It’s interesting that there’s little mention here of simultaneous operation - but many joint activations are done this way now.
N0TA John and I both have KX2 radios and usually operate simultaneously:
- Usually CW
- On different HF bands - 40, 30, 20, 17, 15M
- We both use homebrew bandpass tuners with considerable rejection of out-of-band signals
- We generally run 10W output
- We use end-fed antennas on poles - usually 52 feet or 66 feet long
- We set up at least 200 feet apart, and even more when practical
- We have operated successfully at 100 feet separation with a few minor issues
- There are very few problems at greater than 200 feet separation
When we happen to tune onto the same band, which is inevitable, we can hear the other station’s low-level unwanted products spread across the band. When we’re relatively close physically, the KX2 detects the overload and cuts off the receive preamp to protect it. So far we’ve had no damage, despite numerous instances of being on the same band.
Until recently, we had no voice communication for coordination or other issues. We’ve started using UHF FRS radios for coordination, as well as for problems or opportunities, such as S2S stations on the air.
When we set up 200-300 M apart, we can operate on the SAME band, provided we’re at least about 20-30 KHz apart. For example, one of us can be running a pile at 7.063, while the other is calling an S2S station at 7.033. This is only possible with a radio with a strong front end.
When we must set up more closely, there’s less trouble if the antennas are perpendicular, but we still have significant coupling in the vertical plane. On small summits we just have to do our best and accept some minor aggravation.
If the antennas are close, we notice various effects when operating simultaneously of different bands:
- De-sensing during CW characters, particularly when the receive preamp is on. Usually this is just a nuisance, not serious enough to prevent copying the desired signal.
- Clicks or pops related to the other station’s signals
- Unwanted products audible at various frequencies - ghost signals
- Strong harmonics at 2F, 3F, etc.
Of course, your results may vary, but with 200-300M separation, simultaneous operation on different bands may be practical with many other radios.
Many of our chasers catch both of us, and getting enough contacts has never been a problem. We usually post alerts, and the RBN spots us very reliably, usually within 1-2 minutes. We actually draw large numbers of chasers, probably because they know we’ll both be on several bands, with relatively efficient stations, so they have a very high chance of contacting one or both of us!