Need IFR service monitor information

[littleboss]

I am wanting an IFR service monitor and need to know what to look for- which are good, bad, etc?

I have heard of the blue board issues. Which models have those?

Also that some have a PLL problem that's hard to fix.

What do you recommend?
Also if you don't mind list some of the model numbers and when they were made. Best I can tell the 1000 was made before the 500, but after that the numbers went in sequence- i.e. the higher the number the newer the unit?

Thanks

[Wowbagger]

First, it would help to know what your budget is, and what you plan on doing. If you only have $2000, then you aren't going to be able to get any of the more modern units. If you are going to be doing modern radios (P25, Smartnet), then you aren't going to be too happy with an older unit.

That said:
The 500 is a very old unit, and very low function - no spectrum analyzer, no scope. Unless you can get it very cheaply, I'd almost steer you towards a Ramsey unit.
The 1000 is a bit more, but still a very old unit.
The 1200 is the workhorse, but comes in several versions. The 1200 was the first, then the 1200A (analyzer), then the 1200-S, then the 1200-Super. I'd suggest staying away from anything less than the 1200S. If you come across a 1200-SRA, that is a surveillance unit made for the various TLAs, and doesn't really have transmit functions.
The COM-120 is my baby - I designed much of the software in it. The COM-120A is the first unit, and is very limited. The COM-120B is more desirable, as it has the much better CPU and will support the most recent software. The COM-120C is a B with a different display unit (color LCD vs. orange and black EL). The tracking generator is a software option, while SSB demod is a hardware option. The COM-120 was unfortunately impacted by the knock-off capacitors ("capacitor plague"), so it's worth checking any unit out thoroughly and potentially planning on spending some time replacing all the electrolytic caps with tantalum. Of our monitors, this is what I'd recommend to most hams - but I'm biased.
The 1600 was mostly for the Cellular people, and for the military. The commercial version is no longer supported.
The 2975 is our first software defined radio unit, and is another of my children. But unless you are doing Smartnet or APCO-25 I wouldn't suggest it.
The 3900 is the British cousin of the 2975 - much of the work was done by our UK division (the old Marconi instruments). Again, unless you are doing APCO-25, TETRA, Smartnet, NXDN, or MotoTurbo, I wouldn't recommend it for a ham due to cost. It is currently supported.
You may also be able to find a 2935 or 2945, which are actually Marconi Instruments designs. They are comparable to the COM-120B in features, but in my biased opinion not as fast or easy to use.

[RFguy]

Great overview WB. Thanks for posting.

[Andy Corbin]

I will agree with Wowbagger however, he overlooked two IFR monitors.
The IFR1500 is basically an IFR 1200 Super S, with all of the options. Has the tracking generator, spectrum analyzer, and many more features. The frequency/tone display on the 1500 is LCD. The 1200 series is VFD which I think looks kinda cool.

There is also the IFR1900 which is basically a beefed up version of the 1600. Goes higher in frequency and has some other features.

[bh7juo]

Whit my 120A,I had bought some 10UF/16V SMD 1206 ceramic caps ready to replace all 10UF/16V caps which I can't not find any polarity mark on it but seems like electrolytic capacitor.Most of other electrolytic capacitor on BASEBAND tray allready replaced by tantalum.But self-test still failed in deviation meter......I'll do it this night.

[littleboss]

First, it would help to know what your budget is, and what you plan on doing. If you only have $2000, then you aren't going to be able to get any of the more modern units. If you are going to be doing modern radios (P25, Smartnet), then you aren't going to be too happy with an older unit.

That said:
The 500 is a very old unit, and very low function - no spectrum analyzer, no scope. Unless you can get it very cheaply, I'd almost steer you towards a Ramsey unit.
The 1000 is a bit more, but still a very old unit.
The 1200 is the workhorse, but comes in several versions. The 1200 was the first, then the 1200A (analyzer), then the 1200-S, then the 1200-Super. I'd suggest staying away from anything less than the 1200S. If you come across a 1200-SRA, that is a surveillance unit made for the various TLAs, and doesn't really have transmit functions.
The COM-120 is my baby - I designed much of the software in it. The COM-120A is the first unit, and is very limited. The COM-120B is more desirable, as it has the much better CPU and will support the most recent software. The COM-120C is a B with a different display unit (color LCD vs. orange and black EL). The tracking generator is a software option, while SSB demod is a hardware option. The COM-120 was unfortunately impacted by the knock-off capacitors ("capacitor plague"), so it's worth checking any unit out thoroughly and potentially planning on spending some time replacing all the electrolytic caps with tantalum. Of our monitors, this is what I'd recommend to most hams - but I'm biased.
The 1600 was mostly for the Cellular people, and for the military. The commercial version is no longer supported.
The 2975 is our first software defined radio unit, and is another of my children. But unless you are doing Smartnet or APCO-25 I wouldn't suggest it.
The 3900 is the British cousin of the 2975 - much of the work was done by our UK division (the old Marconi instruments). Again, unless you are doing APCO-25, TETRA, Smartnet, NXDN, or MotoTurbo, I wouldn't recommend it for a ham due to cost. It is currently supported.
You may also be able to find a 2935 or 2945, which are actually Marconi Instruments designs. They are comparable to the COM-120B in features, but in my biased opinion not as fast or easy to use.

