100% duty cycle modes

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I just want to confirm something. Can I run 100% duty-cycle modes at full power? From reading the specs of my 6300 it looks like I can, but I would rather ask a noob question than fry my PA stage.

Thanks
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Guy G4DWV/4X1LT

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Posted 4 years ago

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Steve W6SDM

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I will let someone more knowledgeable than me answer if you can. 

However, it's unlikely that you would want to.  JT-65 is usually done at very low power, around 5 watts.  PSK-31 at high power is going to cause the receiving station to go nuts. 
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KY6LA - Howard, Elmer

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I don't have a 6300 but I have run my 6700 @ 100% duty cycle for extended periods of time

I suspect that if Flex says it in their specs then it's true
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KY6LA - Howard, Elmer

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Guy is probably considering RTTY and the upcoming RTTY contest that need 100% duty cycles.
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KY6LA - Howard, Elmer

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BTW. I I have worked JT65 with 1.5KW. Really helped when I worked a DL who was -29 as he did not have a radio that heard better than about -20. But with full power he copied me OK

BTW with my Big SteppIR MonstIR. The ERP was effectively 15KW

So while JT65 is effective as a low power mode, there is nothing wrong with using power as long as u are not splattering.
(Edited)
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Steve W6SDM

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Wow - now that's gotta be a first.  I feel guilty if I use more than five watts on JT-65.

It's an interesting mode.  You can sit there forever waiting to see if you were copied or not with those once-per-minute exchanges.
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np2g

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Its all about IMD guys . You can produce a clean Hefty powered signal YEP !!!Flex is great ...

Also it really helps using  a amplifier that has lots of GAIN . Little drive ..
(Edited)
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KY6LA - Howard, Elmer

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It's a great mode for remoting as there is virtually no latency issue for Jt65

NP2G. Got it right. U can use lots of power if you can limit ur IMD which is possible and easy to do with Flex as u can easily limit transmit bandwidth by stet ting transmit filters

Ur high gain Amp also has to be very linear or it will introduce new IMD that ur Flex has gotten rid of
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KY6LA - Howard, Elmer

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The trick is to watch ur output signal. Once you,start splattering then too much power makes you hard to copy.


But if u can keep it clean u can use power.


JT 65 uses a 500Hz bandwidth so if u tighten your transmit bandwidth to say 600 Hz. You clean up the splatter so u can use power
(Edited)
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Ken - NM9P, Elmer

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I am surprised that more people aren't switching to JT-9, which has MUCH more narrow BW and several dB advantage over JT-65.  But then, I am still a noob on either of these modes.  I have run them off and on for about 9 months...mostly off... I don't have enough patience to wait through 8 minutes just for a signal report.  I would rather waste 30 minutes trying to bust a pileup!  hi hi.  (At least I feel like I am doing SOMETHING!)

BTW, When running RTTY, I  use a transmit profile to narrow my TX filters down to about 300 Hz and it gives me the advantage of a narrow TX "stripe" that I can use to spot exactly where my TX signal is going to be when I am running splits.  Neat!
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Robert Allbright

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Yes, JT9 is great and generally preferable to the outdated JT-65 which takes uo so much bandwidth!
73 Rob G3RCE
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Bob - G3WKW

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I found I often could not get a JT9 QSO on 10m to complete with my FT897 due to frequency drift. Was OK after I locked the oscillator to an OCXO. The Flex 6300 seems fine but many rigs will drift too much for success on the higher bands. JT9 was designed with the LF bands in mind. Joe Taylor has stated that even propagation path changes will disturb it at higher frequencies.
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KY6LA - Howard, Elmer

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Oops I meant that JT65 runs 175hz so you should set ur transmit bandwidth to no more than 200HZ to prevent splatter

Here is a calculator to figure out how much power you really need

http://dwestbrook.net/projects/ham/dB...

BTW. Ken.

It looks like you found and are are taking advantage of the easy to set XMT bandwidth setting in SSDR
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Ken - NM9P, Elmer

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Yes, So far I have found the Transmit Profile to be implemented very well.  I have made a few suggestions for enhancements in other posts, but I am very pleased to have it as it is!

