Heat Related Frequency Drift 6300

Ben - AE4NT

Having searched this site and the Internet for clues that others are experiencing my specific problem and finding nothing, I'll take the liberty of raising the subject. My 6300 (running SSDR 1.8.3) exhibits heat related frequency drift. As one would expect, it is most pronounced on six meters.

Those of you who are familiar with JT-65 signals displayed on the waterfall will know that the "sync pulses" represented along the left side of the JT-65 signal should be displayed as a vertical line, exactly perpendicular to the frequency axis like this: | . Initially, during a JT-65 session, that is how it is; however, as heat increases (as reported by SDR Monitor 2.0.3), these lines begin to lean, indicating frequency drift. The phenomenon grows more dramatic as temps increase. When the 6300's fan kicks in during a transmission, meaning that the temp has reached 70C, in the next receive sequence those lines lean like this: / , signifying a frequency that is drifting. as the internal temperature of the 6300 decreases. Over the course of the 47 second receive cycle, the drift can be 3-4 Hz. 

Is this inherent in the 6300 XO design? If I could afford it, I know I could buy a 6700 with the GPS disciplined oscillator, but what other possibilities are there that wouldn't break the budget? I never experienced this problem with my FTDX-3000, but I'm a Flex guy now and I ain't going back to knobs and dials. 

Ben - AE4NT

P.S.
de AE4NT

Duane_AC5AA

Probably not the correct answer, but the 6500 is cheaper and takes the GPSDO......

Marty Bluhm

Must be the weather. I experienced the same thing last night. Same freq, same mode. Fan cut on for the first time, aged twenty years real fast. Also interested in solutions. 73 Marty W8AKS

Ben - AE4NT

I knew that someone would propose that alternative! Throwing five grand at the problem is probably not in the cards here, but if you send me a bottle of single malt, it might soften me up.

73 de AE4NT

Martin AA6E

The 6300 master oscillator is supposed to be a +/-0.5 ppm TCXO, same as for the 6500. (6700 is .02 ppm TCXO without GPS.) 0.5 ppm at 50 MHz is 25 Hz, so you're in spec it seems. On the other hand I've been working 6M JT 65 and JT9 without trouble on my 6500. The osc rating is a maximum across the full temperature range, so it shouldn't get that bad normally. Submit a trouble report? Reduce power?

Duane_AC5AA

Just trying to help you save $3000 over the 6700! :-)

Rick Taylor

Just about every piece of literature on JT-65 has a warning to never run full power using this mode. If you do, you run the risk of overheating the finals. (you don't need much power anyway) I have operated JT-65 on my 6300 for over a year now at about 50 watts and the fan seldom comes on if ever. I would think that JT-65 with a higher swr and full power would spell disaster for the transmitter. I wonder if you have problems with drift on the other modes ?

Rick K7CAH

Rhett Aultman

Interesting you'd pose that question; I'm following this thread because, on my 6300, I do get accused of drifting from time to time on SSB.  I've never seen received signals drift, but have had reports of my TX drifting.

Marty Bluhm

Hi Rick, with a vested interest in this problem, I would like to add my 2 bits for what it is worth. Like you, I have been running my flex for a few months on the Jt modes. Only difference for me is 25 watts is qro. On 6 I have a squalo loop at 25ft. The point I was making but I guess it didn't register was about the weather. Yesterday in WV the temp was in the 80's with humidity in the high 60's. My shack was very warm and humid. My line of thinking at the moment as this problem has never appeared before was the room temperature/humidity contributed if not caused the occurrence. 73 Marty W8AKS

David Altekruse

My 6300 almost never kicks into a higher speed when running JT65 even at 80W (rare very weak DX).  I have an inexpensive laptop fan under my 6300.  Without it the fan kicks in.  Other people have stated that just raising the 6300 an inch or so is as good as a fan but I haven't tried that.  I don't know how much difference that would make in frequency drift but it seems worth a try.  I haven't used JT65 on 6M but I have on 10M and never noticed drift.

Martin AA6E

Flex has said iirc that the power amp is well protected against overheating. That's why the fast fan comes on. If it gets really hot, it's supposed to shut down. What's a little surprising here is that heat from the power amp seems to be affecting the master oscillator. You'd think they'd be isolated from each other. (This is a real problem with my KX3.)

RoyS

Ben,
You might try contacting Flex about a trade up to a 6500 with GPSDO. That is what I did.

Roy - W5TKZ

Cal N3CAL

Hi Ben,  I've been on 6m quite a bit and recall seeing what you describe with your TX signal.   I didn't realize you were using a Flex.  Your drift is enough that some times your signal will not decode, so I can confirm seeing your signal drift as you describe and that is not normal for a Flex 6000 rig.     

Does your RX signals also show the drift or is it just TX?   What's your Power Supply voltage during TX?   I've used a 6300 for a full year without any drift issues and now I've upgraded to a 6500 (without GPSDO) and never have any drift like you describe.   The internal fans have never kicked into high gear in my shack even after running JT65/JT9 constantly for several hours.  I keep a small 10" fan blowing air past the rig and power supply and my antenna is a Par Omni Angle resonate on 6m. 

73
Cal/N3CAL

Mike va3mw

I need to check, but I also think that a 3hz drift is within JT65 spec as there is some AFC.  You also don't need to copy the entire 43 seconds.  

Mike va3mw

k3Tim

Realizing this might prove difficult due to only one antenna port being available... One could open a second slice on WWV, USB and tune 1.0Kc off. Pipe the tone into FlDigi and determine how much drift there is. At this station the 6M antenna is dead to HF and MW broadcasts.

Statement of the Obvious: It's not the absolute temperature but the temp delta to be worry about.

