Herley CTI Microwave Oscillator XSMP-1416 hookup? - Page 1
Forum section: electronics / rf-microwave

author: mr ed
author_rank: Regular Contributor
timestamp: December 21, 2022, 01:02:32 am
content: I have arriving in a few days a microwave oscillator and can't find any info on its hookup. It's old. Cti became herley which is now ultra herley. Anyway, I see marks that it needs 24V (assuming positive and ground). Apparently I need a ref input, again I assume 100 MHz from others like it.Can someone help with hookup and what pins do what. Nothing on Ultras' site but before I get brushed off by Herley, maybe someone can provide some basic info? Attached are pictures.

author: mr ed
author_rank: Regular Contributor
timestamp: December 21, 2022, 01:04:04 am
content: Pictures try #2

author: edpalmer42
author_rank: Super Contributor
timestamp: December 22, 2022, 10:53:17 pm
content: I don't have any specific info on your unit, but the original web site for CTI was cti-inc.com . If you search for that in the Wayback Machine, you might be able to find something close. Don't stop if you don't find the XSMP section. Look further. It's likely that other products from CTI share a lot of details like pin layouts, supply voltages, etc.I've played with this type of oscillator a few times so here are a couple of random thoughts that may or may not be close to reality.Notice that there are two SMA jacks labelled "RF Input". That suggests that the bottom block is a synthesizer that takes a standard frequency (maybe 1, 2.5, 5, or 10 MHz depending on the age of the unit) and creates the signal in the 100 MHz range that drives the main block. There's some writing just under the open jack that I can't read. That might tell you more.The leads that are joined together are likely power, but neither pair look like they're ground leads. That makes me wonder if the power for that unit is bipolar, i.e. two supplies - one positive and the other negative. I would recommend a partial disassembly to trace some wires. Look for electrolytic capacitors to determine polarity and approximate voltage. Maybe disconnect those jumpers and try to power up one block first while watching the output for a signal. The choice of which block to start with will be determined by what test equipment is available.The lock pin is an output (maybe TTL) that indicates whether the output is phase-locked to the input.Ed

author: mr ed
author_rank: Regular Contributor
timestamp: December 23, 2022, 02:18:42 am
content: Good ideas. Way back machine is 'tres cool'. It goes back for CTI only to year 2000. This unit is older.The exact unit is not mentioned but similar units are. This is what I found or I assume so far ...15v to 28v (marked 24 in pen on unit)Cavity type, phase locked. . With a 600mA draw at 24v it must have an internal ocxo.If no ocxo, ref input would be around 0dBm. The freq may be 10 or 100MHz or ?. Easy to try, I have a rf gen good to 3GHz.Lock lost output may trigger close to outside PLL lock limits so it won't splatter rf when it does loose lock.It may have a input pin (0 phase) to kill the PLL so the cavity can be free run and tuned more easily.The xtal line output is for tuning up the internal xtal, adj for max.

author: edpalmer42
author_rank: Super Contributor
timestamp: December 23, 2022, 03:43:52 am
content: Quote from: mr ed on December 23, 2022, 02:18:42 amNot quite. There's a horizontal scroll bar. Coverage actually goes back to 1998.QuoteI have a simpler unit than yours. Mine is a P-1344 and has an internal OCXO at 104.25 MHz. Yours may not have an internal oscillator due to the extra block on the bottom. Mine will free run at the cavity's frequency if the OCXO is disabled, but stability will be poor. Do you have any way to detect the amplitude or frequency of an 18 GHz signal? If so, just power it up. Note that these things typically have output levels in the range of +20 dBm so an attenuator may be necessary to protect your equipment.In one of the auction pictures I noticed that the bottom block has a label that reads PXS. That appears to be a phase-locked crystal oscillator. (https://web.archive.org/web/19990218180905/http://www.cti-inc.com/prod_set.htm) So you probably don't need an external reference, but if you have one then the output would lock to that.Ed

author: LaserSteve
author_rank: Super Contributor
timestamp: December 23, 2022, 05:23:59 am
content: I'd check throughly, my CTI 10 GHz bricks are minus nineteen volts with case ground. 200 mA warmed up vs 450 mA cold is typical.Time for some reverse engineering.Steve

author: mr ed
author_rank: Regular Contributor
timestamp: December 23, 2022, 08:56:30 pm
content: I will check supply polarity by opening it up, getting that wrong would junk it. I have a spectrum analyzer to 20Ghz so thats not an issue. Just have to wait 2 weeks for delivery. Should be fun.

author: mr ed
author_rank: Regular Contributor
timestamp: January 11, 2023, 03:19:30 pm
content: Received unit. Filthy so cleared it up. It actually works. Some details...It runs from plus 20 to 24volts, as marked. Sales pictures were not clear. Input voltage has no effect on output level or frequency.It has an internal reference so all It needs is power to gen rf.The external ref works from -20dBm to 0 and shifts the freq up 650kHz when input.Rf output is just under 0dBm (nothing is well calibrated) to -3.as I understand this is typical for this frequency.It runs hot. Case gets to 45C and eventually It will become somewhat unstable with a fm like side lobes.It needs a fan. 12 watts to dissipate at 20v.Wierd stuff. Changing the Input ref has no effect on output frequency other than the fixed 650khz shift. Anything from 5MHz to 20MHz will work as a ref. Wth? I was hoping to get some small shift.

