The Comet HAS

A mobile HF antenna.

Ever since the introduction ol several small HF transceivers there has been a huge influx in the amount ol HF mobiling. it is now very easy for anyone to throw a hg in the car and operate on those long road trips. Choosing the right antenna can be rhe hardest part of the whole installation, With so many different makes and models available deciding what is best suited for your needs can be confusing and difficult

With so many of us driving small cars today and living in urban areas the size of the antenna can be a problem. Several months ago I noticed the Cornet HA4S pictured on the cover of 73 magazine. What a neat-lookmg antenna—small, and having the ability to fold over like some of the fancier VHF/UHF antennas . Finally, it's a small antenna that you don t have to take off the car to pull into the garage.

It is important to understand thai any mobile antenna is a compromise There is no mobile antenna lhal is as efficient as a yagi or a quarter-wave vertical with elevated radials, I have found that generally the bigger antennas tend to be more efficient and have a greater bandwidth. You gain a small size with many HF mobile antennas, but you tend to lose bandwidth and efficiency, I was curious to see how wetl the Comet HA4S performed compared to some of the larger antennas that I have used.

The Comet HA4S

The HA4S is considerably smaller than most HF mobile antennas, measuring only 4'4M tall and weighing just over a pound. It is rated to handle 120 watts SSB, The HA4S comes standard with foui bands: 40, 15, 12, and 10 meters, Each band is a separate coil that attaches to a mast, similar to the Hustler antennas. An optional coil can replace one of the existing ones, adding the 20 meter band. The 40 meter coif screws into the top of the mast while the other three coils screw into a circular hub just below the 40 meter coil. The coils slope downward, making the antenna appear somewhal like a discone Comet thoughtfully includes a wrench for proper tightening of the coils to the masi, The assembly of the antenna was extremely easy and straightforward-Ht took ail of about three minutes to complete

The connector on the end of the mast is a standard UHF male (PL259). Most antennas use the heavier duty 3 8" threaded mount The reason for this is thai the bigger ihe antenna isT the greater the windioad is going to be. and the 3/8' is just a stronger mount capable of handling much larger loads After flipping through my catalogs i found that several manufacturers make heavy-duty mag-mounts as well as rail and lip mounts, with the UHF female, that are more than capable of handling the HA4S

~ne mast on the HA4S folds ovei just like some of the fancier VHF UHF antennas. This is a great feature; no more taking the antenna on and off each time you pufl into the garage To lower the antenna, unscrew the collar surrounding the fold-over hinge lift The masl out of the socket. and it will fold over to the side To right the HA4S, puli the antenna vertical and back into the socket and tighten the collar, locking it back into place.

Tuning the HA4S

As i mentioned, the use of coils and traps limits the bandwidth of an antenna somewhat, and is not as efficient as using a full-size antenna, Comet claims that the antenna will resonate in any 46 kHz section of the 40m band with a 2.0:1 SWR or better. Bandwidth for each frequency range increases up to 660 kHz with a 2.0:1 SWR or better in the 10m range. To adjust the antenna to resonate In the desired segment of the band, you lengthen or shorten the whips on the coils. By making the whip sEightiy longer you lower the center frequency. Let's say I want my HA4S to resonate between 14.180 MHz and 14.220 MHz. i would first go to my center frequency, check my SWR, and adjust my whip accordingly until minimal SWR is obtained, This can be done by transmitting low power into rhe antenna and checking the measurements on your meter. I use an MFJ-259 SWR analyzer, an invaluable toot for tuning antennas or any other type of antenna work. 11 doubles as a frequency counter and an SWR bndge allowing me to check the exact SWR of any frequency t specify. This tells me where my antenna is resonant and allows me to do this without the use of my transceiver, ft is very important that you make sure you have good ground connection from your antenna to your car A bad ground is often the cause of many problems, such as a high SWR

I had no problem adjusting the coil tor 10, 12 15 and 20 meters. I picked my center frequency and adjusted the whip for the minimal SWR, then checked 20 IkHz either side and found the SWR to be fine.

On 40 meters ! had to irim the whip slightly before I was able to resonate the

NCG/Comet NCG Companies 1275 North Grove Street Anaheim CA 92806 Telephone: {714) 630-4541 Fax (714) 630-7024 Price Class; St99 Optional 20 meter coil—S39

Comet Ha4s

The Comet HA4S.

antenna above the CW portion of the band.

Performance

Most of my tests were conducted on 20 meter SSB, due mostly to propagation. Overall. I was impressed. The HA4S performed tike a champ. On my drive back to college I was hearing strong signals from both W6 and W4 land f worked EA30T without any difficulty, and received a 57 report. Soon after, I was chatting with some guy in northern Florida with a 59 signal I also made contacts on the other bands as welt as 40 meter CW

It is important to remember that ;his antenna was more than hkely designed for the Japanese amateur, with small size and versa-tihty in mind. In getting the nice smalt package. you lose bandwidth, making the HA4S fairly frequency selective once you have set your center frequency. If you try to operate outside the 20 kHz on either side of ihe center frequency you will notice a rapid increase in your SWR. However, if bandwidth is not your biggest concern and getting a small excellent mobile antenna that has some unique features is then the HA4S will do the trick.

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