Keying up transceiver when antenna has poor SWR

[TexTAC]

Do modern day transceivers have a fail proof mechanism to ensure damage doesn’t occur when you key up with a lousy SWR? I am specifically interested in how the Yaesu 991a handles this. I do not have an external antenna tester or tuner. Am I correct that the general process is:

• Set mode to AM and power to minimum on an unused frequency
• Press tuner until internal antenna tuner adjusts
• Key up briefly and look at SWR on the meter
• If under about 2.5 it’s ok to use?

The antenna I plan on using is only good for 40m to 10 meters (I have a separate antenna for 2m/70 cm). What would happen if I accidentally key up on 80 or 160 meters. Will the radio protect itself? Is it possible to “lockout” those bands to prevent damage?

 

[jaspence]

Tune the frequency you want to use if it is not in use at very low power. Some radios automatically drop the power level. If it is under 1.5, don't change anything unless you are real fussy. 2.5 is ok, but if the antenna is designed for the frequency you want I would not be real happy at that point. Most new radios do have protective circuits, but I still avoid knowingly tuning into a frequency not meant for the antenna.

I have a FT991A and it has worked well, but the tuner on my G90 is actually quicker. My gripe with the Yaesu is you have to turn the tuner on, press the button to tune and then press the button a third time to turn it off. With the G90, a single push turns on the tuning cycle and the radio automatically goes back to transmit mode.

 

[K4EET]

Tune the frequency you want to use if it is not in use at very low power. <snip>

Just to emphasize that point, NEVER tune using any power level greater than the bare minimum required to get an SWR reading and for the tuner (if you have one) to tune for the antenna selected. To always be safe, turn the power level down to ZERO whenever you are finished making QSOs. That way, the next time you get ready to load up on a new frequency, the power level is always set to zero to start with. Then when you begin the tune cycle on a new frequency, SLOWLY increase the power level until you can get a good SWR reading. It will not take much power to achieve that SWR reading. Once things are tuned up and the SWR reading is below say 2:1, then you can safely run the power up to whatever level you need to establish reliable communications. Reference:

§97.313 Transmitter power standards.
(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

If you tell us what transceiver(s) model number(s) you have, we might be able to give you more information with respect to tuning your radio(s) to the frequency that you desire to transmit on.

73, Dave K4EET

<edit> @TexTAC, I see where you did say that you are mainly interested in the Yaesu FT-991a. Have we given you enough information for you to feel comfortable tuning your rig?

 

[TexTAC]

Thanks. That helps, but I still have questions on what the step by step procedure is to check SWR. Once I set frequency and set low power, do I initiate the internal tuner process and it will show me the SWR … and then I do a test transmission and it shows me another SWR? Also, will I always be transmitting through the internal tuner or can I turn the tuner off if I have a decent SWR without it? I really appreciate the advice. Thanks.

 

[alcahuete]

Thanks. That helps, but I still have questions on what the step by step procedure is to check SWR. Once I set frequency and set low power, do I initiate the internal tuner process and it will show me the SWR … and then I do a test transmission and it shows me another SWR? Also, will I always be transmitting through the internal tuner or can I turn the tuner off if I have a decent SWR without it? I really appreciate the advice. Thanks.

Set your power output. Set the radio to RTTY. Turn your antenna tuner off. Transmit.

At that point, use an external meter to determine your SWR.


Yes, if you have good SWR, then run without the tuner. The key thing to remember is that an antenna tuner does NOT fix your SWR issues. It simply makes the radio think it is transmitting into a low SWR load. If your SWR is 4:1, your antenna system, tuner or not, is still 4:1 and very inefficient. The tuner does not change or fix the inefficiency of your antenna system. That's something a lot of people don't understand. That is why you want to get your antenna system as resonant as possible on the bands you want to use.

 

[jonwienke]

Better yet, get one of the nano VNA devices to check the antenna before turning the transmitter on. You can set the display width to see the SWR (and other parameters) over a range of frequencies (which you can't do with a transceiver conveniently) and not risk damaging an expensive radio.

