Why would one want a GPSDO in their rig?

N8FNR

I am going to order a 6600 very soon and noted the GPSDO option on the order page. Why would one want this option? I operate 160-6 and do some digital modes including WSJT on all of those bands. What functionality would I gain with the GPSDO?

Zack  N8FNR

K9DUR

Zack,

You do not gain any functionality.  What you gain is long-term frequency stability/accuracy.

73, Ray, K9DUR

N8FNR

Does it help much on 160-6 or just for VHF - microwave stuff?

HCampbell WB4IVF

I had the same question when I ordered my 6700, and found the following post, courtesy of K9ZW:

What is a GPSDO and Why Would I Want One? – by Steve Hicks – N5AC, VP Engineering

https://k9zw.wordpress.com/2012/10/12/flex-radio-flex-6x00-series-the-gpsdo-gps-disciplined-oscillator-option/

Howard

N8FNR

Thanks for the replies Ray and Enos.

Ria

For average hams, it's overkill. 

For power users, it's a valuable tool. You can use it for bragging rights in the ARRL FMT too. 

Maybe when I get some spare $$$ I'll get one. I considered during initial purchase but decided it wasn't necessary for most of my needs. Instead, WWV calibration with each new software load worked good enough for regular ham use. 

Oh, and there's also geodiversity whenever that happens. But that seems to be pretty far off their radar for the time being.

Ria

Norm - W7CK

I didn't get one either Ria.  One problem I do have is that 2m is way off frequency on my 6700.  I don't know if the GPSDO would have helped with this issue or not.  Its far frequency enough that I vary rarely use it on 2m now.

Burch - K4QXX

Mine is not way off but when I talk on 144.200, I have to set the VFO to 144.200.250.  I have an external 10Mhz GPS that corrects this.  There are quite a bit of them for sale on Ebay if you don't mind using an external one.

Ria

Yes that would be another use case. However don't feel too bad, when working VHF/UHF I was told that due to the transverters some people are using it was just like HF in the old days - you CQ on a frequency then tune around for the reply.

Burch - K4QXX

I remember when I first got into VHF/UHF weak signal stuff back in the late 90's.  I had a Yaesu FT-736r with the 222mhz and 1.2ghz modele.  Trying to work stations on 1296.100 you had to tune up and down the band to find them.  Now with a transverter and the Flex, I can find the station in the padadapter.  Much easier! 

George KF2T

It's a big help on 6m with weak-signal digital modes. Also extremely valuable when you have transverters and can use the 10 MHz output to sync your whole system to GPS. For satellites, it's a big help. For weak signal and EME, I wouldn't want to be without it. 

For general HF SSB/CW and casual digital, it's not a big deal. The rig is plenty stable and accurate without it.

Norm - W7CK

I'm talking about the 6700 which has 2m built in.  I'm NOT using a transverter.

Would the GPSDO help in this example?  When using 144.200 I have to have it tuned to something like 144.290 or something close to that in order to actually transmit on 144.200.  I then have to dial in a bit of RIT to receive the station.  It is nearly impossible using the digital modes.

Very dissatisfied.

Burch - K4QXX

I don't use a transverter on 2 meters.  I used to use one on 1296 but I have never run a transverter on 2 meters.  I am using the built in 2 meters on my 6700.   You have a problem if it's off that much.  When I hear stations on 144.200, I have to tune to 144.200.250.  I just recently purchased an external 10Mhz reference because my 6700 was drifting really bad.  I just had it repaired under warranty but using the 10mhz reference gets me back to 144.200.  I don't think it will help you if you are off that much as it sounds like there is a problem if you have to tune to .290 to transmit on .200.

Tim - W4TME

Norm- there is a defect for this issue, #3333.  The frequency calibration setting is not scaling up properly from the first Nyquist zone to the 2nd one where 2m is located.  Unfortunately, I do not have any information regarding a delivery scheduled only to say it is on the list for an upcoming release (not 2.0.x)

Norm - W7CK

Thanks Tim.  I bought the 6700 thinking "great it has 2m built in".  Haven't really been able to use it much at all.  Now its 5 years old and still no fix.

Frustrated.

Peter K1PGV

Ahhhhhh.... I still "fondly" remember the SDR-1000. During the first hour or so of operation your PSK31 traces would sloooooowly wander to the right.... it was kind of diagonal PSK31.

Now I'm a fan of the external GPSDO. I like to be dead on the frequency I think I'm on... just as an accuracy thing.

Peter
K1PGV

Tim - W4TME

Those were the good ole days ;-)

philip.theis

I have been using two 6700's on 144 native for some time now. What problem do I have? Haven't noticed it yet.

k3Tim

For mobile / portable operation it gives one unbelievable frequency accuracy. The man pack for Filed Day I'll be using has the GPS ant set up. Another nice feature is it gives your grid square. Maybe someday it can beat of a network timeserver.

Ryan - NC4RA

I was looking at trying one of the external BG7TBL ones. Was hoping to power it with the shack's power supply instead of adding another wall wart. However the input voltage states 11.7-12.9 Anyone have any experience with running one with 13.6V ?

K9DUR

A couple of silicon diodes in series would drop the voltage about 1.4v, making your 13.6VDC supply be 12.4VDC.  -- 73, Ray, K9DUR

Ryan - NC4RA

Great advice!! Thank you guys

Ross - K9COX

My Heath VF-1 was just fine for AM

Bob Brown - N8OB

I'm running mine on 13.8v with no problems.  It is a nice unit that checks out very accurately.  I did not see any reason to add anything else to the radio.  I have used it for FMT and the last one was less than .25 hz off.

Kosmo

I like to add the external modification and use my GPSDO. Ive read as much as I can , my question is: is there a 50ohm resistor across the BNC at the input. What is online is a bit vague.

KD0RC

Hi Kosmo, what rig are you talking about? Which GPSDO? What BNC do you mean, the 10 MHz in of the rig?

You mention an external modification; what mod is that?

I use a Leo Bodnar GPSDO and just plug it right in to the 10 MHz IN jack on my Flex 6400. I set the GPSDO to output an appropriate level signal for the 6400. Very easy to set up and reasonably priced.

fpmacko

It's 50 ohms AC impedance. Perhaps there's a 50 ohm resistor across the input, but perhaps not. You would need a VNA (do you have a nanoVNA?) to verify it. But you don't need to.

There's a simple calculation that confirms it's 50 ohms AC impedance. In the Hardware Reference Manual, section 7.5 gives the limits of the reference input in terms of both p-p volts and RMS power. Using the 1v p-p lower limit as an example, converting this to RMS volts yields 0.3535v RMS. Across a 50 ohm load this results in 2.5 mW or 4 dBm. This tracks the specified 4 dBm lower limit.

73.... Frank / WA3NHK