Batboard

Please excuse my ignorance, but isn't a "Sweep Generator" the same as a "Tracking Generator"? I'm looking at a Motorola R-2001D on EBay. The specs I've been able to find for it online list it as having a sweep generator, and I want to verify if they are the same before bidding.

Also, does the Motorola R-2200 have a tracking generator? Does it have any sideband functions at all? I found some pretty detailed specs of the R-2001D, and it lists some sideband functionality, but I haven't been able to find much on the R-2200 yet.

It really, really sucks to have to try to buy test equipment on a tight budget!

A sweep generator is usually a piece of standalone test equipment, designed to be used with an RF detector and a scope, so it usually has sweep/sync outputs to connnect to the scope as well as the RF output.
Tracking generators are integrated sweep generators, that is, they're integrated with a spectrum analyzer. The high local oscillators of both the spec analyzer and tracking generator are either locked together internally or the same LO is used for both TG output and spec an LO, so they're always at the same frequency at any point in time.
Integrating both units eliminates the need to use outboard detectors, and the need to calibrate the horizontal and vertical channels on the scope that the sweep generator's used with.
As far as the questions on the R2000 & R2001 I've never used either, so I'm sure someone here who's familiar with both will chime in.

I beg to differ (slightly).

Tracking generators are not always integral parts of spectrum analyzers. In fact, one of the best tracking generators I've ever encountered, HP's 8444 series, was built and marketed as a separate component.

Think of the two this way. A sweep generator sweeps across whatever band of frequencies you configure it for. In order for it to work as a true tracking generator, that sweep effect has to be slaved to whatever spectrum analyzer you're using, such that the analyzer's sweep and the generator's are one and the same.

So, in effect, "tracking generator" and "sweep generator" are nearly the same. It's just that the former is slaved to another device, and the latter can be independent if need be.

In the case of the service monitor you're looking at, the 2001 does indeed have sweep-gen capability. Whether it can function as a true tracking generator is not something I'm certain of. Dave (DJP126) would know this far better than I would, as he worked in Moto's test gear service depot for many moons.

Happy tweaking.

The R2001 series instruments have a sweep generator function, not a tracking generator. Their sweep generator function works in conjuction with the oscilloscope function and is intended for use with an RF detector probe.

A suitable probe, RTL4075A, was supplied with the instrument. The procedure for use of the sweep function is described in the R2001 operator's manual.

It is possible to get a quasi-tracking generator capability on the R2001 instruments by activating the "DUPLEX GEN" function while the spectrum analyzer is in use.

The duplex gen offset should be set to zero. The generate output can then be connected through a device and displayed on the spectrum analyzer screen.

The results of this procedure may be somewhat useful for tuning pass devices but not satisfactory for tuning notch devices.

If you want to do proper swept alignment of duplexers and rf filters - this isn't the instrument you're looking for.

"It really, really sucks to have to try to buy test equipment on a tight budget!"
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I'll offer a couple more observations.

Service monitors make sense for someone on a budget - a service monitor combines the functions of serveral stand alone instruments into a single package. The R2001 is a good choice for general work - I particularly like the 'D' models since they are much lighter than the 'A', 'B', or 'C' models and offer more features as well.

Later 'D' models have DTMF encode / decode and a cable fault finder function. I have an R2001D and it is my primary bench instrument.

That said - if you want the best RF functionality - look at the HP8920 instruments. When equipped with the spectrum analyzer option [which does come with a tracking generator] they are outstanding for tuning duplexers and filters and have better RF performance that the 2001 units - better amplitude accuracy, lower phase noise, etc.

First, my standard disclaimer: I am biased as hell. I work for Aeroflex Wichita (neé IFR Systems, Inc.), I helped design the COM-120A/B/C, AN-9XX, 2975, 3900, and have worked on the 1600/1900.

One thing that is a nice to have with a spectrum analyzer with a tracking generator is the ability to offset the tracking generator from the analyzer center frequency, to better sweep and align radio IF filters (the analyzer is placed on the IF, the tracker on the RX frequency).

To the best of my knowledge the COM-120B/C is the only service monitor with that feature.

