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OT - operating QRP at same park

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kevino z

OT - operating QRP at same park

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)

No trees were killed in the sending of this message. However, a large number of electrons were terribly inconvenienced !
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John Hendricks-2

Re: OT - operating QRP at same park

Band pass filters on both radios will solve this problem.

John K7JLT

On Apr 16, 2017 09:45, "kevino z" <[hidden email]> 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)
>
>
> No trees were killed in the sending of this message. However, a large
> number of electrons were terribly inconvenienced !
> ______________________________________________________________
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> Please help support this email list: http://www.qsl.net/donate.html
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Jim Brown-10

Re: OT - operating QRP at same park

In reply to this post by kevino z

On Sun,4/16/2017 9:44 AM, kevino z wrote:
> Would the use of some bandpass filters have helped us?

Maybe. It depends on whether you were hearing the other radio itself, or
intermod created by some nearby non-linear device that re-radiated it.
Bandpass filters will take care of the other radio, but not the
intermod. 30-40 ft is pretty close, even for 10W and KX2s.

> 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?

If you're hearing the other radio, RF loss in the path between the two
antennas can be computed using NEC. To do that, put both antennas in the
model, put a Source at the feedpoint of one antenna, put a 50 ohm load
at the feedpoint of the other antenna (but no source). Set NEC to
compute for 10W (or whatever power you want to run). Then compute the
pattern, and click on Load Data to see how much signal is induced at the
other antenna.

BUT -- another issue comes to mind. You say "resonant end-fed antennas."
All antennas need some form of return conductor for antenna current.
What form do your antennas take? What's the return for antenna current?
Is it the coax? If so, is there a ferrite choke at some point so that
current is confined to the intended length? How close are the rigs? And
when you build that NEC model, be sure to include that coax and any
other counterpoise.

73, Jim K9YC

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k6dgw

Re: OT - operating QRP at same park

In reply to this post by kevino z

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)
>

Kevin - K4VD

Re: OT - operating QRP at same park

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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Richard Thorne-4

Re: OT - operating QRP at same park

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 <[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)
>>>
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
> ______________________________________________________________
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>

Ignacy

Re: OT - operating QRP at same park

In reply to this post by kevino z

Looking at KX3 diagram, the signal goes trough low-pass filters and band-pass filters. Both are separate for 30-20 and 17-15 bands. So soem but probably not much attenuation from 20 to 15 and vice versa. The attenuation between 17 and 40 is likely much stronger. I assume that the front end in KX2 is same as in KX3.

The bandpass filters in K3 also cover two bands but have extra caps switched in, probably for single band coverage. This would explain why K3's are not interfering much cross band.

Ignacy, NO9E

Jack Brindle-2

Re: OT - operating QRP at same park

In reply to this post by Jim Brown-10

I believe Jim’s “BUT —“ is something being overlooked by a lot of folks here. The fact is that the It certainly enters into the situation as a major contributor since the antenna does extend onto the feedline for end-fed antennas (all the way to the radio!). Essentially, everything that is not decoupled is part of the antenna radiator. That’s why Jim’s point about ferrites is so important.

I would suggest that the situation would be greatly different if the antennas were sloping dipoles resonant on each band, and even better if decoupling ferrites were used at the feed points of the dipoles.
End-fed antennas may be easy to put up, but that comes at a cost. Especially at QRP, proper engineering fundamentals are very important!

Playing with Jim’s NEC model suggestion sounds very interesting.

- Jack, W6FB

> On Apr 16, 2017, at 10:24 AM, Jim Brown <[hidden email]> wrote:
>
> On Sun,4/16/2017 9:44 AM, kevino z wrote:
>> Would the use of some bandpass filters have helped us?
>
> Maybe. It depends on whether you were hearing the other radio itself, or intermod created by some nearby non-linear device that re-radiated it. Bandpass filters will take care of the other radio, but not the intermod. 30-40 ft is pretty close, even for 10W and KX2s.
>
>> 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?
>
> If you're hearing the other radio, RF loss in the path between the two antennas can be computed using NEC. To do that, put both antennas in the model, put a Source at the feedpoint of one antenna, put a 50 ohm load at the feedpoint of the other antenna (but no source). Set NEC to compute for 10W (or whatever power you want to run). Then compute the pattern, and click on Load Data to see how much signal is induced at the other antenna.
>
> BUT -- another issue comes to mind. You say "resonant end-fed antennas." All antennas need some form of return conductor for antenna current. What form do your antennas take? What's the return for antenna current? Is it the coax? If so, is there a ferrite choke at some point so that current is confined to the intended length? How close are the rigs? And when you build that NEC model, be sure to include that coax and any other counterpoise.
>
> 73, Jim K9YC
>
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NS9I WI

