[Elecraft] KAT3 losses vs KAT3A

[Joe Subich, W4TV]

 > I’d think the losses would be small (low tenths of dB) in any case,
 > and most likely not worth replacing the KAT3 unless you’re buying a
 > new radio.

The "Tuner" portion of TLW calculates the loss in an L network (the
KAT3) in the low *hundredths* of a dB for 50 Ohms to near 50 Ohms
(50:50 is undefined).  Wayne confirmed that was accurate for the KAT3.

> Only there may be times when it does not get to the correct position,
> so if you’re not using an external tuner the KAT3’s position might
> not be optimum for a resonant antenna presenting a 50 ohm load.

If your K3/KAT3 shows high SWR when working into a 50 Ohm load with
the KAT3 bypassed, the easy solution is to enable the tuner, tune
into a dummy load and then bypass the tuner.  That process will reset
the "bypass" settings.

73,

    ... Joe, W4TV


On 2015-05-19 10:09 AM, GRANT YOUNGMAN wrote:
>
>> On May 19, 2015, at 8:30 AM, Bill McDowell <k4cia at earthlink.net>
>> wrote:
>>
>> The new KAT3A tuner has a relay bypass that results in lower
>> losses.  What are the losses in the old KAT3 without a relay?  And
>> do the losses occur when using a matched antenna with the old KAT3
>> NOT engaged.  The statement: "Lower loss on bands where matched
>> antennas are used." is a little cryptic to me with respect to the
>> KAT3A version.
>>
>> Are the losses in the old version present irrespective of the tuner
>> being inline or not?
>>
>> Clarification would be appreciated.
>>
>
> Eric (or maybe one of the other Elecraft team) addressed this a few
> days ago.
>
> Apparently the KAT3 simply goes to a calculated “50 ohm match”
> position when you put it in bypass, e.g., it’s still in-line, it’s
> just set for a 50 ohm match.  Only there may be times when it does
> not get to the correct position, so if you’re not using an external
> tuner the KAT3’s position might not be optimum for a resonant antenna
> presenting a 50 ohm load.  The KAT3A uses a hard relay bypass to get
> around this.  I can’t say I’ve ever seen an issue related to this
> with my resonant antennas, but others may have.
>
> I’d think the losses would be small (low tenths of dB) in any case,
> and most likely not worth replacing the KAT3 unless you’re buying a
> new radio.
>
> YMMV
>
> Grant NQ5T
>
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