[Elecraft] NOT the feedline

[Bob McGraw K4TAX]

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 <rmcgraw at blomand.net 
> <mailto:rmcgraw at blomand.net>> 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:Elecraft at mailman.qth.net
>     <mailto:Elecraft at mailman.qth.net>
>
>     This list hosted by: http://www.qsl.net
>     Please help support this email list: http://www.qsl.net/donate.html
>     Message delivered to marklgoldberg at gmail.com
>     <mailto:marklgoldberg at gmail.com> 
>