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JUMA 100D with LDG AT-100 ProII

PostPosted: 13 Jan 2019 01:58
Hi Adrian

I have been trying to use my Juma 100D with a LDG AT-100 ProII Antenna Tuner without much success to date. :cry:

It would appear that the Juma 100D VSWR trip is instantaneous once the SWR level is exceeded.

What is appearing to happen is that when the AT-100 ProII Antenna Tuner goes through its tuning cycle that the SWR trip limit is momentarily exceeded causing the JUMA 100D to drop from Operate mode to Standby. When this happens the AT-100 ProII Antenna Tuner then tunes on the lower power from the Transmitter.

The AT-100 ProII Antenna Tuner seems to retune on a changing power level (it is probably looking at the reverse power level to initiate a retune) which means it tries to tune again when I go from Standby to Operate on the 100D with the higher power but fails again as the SWR is exceeded momentarily when the AT-100 ProII Antenna Tuner is going through the tuning cycle.

I have increased the SWR trip level from the default at 3:1 to 6:1 and this helps a bit but does not stop the problem. I could increase it to 10:1 but I would rather not in case I use the 100D with a manual tuner which I also use.

Is there an option in the software to increase the time before the trip is initiated. This would allow me to retain a lower SWR trip level but control how long the SWR is at this level before the trip is initiated?

Any thoughts or suggestions would be appreciated?

Kind Regards



Re: JUMA 100D with LDG AT-100 ProII

PostPosted: 13 Jan 2019 09:14
by 5B4AIY
Hi, Greg,

There are several ways to avoid this high SWR trip.

The first is to match the antenna using the transceiver's power with the amplifier in the STANDBY mode, and then switch to the OPERATE mode. It is always somewhat risky to match the antenna with an auto-tuner with the linear operating at high power.

The second way is to take advantage of the Power Averaging feature. I am assuming you are using my latest firmware, in which case, in the Calibration & Setup menu on page 6 you will find the Power Averaging setting. It is normally left at its default value of 1, but can be increased to a maximum of 16 sample averaging. Each increment of the setting increases the delay time to register an excessive SWR by about 4 - 5mSec, so use this with caution, especially if you intend to do so at high power. This is explained on page 16 of the User Manual.

It is to be expected that as the auto-tuner attempts to find a match, as the relays operate there will be brief periods of time where the contacts are moving where the amplifier is not connected to anything, and thus if a SWR measurement test is in progress this will indeed provoke a high SWR alarm. I deliberately made the SWR trip as rapid as possible in order to protect the output transistors from excessive currents, so be careful. Although the transistors are fairly rugged, they will not tolerate excessive currents and voltages, and so always tune using as low a power as possible.

I strongly recommend tuning using the transceiver's output set to as low as possible, especially as most auto-tuners will work perfectly happily with only a watt or two of power. If you are using the Juma TRX2, then with my firmware the tune power is set to about 4W - 5W maximum thus protecting the PA, and this is more than enough power for the LDG auto-tuner to achieve a match.

73, Adrian, 5B4AIY

Re: JUMA 100D with LDG AT-100 ProII

PostPosted: 14 Jan 2019 10:27
Hi Adrian

I will give it a try and let you know how I go.

The biggest problem seems to be that the Auto tuner retunes with changing power.
I may have to just run it in Manual mode if the power averaging needs too high a level :(

Kind Regards