I think the Global Profiles can use some additional tweaking and improvement.  But as I have said before.... Even incomplete, it is wonderful to have profiles of any kind!
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George Molnar, KF2T, Elmer

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You guys! 

Always a pleasure seeing you in the waterfall, no matter what the signal level. And yes, 100% duty cycle is fine. The fans will kick to high speed after a bit. You can also set a time out timer (Radio Setup, Transmit tab) to prevent going too long key-down. Just to be on the safe side.
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Ken N9VV

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The only printed reference I can find is the Flex-5000 Owners Manual v1.10.0
page 61;
----------------------------
"WARNING!  Do not operate the 100W Amplifier above 40W in continuous carrier modes (e.g. CW, AM, FM and Digital) for longer than 15 seconds. Higher levels can cause damage to the Amplifier. The Amplifier is rated at 100W PEP for SSB duty cycles."
----------------------------
de Ken N9VV
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Bill -VA3WTB

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Hey guy, did you get your radio working? Just trying to keep up with things...
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Guy G4DWV/4X1LT

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Hi Bill,

Up and running. Not many QSOs at the mo, I am testing various RTTY/PSK31 programs and working my way through the manual learning my rig and enjoying every minute of it. It is a shame that development on most of those programs stopped ages ago. The interfaces are quite 'interesting' - seen that for MultiPSK? It will make your eyes bleed.
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KM6CQ - Dan

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I think with this radio, it is prudent not run more then 30 Watts out with JT65, Olivia or a similar digital mode.
I always use my amp, even if I run 25 watts. Let the amp do the work and keep the heat
outside of the radio. 

Dan KM6CQ
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Robert Allbright

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I quite agree, let the amp do the work!
73 Rob G3RCE
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KY6LA - Howard, Elmer

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This brings up an interesting trade off.

As you probably are aware, IMD is a result of nonlinear mixing in the amplifiers

With your Flex you can easily limit your transmit bandwidth to eliminate a significant part of ur IMD
This is why people tend to copy u much farther into the noise with a bandwidth limited Flex

So the question becomes which is the MORE linear amplifier???

The Flex internal Amp??

Or your Linear (?) Amp. ???

Obviously an interesting experiment

BUT. The real solution will be a combination of limiting transmit bandwidth

PLUS Adaptive Pre-Distortion

It will be exciting to use the combination in2015(?) as I suspect you will achieve amazing digital results.
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Ken N9VV

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I heartily agree with KY6LA who has extensive experience with SDR equipment.

There are at least TWO power protocols used in HF equipment;
(a) ICAS = Intermittent Commercial/Amateur Service
(b) CCS = Continuous Commercial Service
Amateur HF equipment typically uses the "ICAS" standard.

One SDR Vendor has this statement prominently displayed in their Users Guide
"Clarification:
AM/FM, CCS (Continuous Commercial Service) 30W;   SSB, CW and all ICAS modes (Intermittent Commercial/Amateur Service) 100W PEP"

Most Hams have never seen their "IMD" displayed on a Panadapter while testing with
the standard two tones of 700Hz and 1900Hz .  It is even more likely that Hams with
Linear Amplifiers do not have an RF Sampler providing an attenuated signal for an
SDR receiver.  The FCC has allowed us to be "self policing" about the quality of our
Tx signals and provides only a minimum qualification for FCC Certification.

The "Big Three" Ham equipment manufacturers DO NOT advertise their Two Tone IMD
Tx measurements because US Hams do not care about how clean their Tx signals are.
But with the advent of high quality equipment, like the Flex Signature Series 6xxx, we
can now clearly see the Tx signals of other stations. This should encourage us to invest
in the necessary RF Samplers and to understand how IMD products mix and create
undesirable Tx signals (splatter) when amplified to 1000W+.

I hope these will be important items for members of the Flex Community to explore in
2015.