You can simulate this feature with a sweep generator + detector probe as has been discussed above, but if there are any signals other than the sweep generator's signal the detector probe won't be able to distinguish between them (unlike a spectrum analyzer which will), and that will throw off your readings.

IF you are tuning duplexers, a sweep generator + detector can work *IF* you are in an RF quiet environment.

IF you are tuning antennas - you want a real spectrum analyzer + tracking generator (and a reflectance bridge as well).

IF you are tuning radio IF sections, you want either a detector probe + sweep generator OR a spectrum analyzer with an offsettable tracking generator.

Thanks for all the info, guys. I'm also watching an IFR FM/AM 1200S right now. I'm waiting for a reply to a question I sent the seller about what options it has. If I'm really lucky, it has the tracking generator option (option 12), and I'll throw my hat in the ring for it. I would like the option to tune all types of filters. I may just have to save my lunch money for a while longer and wait 'till later.

Wowbagger:
"One thing that is a nice to have with a spectrum analyzer with a tracking generator is the ability to offset the tracking generator from the analyzer center frequency, to better sweep and align radio IF filters (the analyzer is placed on the IF, the tracker on the RX frequency).

To the best of my knowledge the COM-120B/C is the only service monitor with that feature."
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The 8920 tracking generator is not only offsettable anywhere in the instrument's range, it can also be inverted for testing receivers where sweeping the RF upward sweeps the IF downward. Are there any other service monitors that do both?

kf4sqb, If you do buy an IFR monitor I think you will be pleased and find that it is a very solid, well made, full featured machine. They [IFR] have been well respected in the two way radio field since their very first machine.

Of recent models, the COM-120 units seem to sell used for a lot more than the 1600 or 1900 units - I suppose that indicates that they are a favorite of the two-way shops. I think the 1600 & 1900 have comparable features. To me, that would seem to make them a better bargain.

I would suggest a strong look at the HP8920/8921 family. I have an 8921 (don't let the "cell site test set" scare you, assuming you find a 60-watt unit, it means all the desirable options are included) and find it to be one of the best service monitors I've ever used. As it was described to me - the IFR is a field instrument, the HP is a lab instrument. I sold an R2660D to buy my 8921, and don't regret it in the least (iDEN functionality wasn't useful to me anyway, and the purchaser was willing to pay a pretty penny for it )

My complaints with the IFR 1600/1900 - the buffering (time between the actual RF measurement on the TG/spec-an and time to display) is very long. The HPs are near instant, making tuning filters and duplexers far easier. The IFRs are bricks... HPs are much lighter (well, the 21 anyway... we won't get into the 8924). And, the IFR interface is politely described as "user-hostile" - I've sat people down with my 8921 who had never used a service monitor before (but had some clue about RF in general) and they were able to make basic measurements within a few minutes of dinking around with it. Not so much on the IFR. And, my HP doesn't essentially require a keyboard and mouse to operate. Sorry Wowbagger - love your boxen, but I'm biased toward my trusty 8921!

Yes, offsetting and inverting the TG is possible with the 8920/8921.

You might also look at the 8935. The 8935 adds more CDMA functions, 1.7-2.0GHz (not continuous 0-2GHz like the 1900, which is necessary if you want to play 23cm), a sharper amber display, etc., and can be had pretty reasonably. We sold an 8935 at Dayton for, if memory serves, $2K... an 8921 went for $1500. If you're looking for one, I have a friend that buys and sells service monitors all the time - drop me a PM and maybe we can work something out.

Power input on the 8921/8935 is usually 60 watts (though some have micropower options and are limited to 3 watts or even less, so be careful). The setup allows the addition of external loss - I use a lab-grade 300-watt dummy load with a precision, calibrated -40dB sample port, which keeps big RF outside the box and allows measurement up to the limits of the dummy load (the biggest stuff I ever play with is a 330-watt Quantro, and that's rare).

But, I ramble on. Any of the boxen listed will almost assuredly do what you need and are excellent choices. Which manufacturer you go with is a religious debate.

xmo wrote: The 8920 tracking generator is not only offsettable anywhere in the instrument's range, it can also be inverted for testing receivers where sweeping the RF upward sweeps the IF downward. Are there any other service monitors that do both?