Hi, it will be for ham radio use- maintaining 2M and 70cm repeaters- no digital stuff. Since I won't be using it very often, I would like to stay under $3000.

[Wowbagger]

I'd shoot for a 1200 or COM-120B then, with a 1600 as a third choice.

[littleboss]

I'd shoot for a 1200 or COM-120B then, with a 1600 as a third choice.

Thanks very much

[littleboss]

I bought a 1220S. Looks like it will do everything that I need and more. Thanks

[drdslam]

I will agree with Wowbagger however, he overlooked two IFR monitors.
The IFR1500 is basically an IFR 1200 Super S, with all of the options. Has the tracking generator, spectrum analyzer, and many more features. The frequency/tone display on the 1500 is LCD. The 1200 series is VFD which I think looks kinda cool.

There is also the IFR1900 which is basically a beefed up version of the 1600. Goes higher in frequency and has some other features.

IIRC...the 1500 is a duplex box with separate receive and gen paths where the 500/1200 is either gen or receive, a lot of relays. I seem to remember, vaguely, that the 1500 had alphanumeric display on the CRT that required the Tek built CRT. The 1200 was designed with the Tek CRT (I'd be interested to know if that part # was used anywhere else, as in Tek or Tek OEM equipment) and when they sold the CRT line to, Toshiba or hitachi, I don't remember which, they had a fire and had to go to a Thomas Electronics CRT which didn't have a deflection plate for blanking, as I recall, so could never be used in the 1500.

The 500 and 1200 are actually contemporaneous and use most of the same boards and modules. Where the 1200 went from the 8 bit to the 16 bit cpu and went from the Low Loop to the Fast low Loop the 500 stayed with the old one since it was controlled by a parallel bus off the rotary panel switches.

I seem vaguely to remember there are two versions of the 1500, one has 1200-like attenuator and audio and the other had two little LCDs for electronic attenuator.

[tvsjr]

Wowbagger may smite me, but you should also look at the HP 8920, 8921, and 8924 (with the 24 being a bench queen, unless you enjoy back problems). These are excellent units and are very simple to operate.

[Wowbagger]

Why would I smite somebody for speaking the truth? After all, I mentioned the Ramsey units.

Use the tools that get the job done.

[Andy Corbin]

I will agree with Wowbagger however, he overlooked two IFR monitors.
The IFR1500 is basically an IFR 1200 Super S, with all of the options. Has the tracking generator, spectrum analyzer, and many more features. The frequency/tone display on the 1500 is LCD. The 1200 series is VFD which I think looks kinda cool.

There is also the IFR1900 which is basically a beefed up version of the 1600. Goes higher in frequency and has some other features.

IIRC...the 1500 is a duplex box with separate receive and gen paths where the 500/1200 is either gen or receive, a lot of relays. I seem to remember, vaguely, that the 1500 had alphanumeric display on the CRT that required the Tek built CRT. The 1200 was designed with the Tek CRT (I'd be interested to know if that part # was used anywhere else, as in Tek or Tek OEM equipment) and when they sold the CRT line to, Toshiba or hitachi, I don't remember which, they had a fire and had to go to a Thomas Electronics CRT which didn't have a deflection plate for blanking, as I recall, so could never be used in the 1500.

The 500 and 1200 are actually contemporaneous and use most of the same boards and modules. Where the 1200 went from the 8 bit to the 16 bit cpu and went from the Low Loop to the Fast low Loop the 500 stayed with the old one since it was controlled by a parallel bus off the rotary panel switches.

I seem vaguely to remember there are two versions of the 1500, one has 1200-like attenuator and audio and the other had two little LCDs for electronic attenuator.

