Re: Curious phenomenon with doublet on 80m

Posted by Don Wilhelm-4 on Jan 03, 2011; 1:33pm
URL: http://elecraft.85.s1.nabble.com/Curious-phenomenon-with-doublet-on-80m-tp5885101p5885564.html

  Igor,

Double check to be certain the KAT3 is bypassed on that portion of the band.
Remember that the KAT3 segments the bands in order to provide greater
coverage after initially tuning with a given antenna.

73,
Don W3FPR

On 1/3/2011 1:30 AM, Igor Kosvin wrote:

> Hello everybody,
>
> Tonight I wanted to work station on 3504kHz but was not able to tune with K3
> to transmit on that frequency. Here are the facts:
>
> -          The antenna is multi-band dipole, a.k.a Van Gorden or Doublet -
> 137ft dipole center fed with 450 Ohm ladder line.
>
> -          I do not use KAT3, it is installed but bypassed in this
> configuration. I use MFJ-986 Differential-T tuner with built-in balun.
>
> -          I able to tune down to 1.1:1 on all frequencies above about 3505
> with K3 and any other transceiver I tried. The optimal tuner settings at any
> given frequency are the same for all transceivers (besides K3 I tried
> Kenwood TS-930S and TS-570D with autotuner bypassed on both).
>
> -          My setting for tune power on K3 is 30W, on TS-570D - 30W, on
> TS-930S - 50W
>
> -          On frequencies 3501 to 3505 with both Kenwood transceivers the
> tuning is normal. With K3 the SWR is through the roof and there is no way I
> can find resonance to see reasonable SWR.
>
> -          There is significant "hysteresis" to the phenomenon. When I move
> down on frequency I am able to tune down to 3505 or so. When I see the
> problem I have to return to about 3520 to see normal SWR again.
>
> -          The problem seem to be apparent only on this small part of the
> band. I took time to go down from 3900 and was able to tune everywhere. Also
> I didn't see any problem on low portion of 40m band.
>
> Unfortunately, I don't have other antenna on 80m to compare. However, the
> fact that I don't see any issues with the same setup with different
> transceivers tells me that antenna and tuner probably are OK. I tried to
> tune K3 with different power: from 10W to 50W - same behavior. I do not have
> dummy load available at this moment, I will try tomorrow with dummy load.
>
>
>
> Any thoughts?
>
> 73,
>
> Igor, N1YX
>
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