questioni re:WSJT-x

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Safe power output on WSJT-X.  Just getting started with WSJT-X.  With the duty cycle of 48 seconds, what is the recommended wattage out for the 6500?  I currently run no more than 15 watts, and have K9DUR SDRMonitor running to keep an eye on the temp.  It never goes above 50 deg C.  Is this about right to protect the 6500?  Also, I will run the amp which is rated for 1200 watts, at 40 watts maximum.  JT65 is a fun mode, but not at the expense of ruining the Flex, or the amp.
Tnx for the input.
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Larry , W8LO

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Posted 2 years ago

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David Ahrendts

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You can bump it a bit, although WSJT-X is a low power program. Typically, I push it to 35-40 watts. Flex 6500 doesn't even flinch. :--) Nice.
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David Ahrendts

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An amp? No need for that on WSJT-X.
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Larry , W8LO

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seems to help with DX
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Jd Dupuy

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WSJT-X  "Low Power Program", "No Need for an Amp"?  Don't tell the rest of my EME friends that. 1500 Watts out of the amp on 144, 1500 watts out on 432 and 800 watts out on 1.2 GHz (I couldn't afford the KW Model). Ha!
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KY6LA - Howard, Elmer

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WSJT- is NOT a LOW POWER MODE..

 it is a WEAK SIGNAL MODE


Your Flex is rated at 100W @100% duty cycle

Running barefoot I typically run 100W on WSJT-X for hours on end with no issues whatsoever.

However... if you are trying to work a really weak one say -24 or less then you need all the power you can get out.. I have a 10+dBi gain beam on 40M -6M... even so, I put on the AMP and run 1500W when I worked DX in the -26 to -30 range or they will not hear me.... need to have ERP in the 10+KW range to be heard.

Before the uninfomed QRP Police rap me across the knuckles.. you also need to make sure that you are NOT SPLATTERING when you run power. Splatter makes it much more difficult for others to copy you which effectively defeats using power.

To avoid splatter usually means that you need to reduce the DAX TX levels so as to minimize your sidebands.  It also helps to have a local ham with a Flex nearby who can SEE your output and tell you if you are splattering...

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NX6D Dave

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I worked a -27 the other day.  Amazing!
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KY6LA - Howard, Elmer

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Try JTDX. It's better than WSJR-X
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NX6D Dave

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The JT modes are weak signal modes, not necessarily low power.  Many contacts are made at relatively low power, but higher powers are needed from time to time.  I ran some 75w contacts this afternoon as propagation was poor.  I also made some cross country contacts on 20W.  YMMV.

Run the Flex PA at 100%, vary the transmit power level of the TX channel gain.

Ambient air temp at the transmitter has a lot to do with the 6500's response to the transmission duty cycle.  In warm air my 6500's fans will go up to full speed at about the 40 second mark, maybe sooner.  In cool air, they never come on.  I assume that the radio will not permit itself to harmed by high duty cycle temps, so I wouldn't be concerned about it.  I'm sure Tim or someone will chime in if this is not the case.

High duty cycle modes are part of the ham radio landscape.  The radio is designed to handle it.
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Ria - N2RJ, Elmer

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I run 1kw on WSJT modes.

I also don't use it except on 160 and 6 meters.
(Edited)
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George Molnar, KF2T, Elmer

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Hope to catch you on both bands!
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Ria - N2RJ, Elmer

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Oh you can. I do skeds even. 6 meters WSJTx is my background music at work during the summer :)

I'm preparing my 20th anniversary card as well. It'll be a keeper for sure.
(Edited)
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David Warnberg

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Holy web of wattage batman.. I'm working the world on 15 watts.. why 1kw?  Just curious.

I also run WSPR, I can receive most signals that are being broadcast in the mW area and can be heard on less then 1 watt, most time 200 mW.
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KY6LA - Howard, Elmer

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Depends on the other guy...


If I am receiving him or her at say -20 or better they usually can receive me on less than 50W.

But if they are -24 or worse, then I need to crank up the power so they can receive me.

Worked a couple of -29's .. had to run 1.5KW into the Beam (10+KW ERP) so that they could hear me.

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David Warnberg

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I understand that.. been there, seen that.. found a little trick, since WSJT-X or JTDX listens to a wider area then what the mode selected transmits on I found it better to move off a bit from the transmitted signal.

Example:  Guy A transmitting CQ on mode JT65, 20 meters, at about 1500 Hz.. I slide off to 1450 or 1550 and reply, why?  Because anyone else that is trying to work him will transmit on his exact same frequency and then usually the loudest signal wins.  I just find it a better chance of getting a reply that way... or if all else fails crank up the power.. have done that as well.
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Ria - N2RJ, Elmer

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David, out of curiosity - do you run JT65 or JT9 on 160 or 6 meters?

