[Yaesu] FT-1000d / Ft-1000MP MkV Ant. Tuner

[Phil]

Hi Hal,
Your internal ATU has a range to antenna mismatches within which it can 
match the load. When you move outside
this range - the ATU will be unable to deal with the high impedances. If 
you read the specs for your rig - it will tell you what these are.  This 
is the reason we often have a large-range external ATU to handle larger 
mismatches.  Keep in mind the ATU inside the rig is only a very light 
duty one. It does not have the 'horsepower' of the dedicated external ones.

The diminished power situation you speak of is normal - and fortunate 
for you - it is saving your finals from blowing.

To your ques:
  you dont need to use an atu to set the ft to 50ohm.  If you have a 
50ohm load - you want to be able to switch the atu out when switching 
through to the dummy load. With it in line while the 50ohm dummy load is 
attached, you risk the possibility of having your atu introduce 
additional and unwanted reactance - which will lead to higher SWR's and 
artificially so.  Your rig provides you with the means of switching it 
it/out. The ft920 does, so should the ft1000

The normal course of events are:  pick your band, maybe do a test 
transmission into your dummy load to make sure your are indeed 
transmitting,  then switch to the antenna with ATU in circuit and have 
it do its work.
If its not getting a match - then it is possible its outside the range 
within which it can operate.  Keep in mind most auto-atu's built into 
rigs can only handle unbalanced feedlines and a very limited range of 
antenna Z. 

If you carnt get a match - its probably time to buy a decent external 
atu with the capacity to handle a wide range of antenna Z'  I always 
have an external atu attached to my rigs - even the ones with built-in 
atu's for this reason.
The skill then is in using the manual ATU quickly and efficiently thats 
makes for a speedy match.

Perhaps the following will help. An antenna (all antennas) is(are) an 
LCR network.  In an ideal world they are just an R network - but we dont 
live in an  ideal world. An atu is a black box which provides you with 
complete control over the L & C values you can add to the LCR network 
which is your antenna.   The challenge for all of us is to know when and 
how to apply that additional L & C so that it cancels out the L & C 
reactance in our LCR network, leaving just R.
You may not have enough L or C in your auto-atu to do the job.
Looked upon this way - you can probably answer your own question.


I hope this sheds a little light.
73's
phil  vk4kvk


ka1xo at juno.com wrote:
> In attempting to tune up an external antenna tuner sometimes the 
> mismatch in getting to a resonance is so extreme the "SWR" illuminates 
> on the FT display.
>
> The power diminishes until I go back and switch to a dummy load and 
> reset.
>
> My question for the group is if I first use the autotuner to set the 
> FT to a 50 ohm dummy load and then disable it, does it remain tuned 
> for the 50 ohm load, or is the tuner completely switched out of the 
> transmit chain?
>
> What do other forum members do when facing this situation?
>
> Thanks,
>
> Hal, W4HBM
>
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>
>   


-- 
Thank you.
KVK Antenna Systems
Ph: 3216 8060 Fax: 3216 8075
http://www.kvkantennas.com.au

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