Power Genius XL Design Details – Installment #2

HCampbell WB4IVF

Pierre Martel

Is it me or ft8 in high power station is not what I call a good match? For the discution, here is section 4.7 fron ft8 operating tips at https://www.physics.princeton.edu/pulsar/K1JT/FT8_Operating_Tips.pdf 4.7 Although FT8 is a weak signal mode, not a QRP mode per se, please keep your transmit power down. Be nice! Generally on HF, if a path is open, just a few watts will do. Put your amplifier on standby. Turn down the wick to QRP levels. Try it! If you don’t get any responses at all, try 10 watts, maybe 20 or 30. If you find that you routinely ‘need’ 100 watts or more, that is a strong hint that your feeder and antenna system are inefficient. Check for corrosion and loose connectors. Try making a simple halfwave dipole as a comparison antenna. You will find that you can receive better if your antenna is in good shape, and reception is kinda useful for DXin. Aside from QRO being antisocial and usually unnecessary, if your signal is too strong, it may be dirty and may overload receivers and audio cards at the DX end, preventing your signal from decoding reliably. Take your cue from the signal reports you receive: if you are getting positive reports, you can probably do just as well (maybe even better) with a fraction of the power. Remember: decibels are logarithmic. Cutting your power in half will reduce average reports by just 3 dB; cut it by half again to lose another 3 dB. If you are receiving mostly negative or zero reports, you are in the right region. I normally adjust my transmit power to get reports between 0 and -10 dB. If you receive a 58 report and you’re not using SSB, something may be seriously amiss!

HCampbell WB4IVF

Pierre -

Thanks for posting.  The article states that QRO is usually not necessary for FT8 - it doesn’t state it’s always unnecessary.  I’m not an FT8 user yet, but from what I’ve read you only use enough power necessary to make the QSO, like for other modes.  If that requires high power that is ok, as long as you follow other good operating practices and don’t drive the amp into distortion. 

BTW, one of the reasons I decided on the PG XL was the clean signal engineering that went into it, which should make it a cleaner amp in any mode. 

Howard

Bill -VA3WTB

I think the design of the XL is that you can run at full power on FT8 for endless hours without problems, most amps just can not do that. The intention of the letter was not to promote operating in that manner.

Pierre Martel

I do agree with you that it is a good way tto promote the design of the amplifier, in fact I am looking at buying one cause I want to run my station remotely and with such amplifier I would run it confident that I wont A) send spurious all over the place wont be in fear of busting the finals if there is an intermitent problem on the antenna system while xmitting remotely. But it would be a nice addition to the install,ent news letter to specify that althought the amp can do it, it is not good practice to do it. Ham radio is like the rest of the population, my car can run 200 miles an hour for many hours, but it is not because I can do it that it is a good idea to do it. Some will take that possibility and use it, like the guys that like to speed run on the highways.

Bill -VA3WTB

Pierre Martel

Just remember how the kilowatt club work, I have legal limit and I will use it! When on 40 meter you dan hear 2 station that both run. Full legel limit and they are in range to shout at each other by the windows.... But they dont care that they are disturbing a qso in barcelona that try to catch that elusive vietnamese signal. This will bring the exact same situation in ft8. At least let hopes that the people using those amp will have the good sense of using the required power only.... And just for that particuliar qso.

Gerald-K5SDR

Let me speak first hand that FT8 is not a low power mode when you can hear better than the station on the other end. I only run 100W at my home QTH. I find that stations below roughly -13 dB cannot hear me on my tri band beam pointed right at them. An extra 12 dB of power would really help. I can copy stations down to -24 dB on my FLEX-6700 but they sure can’t hear me. A better receiver on the other hand would probably help too. FT8 on 6m can surely benefit from QRO as well. FT8 is taking over that band for DX that would never be worked otherwise especially at the bottom of the sunspot cycle. Gerald

Pierre Martel

Like I said before, the problem is not people that use there power amp properly but the one that will run a power amp no matter what it need it or not. We have some guys that runs 3 kilowatt on local nvis net just cause they can. Every one hear them. Every one is heard at 10 watts