May have been the same issue if the radios were on opposite frequencies.
The station on 20 was, more than likely, getting hit with 40m
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
if I'm transmitting on 7.025 I'm going to hear the harmonic around 14.050.
Rich - N5ZC
On 4/16/2017 1:58 PM, Kevin - K4VD wrote:
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 <[email protected]> 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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