73 de Ken N9VV


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Lee, Elmer

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Its not just imd in the transmitter but dynamic range in the receiver that limits digital communications. Receivers with poor dynamic range overload but its always the transmitter that is blamed. Many digital Rx systems have terrible dynamic range
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np2g

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All this is absolutely true  '''''''2 tone  tests  Yea sure   .IMD  well its suppose to be   but there is no rule  that says  should be or (Must Be)  

I think "Pure signal" is one of the wish list events for flex.For any radio   -25// -30 DbM isn't good for the neighborhood  (far better -45 //   -60dbm   ) 

Duty cycle  It is an obscure rating to find  and page 61 /flex 5000 manual does state this .
Don,t have a 6000 series manual to look it up .

So presuming that was true with the 5000  then a suggestion of 50% on those hard use modes would be pretty smart.

Oh If you are going to use that 6300 on RTTY at 100%  Be prepared to make friends with the repair department.
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KY6LA - Howard, Elmer

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I ran a RTTY contest barefoot 100W. --- albeit life is far too short for QRP(100w) just to see how it survived

The fans ran full blast. The rig got warm but other than that. No issues.
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Guy G4DWV/4X1LT

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Cough, cough 100W + QRP? We call that 'willy waving' on this side of the pond, hi, hi. Vy impressed with your erp (envy).

From what you have said, and the specs from FRS "RF Output Power:  1-100W nominal SSB, CW, FM, RTTY, Digital; 1-25W nominal AM", 100W it is on RTTY.

cheers
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Steve W6SDM

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Willy waving?  I love what you Brits have done with our language.  :)
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Ken N9VV

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Re:  "but there is no rule that says should be or (Must Be)" .....
well I think I can find a statement in Part 97 that says: Amateur Radio Operators MUST adhere to the best Engineering practices...  and a Ham is responsible to be sure his output signal complies with all FCC rules.
How can you comply if you don't see/hear/measure your own output signal?

In the "old days" you could HEAR a key click, keyed oscillators whistling, bouncing dot contacts on a bug, or harmonics. The "T" in RST was just for the purpose of reporting what the other guy sounded like. 

But, sadly, those days have passed into history.

"CQ DX" and "599" my friend,
73 de N9VV
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np2g

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To be regulate it must be defined as an empirical level . To fall under best engineering practices  well we all fall for that  .don't we.

It,s the difference between a  wish and a must . 

On a similar note if the FCC mandated this magical IMD  (From today on)  to lets say -40 DBM we would be using CW  or buying something else.
(Edited)
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W5XZ - dan

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I have been 'shooting into the dark' with poor summertime condtitions on top band with jt-65 and jt-9 with my 6500 as high as 75w out, to drive my final to legal limit...no problem, even with the 47-48 sec continuous transmit cycles, repeated every 2 minutes. Of course, the fans do run at full blast, toward the end...

73, w5xz, dan
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Al K0VM, Elmer

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Guy, 
   You may not have gotten this far yet, but DDUtil does display the internal PA temperature.. The fans will kick into high speed when the Temp reached 70 Deg Cent and stay in high speed until the temp drops to about 55.. I am told that if the temp gets too high ( 100 C ?? ), the PA will shut down and protect itself.   How long it takes to reach the high speed fan condition depends on how much power your running AND the feed line impedance that  radio sees.

AL, K0VM
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Guy G4DWV/4X1LT

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Hi Al, I have got DDUtil up and running. I needed to use it as Ham Radio Deluxe does not play nice with SSDR so I read. Connecting to the radio was certainly much more reliable with the DDUtil server up and running. HRD a tad too flaky and too expensive for my needs but I do like the way things are laid out. I will have it running to monitor the PA temp - thanks for the suggestion.
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KY6LA - Howard, Elmer

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I cheat!

Actually I should have qualified my full power comments in RTTY.

I have a SteppIR MonstIR. It's virtually SWR 1:1 everywhere

So I likely can run high power for much longer than most people as most of my power goes out the antennaz
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np2g

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That is not cheating .' its utilizing your environment '

Similar here just separate  beams for bands used and amps with low IMD  .

Can run "legal out all day long" in any mode .

Flex is fantastic.... DAX inter-phase  is hard to beat using just about everything out there.