Your memory is spot on. The 1500 did indeed sport two styles of attenuators. The analog style such as found on the 500 and 1200 and a digital style. My understanding, the 1500 series with the analog attenuators were plagued with a lot of problems (with that attenuator). The digital attenuators are much more reliable. I have a 1500 on my bench which has the digital attenuator. The only thing I do not like about the digital attenuator is it reads only in dbm and cannot be switched to volts/microvolts. I never used a 1500 with the analog attenuator nor have I used a 1200. I do have a 500 which I will take with me when I go to a remote site.

AC

[tvsjr]

Why would I smite somebody for speaking the truth? After all, I mentioned the Ramsey units.

Use the tools that get the job done.

You overlooked my sarcasm tag

The biggest thing that I like about the 8920/21/24 over the 1600/1900 is the speed of the interface. Tuning duplexers or filters on the 1600/1900 is painful - there's enough buffering going on that you overshoot where you want to be and have to tweak very slowly.

Now, with that being said, I'd gladly trade my 8921 in for a properly-optioned 3900... if I could afford it!

[drdslam]

Your memory is spot on. The 1500 did indeed sport two styles of attenuators. The analog style such as found on the 500 and 1200 and a digital style. My understanding, the 1500 series with the analog attenuators were plagued with a lot of problems (with that attenuator). The digital attenuators are much more reliable. I have a 1500 on my bench which has the digital attenuator. The only thing I do not like about the digital attenuator is it reads only in dbm and cannot be switched to volts/microvolts. I never used a 1500 with the analog attenuator nor have I used a 1200. I do have a 500 which I will take with me when I go to a remote site.

AC

The 500 is a 1200-8 bit set (low loop vs. fast low loop) with no microprocessor or CRT, scope, or spectrum analyzer in a shorter case. The entire RF chain is identical, the IF block, etc. The mechanical 1200 attenuator is identical to the 500, although a few 1200s had, or were retrofitted with an electronic attenuator, although I don't recall whether it was a PIN diode type or if it just used switched resistor elements bypassed by solenoids. It might have been the same basic unit fitted in the later 1500s. So if you used a 500 the knob and attenuator are the same. I recall some discussion that this electronic atten could be adapted to the 500 but the battery would have to be sacrificed for space. It was a tightly packed unit, even worse than the 1200 as I recall. 500s go for a greater portion of their selling price than 1200s used, maybe because of portability.

IFR used to replace an immense number of these mechanical rotary atten's because they would be oh so slightly out of limit in the UHF range, they never went bad at below something like 200-250 MHz if memory serves. I have to state I haven't seen one in long enough for someone born then to have a driver's license, maybe a pilot's license now!

The dial assembly for the attenuator on the 500/1200 is an interesting piece and you needed a little machined cylindrical piece to get the dial back together. it could be turned on a lathe by any "model engineer" or gunsmith. IFR was more of a machine shop than an electronics plant and the plethora of stuff made for inhouse use to cal and repair them was mindboggling. There were case-up frames, a scope jig made out of heavy phenolic, et al. One wishes someone had snuck a screw mount Leica in (before the ubiquitous cellfone cam) and documented all this stuff, none of it "secret", just interesting. My understanding is that the current Aeroflex company no longer supports the 1200 and all this went to some third party, perhaps

Someone put a tech's "book of knowledge" for the 1200 and the 1000/1100 on scribd a while back with their notes, but it disappeared within a week or two. I didn't save a copy because to download it you had to pay or upload some stuff and I had neither. I don't know if Aeroflex objected and issued a C&D or whether the (presumably) tech took it back down for whatever reason. Since Aeroflex has apparently not objected to BAMA and other sites posting the service manuals for a couple of IFR boxes I don't know. They've been up for years. Some of these may be "military" manuals and therefore public domain.

[drdslam]

I am wanting an IFR service monitor and need to know what to look for- which are good, bad, etc?

I have heard of the blue board issues. Which models have those?

Also that some have a PLL problem that's hard to fix.


Thanks

"Blue boards" were used for a certain length of time on the 500/1200 and many other IFR boxes. These have a board substrate that is made out of a blue opaque plastic instead of the green or bluish translucent fiberglass used before and since. Although pretty, the adhesive bonding the copper to the substrate doesn't hold terribly well making the traces subject to peeling up when soldered on or just with time and set heat. At one time IFR management was going to summarily throw out all the old blue boards in the repair/rotable used inventory but that didn't happen. It should have.

Unless you are a pro rework artist or are willing to spend a lot of time doing manual board art, figure that if you have to change a part on a blue board traces will come up.

There was a sync issue on, if I remember right, the high loop that caused the set to lose sync and make a characteristic noise on startup. There was a simple fix and I think the fixed schematic is in the later Super S manual but the rework note was treated as sort of a secret thing IIRC. I'm guessing that any set that came back for cal/repair received this fix.