Wednesday, March 14, 2018

More Pile-up Techniques

After a period of relative quiet this month numerous DXpeditions are on the air. It's been a lot of fun. While only one new country made it onto my list (9M0W, Spratly Islands) quite a few new band slots have been filled. Particularly challenging has been the highest bands and the low bands, and in the case of 9M0W finding just the right combination and band and time to find effective propagation in this time of zero sunspots.

More so than in the past I am able to rely on brute force to get through the pile-ups. Antennas up high is a great help even without the aid of high power. About half the time I must still rely on agility and technique to get through the pile ups quickly. This is not strictly necessary since all these DXpeditions are one to two weeks long and eventually the depth of callers will thin and even those with small stations, and QRP, are likely to get through.

Jumping in early is more about the fun of the chase and honing my pile up skills. There is always more to learn. Some pile up skills apply equally to chasing contest multipliers, so this is good practice. In contests the technique must adjust for pile ups on the DX's transmit frequency; that is, no split.

This is an opportune time to review a few advanced techniques applicable to DXpeditions and contests. For many veterans there will be nothing new to read here. It can still prove helpful by reminding ourselves of what lurks in the bottoms of our toolboxes, digging them out and blowing off the dust. For some readers the information will be new and therefore of greater interest. Search this blog and you'll find similar articles covering a variety of pile up techniques.

Brute force

When propagation, antennas and power favour you it is best to rely on brute force to get through. Learn the DX operator's pattern -- listening frequency change between contacts -- then find the current lucky DXer and transmit where the DX is most likely to listen next. Don't worry about the presence of many others doing the same since you count on your superior signal to stand above them all. Or at least enough of them that you'll get through within a minute or two.

You may be thinking that this is hardly a pile up technique! Yet it is. Even if you have a modest station there will be times when propagation favours you and brute force works. When it does it is the most reliable and predictable way to get through pile ups fast. Spending time jumping around will only slow you down.

Leave the more advanced techniques for when you really need them. On the other hand, the big guns have to be wily when propagation is unfavourable and brute force doesn't work. For us in North America this is common when propagation favours Europe for DXpeditions such as Spratly Island. The reverse is true for Pacific Ocean DXpeditions.

Going below

Many DXers hamper themselves by collaring themselves the same as dogs restrained by invisible fences. On CW the spectrum within 1 kHz of the DX transmit frequency is avoided since it is a guard zone to prevent QRM on the DX who is operating split. There are times when the prohibition can be ignored to increase success if it is done respectfully and carefully.

Pay attention to whether the DX operator ever works stations below the edge of the 1 kHz guard zone -- listen and you'll notice that some use larger guard zones, such as 2 kHz, and on SSB it is typically 5 kHz or more. Should you probe below without that indication try to keep the split to no less than 800 Hz, and 900 Hz is a better limit if you want to be heard. I strongly recommend you never transmit closer to the transmit frequency even when the DX operator shows a willingness to listen there or bedlam can ensue.

This technique works because the majority strictly respect the guard zone regardless of the DX operator's observed behaviour. As I said, be careful when you do it. Don't QRM the DX!


A typical listening pattern for the DX operator is to shift the listening frequency in small steps. When he judges that the split is great enough he'll do one of two things: reverse direction or jump back to the edge of the guard zone. You usually notice this has occurred when your natural inclination to QSY up results in your inability to hear the station being worked.

When you determine that the listening frequency has been "reset" to the edge of the guard zone you have learned an important datum. The next time that invisible line is approached that is your signal to QSY to the edge of the guard zone and wait for the reset to occur. Should there be others doing the same it can help to move up slightly from the edge (say, from +1 kHz to +1.1 kHz). Also consider dropping into the guard zone slightly (+0.95 kHz) per the previous section.

There is another time when a reset can occur and catch everyone sleeping. This can be your opportunity if you stay nimble. The DX operator may show evidence of frustration when copying become difficult because the pattern is well understood by many and they then keep calling despite the attempt to focus on one identified caller. They may QSY randomly or they may do a reset.

