Comet CHA-250HD
$$$$ยท
| Frequency | TX 3.5-57 MHz continuous; RX 2-90 MHz |
| Bands | 80m-6m continuous (TX 3.5-57 MHz; RX 2-90 MHz; no tuner needed) |
| TX power | 250 W (250 W PEP (SSB)) |
| Modes | SSB, CW, AM, FM, digital |
| Connector | SO-239 (UHF female) at the base matching transformer; 50-ohm coax, no radials |
| feedpoint | base matching transformer, SO-239 |
Estimated (unverified): per-band efficiency is now community-characterized rather than only inferred: independent analysis measures ~3 dB below a quarter-wave on 20 m (low bands worse); exact figures vary by install height. Introduction year of the HD revision not firmly established.
About the most convenient HF antenna there is: one 23-foot vertical, one coax, no radials and no tuner, covering 80 through 6 meters continuously. Put it up on a mast bracket and you are on every HF band plus 6, with a clean match the radio is happy with and a receive range wide enough to double as a shortwave listening antenna. Real-world A/B testing confirms it makes genuine contacts - everyone in a 20 m net could still hear the testers on it - and on 80 m its broadband match can even beat a dipole tuned for the wrong part of the band. For restricted lots, rooftops and operators who hate laying radials, it removes almost every install headache at once.
Efficiency is the price, and it is well-documented, not theoretical: independent analysis puts it about 3 dB below a simple quarter-wave on 20 m, the broadband match is a lossy transformer that turns real power into heat (hence the recurring 'dummy load' jibe), and the low bands pay most. Its low takeoff angle also makes it weak on short-skip/NVIS paths - one test saw a 59 on a dipole drop to 33 on the Comet to a 400 km station. The 250 W PEP ceiling rules out amplifiers, and a resonant antenna or cut dipole will outtalk it on any single band.
The no-fuss multiband vertical, with eyes open. If your priority is to get on all of HF and 6 meters with the least possible installation - no tuner, no radials, one bracket - the CHA-250HD is one of the genre's benchmarks, and on-air tests confirm it makes real contacts. But buy it understanding the well-measured bargain: roughly 3 dB down from a quarter-wave and weak on short skip, it trades genuine efficiency for total convenience. Where space allows even a simple wire, the wire will usually outtalk it.
The Comet CHA-250HD belongs to the same small, honest category as the Diamond BB7V: an antenna engineered around installation problems rather than around physics. It is a 23-foot vertical with a wideband matching transformer in its base that presents a usable SWR - under about 1.6:1, confirmed flat on an analyzer across the range - continuously from 3.5 to 57 MHz, which means 80 through 6 meters with no antenna tuner and, crucially, no ground radials. It even receives from roughly 2 to 90 MHz, doubling as a general-coverage listening antenna. For the operator on a small lot, a rooftop, or a rental where laying a radial field is out of the question, that combination is close to irresistible. The 'HD' marks a sensible mechanical update to the long-popular CHA-250B: the old aluminum top section becomes a solid flexible whip that bends in the wind and spares the lower sections.
The efficiency question is where this antenna earns its reputation, and the amateur community has done the homework so you do not have to take it on faith. A well-known independent teardown shows the broadband match is achieved with a lossy transformer that dissipates heat, and pegs the antenna at roughly 3 dB below a simple quarter-wave vertical on 20 meters; more than one reviewer has bluntly called it a 'leaky dummy load.' That is the physics tax of a no-tune match across more than four octaves from one short radiator, and the low bands pay the most. But the same scrutiny is fair about what it can do: in a careful on-air A/B test by an independent on-air A/B test, the Comet surprised the testers on 80 meters - its broadband match worked an 80-meter net at 59 where their dipole, tuned for the wrong end of the band, could not - while predictably losing to a dipole on 40 and a beam on 20. The telling weakness was short-skip: a 59 report on the dipole dropped to 33 on the Comet to a station 400 km away, because the vertical's low takeoff angle is wrong for near-in NVIS work.
So the honest framing is the one the data supports. As radio engineering the CHA-250HD is a deliberate, measurable compromise - 'quiet,' as reviewers diplomatically put it, which on transmit means down a few decibels - that a resonant no-radial vertical or even a simple cut wire will beat watt for watt on any given band. As a solution to having almost no space and no permission, it is among the best of its kind: it makes real contacts on every HF band plus 6 from one bracket with zero tuning, and its receive signal-to-noise holds up fine. Buy it for the convenience, run it barefoot, keep expectations realistic - and if you can fit even a wire dipole instead, fit the wire.