two transmission paths are provided but they are not independent.
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What is the typical mating cycles for connectors?

If the part is made of brass, the typical number of mating cycles are 100. If the part is made from stainless steel, the typical number of mating cycles is 500.
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What makes an RF limiting amplifier different than other RF amplifiers?

Limiting amplifiers are different than other amplifiers because of their ability to maintain a constant output as it is driven into saturation/compression. As an example: the SLA-080-40-50-SMA amplifier specifications indicate a +/-1dB flatness at Psat (saturation). The most important performance requirement of a limiting amplifier is to minimize output power variations and provide a constant output over a wide input dynamic range. Limiting amplifiers are good for maintaining constant envelopes, but will not provide a linear output. Because the output of limiting amplifiers will be into saturation/compression, distortion will occur.
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What is the definition of RF amplifier terms: P1dB vs Psat?

P1dB definition: The point the input power that causes the gain to decrease 1 dB from the normal linear gain specification. Psat definition: Is the saturation point of the amplifier, which is the point where the departure from linear gain is -3 dB. Psat is typically is equal to or no more than 2 dB higher than the P1dB power level.
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What is 3rd order intercept point for RF amplifiers?

When an amplifier becomes non-linear, it will begin to produce harmonics of the amplified inputs. The second, third and higher harmonics are usually outside of the amplifier bandwidth, so they are usually easy to filter out if they are a problem. However, non-linearity will also produce a mixing effect of two or more signals. If the signals are close together in frequency, some of the sum and difference frequencies called intermodulation products produced can occur within the bandwidth of the amplifier. These cannot be filtered out, so they will ultimately become interfering signals to the main signals to be amplified. That’s why every effort must be made to control the biasing, signal levels and other factors to ensure maximum possible linearity, greatly reducing the intermodulation distortion (IMD) products. The 1-dB compression point is important since it shows you the input power point where compression begins and distortion will occur. Amplifiers should be operated below the compression point. Third-order products are the most troublesome of the intermodulation effects caused by non-linear operation. The IP3 value is an imaginary point that indicates when the amplitude of the third-order products equals the input signals. This point is never reached, as the amplifier will saturate before this condition can occur. Nevertheless, it is a good indicator of amplifier linearity.
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What is RF blanking for RF amplifiers?

Blanking controls the state for RF output blanking circuitry. Blanking occurs when the RF output is momentarily turned off as the sweep transitions from one frequency segment (band) to another, allowing the signal to settle. Blanking also occurs during the retrace, so the signal can settle before the next sweep. In CW mode, blanking occurs whenever you change the frequency. When blanking is set to off, blanking is always disabled. With blanking disabled (off), a momentary loss of RF power will still occur while the hardware is being reset at band crossings. When the RF power returns after dropping out the power level will exceed the set power level until the ALC loop can respond. The length of time from the signal dropping out, reappearing, and ALC leveling occurring is shorter than the period of time the signal is turned off when output blanking is set to on or auto. When blanking is set to on, blanking occurs on all frequency changes, including segment transitions and retrace. The effects on the RF output signal with blanking on is at band crossings and switch points no RF signal will be present. Whenever RF power is present it is leveled and at the set power level.
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What are the Advantages of the 4.3/10 Connector Interface?

DIN 7/16, N-type, 4.3/10, and 4.1/9.5 are all coaxial cable standard types used in wireless infrastructure and mobile wireless equipment. Each are different in size, power handling, frequency, and other electrical and mechanical specifications. Specifically, 4.3/10 and 4.1/9.5 are more compact versions of DIN 7/16, optimally designed for use in dense interconnect scenarios, such as distributed-antenna systems (DAS) for connections between the base station and remote radio units (RRUs). Both 4.3/10 and 4.1/9.5 are more compact and present much better torque specifications and passive intermodulation (PIM) distortion metrics compared to N-type connectors, which make them better suited for reliable installation for wireless infrastructure and to account for the increased PIM requirements of the modern crowded spectrum and congested tower sites.

4.1/9.5 precedes 4.3/10, and the connector standards are, in many ways, similar. However, 4.3/10 connector standards are designed to more completely address modern application requirements by its low PIM under various torque conditions allowing enhanced reliability and hand-tightening, and 4.3/10 has separate mechanical and electrical planes, providing enhanced PIM performance. Hence, 4.3/10 is continually likely to increase in adoption over 4.1/9.5.
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What is a Triple Balanced Mixer?

