Yaesu: Tuner drops power

[KF0AWL]

I have a Alpha vertical multi band antenna that I used for Pota with a small mfj 971 portable manual tuner and my Yasue 891.
The setup worked fine for the most part, I hooked a MFJ versa tuner up yesterday to test it and it seems I cant get more then 10 watts output on it when I tune according to the power output on the 891 and the tuner gauge. Any idea what I should look for? It's basically exact same coax and everything except the tuner.

 

[KF0AWL]

But if I run to my normal Coil based Super Antenna no tuner the 891 puts out normal power.🤔

 

[prcguy]

How and where are you checking SWR, at the radio or antenna?

 

[KF0AWL]

I'm going by the meter on the tuner setup at the radio and the power scale on the radio readout both.
Setting the tune at 10w for lowest swr then bringing the output power to 50w and it still says about 10w forward on the tuner and approximately the same on the readout

 

[prcguy]

I'm going by the meter on the tuner setup at the radio and the power scale on the radio readout both.
Setting the tune at 10w for lowest swr then bringing the output power to 50w and it still says about 10w forward on the tuner and approximately the same on the readout

If the SWR is off at the radio the watt meter can read wrong as they are only accurate into a 50 ohm resistive load, but the radio limiting at 10w sounds like its folding back power for some reason. Are you sure the tuner is doing its job and getting the SWR low so the radio doesn't fold back? Some of the Alpha Antennas use a 5:1 balun and without an extensive counterpoise system the coax will be hot with RF and radiate. Do you have a good ground radial/counterpoise or any RF chokes in the feedline?

 

[KF0AWL]

If the SWR is off at the radio the watt meter can read wrong as they are only accurate into a 50 ohm resistive load, but the radio limiting at 10w sounds like its folding back power for some reason. Are you sure the tuner is doing its job and getting the SWR low so the radio doesn't fold back? Some of the Alpha Antennas use a 5:1 balun and without an extensive counterpoise system the coax will be hot with RF and radiate. Do you have a good ground radial/counterpoise or any RF chokes in the feedline?

Right! I follow the manual https://static.dxengineering.com/global/images/instructions/mfj-962d.pdf and adjust the settings as it says. Turn the 891 power down to 10w and voice into the mic to get a reading adjust my induction to the dip then adjust the (antenna-inductor-tranmitter) controls for lowest swr.
At that point I turn the power back up say to 50w and when I try to transmit on both the tuner gauge and the power meter on the radio only went up like 2w to a 12w forward power.
The Alpha has the ground plane wires attached no chokes on the feedline

 

[prcguy]

Right! I follow the manual https://static.dxengineering.com/global/images/instructions/mfj-962d.pdf and adjust the settings as it says. Turn the 891 power down to 10w and voice into the mic to get a reading adjust my induction to the dip then adjust the (antenna-inductor-tranmitter) controls for lowest swr.
At that point I turn the power back up say to 50w and when I try to transmit on both the tuner gauge and the power meter on the radio only went up like 2w to a 12w forward power.
The Alpha has the ground plane wires attached no chokes on the feedline

You should turn the radio down to 10w and use FM mode, its not possible to get a constant power out in SSB mode using your voice. I hope you are "dipping" the SWR meter and not the forward power meter but yes you would find the lowest SWR with the recommended ANTENNA and TRANSMITER settings per band in the manual then turn the inductor for lowest SWR. The go back and turn ANTENNA and TRANSMITTER and inductor for lowest SWR at full or operating power. A roller inductor tuner is a huge PIA to use in most cases and that tuner seems kind of large for a portable setup. I've had a very nice Palstar AT2K roller inductor tuner for about 20 years and I've not used it in about 20 years due to the excessive time it takes to tune it.

What about a small LDG tuner which can be set up to push the tune button on the tuner and it will make the radio transmit in CW mode at low power during the tuning process and return to normal when its tuned? That would be much smaller and lighter for portable ops and will tune your antenna in a couple of seconds.

Otherwise it looks like your radio is working ok as the SuperAntenna is tunable at the antenna to make the radio happy and that seems to work, except for the low performance of the SuperAntenna. Its called a SuperAntenna because it produces SuperProfit for the company owners and not because of SuperPerformance.

 

[KF0AWL]

You should turn the radio down to 10w and use FM mode, its not possible to get a constant power out in SSB mode using your voice.
Shoot good point i forgot that part. With my Super antenna I don't have that step and forgot. 👍🏻
No not useing it portable lol just testing it as i have a remote tuner at the qth and don't think i can tune through it with a manual also 🤔
I'll go out and recheck things.

 

[prcguy]

You should turn the radio down to 10w and use FM mode, its not possible to get a constant power out in SSB mode using your voice.
Shoot good point i forgot that part. With my Super antenna I don't have that step and forgot. 👍🏻
No not useing it portable lol just testing it as i have a remote tuner at the qth and don't think i can tune through it with a manual also 🤔
I'll go out and recheck things.

You can get a manual roller inductor tuner in the ball park by just using the recommended settings in the manual then tune the inductor for best receive then tweak the ANTENNA and TRANSMITTER for best receive. When you finally transmit it should be close and easy to get the SWR down.