FS KXV3-2 REV A

In reply to this post by Ignacy

I updated my K3 to with the KXV3B thus have a KXV3-2 REV A (2007).
Includes cover panel, mounting screws, installation manual and TMP cable.

$70 shipped CONUS USPS Priority Mail

thank you 73 Dwight NS9I

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Jim Brown-10

Re: OT - operating QRP at same park

In reply to this post by Richard Thorne-4

Yes. This is easily (and cheaply) killed by a stub.
http://k9yc.com/Coax-Stubs.pdf Pay careful attention to the Q&A
beginning on page 7 "Does it matter where a stub is connected? Why?"

And for a detailed "how to," study http://k9yc.com/LocatingStubs.pdf

73, Jim K9YC

On Sun,4/16/2017 12:18 PM, Richard Thorne wrote:
> 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.

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Don Wilhelm

Re: OT - operating QRP at same park

In reply to this post by kevino z

Kevin,

The perpendicular antennas likely contributed to the interference.
Best situation for nearby antennas is to orient them co-linear - that is
end to end.

73,
Don W3FPR

On 4/16/2017 12:44 PM, 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.
>
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Elecraft mailing list

Re: OT - operating QRP at same park

In reply to this post by kevino z

Jack, W6FB, made a good point about resonant antennas. Going with this
idea, separate resonant antennas should be used for each band, and mobile
antennas, being high-Q may be particularly desirable. However, minus separate
bandpass filters (to augment interference rejection), physical separation of
the antennas by some(?) distance is also desirable. In the case of
horizontal antennas (dipoles, yagis, etc), orientation (right angles or end-to-end)
along with physical separation is key.

Multiband and non-resonant antennas can't be counted on for signal
rejection in most cases.

The best lessons for minimizing station-to-station interference can be
gleaned from multi-multi stations; their challenges and how they overcome them
are always insightful.

73, Bert N4CW

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Doug Smith [W7KF]

Re: OT - operating QRP at same park

I used to work Field Day with a friend in the two transmitter class. At our first Field Day, we had the usual problems as described by the original poster. Especially so because we were both running 500 watts.

On our second and all subsequent operations we operated with one station on a vertical and the other with a horizontal antenna. That helped a lot.

On our third and subsequent mountain top FD expeditions we put a receive-only antenna 800 feet away and fed the sigs back to the operating tent with a big roll of RG-6 quad shield.

Problem solved.

There are a few mechanisms available to aid in “separation”. Get the antennas physically as far apart as possible. Try cross polarization. Operate on bands as far apart as possible. Band pass filters. Stubs. Some antenna tuners are configured as low pass; some are configured as high pass. Single band resonant antennas are band pass filters (watch out for odd harmonics).

73,
Doug, W7KF
http://www.w7kf.com <http://www.w7kf.com/>

> On Apr 17, 2017, at 9:14 AM, Bert via Elecraft <[hidden email]> wrote:
>
> Jack, W6FB, made a good point about resonant antennas. Going with this
> idea, separate resonant antennas should be used for each band, and mobile
> antennas, being high-Q may be particularly desirable. However, minus separate
> bandpass filters (to augment interference rejection), physical separation of
> the antennas by some(?) distance is also desirable. In the case of
> horizontal antennas (dipoles, yagis, etc), orientation (right angles or end-to-end)
> along with physical separation is key.
>
> Multiband and non-resonant antennas can't be counted on for signal
> rejection in most cases.
>
> The best lessons for minimizing station-to-station interference can be
> gleaned from multi-multi stations; their challenges and how they overcome them
> are always insightful.
>
> 73, Bert N4CW