Posted by
Ed Pflueger on
Jun 02, 2020; 4:19pm
URL: http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661583.html
I have a HY-Gain VB-66DX and 1.4 is the normal case basically across the whole band. I must be messing up somewhere, even the KPA1500 likes it. I have never run it over 1200 Watts on 6 meters and never requires over 30 watts drive to obtain 1200 out. I have three feet of 213U from amp to Palstar HF-AUTO (Bypass Mode), 70ft. of 9913 from the Palstar to a DX-Engineering 8 position Antenna switch, to my lightening protection and the final trip of 40ft of 213U to the antenna. The antenna is actually 10ft. above my HY-GAIN TH11 which also does not require a tuner. The Palstar is my antenna switch essentially but I do need it on my HY-GAIN HY-TOWER only on 160 and 80 meters when needed.
That's the end of my good luck story. LOL
Ed..AB4IQ
-----Original Message-----
From:
[hidden email] [mailto:
[hidden email]] On Behalf Of Bob McGraw K4TAX
Sent: Tuesday, June 2, 2020 10:27 AM
To: Mark Goldberg <
[hidden email]>
Cc: Elecraft Mailing List <
[hidden email]>
Subject: Re: [Elecraft] NOT the feedline
As a rule, if one needs a tuner to get a good match on 6M, I'd say they need to look carefully at their antenna system. My 6M yagi shows less than 1.5:1 over the lower 2 MHz of the band, 50.0 - 52.0 MHz. The lowest SWR occurs at 50.2 with a Z value of 42 ohms and an X value of 0.0. Of course higher gain antennas typically have a bit less bandwidth, but still, the lower 1 MHz should be totally usable without a tuner.
Besides, tuners only make the transmitter happy and the added feed line loss due to SWR still remains.
73
Bob, K4TAX
On 6/2/2020 1:09 AM, Mark Goldberg wrote:
> I want to mention that my LDG AT-600Pro has a minimum capacitance that
> is too high for a good match to my antenna on 6 meters. Certainly
> seems like removing the Ten Tec tuner would be a good thing to try.
> Can you open the Ten Tec tuner and use an IR thermometer to monitor
> the components? I don't know anything about it's construction. You
> could see them heating up.
>
> Just running medium power of maybe 500W would slow things down and let
> you see the SWR increasing before the amp trips. That would confirm
> that something is heating up vs arcing.
>
> 73,
>
> Mark
> W7MLG
>
> On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <
[hidden email]
> <mailto:
[hidden email]>> wrote:
>
> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position. This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
> The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions. They heat, change
> value,
> and the SWR creeps up. Allow them to cool and the SWR is back to the
> starting point. I usually tweaked mine such that the SWR
> started off
> a bit high, came down as I transmitted and if transmitting a bit
> longer
> the SWR increased. Later I got tired of this and changed the
> group of
> disk ceramic caps to 470 pf Russian doorknob caps. Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read
> about
> > it somewhere and replaced those in my tuners with caps having
> higher
> > power ratings.
>
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