I recently was given what is obviously a rather old Motorola FM rig, a Maxar 80. The model number on the attached panel is D34TSA6300AK. The plug-in crystals are is two sets, one set marked 16730.55 and 16916.7. The other set is marked 49002.77, and the other marked 49002.77. I'm sure that some of you Motorola gurus can tell me enough about this rig that I can decide whether it would be worth my time and trouble to attempt to make it useable on any of the vhf or uhf bands. I need to know exactly what it is I have, and what I may be able to do with it. Thanks and 73 de Bob, kd5wvu.
The model number tells us that is a mid-powered dash mounted UHF radio. As you've already discovered, it's crystal controlled.
The Maxar series was not known as one of Motorola's better lines. It was a mid-level economy radio for folks who like the Motorola name but couldn't really afford the "good" stuff. However, they are serviceable radios if in well maintained condition. One bad part is the cost of crystals. Another is that I don't know if the Maxar is one of the radios with the split info in the model number. And if it is, I don't have that data anyway.
The "split" refers to the frequency range of the radio. UHF radios tend to come in 403-430, 438-470, 450-470, etc. If you have a 403-430MHz radio for example, you would be beating your head into the wall trying to get it going on the 440-450 ham band. So I don't know what you have there. Maybe it's good, maybe it's not so good for the ham band.
International Crystal of Oklahoma City (www.icmfg.com) is the only place I would buy crystals from, and they will run about $20 EACH! That's $40 per channel (one for receive, one for transmit.) That radio isn't worth $40. To invest that to get on one single frequency pair really doesn't seem practical. Not to me anyway.
Sad to say, you probably aren't going to have a lot of use for that radio. Yes, it's for you to decide if you want to crystal it up for your favourite repeater pair, but . . . eh. Then of course it will need alignment, etc.
The one crystal really should be 16.9157 MHz and not 16.9167 MHz Basically, the lower frequency comes out to 451.725 MHz and the higher frequency comes out to 456.725 MHz. These are the transmit frequencies. The two higher frequency crystals are the receive frequency and they come out both to be 451.725 MHz.
The 456 MHz frequency is the repeater input frequency and the 451 MHz frequency is the "talk around" frequency. Talk around is used when it is not desireable to go through the repeater or else when the mobiles are outside of the range of the repeater.
The D34 indicates a power between 10 and 15 watts output, dash mounted, UHF radio. Since the original crystals are in the 450 MHz to 470 MHz range it is safe to bet that this is the range of the radio. Most, but not all, of these radios are in this range. It will work fine if retuned to the 440 - 450 MHz band for amateur use. I should not require any modification unless you get really close to 440 MHz or below. Even then, it might be OK.
If you decide to use this rig I would suggest using crystals that are "high side" injection. That gets the injection frequency in the range that it normally is with the 450 - 470 MHz band. The crystal formula for the receiver is normally (F - 10.7)/9 where F = the desired receiving frequency in MHz. I would use (F + 10.7)/9 to get the injection frequency well into the "normal" range. Either way works in terms of how the receiver actually determines the received frequency.
The transmitter formula is (F)/27. However, both crystals have to be of a certain "cut" in order to be able to be "pulled" on frequency and then stay there. You can't just buy any old crystal and expect the rig to stay on frequency. If you do decide to order crystals from International Crystal Company, I would specify the receive to be "high side injection". They can handle that with no problem.
The Maxar 80 is pretty much Motorola's lowest line. However, the quality of even this grade of commercial equipment is still better than virtually all of the equipment made for use on the amateur bands. The Maxar 80 definitely meets type acceptance criteria and can be used on the various commercial FM frequencies including GMRS, BRS, etc.