BTW - in my ham radio "frequency stability progress"  I've gone from rock solid crystal control to an Eico Drifty-60 (760) to TenTec with PTO (not bad) to TT synthesizers, and finally to GPS in the 6500. 

Good luck....
k3Tim

Mike va3mw

Don't forget, sound cards drift too and that can also affect our interpretation of the actual RF drift.

Mike

KY6LA_Howard

if you are really concerned about the apparent drift, suggest you open a Helpdesk ticket with Flex rather than deal with all the speculation as to what might or might not be the issue.

Ben - AE4NT

Cal, good to see you here in plain English instead of "RR TU 73speak". I suppose that with all my sloppy drift you thought I was using a TS-830 or something HI HI.

Yes, both TX and RX are affected. 

I adjusted my Astron RS-70M power supply to 13.8V. However, SDR Monitor reads 13.3V in RX and 12.8V in TX. I do not know where or how SDR Monitor reads voltage, but given the half volt difference between its reading and two different VOMs, I don't trust it very much. I haven't measured the voltage at the power supply output terminals during a transmit cycle yet, just receive.

I typically run between 10 and 35 watts on 6M JT65/JT9, increasing power if the opening is waning or if I am not getting responses. At lower power levels, the heat related drift is still there, but nowhere near as pronounced. Of course, if the drift is resulting in decoding problems, I could go into a death spiral of increased power and increased drift. 

I'm feeding an M2 HO-LOOP tuned to < 1.2:1 SWR at 50.276.

I get a kick out of people telling me that reducing power will solve the problem. Duh! That's like responding with "drive slower" if I complained about the gas mileage my car gets. I think I could probably solve the drift problem by not operating at all, too!

I haven't tried increasing the air flow around the Flex. Although I have air conditioning and I know how to use it, the Central Florida summer with its daily ration of 96 degree heat and humidity to match doesn't help any with heat problems. (Now someone will tell me to move to Minnesota HI HI).

Thanks a lot for the comeback.

73 de Ben AE4NT

Ben - AE4NT

I suppose I might do that eventually; however, I always learn lots by reading of others' similar experiences and general comments on related subjects. In doing so, I might just stumble on a solution (other than going QRT to solve the problem HI HI).

73 de AE4NT

Ben - AE4NT

I can do that but I'll have to buy the XYL a Kobe Bryant class diamond.

73 de AE4NT

Ben - AE4NT

I'm thinking that the heat from the PA causes enough heat buildup inside the enclosure that it affects any heat sensitive components. 

Ben - AE4NT

True, but I would expect the sound card drift, if any, to not correlate with indicated temperature changes inside the Flex enclosure. 

Ben - AE4NT

I missed your response earlier. I think the external fan (or riser) would be a good, cheap first cut at reducing the heat build-up. Thanks for the suggestion.

73 de AE4NT

Ben - AE4NT

Just for grins, I sent a Trade-Up request to Flex sales. Not that I consider it an appropriate solution, but new stuff is always a fun prospect. OTOH, if they give me as uninteresting a deal as they gave me on the Trade-In request for my Flex 3000 a while back, at least I'll know where I stand.

Steve G1XOW

Try one of these laptop coolers. My F6300 was really annoying during contest working due to the fan screaming like a banshee every 5 mins. I put this cooler underneath the F6k (its fits really well) and now the internal fan is never used. The internal case temp drops by 8 degrees C after 20 mins.

https://www.amazon.com/Connectland-Gaming-Laptop-Cooler-CL-NBK68022/dp/B007X26SLI

Ben - AE4NT

Thanks, Steve. I believe I'll give that a go.

73 de AE4NT

Tim - W4TME

As Martin Ewing AA6E correctly noted, 0.5 ppm at 50 MHz is 25 Hz so a 3-4 Hz drift is well within spec.

I did not see any references to the ambient temp in the shack or any description of how the 6300 is installed.  It should have unrestricted air flow around it.  Putting it in a cabinet or a shelf with a back may not allow for adequate dissipation of the heated air coming out the back of the radio.

A laptop cooler recommended by Steve Wragge G1XOW is also a serviceable idea since the chassis is part of the thermal mass of the radio, so removing heat from it will cool down the unit.

if that does not provide any relief, I recommend opening a HelpDesk support ticket so we can do a more detailed analysis of your issue.

Gerald-K5SDR

Let me add the calculation that a drift of 4 Hz at 50 MHz is 0.08 ppm against a specification of 0.5 ppm over the operating temperature range. 

Mike va3mw

JT65 compensates for drift, so this isn't a concern. The moon doppler is huge compared to what we see on HF. http://physics.princeton.edu/pulsar/k1jt/doc/wsjt/

Ben - AE4NT

Tim and Gerald,

Thanks for your comments. Ambient temp in the shack is about 25C and the installation is on an open shelf with space all around the 6300.

One of the responders in this thread suggested elevating it to increase the air flow, so I've tried that, but I continue to get the increasing heat build-up from the PAs. I've ordered the laptop cooler recommended by G1XOW, and will see how that works for me.

I understand the 0.5 ppm spec well, that it can mean up to 25 Hz drift at 50 MHz. I also understand the heat sensitivity of crystal oscillators (or I wouldn't have sprung for the crystal oven for my 432 MHz transverter). I suppose I am guilty of not doing my homework. Had I done so, I might have taken a different direction. While 0.5 ppm is certainly acceptable for SSB on 40M, digital modes at VHF frequencies are a horse of a different color.

Who knows, maybe your sales guys will give me a decent deal on a 6500 with GPSDO!

Thanks for all the valuable info. You guys rock!

73,
Ben - AE4NT