[Elecraft] K3 FD report in high RF (K3 vs Flex 6xxx)

[Dave Olean]

Hello Matt,
Wow, with those power levels and a 20 ft spacing between 3 el yagis, you are 
"cruisin' for a bruisin'". I made some measurements at my home station with 
two K3s on ten meters feeding different antennas. The antennas were 300 ft 
apart.  I aligned the two yagis to face each other and saw only 17 dB of 
isolation. One of my K3's was hooked to a 1500 watt amp. With the antennas 
aimed at each other, there would be 30 watts coming down the feedline of K3 
#2! Now my yagis were bigger than 3 elements: I had 5 and 6 element HB 
beams, but the problem is lack of isolation between any directional antenna. 
A few dB makes little difference.
    I still have not solved the in band overload problem entirely. 1500 
watts is a lot of power. Cross polarization is a good way to go. Make one 
antenna vertically polarized and pick up a bit over 20 dB. The other 
technique is to avoid aiming antennas in directions that aggravate the 
problem. I think you would want 60 dB of rig to rig isolation with a legal 
limit amplifier for really good results.  Having antennas at differing 
heights, cross polarized, and widely separated, can get you close, but I am 
afraid that boresighted antennas will still cause problems at 1500 watts. 
QRP looks better and better!!

Dave K1WHS
----- Original Message ----- 
From: "Matt Z via Elecraft" <elecraft at mailman.qth.net>
To: <elecraft at mailman.qth.net>
Sent: Thursday, July 02, 2015 4:33 AM
Subject: [Elecraft] K3 FD report in high RF (K3 vs Flex 6xxx)


> KL7AA had two elecrafts at FD, a KX3 for SSB and a K3 for CW, and 
> interference was a definitely noticed. Each rig was wired to separate 3 
> element stepIRs, about 20 feet apart. One rig used the elecraft 500w amp 
> and one used a 1.5kw amp. The two elecrafts could not operate on the same 
> band at all. Maybe it was something with the setup.
>
> Date: Wed, 1 Jul 2015 12:43:16 -0400From: Guy Olinger K2AV 
> <k2av.guy at gmail.com>To: N1EU <n1eu.barry at gmail.com>Cc: Elecraft Reflector 
> <elecraft at mailman.qth.net>Subject: Re: [Elecraft] K3 FD report in high RF 
> (K3 vs Flex 6xxx)Message-ID: 
> <CANckpc1sUaYtmRtJLJn0KBdYZaY+-gACJqqUWBKGVM0VxSPjNw at mail.gmail.com>Content-Type: 
> text/plain; charset=UTF-8
> On Wed, Jul 1, 2015 at 8:34 AM, N1EU <n1eu.barry at gmail.com> wrote:
>> The Flex ops should have dialed in a little front-end attenuation to> 
>> alleviate the ADC overload problem.>
> Understand the sentiment, but more attenuation is 
> operationallycontra-indicated if the signals you're trying to work are 
> weak due totemporary emergency antennas and QRP.
> Part of emergency preparedness is understanding various 
> rigsnon-prejudicially for their various strengths and weaknesses and 
> choosingrigs for strengths and avoiding rigs for weakness as those apply 
> to thespecifics of an application.
> These days weak signals and close multiple transceivers call for the 
> likesof K3's.
> At N4C field day we frequently had a CW station and SSB station on the 
> sameband with no interference, and actually without being aware of each 
> other.No noise, no anything. I know what a K3's hardware AGC kick-in 
> sounds likeand that was also absent. This has been our experience for five 
> or sixfield days now, and together with the small light size and 
> portability,makes the K3 a top pick for FD. Not because of Koolaid, but 
> because ofproven suitability to the application.
> I'm waiting to hear about KX3's for FD, especially battery operation, 
> longa specific niche for K2's.
> We did not have a K3S or K3 with KSYN3A for evaluation. We have a 
> standingquestion of whether K3S/upgraded K3, with some horizontal 
> separation, willbe able to operate a few KHz away from each other on the 
> same band/modesegment, e.g. the 40 CW station, and the GOTA station on 40 
> CW at the sametime. Perhaps next year we will find out.
> N4C operated at the Grey Goose Farm near Creedmore, NC. The group was 
> alarge portion of the North Carolina East chapter of the Potomac 
> ValleyRadio Club. This group contains a significant supply of K3 owners, 
> whoregularly bring K3's to FD and multi-op contest events. For 
> themportability and immunity to high RF environments are 
> top-of-the-listreasons for purchasing K3's as opposed to other choices, 
> easily serving FDstyle applications.
> At NY4A, also primarily manned by PVRC NC East members, going back 
> pre-K3the FT1000MP was the main rig, which had gradually replaced all 
> thestalwart Japanese rigs of prior years. For some time the MP was the 
> onlyrig seen there. When the K3's and other rigs with new generation RX 
> cameout, and the differences became known, The MP's were gradually 
> replaced. Atally of the list of MP owning operators who had manned NY4A at 
> some pointindicated that 11 MP's had been replaced by 14 K3's and one 
> Orion. Of thatgroup, no one owns a Flex to this date. But neither would I 
> consider any ofthem to be a "Flex-basher".
> I do know Flex owners, single home stations, who get 
> outstandingperformance away from high-RF multi-TX operations. Various 
> problems with CWand spectral purity seem to be a continuing manufacturer's 
> emphasis forsolution. They're out there on a particular bleeding edge, 
> with aparticular emphasis, with its own set of problems. We'll just see 
> what theydo. Bashing not necessary.
> UPS currently has my 2015 K3 upgrade round: KXV3B, KSYN3A's, a second 
> KBPF3(A version) and finally a P3 and P3SVGA. I will get the new audio 
> boardwhen it's available.
> Regards All,
> Guy K2AV
>
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