If I'm using them on other bands like 20 or 40 meters, I don't exceed 5 watts usually. But 160 and 6 are very tough and I usually run high power because of path loss. The other end runs high power too! That's just how it works. Often we have skeds. 

Then again I don't run those modes on other bands because it is very easy to make digital contacts on RTTY, Olivia, Hell or other modes on those bands. Or even SSB or CW. 

I don't do WSPR but from what I understand that is a low power mode and more for prop beacons, rather than general contacts. In that case it makes sense to run low power. 
(Edited)
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NX6D Dave

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This is working split -- I do it all of the time when working a DX that is attracting a lot of attention.  Many times the guy at the other end can't decode anything and winds up calling CQ again.  Unlike SSB, in the JT modes you can see all of the signals coming to you, if they are on separate frequencies, and just work them in turn.  Sometimes you just throw your call out there on some apparently unused frequency, then wait.  A good op will get back to you in turn.

From the west coast, I try to run about 30 watts on most contacts on 15 through 80, and will raise or lower the power as needed.  Sometimes I can hear a station plainly, but can't make contact at any reasonable power.
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David Warnberg

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Ria.. I do work 6 meters on both JT65 and JT9 but have not dabbled with 160 yet, this time of year here in Florida I have way too much interference for 160 and yes from time to time I do run power on 6 meters, try not to but sometimes as Howard pointed out, one has to to be heard...

 And you are correct WSPR is not a "make contacts mode"  not even sure it qualifies, it's more of a propagation thing, where a station will listen to see what they can receive, knowing location of said station as well as equipment (antenna used) and what output power can help determine what best to use to make a contact wherever you are seeking DX from.  You can also beacon to see who can hear you, where they are, etc....

I'm currently in the processes of building a QRP WSPR Beacon, then I plan on putting it on the air on 6 meters first to get an idea of best propagation times, then I will target working JT65 or JT9 contacts on 6 meters during that time.  I'm also planning on the same idea on 630 meters,160 meters, 2 meters and 70 cm... currently early mornings here in Florida 2 meters is really opening up.
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David Warnberg

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This morning...  I'm hearing stations all up and down the east coast this morning
(Edited)
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Larry - W8LLL

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JTDX is able to decode multiple signals all transmitting on the same frequency. I have had as much as 3 replies to my cq all of them transmitting on my cq frequency. With as much as a -20 difference in signal.
(Edited)
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Dan -- KC4GO

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No wonder I can't work some of the DX with 50 watts a long wire and SGC tuner :) and when facing "ERP in the 10+KW range" it makes a great challenge.  I have found JT-65 great after I lost my voice in Dec.  Voice is back but JT-65 still part of my world.
Howard not a shot at you my friend just having some fun.   

 
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KY6LA - Howard, Elmer

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I think I worked you with 100W ERP
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Cal Spreitzer

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It took 250 watts (Elecraft KPA-500) on 160m JT65 to bag Hawaii from Maryland.    Like Howard said you need to keep you DAX TX level in check. 

Cal/N3CAL 

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David Decoons wo2x, Elmer

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I got Japan and Alaska two nights ago on 20 JT65 @ 35 watts from NJ. Doesn't take much if propagation is good. But with declining propagation I can see an amp may be needed for the very weak ones.
(Edited)
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KY6LA - Howard, Elmer

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I get Japan, Hawaii and Alaska every day on 20 for SOCAL.

But New Jersey and Maryland on 20 is very hard no matter what the power

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NX6D Dave

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I worked an ATNO today on JT65 on 20M.  San Andres island, HK0RMR. RST -09 both directions.  I sent 45 watts on a Hexbeam at 40 feet.  I was one of the first to hear him when he came on the air -- there was no pileup.  Thirty minutes later he had his hands full.  That one contact made my day.
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KG9DW

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This made me chuckle. What's it like being on the receiving end of a JT65 pile up? I can't imagine it is that bad. Pick someone that decoded, click a button, and wait 2 minutes to see if they heard you!
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Jd Dupuy

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A pileup is really fun on moon bounce.
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Hermann Fernandes Pais

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Today I had a QSL on 30m with a station in Chile, from southern Ontario. 5,000 nautical miles, or 9000km. It took 100W on my side and I got a report of -17dB. I was "seeing" the Chilean station as -25dB

JT65. I normally leave the power on SSDR at the max, and modulate the power from the WSJT-x power control. The radio never kicks into high fan speed even at that setting.

BTW my antenna is a Cushcraft R-8 vertical, and using the ATU..
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Tim - W4TME, Customer Experience Manager

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Official Response
"I currently run no more than 15 watts, and have K9DUR SDRMonitor running to keep an eye on the temp.  It never goes above 50 deg C.  Is this about right to protect the 6500?"

The radio has thermal protection logic to prevent damage from overheating.  If you are not getting errors, I wouldn't worry about it.