http://elecraft.85.s1.nabble.com/OT-operating-QRP-at-same-park-tp7629369p7629377.html
harmonics. I have high power band pass filters (4O3A products) and I
can still here my 40m signal on the exact harmonic on 20m. For example
> I understand we are speaking about the KX2 here but I'm curious... would
> roofing filters have helped in this situation?
>
> In a recent WWFF outing we had a KX3 and an FT-817 set up. We separated the
> antennas best we could but really didn't pay a lot of attention to it. I
> believe the KX3 was on 40 and the 817 on 20 meters. The KX3 never heard the
> 817 but the 817 (no roofing filters I think) washed out when the KX3 was
> keyed.
>
> The radios were about 30 feet apart and the antennas maybe 40-50 feet apart.
>
> If the KX3's success was due to the roofing filters installed, could some
> sort of external filter added to the KX2 contribute to a solution? Is the
> KX3 meant to play well with others while the KX2 is intended more for a
> solo trip? I understand W4RT has optional roofing filters for the FT-817. I
> wonder if he or someone might come out with a good option for the KX2.
>
> Then again... am I way off base here?
>
> 73,
> Kev K4VD
>
> On Sun, Apr 16, 2017 at 2:08 PM, Fred Jensen <
[hidden email]> wrote:
>
>> 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)
>>>
>>>
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