Single-, double-, and triple-balanced mixer architectures are designed to optimize the electrical performance, cost, complexity, and technology limitations of a fabrication process. Hence, mixer architectures can be discussed in terms of their benefits and trade-offs compared to other mixer architectures and value in specific applications.

A triple-balanced mixer is composed of two diode quads, with a total of eight junctions. Power splitter at the RF and LO microwave baluns feed the mixer structure, which enables both of the diode quads to be coupled, with matching RF/LO isolation. This allows for the IF signal to be available at two separate isolated terminals, that typically exhibit very large bandwidths compared to other mixer architectures. Though, a DC IF is not available in this architecture. Practical, and available, triple-balanced mixers generally demonstrate better spur suppression than other mixer architectures, with the exception of some high port isolation double-balanced mixer designs.

Triple-balanced mixers enable low intermodulation distortion (IMD) upconversion and downconversion over very wide bandwidths, even into the high microwave and millimeter-wave frequencies. Double-balanced mixers, on the other hand, are less complex and lower cost circuits that are fit for applications where moderate LO power is available and there are no concerns over overlapping RF and IF frequencies. The above, and the DC IF capability of some double-balanced mixers make them suited for demodulator, I/Q modulators and phase detector circuits for narrow or wide bandwidths. Generally, triple-balanced mixers also require about 3 dB more LO power, as the LO power is divided between the two diode quads.
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What is the difference between a monopole and dipole antenna?

In essence, the difference between a monopole and dipole antenna, is that a dipole antenna uses an additionally radiator to generate a synthetic ground plane between the symmetric radiator elements, where a monopole antenna requires a physical ground plane. For a dipole antenna, the radiator elements are connected 180 degrees out-of-phase to each other, such as with the inner and outer conductor of a coaxial cable. For a monopole antenna, the reference plane of the transmission line connection, outer conductor of a coaxial cable, is the ground plane of the monopole.

Both monopole and dipole antennas exhibit similar radiation patterns and performance, except that monopole antennas are not symmetric vertically. Dipoles tend to be more common. The size and design constraints of requiring a ground plane for monopole antennas is often restrictive and the radiation pattern of the monopole depends on the orientation of the ground plane. Dipole antennas, however, have a vertically symmetric radiation pattern, and can relatively easily be oriented in the direction of optimum reception/transmission.

As dipoles tend to be more common than monopole antennas, there are more varieties and typologies of dipole antennas, including the common half-wavelength dipoles. Common monopole antennas include automotive AM antennas, naval low frequency antennas. There are types of monopole antennas used in the very high frequency (VHF) broadcast applications that use several grounded radial wires as the ground plane of the monopole antenna, and these conductive wires can be designed and oriented to optimize the radiation pattern of the “ground-plane” antenna for ideal broadcasting performance.
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What is the difference between a Balun and a RF Transformer?

Though certain types of baluns and RF transformers may be similarly constructed, and the circuit diagram symbols are easily confused, the designation of balun and RF transformer imply different operational characteristics and purposes, with some overlapping characteristics. Baluns convert between balanced and unbalanced lines, and RF transformers perform impedance matching, voltage or current step-up or step-down, and DC-isolation between two circuits. However, there are some balun configurations that perform both balun and RF transformer functions, known as autotransformer baluns or voltage baluns.

The term “Balun” comes from the function of converting between a balanced signal pathway and an unbalanced signal pathway. A balanced signal pathway requires two 180 degree out-of-phase signals in the same transmission pathway, where an unbalanced signal is a single signal with a ground plane or pseudo-ground return path. A balun can be fabricated by appropriately taping and configuring a winding-based transformer, transmission line-based transformer, with a delay line, or other means. An RF choke can be used in the place of a balun for some applications, by attenuating one of the signals in the transmission pathway and allowing the other to pass.

RF transformers use magnetic coupling between two or more circuits to transform, or isolate, the voltage, current, or impedance amongst the coupled circuits. Common RF transformers are composed of twisted-pair, or coaxial, transmission lines would around toroidal ferromagnetic cores, though there are also thick-film, thin-film, and planar RF transformers. Hence, there are many overlapping properties, functions, and fabrication methods between Baluns and RF transformers, and some types of Baluns can be considered modified RF transformers, though this is not always the case for every Balun.
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