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Author Topic: Hookup and tune procedure ft_991 sb-200 dentron 3000a tuner  (Read 222 times)

Posts: 39

« on: July 18, 2019, 01:29:07 PM »

Been getting different answers on this topic hope someone can set me straight.  I have an FT-991 transceiver, SB-200 amp, bird watt meter and Dentron 3000a tuner. The system is hooked up in that order with the ft-991 out going to the in of the amp. The out of the amp is going to the in of the watt meter. The out of the watt meter in going to the in of the tuner and finally the antenna going to the out of the tuner. First of all is this the correct way to setup this station?  Also in tuning does the radios internal tuning need to be a factor? When I tune the station this is how I have been doing so. Bypass the amp and tune the radio with the internal tuner for low swr. This is done with about 10 watts or so. Then I tune the dentron for lowest swr on the internal meter of the tuner. Flip on the amp and increase the power to about 50 watts and tune the amp for highest rf readings on the tuner. I cannot say if this is correct or not but while doing all the tuning, if I put the transceivers meter on the swr setting it reads high BUT if I retune everything to bring the reading to the lowest swr reading on the transceiver I am not sure if this will create any damage or not.  What is the correct for all above?

Posts: 507

« Reply #1 on: July 18, 2019, 03:26:53 PM »

If your amp is in line (not bypassed), your transceiver SWR is indicating the mismatch into the amp, not the antenna. Also, what you describe is poor operating practice by tuning up on the air. You should be doing so into a dummy load which you would switch in/out. 

Posts: 39

« Reply #2 on: July 18, 2019, 03:40:17 PM »

Sorry for not making it clear.  I am transmitting into an HM-2103 Heathkit dummy load. I was advised to not look at the swr meter on the transceiver but to look at the one on the dentron.

Posts: 1226

« Reply #3 on: July 18, 2019, 04:37:39 PM »


How do you adjust the (in this case) Dentron 3000A tuner without feeding power to the antenna?

Posts: 2948

« Reply #4 on: July 18, 2019, 05:32:40 PM »

Your sequence is correct in the way you have the things hooked up.  However you need guidance on the the operation.  First and foremost before you do anything you have to make a couple of prerequisite decisions.  When you intend to transmit you have to know if you will be running just exciter power or if you are going to use the amp.  Then if you decide you are not going to use the amp then you to decide if you want to tune the antenna using the Denton tuner or the tuner in the radio.  It’s your choice but if your swr isn’t crazy I’d suggest, of course, bypassing the amp and also bypassing the Denton tuner. The tuner in the radio will tune the system automatically.  Now things change when you use the amp.  When you do you are committed to using the Denton tuner.  Now you must not use the tuner in the radio.  It MUST be turned off.  Now you can tune the antenna with low power from the radio and adjusting the Dentron for lowest swr using either the radio swr meter or the Denton meter.  Once the Dentron is tuned then you turn the amp on and load it up.  You can touch up the Dentron at full power if things change slightly.  The tuner should always remain off when driving the amp.  If the input tuning is bad on the amp you could use the radio tuner but you are better off retuning the input network on the amp.  That’s it.
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