Following some discussions regarding the performance of the various antenna options available for VHF/UHF HTs I decided to use my spectrum analyzer to measure the performance of three types of antennas on TX and RX.
The test jig was as follows for RX testing:
- Transmitter remotely keyed
- Approximately 15 meters between TX and RX antenna
- Fixed 1/4 wave on VHF, fixed 1/2 wave on UHF
- 1W RF power (nominal)
- Result read on spectrum analyzer
- Antenna connected to spectrum analyzer, mounted vertically
- Me standing in the same place about 1.5 meters away
And the following changes were made for TX testing:
- Fixed mobile antenna for spectrum analyzer
- Antenna under test replaced on the remote transmitter
- Distance shortened to about 7.5 meters
RX performance on UHF was difficult to reliably measure as my position and posture could change the reading by up to 10 dB.
Reference antenna was a Nagoya NA-771.
Some antennas also perform better when held by a person or provided with additional ground plane.
TX performance can be affected by the SWR of the antenna affecting the power limiter of the radio. This still indicated typical performance of the antenna on a radio.
Reference radio was a Puxing UV-973 in cross band mode.
Reference RX antenna was a Nagoya NL-R3 mobile antenna with a small ground plane.
Antennas tested (antenna type on VHF+UHF)
- Nagoya NA-771 BNC 1/4+1/2 wave
- Comet SMA-24 1/4+1/2 wave
- Diamond CH-32 (~1” coil)
- Diamond SRH-805S (~1” coil)
- Icom FA-S270C (1/4+??, Icom standard HT antenna)
- eBay brand spring VHF antenna
- Celwave 2506 commercial helical VHF antenna (cuttable 1/4)
Of these antennas we would typically expect the NA-771 and the SMA-24 to perform very well, followed by the Icom and coil antennas and the stubby antennas performing significantly worse. The results were still a bit surprising, they are presented as dB relative to the first reference antenna.
VHF TX/RX performance
- NA-771 +0/+0 dB
- SMA-24 +0/+0 dB
- CH-32 -20/-25 dB
- SRH805S -12/-15 dB
- FA-S270C -1/-3dB
- Spring -1/-6 dB
- 2506 helical 0/-3 dB
UHF TX/RX performance
- NA-771 +0/+0 dB
- SMA-24 +3/+1 dB
- CH-32 -3/-3 dB
- SRH805S -1/-3 dB
- FA-S270C +3/-1dB
What we’re seeing is that the long whip antennas perform quite well on 2m TX/RX, the ultrashort stubby antennas might as well be left at home, and the Icom stock antenna + the helical commercial antenna both perform very well. Keep in mind the helical is a single band antenna as well.
On 70cm the SMA-24 performs very well but so does the Icom stock duck antenna, with only marginally worse performance I don’t see much of a reason to bring anything else with me if I’m going to be operating 70cm. Another surprise is how much better the stubby antennas are on 70cm, performance for the SRH805S is only 6dB down from the best antennas tested, one wonders why they claim this antenna works on 2m at all though.
As expected, in general the larger the antenna is the more signal it’s able to capture, and transmit performance is actually quite good even for quite short antennas like the stock ducky antenna from Icom. Personal experience and anecdotal evidence from testing suggests that larger antennas may be less sensitive to phasing issues, and may perform better while mobile because of this.