Selecting a VHF Yagi Antenna: A Practical Guide

Yagi antennas are among the most requested VHF products in the Renair range. When a directional, high-gain solution is required in the 136–174 MHz band, a well-specified Yagi delivers performance that omnidirectional designs cannot match. Selecting the right element count, gain and mounting configuration for a given application, however, requires some understanding of what each parameter actually means in practice.

How Gain Relates to Element Count

A Yagi's gain increases with the number of parasitic elements. In the VHF band, a 2-element Yagi typically provides around 5–6 dBd of forward gain; a 4-element reaches approximately 7–8 dBd; and an 8-element Yagi delivers 10–11 dBd. The trade-off is beamwidth. A 2-element design may cover around 70 degrees horizontally; an 8-element narrows to 35–40 degrees. For fixed-point links or repeater receive antennas where the source direction is known, this narrowing is an advantage. For wide-area base station coverage, a lower-element, wider-beamwidth design will serve better.

Sub-Band Matching

UK VHF PMR allocations sit in the 146–174 MHz portion of the band. Marine VHF operates at 156–174 MHz. Air-band communications use 118–136 MHz. A Yagi optimised for 162 MHz will not perform well at 130 MHz. Always confirm the operating frequency range and match it against the antenna's stated specification before ordering. For PMR and marine applications, broadband designs covering the full 146–174 MHz range are available and practical. For repeater sites, a narrowband design optimised to a tighter range delivers better performance within that window.

Polarisation and Mounting

VHF PMR, marine VHF and land mobile applications use vertical polarisation. For rooftop or mast-top installations, stainless steel U-bolt clamps rated for the mast diameter in use are the correct choice. For vehicle installations, a Yagi is not practical — omnidirectional whip or blade designs are used for mobile applications. A VHF Yagi on a rooftop mast presents a significant wind load, particularly for longer-boom designs; mechanical integrity of the mounting structure must be assessed before installation.

Feeder Cable and Connectors

At VHF frequencies, cable losses are modest compared to UHF or microwave. For a typical installation with a 15-metre run to a rooftop Yagi, LMR-240 or equivalent is a reasonable choice. For runs of 30 metres and above, LMR-400 or equivalent keeps cable losses below 1 dB. All external connectors should be weatherproofed with self-amalgamating tape. PL-259 or N-type connectors are the standard choices for VHF Yagi installations.

Browse Renair's VHF Yagi range at renair.co.uk/products.

Frequently Asked Questions

How many elements do I need for my VHF Yagi?

For a general-purpose base station or repeater receive antenna with clear line of sight, a 4 or 6-element Yagi is a good starting point. For long-distance or marginal path applications, an 8-element design is worth specifying. For wide-area coverage from a single antenna, a lower-gain, wider-beamwidth design may serve better.

Can I use the same VHF Yagi for transmit and receive?

Yes. VHF Yagis are passive, reciprocal devices — the same antenna works equally for transmit and receive. Ensure the power handling rating is appropriate for your transmitter output with an appropriate safety margin.

What is the difference between VHF and UHF Yagis?

VHF Yagis are physically larger because elements are cut to resonate at longer wavelengths. UHF Yagis (400–500 MHz) are more compact and can achieve higher gain in a smaller structure. For the same element count, a UHF Yagi will be physically smaller but will have a narrower beamwidth than a VHF equivalent.