author: edpalmer42
author_rank: Super Contributor
timestamp: January 11, 2023, 06:25:50 pm
content: Quote from: mr ed on January 11, 2023, 03:19:30 pmSounds like a PLL. The lock range will be limited. You may be able to figure out the required input frequency by slowly sweeping the input signal while monitoring the output frequency. Watch for a jump (up or down) in the output frequency. It may jump and stay at the new frequency or it could jump and return to the old frequency so you'll have to tune slowly and watch carefully. Start by checking the standard reference frequencies. Depending on the age of the unit and the particular application, try 1, 2.5, 5, and 10 MHz. If you don't see anything at those frequencies, then it gets harder. If you're really lucky, a frequency that's too low will cause the output to sit at it's lowest value and as soon as you move to an input frequency that's too high, the output will jump to it's highest value. But don't bet on that!QuoteHave you tried to tweak the cavity adjust to maximize the output level?QuoteWhat happens if you reduce the power supply further? These units might have been spec'ed to function with wide input voltage ranges. With a stable voltage, all the extra power is just being converted to heat. Try reducing the supply voltage until the frequency starts to shift or the output level starts to drop.QuoteI suspect that the range of the frequency input is very limited. Its purpose isn't tochangethe output frequency, it's tostabilizethe output frequency. Whatever the input frequency is supposed to be, the total range might be only a few or, at most, a few tens of Hz around that frequency.Disconnect the SMA jumper and measure the frequency and level that's being output from the bottom section. Input a similar signal into the top section. You may be able to move the frequency over a wider range. But note that the block on the side of the unit with the RF output jack is a fixed frequency bandpass filter that selects a harmonic from the cavity. The unit I described earlier only has an output near 1 GHz and doesn't have that filter block. I can move the frequency on mine from about 808 - 1186 MHz. I don't know if those limits are due to the electronics or the tuning of the cavity.Ed

author: joeqsmith
author_rank: Super Contributor
timestamp: January 11, 2023, 06:38:36 pm
content: I have a few bricks from Frequency West. One has an internal oscillator that they lock to and it provides a reference output. The other requires a reference input. These were common enough that people made documents available for them. I've not seen any like what you show but at 18G, I suspect someone is having some fun.

author: mr ed
author_rank: Regular Contributor
timestamp: January 13, 2023, 12:03:42 am
content: Today I opened the hardline going from the bottom to the top unit and measured a 90.272 MHz fundamental at around 0dBm and a bunch of harmonics reaching to over 600MHz. This is exactly 1/200 of the output 18GHz frequency to 7 digits. As there are 2 lock indications it makes sense that two PLL are running.So, I then injected 90.272 MHz into the top unit and then subsequently each exact harmonic up to 450MHz at odBm - and it refuses to lock. So, I have no idea how this thing really works. I can see the output PLL trying to lock, but no joy. I fiddled with the frequency and levels too.The mechanical tuning control does move the output ever so slightly. I didn't touch the cavity tuning screw.It's a mystery why I can't move the frequency around electronically by changing the ref.

author: edpalmer42
author_rank: Super Contributor
timestamp: January 13, 2023, 04:53:40 am
content: Quote from: mr ed on January 13, 2023, 12:03:42 amI can't really help you without more info on what you're doing.It sounds like you've got a spectrum analyzer. Do you have a good frequency counter or are you relying on the spectrum analyzer for the frequencies?Do you have a frequency counter that can reach 18 GHz?What are the '2 lock indications' you mentioned. If you've disconnected the hardline, nothing on the bottom unit is important. With no input to the top unit, it should free run at the frequency of the cavity multiplied by whatever harmonic the output filter is tuned to, but the frequency will drift all over the place.When you're injecting signals into the upper unit, how are you determining that it isn't locking?You saw "the output PLL trying to lock". What did you see?You say that "It's a mystery why I can't move the frequency around electronically by changing the ref." No it isn't. The bottom unit is a crystal-controlled phase lock oscillator. You can only pull a crystal so far. The upper unit is a tuned cavity followed by a tuned output filter. You have more range here than with the crystal, but you're still somewhat limited without retuning both the cavity and the output filter (if the filter can be retuned). You mentioned a frequency shift of 650 KHz. That works out to ~36 PPM which is reasonable for a quartz crystal. Some can be pulled more, some less.You haven't stated what you want to use this for or how far you want to change the frequency. It's starting to sound like this unit won't suit your needs.Ed

author: mr ed
author_rank: Regular Contributor
timestamp: January 13, 2023, 04:07:49 pm
content: Today it's working as I expected. I can input 90MHz at 0dBm nto the cavity PLL and it locks and it generates the 18GHz carrier ... and I can shift the output freq by changing the 90MHz ref freq. I think the issue was a bad sma connection, it's at least 30 years old and cruddy.The 18GHz carrier generated by my rf synthesizer ref has way more noise than that from the brick native ref, its multiplying the 90Mhz phase noise by I guess 200 times. Way worse. Another issue for another day.