OK, I'll note that (I've not worked with the 8920). Unfortunately, the COM-120 won't do inverted tracking, but there is a trick to work around that: just open up the resolution bandwidth of the analyzer to 3MHz, and then it acts much like a detector probe.

I have application note on Aeroflex's web site on that.

As for the Motorola monitors, The R2200/R2400 series have standard generator functions only. No sweep generating and no SSB. The R2000 series does AM/FM/SSB and has a sweep generator. The R2600 series has the tracking generator but they dropped the SSB capabilities.

Personally, if I was looking for a good monitor, I would look for an R2670, an 8920 or a COM-120. Unfortunately, the 8920 isn't supported any more making servicing that piece of test equipment a little more difficult. The R2000D series is still supported by the CTDI depot but parts are getting harder to get due to age. I expect that they will be dropping support soon. As for the COM-120, I don't know if IFR still supports them or not but Wowbagger can answer that question. Since General Dynamics is/has brought out a new box, I think you will see quite a few R2600 series pieces coming to the used equipment market.

DJP126 wrote:As for the COM-120, I don't know if IFR still supports them or not but Wowbagger can answer that question.

IIRC service and calibration are still done, but the 120 is discontinued as a product. The electroluminescent panel used in the 120A|B is unobtainium, and while a limited number of 120Cs with an LCD were produced, the cost of the other parts in the box made it not sufficiently profitable to produce.

Semi-OT: that's one of the downsides of the rapid development of the electronics field: you can no longer spec a part and have an assurance you will be able to get that part for a decade or more, unless you a) choose from a very limited set of parts, none of which are "state of the art", b) are a large company that makes all of its own parts (which is usually very expensive) or c) buy up all the parts (you think) you will ever need and warehouse them (paying large amounts of inventory taxes every year). Otherwise, you spec a part that will be unobtanium at the start of your design cycle (because it is so new), with the (reasonable) hope that the part will be merely expensive when you first go into production, will be cheap when you hit your production peak, and will have to be designed out when you go into long term maintenance.

tvsjr wrote:I would suggest a strong look at the HP8920/8921 family.

I've seen several of these on EBay recently, for excellent prices, but they bottom out at 30 MHz, and I'd like to go lower. They also don't do SSB. I'd like to have a unit that I can use for HF equipment as well a VHF and UHF. Looking at current pricing trends in the used market, I think I'll just save my lunch money for a while longer to get a little more in the pot before I start looking again. Once again, thanks to everyone for all their help, opinions, and suggestions.

You have been misinformed. The frequency range of the HP8920A RF generate function is from 250KHz to 1 GHz, the RF analyzer from 400 KHz to 1 GHz, plus it does SSB measurement from 400 KHz to 1 GHz.

I suggest you go to Agilent's web site and download the 8920 documentation, particularly the Applications Handbook. In that manual you will find a description of all the tests that the analyzer can perform and instructions on doing them.

SSB tests listed are: Audio output power, Carrier suppression, Distortion, Frequency, Frequency error, Harmonic output, RF output power, Sensitivity, Spurious output, and Squelch sensitivity.

XMO is correct. The 8920/21 are capable of generating and demodding SSB... I generally don't play down there, but mine will go as low as 25KHz. I'm probably missing a configuration option, thus xmo's probably right on the 250KHz part. However, it will work.

XMO, not that I'm doubting you, but the writing in the upper left corner of the front panel of all of those on EBay have "30-1000 MHz" written quite clearly on them. I may be mistaken, but if what I've been able to find on these is correct, there are two versions. One covers 30-1000 MHz and the other covers 250 KHz-1000 MHz. If I've misunderstood what I've read, or perhaps read incorrect info, please correct me. I'm just going by what I've been able to find so far.

kf4sqb wrote:XMO, not that I'm doubting you, but the writing in the upper left corner of the front panel of all of those on EBay have "30-1000 MHz" written quite clearly on them

I cannot and will not speak directly to the 8920, but I can tell you what Aeroflex does and why: While our instruments will tune low (the COM-120B will tune all the way to 0), but the specifications only go down so far (e.g. 0.25MHz). This is due to the difficulty of keeping things like the power meter calibrated all the way down, and keeping generator level accuracy. So anytime the instrument's range is quoted, only the specified range over which the instrument 's accuracy is guaranteed is quoted. Usually, in the fine print of the spec sheets it will say something like "30MHz-1GHz specified, 250kHz-1GHz typical" or some other weasel wording.

