Batboard

Have a vhf 100 watt mtr with an external preselector. I heard that a jumper is removed from the internal when useing the optional
external. Does any one know if this is true? and where do you find tuning info on the external? best route to go? I believe the receivers are wide band as no tuning to the rx, still plays well, sensitivitys good.
Any help or ideas would be great
thanks

ggn420 wrote:Have a vhf 100 watt mtr with an external preselector. I heard that a jumper is removed from the internal when useing the optional
external. Does any one know if this is true? and where do you find tuning info on the external? best route to go? I believe the receivers are wide band as no tuning to the rx, still plays well, sensitivitys good.
Any help or ideas would be great
thanks

Unless there is a pressing need for an external preselector, why are you considering it? These are normally reserved for interference issues.

Jim

The HELP screen in the programming software explains how to align the receiver. They offer two receivers for MTR2000 stations: one with an internal varactor-tuned front end and one without. The latter requires an external slug-tuned preselector, however this same preselector can also be used with internal-tuned receivers for additional filtering.

You normally bypass the external preselector and align the receiver first (if the station allows it), then connect the external preselector and align that. There are no jumpers to change other than the coax lines going to and from the preselector, and in fact Motorola does a pretty good job sealing the receiver module and they don't want you opening any of those Field Replaceable Units (FRUs) up.

Bob M.

It came with the external, however I do not need it. Am I safe to assume it has a varactor internally and can I just bypass the external coming from the receiver?
Thanks, appreciate your help
Gordon

Obviously you will need something. So, if you have for instance a good quality pass reject duplexer, then it's fine to take the factory bolt on bandpass filter / presel off and plug your filter in. Who needs the loss? As for the rcvr varactor tuning, you won't know if you have that until you run the rcvr alignment in the RSS. If you have a choice for rcvr alignment, you have varactor tuning. If it's greyed out, then you don't. The process explains itself. Pretty straight forward.

Or, you can find the model number sticker ON THE RX ASSEMBLY and check a list of FRUs. It'll tell you the band split and whether it's varactor-tuned or not. But plugging in a computer and poking around the various screens is probably easier, as the program knows about all the FRUs and options and will tell you the station's capabilities.

Bob M.

Thanks to both who replied. I do have a RFS/Celwave duplexer that will be tuned and put in so isolation is not a problem here, also a single radio at the site so no qrm....didn't think of looking for the greyed out, that will tell me for sure, as well as the fru's.
I don't need the filtering/isolation so assuming it has no varactor internal whats required or procedure in tuning the external? Is this a pass filter tuned for the rx frequency? I see 3 coils, are these similar to a reject only filter like the small rfs used in rick applications, etc?
thanks again...

About 98% of what you need to know, and 99% of the answers to your questions, can be found by starting RSS and reading the information in the HELP screens.

Bob M.

Thanks

Does this varactor-tuned receiver vs. non varactor-tuned receiver stuff apply to the UHF MTR 2000 stations as well, or just VHF?

From the MTR2000 Product Planning and Ordering Guide R4-2-97B November, 1997:

Wide Receiver:
The standard configuration for UHF and VHF stations utilizes a receiver module that includes a wide (electronic varactor-tuned) preselector. This wide preselector is best suited for low density RF environments, when stations are used with external multicouplers, or when multifrequency operation beyond 4 MHz is required. This wide receiver uses a single receiver module to cover the entire band, 132-174 MHz or 403-470 MHz.

Narrow Receiver:
The optional configuration (X265) for UHF and VHF stations utilizes a receiver module and an externally mounted High Performance narrow preselector. This configuration provides better performance for customers intending to locate the MTR2000 with other stations in the same frequency band.

The optional High Performance narrow external VHF and UHF preselectors are tuned to cover a 4 MHz section within the operating bandwidth of the receiver module without any change in performance. On VHF Stations, two ranges of external preselectors cover the entire band: 132-154 MHz and 150-174 MHz. (If frequencies in the 150-154 MHz overlap region is specified, the lower band preselector may be selected with the X326 option, otherwise the 150-174 MHz preselector will be automatically selected.) On UHF Stations, two ranges of external preselectors cover the entire band: 403-433 MHz and 433-470 MHz.

The 800 and 900 MHz station includes as standard a high performance preselector covering the entire band, 806-825 MHz or 896-915 MHz.

Bob M.

Interesting. I've got an MTR 2000 transceiver and an MTR 2000 receive-only station. I'll have to look into these to see what all they are equipped with. I know one of them has the external preselector on the back. I'll have to see about the varactor-tuned front end.

The external preselector will be obvious; it mounts in the empty space behind the I/O connectors between the PS and PA and has the RX Input N connector wired up to it.

The internal preselector can most easily be determined by connecting RSS to the box and looking at the configuration, Slightly more difficult is by checking the label on the RX assembly, if you can find it. Sometimes it's on the non-visible side of the casting and you have to remove the entire cluster to find it.

All four possible combinations seem to be allowable configurations, but certain installations required the narrower front end, hence the external preselector.

Bob M.

Another senario....I am looking at one to purchase, have no access to read the rss. It had,(but was removed) an external. The cable is coming from the usuall place, but is not attached to the chassis in the usuall place when no external mounted. Is it safe to assume that there is an internal? or could the internal be omitted when adding the external when ordering?
Thanks again, different application, but had an external and was removed.
Gordon