Peter,

There is a business reason the two meters have such different RF hardware. The original design was based on the 8558 spectrum analyzer plugin. That plugin was already quite old by the time the 8970A came out. Noise figure meters are a very small market, so the meter had to use parts from something that's made in higher volume. As a result, the later 8970s used some hardware out of the 8590 series spectrum analyzers. At the same time, the frequency range was extended because it was easy to do with the parts out of the 2.9 GHz spectrum analyzers.

The YTO in the old units is the very common 2-4GHz oscillator from the 8558, 8568, and some 8350 sweeper plug-ins. You should be able to find one that is similar enough. Also, unlike the EYO oscillator, those old ones don't break often. They can be found.

Once you get the thing(s) running, check the backup battery. If it runs low, you will see some error codes and lose some calibration data.

Vladan

serial number prefixes for the two???



On 10/10/2018 2:26 PM, Peter Gottlieb wrote:

A while ago I bought a 8970B noise figure meter but never got it running due to a bad YTO. Recently, thinking it would be interesting to play with, I bought another for parts, figuring I would make one good one.

To my surprise, internally they are quite different!? The YTO in the second one is completely different, with an entirely different frequency range. Hmmm, that’s interesting...

It turns out that the second unit has option 20, meaning it can go to 2 GHz. I am amazed how different these units are internally!

In any case the initial problem in the second unit appears to be in the controller which usually doesn’t run at all. Or maybe power supply, I haven’t dug into it. The unit was dropped hard at one point in its life as the back panel where the transformer is mounted is bent so I’m going to look for a mechanical cause for the problems and instead of looking to fix the first unit concentrate on the option 20 one. Hopefully the YTO wasn’t damaged in the drop.

It is just interesting to me that the slight increase in the top end frequency required such massive RF system changes.


Peter

On Wed, 10 Oct 2018, 22:37 bownes, <bownes@... <mailto:bownes@...>> wrote:

The trick on that one is not bidding against a fellow volt-nut. :)


It would be nice if volt-nuts and time-nuts could come up with a way so they don't bid against each other.

On Mon, 8 Oct 2018 at 13:26, Dr. David Kirkby <drkirkby@...> wrote:

This seems to be a regular occurrence on high end test kit. I have seen it many times. It usually occurs at a weekend when businesses are closed and so I guess less likely to spot their account has been hacked.?

Once I decided to play along, to see what happened on a Keighley 2002 8.5 digit multimeter. I claimed I would make the bank transfer requested, but could not do it within the 24 hours requested. With that the seller said he sent via FedEx, but would ask FedEx to return if he didn't receive the money. The email had a link that looked like the FedEx website, which showed the parcel in transit, but was clearly not the FedEx website

I "won" the auction for a faulty RF impedance analyzer at ?310

but needless to say I am not going to pay for it. If it was genuine it would be worth getting repaired, but of course it is not genuine.

Dave

I'm quite surprised eBay are not more on the ball. I won that auction, and they keep sending me messages to pay for it. Today I rang and told them it was a scam. They said it would be reported, but I could ask the seller to cancel the order. I suppose the poor seller had a hard time, as someone put 1500 items up for sale, some of which people have paid for by PayPal.

I could not convince the lady at eBay it was a scam, despite there was a link to a site off of eBay, and despite what the seller has written in their shop.

I have sometimes bid on a couple of accounts to push the value of these fraudulent items up, to stop anyone else bidding. I push a 3458A multimeter up to ?50,000. I thought that would stop someone else bidding and being caught out. But as someone pointed out, that could backfire, as someone could think it worth taking ?50,000 for a multimeter they can buy for about ?8,000.

I would like to get a 3458A, but I am not spending ?8000 on one, or even ?4000. If one pops up at a couple of thousand pounds I would buy it, but they tend to be around ?3500.

Dave

Wheat range do you need… I have some I made that are 30mhz to 8ghz

Pete

On Wed, Oct 10, 2018, 5:00 PM Peter Gottlieb <hpnpilot@...> wrote:

Thanks for that background, just the kind of info I was curious about.?

If I can locate a proper replacement YTO for that first unit it would be great and now knowing where else it is used is a big help. I do have an extra 8568 but don’t want to pull the YTO from it. The fault is that the output amp is bad so the output is very low. I did try making up an amp but never got it to work right over the full freq range.?

Peter

On Oct 10, 2018, at 4:45 PM, pianovt via Groups.Io <pianovt@...> wrote:

Peter,

There is a business reason the two meters have such different RF hardware. The original design was based on the 8558 spectrum analyzer plugin. That plugin was already quite old by the time the 8970A came out. Noise figure meters are a very small market, so the meter had to use parts from something that's made in higher volume. As a result, the later 8970s used some hardware out of the 8590 series spectrum analyzers. At the same time, the frequency range was extended because it was easy to do with the parts out of the 2.9 GHz spectrum analyzers.

The YTO in the old units is the very common 2-4GHz oscillator from the 8558, 8568, and some 8350 sweeper plug-ins. You should be able to find one that is similar enough. Also, unlike the EYO oscillator, those old ones don't break often. They can be found.

Once you get the thing(s) running, check the backup battery. If it runs low, you will see some error codes and lose some calibration data.