 

[prcguy]

Usually, probably more often than not, but not always and sometimes no. It all depends on the type of antenna and feedline.

If your SWR is 4:1, your antenna system, tuner or not, is still 4:1 and very inefficient.

 

[TexTAC]

I am planning to use an off center fed dipole with a lmr240 feed line which should cover 40/20/10 meter bands with a low SWR. Some intermediate bands will be a little off. The 160/80 bands may be way off. Don’t really know.

One question I have is after I use the internal tuner on the 991A and it improves the SWR, do I transmit with the tuner light still on or do I turn the tuner light to off. I am thinking “on” means the transmission goes through the tuner with the improved SWR and “off” means it is not using the tuner and will transmit without the improved SWR (ie the SWR as if the tuner did not exist). The instructions are not clear.

page 61/62…

https://static.dxengineering.com/global/images/instructions/ysu-ft-991a_jy.pdf

 

[prcguy]

If its a 64ft version it will do well on 40/20/10 and some brands also work well on 15 like the MyAntennas version. With a tuner you can force feed it on some of the WARC bands like 30 and 17 and it can put out a useable signal. 80m will be grim and you need a good tuner to match it but you can make some contacts when conditions are good. 160 will not be possible, nope, not at all.

I am planning to use an off center fed dipole with a lmr240 feed line which should cover 40/20/10 meter bands with a low SWR. Some intermediate bands will be a little off. The 160/80 bands may be way off. Don’t really know.

One question I have is after I use the internal tuner on the 991A and it improves the SWR, do I transmit with the tuner light still on or do I turn the tuner light to off. I am thinking “on” means the transmission goes through the tuner with the improved SWR and “off” means it is not using the tuner and will transmit without the improved SWR (ie the SWR as if the tuner did not exist). The instructions are not clear.

page 61/62…

https://static.dxengineering.com/global/images/instructions/ysu-ft-991a_jy.pdf

 

[TexTAC]

Yes. I am starting out with a cheap 64 foot off center fed dipole just to get up and running. It won’t be a permanent antenna. I can’t fit a longer wire antenna on my property without zig zagging it around the property. I just wanted something to get me started on the HF bands until I come up with a better solution. I appreciate all the input and advice. Good crowd.

 

[prcguy]

In Richardson I'm running a resonant half wave end fed, also 64ft long and 40/20/15/10m. I have plenty of room for a 133ft 80m version but I don't want to freak out the neighbors.

Yes. I am starting out with a cheap 64 foot off center fed dipole just to get up and running. It won’t be a permanent antenna. I can’t fit a longer wire antenna on my property without zig zagging it around the property. I just wanted something to get me started on the HF bands until I come up with a better solution. I appreciate all the input and advice. Good crowd.

 

[TexTAC]

I could make an 80 meter band wire work in my backyard, but it would have to be an inverted Vee with both ends sloped at about 90 degrees both on the vertical and horizontal planes. Not ideal.

We are neighbors btw cause I live in Plano. I can hit the K5RWK repeater in Richardson with my handheld.

 

[prcguy]

I'm a member of the K5RWK club but live in CA most of the time. I have a remote HF/VHF/UHF radio in Richardson that I can usually operate from anywhere but its not working at the moment and I need to troubleshoot the Internet connection next trip out there.

I could make an 80 meter band wire work in my backyard, but it would have to be an inverted Vee with both ends sloped at about 90 degrees both on the vertical and horizontal planes. Not ideal.

We are neighbors btw cause I live in Plano. I can hit the K5RWK repeater in Richardson with my handheld.

 

[TexTAC]

We had about 2 weeks of straight rain and thunderstorms so I wouldn’t be surprised if that took out your internet and maybe an antenna too. A couple of local repeaters were damaged.

 

[prcguy]

I think its the grandkids staying at the house unplugging my stuff and plugging in their gaming equipment.

We had about 2 weeks of straight rain and thunderstorms so I wouldn’t be surprised if that took out your internet and maybe an antenna too. A couple of local repeaters were damaged.