[Elecraft] OT - operating QRP at same park

[Kevin - K4VD]

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 <k6dgw at foothill.net> 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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