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[SOCAL_RADIODUDE]

Can anyone out there comment on impact of running dig modes on the 817/818 versus the lifetime of the finals ? Meaning, do you run full out at 5 W or do you run lower in order to protect the finals, or have you experienced any issues with the durability of the xmit side when running dig for extended periods. Just wondering how the rig holds up under high duty cycles or related heat dissipation. Thanks !

[VK3LU]

I have run 5W on WSPR for weeks with no problems, BUT I tx into a matched load. That way the rear panel of my FT817ND stays just warm. If the VSWR is high, the rear panel (the finals heatsink) gets quite hot. When bandhopping tx I can't have a match on all bands so I only run half a watt and have a small fan blowing in the rear panel which keeps it at about 40 degrees C.
I might add I only run 1 watt max these days. I consider 5 watts on HF as QRO.

Nev

[WB0FDJ]

I have owned an FT-817ND since 2004 (on my second one) so the question caught my attention. After searching through the owners manual and online I cannot find a specific recommendation from Yaesu regarding operation during 100% duty cycle. Maybe it's out there? So the owner is left to make his own technical decisions.

FWIW I found that when running PSK my signal started getting "dirty" at between 3.5-4 watts output. As a result I got in the habit of running no more than that and always into a well matched load, while doing any digital. (My first 817 was 14 years old and it was running fine but the power connector can lose from the board and after repeated fixes was retired).

I'm of the same mind as Nev, having done QRP for a long time, 5 watts "feels like' QRO. I never run more than a watt running WSPR and back in the JT-65 days I made all my state side contacts running 2 watts or less. When JT9 came along I made a lot of stateside contacts running 500mW.

WB0FDJ Doc 73

[W1ITT]

Inasmuch as the FT817 series is also designed for FM operation, it would appear that the rig will stand key-down operation as long as anyone could talk on 2M FM.  The early 817s, prior to the ND series, had occasional problems with losing the final transistors when operated into loads with higher SWR.  The finals were changed in the later models.  If you derate by 50% it should outlast you.
73 de Norm W1ITT

[K6OK]

After searching through the owners manual and online I cannot find a specific recommendation from Yaesu regarding operation during 100% duty cycle.

Common misconception.  FT-8 does not have a 100% duty cycle.  FT8 is 12.6 seconds transmit and 17.4 sec receive, which equates to a 42% duty cycle.  Note that transmit period is shorter than the receive (cooling off) period.  The vast majority of radios can handle FT-8 at full power, assuming an antenna with a good SWR match is used.

[WO7R]

FT-8 does not have a 100% duty cycle.  FT8 is 12.6 seconds transmit and 17.4 sec receive, which equates to a 42% duty cycle.

Yes and no.  FT8 is 100 per cent while it is transmitting.  You could make the same argument about RTTY and AM, but if you look at enough rig specs, you'll see that most recommend reductions in power for those modes.  FT8 is like those modes.  Every radio has engineered its own decisions about heat dissipation and how much heat sink, fan, and so on to have.

SSB and CW have what amounts to power reductions even while transmitting and this makes a difference versus things like RTTY, FM, AM, . . . and FT8.

[K6OK]

FT-8 does not have a 100% duty cycle.  FT8 is 12.6 seconds transmit and 17.4 sec receive, which equates to a 42% duty cycle.

Yes and no.  FT8 is 100 per cent while it is transmitting.  You could make the same argument about RTTY and AM, but if you look at enough rig specs, you'll see that most recommend reductions in power for those modes. 

Maybe you're confusing rigs versus amplifiers?  Yes, most amps are recommended to operate at lower power on RTTY and FT8.  But not true for 100 watt transceivers from the major manufacturers.  The FT-817 manual does not call for reduced power on digi modes, only a warning about excessive battery drain.