Re: NOT the feedline

Posted by Bob McGraw - K4TAX on Jun 02, 2020; 3:26pm
URL: http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661577.html

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.
>
>     ______________________________________________________________
>     Elecraft mailing list
>     Home: http://mailman.qth.net/mailman/listinfo/elecraft
>     Help: http://mailman.qth.net/mmfaq.htm
>     Post: mailto:[hidden email]
>     <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]
>     <mailto:[hidden email]>
>

______________________________________________________________
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]