Simplex Operating on VHF/UHF in Hawaii

Simplex VHF operation works better than most expect. In time of an actual disaster, many of the repeaters would be offline and unavailable. There is VHF Ham Radio without repeaters!

Nearly 200 miles on an HT!

A recent series of experiments have shown that even HT's can span hundreds of miles with proper line of sight and good conditions. KH7CL, Chris, contacted many Oahu hams with his HT from the telescope site on the top of Mauna Kea. This is a range of approximately 180 miles or more depending on the exact location of the Oahu station.

Sometimes he used a roll up J-pole antenna and sometimes a portable Arrow beam to augment the rubber ducky, but otherwise he was using a stock HT on his end.

Using a pair of seven-element hand-held Arrow Beams on 446 Mhz, conversations from a condo Lanai in Honolulu to the telescopes on Mauna Kea was limited only by the ability of the Mauna Kea end operator to stand the cold wind on the telescope lanai. HT's running a few watts were used on both ends of the circuit.

There are four ARRL VHF contests each year which offer excellent opportunities to monitor simplex frequencies and see who is around and find all the places your home QTH signal will get to on simplex. The ARRL QSO Parties are relaxed and fun without any of the usual stress of contesting. They are great to find out what your rig will do in simplex, either mobile or base. Perhaps one of the roughest awards to seek in Hawaii is the VUCC.

One of the most famous VHF DXers lives in Hawaii on the Big Island, KH6HME, and you will find his callsign beside all sorts of VHF distance records using Tropospheric ducting between his site and California. Of course he uses a lot more than an HT and a few watts! But it certainly shatters the idea that VHF simplex is a "just down the street" mode.

Two Meter Simplex Frequencies

The classic two meter FM simplex frequencies are 146.52, the national simplex calling frequency and the secondary frequencies of 146.55 and 146.58. Be certain to set your rig for no offset when running simplex. Contest operation is prohibited on the main calling frequency of 52, so 55 and 58 are the places to monitor.

Often one can catch tourists newly arrived calling CQ on 146.52 simplex out of their hotel room in Waikiki if you monitor that frequency and are in range of that area.

Simplex is great fun and all sorts of tricks extend range and coverage besides the obvious one of being high and clear with a great line of sight.

You can bounce signals off big flat area to execute "pool shot" like contacts around corners and in and out of valleys. Often the correct beam heading will be a surprise. Knife edge and Tradewind Inversion reflections will often form reliable paths from the Windward Side to the Honolulu Side of Oahu as though the signals were going right through the mountains.

The important thing about simplex operation is that you never can tell where your signal might get to. Assuming it will only go a couple of blocks without a repeater is very wrong. In Hawaii things are complicated by all the valleys and mountains, tall buildings and other obstructions, but just because repeaters are down, it does not mean your VHF station or HT is useless.

Conducting nets on simplex is a bit trickier than on a powerful repeater, but it is a critical skill for emergency operations. The basic simplex net control techniques are easy to understand if you apply common sense.

The Howling Curse of Beeper Intermod

Intermod is the biggest problem in areas like Honolulu. HT's are notorious for being susceptible. Various filters exist to help. The big brick like DCI filters are huge, often twice the size of an HT, but they work GREAT! At the home QTH, one of these connected to your outdoor antenna often makes the difference between being able to work VHF or having to just leave the rig off because of the constant howls, squawls and BEEEEHAAAAAS from the plague of high power beeper amps sprouting from the tops of all tall buildings.

Some mobile rigs such as the Yaesu FT-2500 have very good front ends with tuned sections and have a good intermod resistance, vastly superior to the average Kenwood Handheld for instance. But even these rigs Yaesu FT2500 benefit from a heavy duty bandpass filter like the DCI unit for base station use with a good outdoor antenna. Just fitting one of the fancier larger duckie replacement antennas can cripple an HT in many areas of Honolulu such as the UH Manoa Campus area, with its increased signal capture and resulting intermod overload of the front end of a typical HT.

The problem is that if you install a better antenna than just the factory supplied rubber duckie, you often overwhelm your HT with intermod, unless you also add some kind of filter. One excellent filter is made by DCI , a Canadian Company. It is chunky but it works like a champ to make VHF operation possible and pleasant in even the worst areas.

It has often been said that the limitation on all VHF operation in urban areas of Hawaii like Honolulu is intermod and the intermod resistance of your selected rig. Until this problem is solved with a decent filter, or at least a rig with a reasonable front end, there is little reason to put up an outdoor antenna in many urban areas like Moiliili.

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08/99