So often these instruments will TUNE to those frequencies, they will make measurements at those frequencies, those measurements may even be accurate - but don't hold us to it!

It may be the same with the 8920.

"XMO, not that I'm doubting you, but the writing in the upper left corner of the front panel of all of those on EBay have "30-1000 MHz" written quite clearly on them."
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ALL of those on ebay??? I think not.

We are talking about 8920A, 8920B or 8921 units here. These all cover 0.4-1000MHz.

Show us a listing for even ONE of those that says 30-1000 MHz. on the instrument.

You are undoubtedly looking at some other instrument like the 8924. Those do cover 30-1000.

For my personal use I own a 8920B. Engraved on the scope escutchion is the frequency range .4-1000 Mhz. It will generate lower uncalibrated.

I purchased an IFR 1600 on Ebay and then came into a HP 8920B for about the same price. Both are fine boxes but I finally decided I liked the HP better.

Recently my manager's old Cushman kicked the bucket. Two people that were trying to sell him an IFR 1600 and a HP 8921A left them at the shop for evaluation for a couple of weeks. John went the other way and chose the IFR. It fit his needs better and the HP fit my needs better.

While I had the IFR Wowbagger was very helpful answering questions for me.

By the way, The utterly clean HP 8921A is still available.

XMO, you are correct, I was looking at an 8924, not an 8920. My mistake.

Glenn, I'm probably wasting my time here, as its probably out of my price range right now, but how much for the 8921?

It belongs to my co-worker John Johnson WB6LMN. I would not get in the middle of negotiations so contact him directly at the Long Beach shop. The phone number is (562) 570-4801 7:00 AM to 4:30 PM or [email protected].

I believe the difference in 8920 specs for the lower freq is based on the attenuators used at the time.
I believe one had the mechanical attenuator & the other had a pin diode type attenuator.

The mechanical switched attenuator was spec'd for the lower frequency.
Plus, the power meter had an calibration option for use below 30mhz.

I seem to recall there were other options necessary to guarantee the use below 30mhz.

As an aside, I'm glad IFR purchased Marconi's test equip dept.
That merger/acquisition? brought IFR out of the dark ages with much better devices.

Years ago I bought several new IFR1200s's which worked ok for what they were but...each one had problems &
they left a lot to be desired even in the face of the spectrum analyzer lacking Marconi 2955/57's.

The Marconi & HP's of that time were light yrs ahead of IFR as far as dependabilty, function & accuracy.
Alongside the Marconi's, the HP8920's A/B are still the best at what they do & I would never hesitate to pick either one up.
** That is unless you need to work with P25 or Motorola trunking formats.**

I heard through the grapevine that IFR COM120B is aka the Aeroflex 2975. Can anyone confirm? Also, I know the IFR 120B is capable of LTR/EDACS trunking but can anyone confirm if they can be capable of SmartZone/SmartNet?

wjohnny wrote:I heard through the grapevine that IFR COM120B is aka the Aeroflex 2975. Can anyone confirm? Also, I know the IFR 120B is capable of LTR/EDACS trunking but can anyone confirm if they can be capable of SmartZone/SmartNet?

NO. The COM-120B is the predecessor to the 2975. The COM-120 family design started about 1992, and the project was "put to sleep" about 2002 or so. The 2975 design started in 1999. (I know, as I was one of the designers of the COM-120A, was the lead designer of the COM-120B, and the systems architect on the 2975).

The COM-120B *cannot* do Smartzone: only the 2975 and the 3900 family can do Smartzone (the 3900 Smartzone is in final code lockdown prior to release).