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 <[email protected]
<mailto:[email protected]>> 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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