[Elecraft] OT - operating QRP at same park

[Fred Jensen]

At 30-40 ft separation on 15 and 20, your two antennas are probably 
within each other's near-field and each is thus "part" of the other.  
The coupling in the near-field can be very high.  The general rules are:

1.  Separate the antennas by as much as possible, preferably several 
wavelengths.  A wavelength on 20 meters is ... well, ~20 meters [roughly 
67 international feet].

2.  Orient/position the antennas such that one is in the other's null.  
For half-wave dipoles, that's off the end and FD experience suggests 
colinear with each other and well separated works best. Note however, if 
they are within each other's near-field, orientation may have little if 
any effect [see #1 above].

During the BPL bruhaha a number of years ago, I modeled my my 
non-resonant sloping-V and a couple of 12 KV distribution lines [which 
would have been the BPL carrier] together using NEC-2, similar to K9YC's 
suggestion, to see how badly I would disturb my neighbor's BPL I'net if 
he had it.  The coupling coefficient on 40 meters and higher was pretty 
stable at around -30 to -35 dB.  On 80 and 160, where the power line and 
antenna shared a near-field, the coupling was in the -10 to -15 dB range.

As you describe them, and with perhaps 10 watts for easy math, the 
received power might be one or two tenths of a watt.  It's not real 
surprising the receivers "cried out in pain" [:-).

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 4/16/2017 9:44 AM, kevino z wrote:
> A friend and I both had our KX2 transceivers and some resonant end fed antennas. He was on 15m and I was on 20m. Our antennas were placed about 30-40 feet apart, as slopers with the radiating ends up 30+ feet in the air using Jack-kite poles. The plane of the antenna's slope were perpendicular to each other.
> We were both on 10w SSB.
>
> Every time one of us keyed up, the other person's KX2 would experience a nasty noise from the signal. Pre-amp was off, as was attenuator. My question is this: Would the use of some bandpass filters have helped us? This is a situation we are trying to resolve before operating QRP in a similar park for a QSO party.
>
> If more distance between the antennas would have helped, what is the proper way to determine the needed separation?
>
> I read the other day about someone in a car using 3 or 4 Elecraft radios with antennas on the roof, so I imagine there has to be a way.
>
> Thanks,
> -Kevin (KK4YEL)
>