Other indications of an impending reset include when they stop to identify several times or seem to be responding to no one for a while. In the latter case they may be changing operators. It is well worth the gambit of QSYing to the edge of the guard zone and calling there. I did this with one of the African DXpeditions currently active (I believe it was TN5R) and put them in the log with just one call precisely 1 kHz above the transmit frequency.

Calling in the hole

I discussed this item in the context of CW DXing. It can also be applied to good effect when encountering SSB pile ups. The technique also happens to be easier to apply.

A typical SSB split operation will announce a range of where the DX station will be listening. For example. 5 kHz to 10 kHz above the transmit frequency. On 40 meters and sometimes 80 meters the range will be similar but with a greater separation to take advantage of the frequency allocations available in different ITU regions.

What you will soon discover is that the bulk of the callers will transmit exactly at the boundaries of the range; that is, 5 kHz and 10 kHz up. In wider ranges, every 5 kHz. There is some sense to this behaviour because SSB requires greater signal separation to avoid an impenetrable wall of QRM. Many DX operators tend to jump in 5 kHz steps and we respond in kind, and so we all become accustomed to it.

Of course many of the pursuers are listening to learn the split of the last successful caller which results in deep QRM centred on these discrete frequencies. As often happens the DX station will work numerous stations at one frequency before listening elsewhere in the range, making the QRM worse for a while.

When brute force is not an option there is a way, obvious perhaps, to get through. That is to call in between those discrete steps. For example if the range is 14.195 MHz to 14.200 MHz, most of the callers are exactly at those two frequencies and you should call in the hole at 14.1975 MHz. Since this is 2.5 kHz from both those frequencies it is relatively free of QRM. Keep calling there. When the DX operator finally spins the VFO you'll be right there.

It's as simple as that. Even dogs have figured this one out. Ever notice how it is when they want attention that they're underfoot when you turn around? That's no accident!

The secret

Calling this next one the secret is a bit of a joke. It isn't much of a secret despite so many hams being unfamiliar with it. I don't mind sharing it since, even worst case, my readership is modest and, frankly, most won't use it anyway. Thus there will be little impact -- perhaps I'm being too cynical.

It is most useful in CW contests where even the most wanted multipliers operate simplex. When the pile up is on the DX station's transmit frequency the DX station has difficulty isolating one station (often it's the loudest one) and few in the pile up can hear the DX station underneath the QRM. Everyone's rate suffers. Discipline is usually good since otherwise no QSOs take place.

Unless you're that loudest of stations you are faced with a challenge. Since you aren't the loudest what you want to do is sound different. You do this by offsetting your transmit frequency. The shift must be enough to be distinctive yet still within the DX station's receiver pass band. Many DX stations are looking for that difference as well and will use their RIT feature to allow a wider shift.

In the former case a shift of at least 50 Hz is necessary but probably no more than 100 Hz. Aim for the high side (positive offset) since most receivers place the BFO at the bottom of the pass band (USB reception) and lower pitched tones are not as easily noticed. Don't be afraid use a negative offset since they may be using LSB reception (e.g. Elecraft transceivers).

Try it. You'll be surprised at how much of a difference it makes. If you've ever been on the receiving end of a pile up you'll know that all those zero beat callers are nearly impossible to separate, yet a shifted tone that's weaker than the others will be copied at least well enough to capture part of the call sign. It is for this reason that N1MM Logger contest software introduced jitter by default when clicking on a spot to minimize the risk of zero beating. Most rigs are so frequency precise that otherwise everyone clicking on a spot will end up 10 Hz of each other!

When the DX station is in on the game and you are paying attention you'll notice how he will split further and further, and then suddenly shift to the opposite offset. The vast majority of callers never seem to catch on. Get in the game and in moments you'll be trawling the bands for the next multipliers and leaving the messy pile up behind.

That's all there is to the secret. Have fun with it.

1 comment:

  1. Great tips for all contesters & DXers.... Very generous of you to share these. Thank you Ron !


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