Vladan

Peter,

There is a business reason the two meters have such different RF hardware. The original design was based on the 8558 spectrum analyzer plugin. That plugin was already quite old by the time the 8970A came out. Noise figure meters are a very small market, so the meter had to use parts from something that's made in higher volume. As a result, the later 8970s used some hardware out of the 8590 series spectrum analyzers. At the same time, the frequency range was extended because it was easy to do with the parts out of the 2.9 GHz spectrum analyzers.

The YTO in the old units is the very common 2-4GHz oscillator from the 8558, 8568, and some 8350 sweeper plug-ins. You should be able to find one that is similar enough. Also, unlike the EYO oscillator, those old ones don't break often. They can be found.

Once you get the thing(s) running, check the backup battery. If it runs low, you will see some error codes and lose some calibration data.

Vladan

CHeck for a bad bleader resistor on the reset line.? I have seen that same thing before.? Once it charges it keeps the processor in reset.

Pete

On 10/10/2018 2:51 PM, Peter Gottlieb wrote:

No I’m happy enough just amazed! ?And I will end up learning a bunch more about these instruments as well as ending up with a better capability unit.?

Of course it would be even better to end up with *two* working units, right?

While I wasn’t able to find a direct replacement YTO for the first unit, I did retrofit a different model but it doesn’t seem as stable as I imagine it should be. Maybe I’m expecting too much from an open loop? ?

The YTOs in these units are mounted in a mu-metal shield but the replacement it physically too large for that and I even had to make a new mounting bracket.?

Once I clean up the second unit and dig in and get running I may have more questions from the operational side but for now it’s just some time on the bench.?

The unit did fire up when I first powered it on but gave an error (maybe 80?) so I hooked up a noise source to see if that was the issue and hit instrument preset but then it stopped responding and further attempts to start it showed a locked up display. Thus my initial guesses at the controller or power supply or mechanical connection.?

I know the theory of NF measurement just never used an instrument to play with it on the bench.?

Peter

On Oct 10, 2018, at 2:38 PM, Pete Manfre <pmanfre@...> wrote:

BTW… if not happy I can take it back.?

P

On Wed, Oct 10, 2018, 2:27 PM Peter Gottlieb <hpnpilot@...> wrote:

A while ago I bought a 8970B noise figure meter but never got it running due to a bad YTO. Recently, thinking it would be interesting to play with, I bought another for parts, figuring I would make one good one.

To my surprise, internally they are quite different!? The YTO in the second one is completely different, with an entirely different frequency range. Hmmm, that’s interesting...

It turns out that the second unit has option 20, meaning it can go to 2 GHz. I am amazed how different these units are internally!

In any case the initial problem in the second unit appears to be in the controller which usually doesn’t run at all. Or maybe power supply, I haven’t dug into it. The unit was dropped hard at one point in its life as the back panel where the transformer is mounted is bent so I’m going to look for a mechanical cause for the problems and instead of looking to fix the first unit concentrate on the option 20 one. Hopefully the YTO wasn’t damaged in the drop.

It is just interesting to me that the slight increase in the top end frequency required such massive RF system changes.


Peter

Virus-free.

On Oct 10, 2018, at 2:37 PM, Artekmedia <manuals@...> wrote:

serial number prefixes for the two???

On 10/10/2018 2:26 PM, Peter Gottlieb wrote:
A while ago I bought a 8970B noise figure meter but never got it running due to a bad YTO. Recently, thinking it would be interesting to play with, I bought another for parts, figuring I would make one good one.

To my surprise, internally they are quite different! The YTO in the second one is completely different, with an entirely different frequency range. Hmmm, that’s interesting...

It turns out that the second unit has option 20, meaning it can go to 2 GHz. I am amazed how different these units are internally!

In any case the initial problem in the second unit appears to be in the controller which usually doesn’t run at all. Or maybe power supply, I haven’t dug into it. The unit was dropped hard at one point in its life as the back panel where the transformer is mounted is bent so I’m going to look for a mechanical cause for the problems and instead of looking to fix the first unit concentrate on the option 20 one. Hopefully the YTO wasn’t damaged in the drop.

It is just interesting to me that the slight increase in the top end frequency required such massive RF system changes.


Peter

--
Dave
Manuals@...
www.ArtekManuals.com

BTW… if not happy I can take it back.?

P

On Wed, Oct 10, 2018, 2:27 PM Peter Gottlieb <hpnpilot@...> wrote:

A while ago I bought a 8970B noise figure meter but never got it running due to a bad YTO. Recently, thinking it would be interesting to play with, I bought another for parts, figuring I would make one good one.

To my surprise, internally they are quite different!? The YTO in the second one is completely different, with an entirely different frequency range. Hmmm, that’s interesting...

It turns out that the second unit has option 20, meaning it can go to 2 GHz. I am amazed how different these units are internally!

In any case the initial problem in the second unit appears to be in the controller which usually doesn’t run at all. Or maybe power supply, I haven’t dug into it. The unit was dropped hard at one point in its life as the back panel where the transformer is mounted is bent so I’m going to look for a mechanical cause for the problems and instead of looking to fix the first unit concentrate on the option 20 one. Hopefully the YTO wasn’t damaged in the drop.

It is just interesting to me that the slight increase in the top end frequency required such massive RF system changes.


Peter