40 birthday gift idea

PROJECTS AND INFORMATION FOR THE ACTIVE AMATEUR

Q Frank, N3ZOC, asks: What is a CW frequency? When I want to operate CW and after listening and then sending "QRL?" (is this frequency in use?), just what is the definition of the frequency spectrum that I am asking about being in use? For SSB it would be from the "dial setting" down 3 kHz for LSB or up 3 kHz for USB as far as selecting a spot to operate.

To phrase it another way, as a "considerate CW operator," how far away from an existing CW QSO do I have to go to consider it an unused frequency? For SSB operation it is 3 kHz. What is the nominal frequency separation for CW that is acceptable as good operating practice?

I am not looking for descriptions of faulty signals, but what is the nominal bandwidth for CW that I can consider "my frequency in use" or another QSO's frequency in use.

It appears from my experience that some hams are utilizing their equipment to receive in a wideband mode when operating CW and then complaining of interference when they hear any CW signals within the wider than needed bandwidth they are listening to. Some contend that CW filters are optional. I contend that the CW mode is optional and that if they want to operate CW, then they should not use a bandwidth appropriate for SSB and then complain of interference.

I have searched through my references and have been unable to find the answer to the bandwidth of a "QRL" (this frequency is in use) or "QRL?"

A This is a really good question! Your 3 kHz number is a reasonable one for general SSB use, if signals are all about the same amplitude. A look at the product review of any recent SSB transceiver will show you that the SSB transmit IMD products have significant components down 40 to 50 dB out to 8 or 10 kHz on the selected sideband side of the carrier. If someone is trying to listen to a weak DX station, and you would be 20 dB over S-9 at their house, your IMD products could be louder than the station they are trying to copy, so a 10 kHz spacing would be even more considerate on SSB.

For CW, it's a bit of a trickier question. You need to imagine both the other operator's equipment and skill. If they have a transceiver with just an SSB filter, staying 2 to 3 kHz away should keep you out of their passband-hopefully they won't even know you're there. Some early transceivers (Collins KWM-2 and Heathkit HW-100, for two popular examples) didn't even have provision for a narrower filter. On the other hand, especially in the lower 25 kHz of the band, it may be more reasonable to assume that operators will have the usual 500 Hz or sharper CW filters in place. If so, being 1 kHz away should keep you safely out of their filter skirts and would be reasonable in my opinion. A skilled CW operator, such as you have reason to expect in the Extra Class segments, should have no problem separating signals 1 kHz apart in their brain, even if they don't have a filter in or behind the radio. If you do send "QRL?" and get back a "QRL" or "yes," that means you are indeed interfering with someone, even if you don't think that you should be; they may be operating "split-frequency" and listening to someone right on your frequency, even if they are 2 kHz away. If they do say yes, the considerate and legal action is to move farther away.

In summary, if there's room, why not leave 10 kHz for SSB and 2 or 3 kHz for CW, especially in the parts of the band that cater to casual and beginning CW operators. If it's tight, I agree that it's reasonable to use 3 kHz, or even a bit less for SSB and 1 kHz for CW. When you do, it's always good to ask "QRL?" to be sure.

Q Dick, K6TRZ, asks: I own several pieces of equipment that require small batteries. I got tired of buying batteries all the time, so I decided to try the rechargeable kind. I bought some from the local electronics store, along with a charger.

All was fine until a family member gave me a birthday gift of another charger and a supply of batteries. I realized that the two sets of batteries were not the same. My original set consisted of nickel-cadmium (NiCd) batteries, while the new ones were nickel-metal-hydride (NiMH). I have read the instructions and they tell me not to mix the two types of batteries within the same equipment. I wonder if I can charge the two types of batteries in the same charger, or should I go by the manufacturers' recommendations and use the proper charger.

A Before I get to the answer to your specific question, I'd like to make a comment about rechargeable batteries in general. Even though the rechargeable batteries are often in the same size cases as non-rechargeable ones, such as the popular AA size, they are not always directly replaceable. The non-rechargeable batteries provide 1.5 V per cell (a bit higher when fresh), while the rechargeable provide 1.2 V per cell, both at full charge. For some applications this doesn't matter, but for some it can make a difference. For example, a flashlight will put out less light with rechargeable batteries than with the regular ones. Handheld transceivers will likely put out less power on transmit with rechargeables, and some may not even work. A typical six cell package will drop from 9 V with alkaline batteries to 7.2 with either type of rechargeable. I prescribe that you check your manual before you assume you can make the change.

The next soapbox item is to agree that unless you have solid information to the contrary, instruction manuals should always be followed. Batteries are a particularly good place to do so, since improper charging can result in fire and explosion. So what's the story with these two types of batteries?

NiCd batteries have been around for a long time and have delivered good service as rechargeable batteries for radio and other uses. They do have some limitations-many NiCd chargers tend to overcharge the batteries if left on charge, leading to premature failure. The cadmium in NiCd batteries is a toxic material and thus requires special disposal to avoid environmental damage.

NiMH batteries are a newer technology that eliminates the toxic material problem and has a plus of being able to deliver more power in the same size and weight package (although not all batteries offer larger capacity-check the rating to be sure). One concern about NiMH batteries is that they can get quite hot during charging. It's best to make sure that any charger used with them not have a lid closed over them during charge and that they have plenty of ventilation. It's a good idea to keep flammable material away from them and let them cool down after charge before inserting into equipment. Some may have different thoughts that I'd like to hear, but so far I haven't heard of any application for which NiCd is a better choice than NiMH. They do seem to be fussy about charging as noted below.

Finally-back to your question! Charging requirements are different for the two battery types. First the recommended charging rate for NiMH is generally lower than that for NiCd, so a NiCd charger can easily overcharge and overheat a NiMH battery. Many NiCd chargers are controlled by charging over a time period, while NiMH chargers are generally smarter and monitor the charge state (by measuring the voltage) and reduce the charge current to a trickle as appropriate. By mixing batteries and chargers, you run the risk of overcharging (and overheating) NiMH batteries in a NiCd charger, or confusing the smart circuitry in a NiMH charger resulting in an uncertain output. Since the batteries are likely to have different capacities, you will not get the benefit of the larger capacity unit if they aren't the same.

Your doctor recommends that you use them both until they start to fail, but keep them in separate equipment and charge them in the proper charger. When one group starts to fail, you may wish to dispose of the batch and migrate to a single type and charger. If I had the choice, I'd settle on NiMH, but your mileage, and experience, may vary.

Q Steve, K8JQ, asks: I'm in need of some open wire line that looks like the picture in Paul Danzer's article1 in the April 2004 issue of QST. I bought a 500 foot roll of Saxton Products open wire line a few decades ago and it's almost gone. A Google search did not return any hits on Saxton Products. Do you know where one can buy open wire line similar to that shown in Figure 1 of that QST article? That's about what my now-exhausted roll looks like.

A Steve, you're in luck. There are still a number of sources, although it is getting harder and harder to find real open wire line. Window line is a reasonable substitute; however, open wire line has even less loss and is less subject to the effects of rain and particulate matter on the insulation web. Check the advertising pages of QST and look for dealers that carry wire and cable. Several still sell open-wire line. If you will be using the line for unsupported runs I suggest using stranded wire line instead of solid to avoid the type of break shown in the photo.